Electric Heat Troubleshooting, Service, and Math Class

all right so we're going to talk about electric heat electric heat is electric woogie woogie woogie to quote the electric slide this is turning bad really bad [Music] um we already talked a little bit about electric heat when we did the heat pump heating diagnostic and troubleshooting and servicing section but we're just going to kind of keep rotating rotating through as we go so one thing you are going to need is you're going to either need the calculator on your phone or a scratch pad with paper i think we'll do the calculator on your phone uh for most of you here because we're going to do just a little bit of math just a tiny tiny bit bert attempted to do some of this in his class and i think it's helpful when you're going to give a class for something that you actually know what you're talking about before you give the class that's usually something that i advocate for not that i'm picking on bert we're going to do just a little bit of math we're not going to focus on math because math is not the main thing with this we're mostly going to focus on just the relationships what happens when different things change with electric heat so the first thing is i always start with a story i've told the story like a thousand times so if you've heard it before you know what story i'm gonna tell sam which one which one is gonna be because there's two okay the bank yeah okay do you want it you want to tell that one better okay it's better for me okay well i wasn't gonna tell the bank one but we will tell both i'll tell both stories actually let's just start with both stories you know start with the you know don't bury the lead is what they always say so the bank story is i was probably i was sorry 19. i was doing maintenances for a bunch of suntrust banks they used to be called sunbank back in the day and i was actually doing the maintenance on the one in claremont and they have a big rooftop unit that does most of the bank and a couple splits but i was going through and i was testing the heat strips because i was told that that's what you're supposed to do so i was running them in heat and i was doing it just by jumping out to white so jumping red to a red to w and heat trips would come on and i would check the amperage and whatever well i was doing that and um as i was doing it because i had to set an extension ladder up against the parapet wall on this bank uh the manager the bank manager came up poked his head up and said what the heck are you doing there's smoke blowing everywhere the bank's on fire and so the so i'm like okay shoot and i come down and sure enough there's just i mean they've already got the doors open there's smoke billowing and the fire department's already uh already pulling up well as it so happens my parents back there and so my dad shows up while this is all going on hey what's going on you know let's talk about it for half an hour and uh so i finally you know we got it all cleared out of course i wasn't very popular in the bank and then got done with all my maintenances left and then i was i think i was either on call attack or the on-call tech called me and i was like what did you do the bank is like 95 degrees something like that um maybe it wasn't even on call it was just later in the afternoon because banks aren't open that way so this story isn't really working too well but anyway so it's really hot in the bank and so i show up and yeah it's like super super hot i go up and the this package unit was a heat pump and it was running in heat mode so like what gives as it turns out uh when they had originally wired up the smoke alarms the smoke alarms were supposed to break red in order to shut the unit off and the smoke alarms went off well they didn't they broke orange and so when you break orange you have no 24 volt call on your reversing valve and it just locked the thing in heat mode and so i didn't test out the way i was supposed to so a couple mistakes there one is whenever you're going to check electric heat especially if you don't know when the last time it's been tested you need to talk to the occupants if you think it's been a really long time like in a commercial application where maybe the heat strips have never run it's a good idea to just pull them out and you know clean them with some compressed air nitrogen or something like that rather than burning them off so that's the lesson there that was a great story wasn't it i feel like i really told it dynamically there you didn't know about the about the no that was that was true it's true i didn't make it up i just haven't told that part before so that's just a lesson in being thorough um i was i was thorough but i wasn't communicative about my thoroughness and then i wasn't throwing the end and testing out the other story is about i forgot what the other story is hold on hold on hold on what was the other story that i always tell about electric heat oh there is actually another story that i'll tell a little bit later about wire sizing that's another that's another key one that we'll get to um oh that was the other story i want to tell was i was working on a package unit uh in leesburg actually very close to where you live nowadays sam i know that adds to the story just having that personal connection to the story yeah okay so we're on a package unit and back in that at that time the company i was working for they would give us heat restring kits so they had a failed heat strip it was shorted out or open or whatever was actually burned and they gave us this kit a five kilowatt heat restring kit so it had the entire thing it was in a little plastic bag and you were supposed to take it and restring this whole thing and put it back on the insulators and all that that's what we had on our trucks first time i'd ever done it so as you can imagine i kind of bungled it as i was making the terminations or whatever it kind of kinked and like broke and it was in bad shape so i thought well this customer you know it's just heat strips so if i take a little bit of heat strip off you know just a little bit the part that's broken that's not going to hurt anything it just won't heat quite as well right is that standard reason stands the reason that if you take a little bit of heat strip off it just won't heat quite as well everybody agree with that there's still heat it just won't eat quite as well just took a little strip off right okay here's the problem with that i i knew ohm's law and watts law but i didn't pay very close attention to it and i don't care that you know how to do the math or don't know how to do the math but ohm's law is e equals i times r okay so that means that voltage equals amps times resistance well in this case the voltage is fairly fixed going into a unit right so that part is the part of the equation that's fairly fixed so we'll say that our voltage is 240 volts so 240 volts equals amps times ohms all right so if 240 is fixed and i change ohms which is what i'm doing when i cut a piece off of that heat strip and i change them down does my amps go down or up if i decrease my resistance the amps go up this is a very simple concept so you don't need to know the math you decrease resistance do you get more flow or less flow you get more flow right you decrease resistance in a pipe do you get more or less water flow you get more flow you decrease the resistance you increase the resistance you get less flow easy and so what did i do when i cut a piece of heat trip off did i decrease the resistance or did i increase the resistance i decreased the resistance i took some of the coil off if you take some of the coil off there's less resistance to electricity do i get more current or less current i get more current so what happened was i took a piece off and when i lit it up when i fired it up it was drawn high amps and the thing was glowing red and didn't work right so and i don't know maybe it wasn't maybe it was glowing red because i was testing it without proper airflow over it who knows at that time i was a dummy and didn't know anything so it's hard to know what exactly i was doing but the point is that with heat strips if you reduce the resistance you're going to get more current and so that's what happens sometimes when heat strips touch something touch a piece of metal you create a short circuit path and they will burn out because they're drawing too much current makes sense so it's important when you install heat strips one of the most important things is that you don't short them out you don't shirt them out to the casing around it you don't short them out to each other pretty obvious so you you will run into cases where things will lay across here just in the installation process sometimes they're you know something like a piece of duct board or a piece of cardboard or something which will catch you know the cardboard will catch on fire the duck board won't do much other than block airflow but sometimes it could be metallic and that can lead to heat strip failure make sense so make sure that's that you don't do that benefits of electric heat that's what we've got up on the on the screen here one nice thing about electric heat is the math is really easy with electric heat one watt equals 3.41 btus all the time so here's a question this heat strip here is it more or less efficient than an electric space heater so if i took this to heat the house or i heat a house with a bunch of electric space heaters which is more efficient this right agree you agree this is more efficient well no there it doesn't matter in terms of now you could if you want to add in the little motors for everyone maybe it's a little more efficient but in terms of the heating function with electric heat strips no matter if it's a little tiny heat strip on a space heater no matter if it's an oven coil no matter if it's the the element on your oven or on your stove they're all going to equal 1 watt in equals 3.41 btus out just that simple and so when we if you've ever heard of cop coefficient of performance cop is a measurement where you compare the efficiency of a refrigeration device or some other device that moves heat around to electric heat and it's always more efficient so a typical cop for a pool heater for example would be like a cop of three something like that which means that it's three times more efficient under normal operating conditions than if you were just running electric heat to heat the pool makes sense because in the case of electric heat we're taking electrical energy and we're converting it directly to heat energy electrical energy directly to heat energy in the case of the refrigeration circuit what are we doing how what are we doing with heat ronnie refrigeration circuit what are we doing with heat getting rid of it we're getting rid of it but we're moving it from one place to another place so we're not taking one form of energy and converting it directly to another form of energy we're taking energy from one place and moving it to another place that's the definition of refrigeration is to move heat from a place that it is unwanted to a location to where it is unobjectionable you remember that one unobjectionable that's what it is we're taking heat and moving it from a place that we don't want it to a place we don't care basically right but in electric heat we're taking electricity turning it straight to heat so it's not efficient but one nice thing about it is we can count on it we know what's going to be produced it doesn't matter it doesn't matter if it's 0 degrees outside doesn't matter if it's 90 degrees outside it doesn't matter it doesn't matter it doesn't matter electric heat 1 watt in 3.41 btus out it's reliable super simple right electricity in heat out no moving parts very simple and it's easy to work on so that's the good news what's the bad news well one of the biggest things and this is the main thing i want you to take away from this when we work in a market which we do where we have a lot of electric heat strips we need to make sure that we burn them off we need to test them at least once a year and we need to let the customer know that there's going to be some motors maybe even some smoke in extreme cases if it hasn't run a really long time when we first test them so that is an indication to the customer that we've done our maintenance if we do a full maintenance and they first run their heat come december you know right at christmas time right when we don't want to be working and we want to be with our families and there's a bunch of stinky smell what are they going to do they're going to call us because we were supposed to do the maintenance and we didn't do it properly so at least burning off the heat strips is critical it's very easy to do so quick quick pull here what's the very easiest way to burn off heat strips most simple way to remove it from the unit and turn it on and let it burn off on the side yeah you wouldn't want to do that because if you remove it from the unit and you apply voltage to it it doesn't have air flow over it so you will destroy the heat strips heat strips are not designed to run with no blower in fact they will that's why they have these thermal limits and stuff so if you pulled it out of the unit and you did power it up it would they would heat up and they'd go off they'd heat up and they'd go off so you could do that be fairly dangerous not the suggested way i mean you should already be in the air handler so wr yeah w r that's it you take your white circuit white low voltage circuit jumper it to your red low voltage circuit and heat strips come on you measure the current on them you let them burn off for a minute or so and now you're good to go you make sure they go back off once you take the jumper out that's the easiest way now why isn't that a perfect test because you don't know what the thermostat is actually yeah you don't know if the thermostat's actually calling it on you don't know if it's actually going to work but at least you know that they're not going to smell up the place and at least you know that there's nothing wrong with the strips themselves so now you've tested the heat strips on the high voltage side but you haven't tested the controls is that okay in some markets yes in some markets no right in our market these trips aren't that critical anyway and in fact we would probably benefit in many cases by not even having them in terms of people's power bills so in general that's going to be a perfectly fine way of testing your key strips what's a better way to test them that's not quite the most extreme but is also a good way yeah at least use single thermostat from the thermostat but doing it through the thermostat service controls the service menu where you actually go in and you drive on electric heat so you go into running your second stage heat and then you test it so you're not jumpering it you're telling the thermostat to do it you're still not running it under normal conditions because normal conditions would be to go to the thermostat set the temperature way up and then wait for the thermostat to turn the heat strips on problem with that is the sun some thermostats have built in an algorithm that either uses outdoor temperature like the modern fancy ones it won't even allow them to come on if the outdoor temperature's high enough and we're going to talk about that or they have a time function so it has to run a certain amount of time before it's going to let it come on so you could just be sitting there a long time depending on the settings so probably not your best way going into the installer setup or to your installer service setup and just driving on that mode is probably going to be a better way ecobee is like the easiest for that the test equipment exactly yeah test equipment also carrier infinity same thing if you go up and you're doing a maintenance or a service on a carrier infiniti system just go through into the installer setup and set it into the mode you want it to run in and then that way you can actually test all the different modes very easily because you actually get a read out too of a lot of your key readings right from the control that's kind of kind of nice a lot of those are even though even the less fancy than the stats there's an emergency emergency well yeah but it depends on if emergency heat is actually connected in the way that it's supposed to be with a lot of modern thermostats that's kind of you put in emergency heat it calls for w-2 but on older thermostats and we're going to talk about this a lot of times that e isn't actually even hooked up so it depends on how they're wired these trips are extremely inefficient so we do not want heat strips to run unless we need them to run and that's some of the strategies that we use have to have to do with that so they can cause high bills when they run too much high current can cause electrical damage this is another thing so heat strips are one of the highest current drawing devices in the entire home there's almost nothing in your home that's going to draw a continuous and this is just 5 kilowatt a continuous 20 amps at 240 volts that's nothing else in your house draws that much current which means that nothing else in your house is it is important that the electrical connections and the wire sizing and everything is correct i'm going to pause here let that sink in not your compressor not your not your dryer not anything else in your house that electric heat strip is going to be one of the highest if not the highest i said your dr your dryer is also a pretty high one but so that's where electrical connections are really key and one of the big mistakes i see people make one of the things i want to protect you from when you're going in and you're a genius because you've gotten good with electricity and you know how to diagnose things you know how to rig things together when you're dealing with electric heat and this is also true of gas furnaces too they would even be higher on the list don't go in and start rigging things up without paying attention to the wire sizing you're using and making sure that those electric heat strips go on when they're supposed to go off when they're supposed to and aren't run through a relay that can't handle that current that was a complicated sentence that i just used there the point is don't run it through some sort of control that can't handle the current and that's easy to do because it's a lot of current make sense so wire sizing to a system that has heat strips in it is going to be one of the most important elements even if you're say all right i have a burned up wire inside this unit well i'm just gonna grab a number 14 off my truck and wire it back up in fact one of the guys who i worked with at my previous employer before i worked here he actually got let go because he rewired heat strips with just a roll of number 14 off of his truck not paying attention to the fact that that obviously isn't going to handle the current that it was drawing and it ended up creating a little fire inside the unit which was very problematic make sense so just quick pull 20 amps what size wire does that need to be typically number 12 wire right typically that's the size wire that you would use now there's some exceptions to that rule like we talked about in a class that we did recently on wire sizing but generally speaking that's the that's what we're looking for another common issue is mistakes with blower interlock so we want to and we're going to talk about how to wire these but blower interlock back kind of what mario was talking about earlier we do not want to run our electric key strips if we do not have blower running and so we have some method to make sure that if the heat strips are running the blower also runs and that's what we call blower interlock sometimes that's done on low voltage sometimes it's done on high voltage but it always has to be done in some way something that makes sure that those heat strips or that the blower runs when the heat strips are on why why do we need the blower to run when the heat strips are on potential fire has a potential fire hazard right they get very hot very hot and so if they keep cycling on and off on and off on and off something gets in there it could potentially cause a fire and then stress on the electrical surface this is another one so when we go from a gas furnace to a heat pump with heat strips can we just count on the fact that we can just swap that because hey you got a gas furnace we're just going to put a heat pump in with these strips no we can't count on that you got a lot of older homes that are running gas that may have 100 amp service on the house so you may be able to slam an electrical panel in there well hey i can put a new panel in run some new wires put a breaker in good to go right but did you think about the breaker that runs the entire house and the wires that feed the entire house how often do we think about that with what we do like never right because it's not our that's not my job right not my job to worry about that that's the electrician's job well if we're not calling electrician out to look at it or we're not thinking about it then we could potentially overload the entire home service which could be a potentially dangerous problem especially on older homes that aren't wired very well to begin with maybe you have all the old rag wiring or whatever or aluminum wire for example you still have a 100 amp house where you probably wouldn't put above a 5kw in anyway but you've seen it look like a 10kw i've seen it yeah and and again we're not qualified to do electrical load calculations because it's not just as easy as just adding all the loads up like it's not like that there's like a whole formula there's a whole sheet that you have to fill out in order to do that the point just being that if you go to a house that has 100 amp service on it this is even 125 and you're pulling a furnace out stop ask the question look at what's else is in that home and see is it going to be potentially a problem because let's say they already converted a gas dryer to an electric dryer okay well they're right there you've already you know you've already kind of screwed up and now you're just going to keep adding to it keep adding electric appliances to it so it's not always it's not in many cases it's not a huge deal to upgrade a service it's not like the end of the world uh you know maybe four or five thousand dollars something like that but you know if that has to be done it has to be done before we put our system in and even inspectors aren't often gonna blow the whistle and have you stop because they're not gonna think about it it's a change out they don't think that oh you changed out a furnace for a heat pump with heat strips or a stray coil unit with heat strips make sense cool all right let's do some math this is going to be fun bert's really good at this now he's an expert at this math right right am i right am i right am i right or am i right all right oh man all right so let's do some basic math here how many watts is a five kilowatt heater all right so we're going to say it's 5 000 watts right there all right now this heat strip here see what it says on it it says that we are this is an 8.9 kilowatt heater so this is not this is what we call a 9kw right if you look at the individual heat strips these are 4.45 each right so if we're going to do the math on this we would have to do it that way but we're just going to do the math on the board here so you have 5000 watts we're going to divide it by whatever the rated voltage is for the unit so let's say that well let's look at this one over here look at what we got here we've got uh it's got a rating for 208 it's got a rating for 230 and actually it says right here heater watts 4600 we would call that a 5 kilowatt heater but it's actually only a 4600. kilowatt heater at 230 volts so it says that right there 230 4600 so let's do it that way instead that's 208 right it has both so it's got 230. he's just looking at it yeah i'm literally just looking at the tank so it says right here 4600 230 37.50 at 208. what just happened there let's let's stop and address that quickly so this is only 3750 watts at 208. why does the wattage decrease when the voltage decreases what is voltage correct amperage is current what is voltage voltage is potential or electrical pressure so we're putting more electrical pressure on the circuit right you put more pressure you get more current flow or less flow more pressure more flow less pressure less flow this is also resistive load so there's less going on in it it's more simplistic circuit than a motor so it's very steady like we talked about you put one watt equals 3.41 btus all the time all day or day right so let's let's use the math here if we go to 230 we've got what did i say again 4600 it's right here on the data tag 4600 so that's what we're going to use we're going to use the one that we've got here 4 600 watts at 230 volts okay so if the calculation is e equals i times r we first have to get our current out of this so how do we get our current out of this well we have watts law 2 which is a really simple one which is watts equals volts times amps so all we got to do is divide our watts by our volts and it gives us our amps what's interesting about that is if you look on this data tag over here it tells you exactly 20 amps if it was 208 to be 18 amps if we do that math that's how it would work all right so now let's figure out how many btus this bad boy produces this particular heater this is really easy because we already have the watts right we did the math this all adds up 20 times 230 equals 4 600 right so now what are our btus so didn't that say uh 3.41 3.41 yep so we take 4 600 watts times 3.41 equals what wait till we get a consensus 15 686 right so that's how many btus we're getting out of it so we're getting somewhere between a ton and a ton and a half of heating capacity out of one five kilowatt heater which ain't much right it's a lot to get that much right how much btus do we get out of 20 amps normally on a running system you know you may have a three ton system that's giving you that total is drawn 20 amps but the time you had the compressor the fans transformer everything right so you can see you're not getting much in terms of btus based on what you're spending here makes sense so that's the math now let's go ahead and change one of the variables and see what we get okay so right now we're matching up exactly with what the data tag says and so that's handy it's easy for us but what happens if we change the voltage what happens if we change the voltage from 230 to 240. our amtrak is going to go up our wattage output is going to go up because we increase the pressure now the problem is we cannot do this math this way you're going to be tempted to take this and multiply that times amps and get watts but the problem is that the amps also change when i change that we have to go back to ohm's law okay and in order to do that we have to figure out the resistance you're going to notice here we don't have the resistance anywhere on this board we didn't figure out the resistance yet so let's go back if e equals i times r e is voltage i is current or amperage and r is resistance in ohms okay volts amps ohms so what do we know we know in this case that our voltage is 230 divided by 20 equals what 11.5 11.5 so what we know now is that the thing that stays the same or pretty much the same it actually does change a little bit but because things actually change in resistance as their temperature changes but generally they're pretty stable now we know that the heat strips are 11.5 and that's the thing that doesn't change that's the part that's not a variable actually right that makes sense the resistance of that heat strip doesn't really change because we can change the voltage which changes the amperage changes the wattage all that stuff is a moving target but the resistance isn't a moving target right so now we've got to delete amps because amps change when we change volts we're going to delete watts because watts change we've got to delete all of this so what are we left with we're left with whatever our input voltage is which we measure so we're going to say that goes up to 240. right e equals i times r so we know e 240 equals blank question mark times 11.5 so now we divide 240 by 11.5 what do we come up with 20.86 20.86 what was it before 20. at 230 volts it was 20. now when we increase our voltage to 240 we now get 20.86 and now we can figure out the rest of it again 20.86 multiply that times 240 what do we get 20.86 times 240. now we're doing watts law amps times volts 5000 and 6. so now we have a 5k heater before did we have a 5k heater at 230 it was 40 600. now at 240 it's over 5000 so it's actually not an insignificant difference now we take that we multiply that times 3.41 equals what oh 17070 it says decimal but so now that is our btu output so you're not you're never going to do this math okay i'm not it's not i'm not doing this for the sake of you doing the math i'm doing this so that you can understand what you really have in a heat strip what you really have is essentially a fixed resistor stays the same i really had my hand on my hip there that was really that was really iffy it was really really it was kind of yeah that's nice um you have a fixed resistor and now depending on the voltage that we apply that changes the amperage and once we have the amperage and voltage that gives us our wattage which then gives us our btus and you can see that 10 volt difference not insignificantly impacted the amount of btus that we output if we drop this down to 208 it's going to be a huge drop in the output make sense everybody get that okay so that's something to know about these because they're not like a compressor in that way they're fixed resistance whereas a compressor or a motor the resistances vary quite a bit depending on load these are pretty fixed all right so what's proper wire size to feed an error handler well the easiest way is just to look at what the data tag says right it's going to tell you what your mocp is or you're sorry your mca minimum circuit opacity it's going to tell you what that is so you base it on that you start we're going to typically size our wiring based on our standard 60 degree celsius column which is like you know your safe zone and that's going to be if you got 30 amps number 10 um 20 amps number 20 so and so forth now if you have 10 kilowatt heat that's where it gets tricky because what do we normally run what do most people run to a 10 kilowatt heater size wire number six is typical but it is number six 60 amps number six in the 60 degree column is actually 55 so you have to use slightly better wire in order to be able to use number six you can't use number six romex in order to do that so and again all these charts are readily available i'm this isn't a wire sizing class we've already done that class but you know ad nauseam right all right so we talked about this it isn't always 5kw just because you see a single heat strip that looks like this don't count on the fact that this is a 5 kilowatt heat strip it's an individual heat strip but look at the actual look at the actual strip to tell you what it is or look at the data tag and right here it shows you 4.45 kilowatts at 240 volts on this one this one's rated at 240. what was this one rated at on the data tag 230 right so it changes it's an interesting thing because even even when you look at it's it's just a silly thing that happens when you look at what it tells you the breaker size should be what the mca is is it telling you what we actually have here in florida no it's telling you 230 what do we actually have in florida most commonly what voltage do you typically see in houses 45 245 right so what's going to happen to your current on a heat strip that's running 245 when the data tag says 230. it's going to run higher current which means what does that mean that the data is that data tag valid now in terms of what size wire it tells you to put on it the answer is yes it is because it's what we got but it's kind of a goofy thing that manufacturers do sometimes they're going to give you 230 sometimes they're going to give you 240 but even 240 isn't enough that's why you're going to see uh amperages on your heat strips that are higher than 20 amps if your voltage is higher your current's going to be higher your wattage is going to be higher your btu output's going to be higher all right let's talk about some of our different terminal designations here letters are a little small on the slide but so w we see w w just means heat does it mean heat strips no just means heat so generally speaking w is going to be used on old school furnaces where you only had a single source of heat it says just w w white that's heat bring the furnace on right w1 means first stage of heat which could mean in a heat pump is what what is first digit heat in a heat pump carlos first stage of heat in the heat pump first uh it's the compressor yeah the the compressor with the reversing valve de-energized typically that's first stage of heat w2 is electric heat in a typical single stage heat pump but beyond that you know you could have a single you could have a system that was a straight cool system that had two stages of electric heat and w1 could be one stage and w2 could be both heat strips running simultaneously so it's not always the same thing and then w3 would be the next stage and so if you have a you know two stages of electric heat on top of a single stage heat pump then w3 would be your second stage electric key but you could also have a system that has two stages of compression like a two-stage compressor w1 would be first stage compressor w2 would be second stage compressor w3 would be heat strips that's why when you had when two stage compressors first came out we had to use uh two stage cool three stage heat thermostats that was a really big deal to find them that were that way they weren't wearing a lot of the maid the old honeywell chronotherm back in the day was one of the first kind of fancy thermostats and you had to had to get the one that had the three stages of heat in it because you know first stage is first stage compression you get what i'm saying so and then emergency heat is usually just a way to manually drive on your backup form of heat it really is not ideal for heat pump markets where you only have five kilowatt heat because what it does is it locks out your heat pump mode and it only drives the electric heat which usually isn't going to do much of anything you know if it's 20 degrees outside do you think this little 17 000 btus is going to do much to heat a house no it's going to do very little to heat a house so it's i mean it's better than nothing i guess but generally speaking we're not going to use emergency heat much in a market where you have very large heat strips or in a market where one of your stages of backup heat is actually a gas furnace well now that makes perfect sense because there are markets they call it you know hybrid heat or whatever where you actually run the heat pump when the temperatures allow for it and then you get to a certain point and you run the gut you shut the heat pump off you run the gas furnace and in that case if your heat pump's failed you put in emergency heat so it just runs the gas furnace that makes perfect sense right make sense cool this illustration shows kind of an early way that we used to wire up thermostats where we would actually have to always jumper aux and e or w2 and e together we'd have to actually put a physical jumper in there used to be a lot of physical jump ring in many cases old thermostats you would even have to jumper y1 and w1 together we're going to pause here because i see you falling asleep older thermostats y1 and w1 we would actually jump her together why would we do that on some older thermostats what do you think function because if it's a heat pump y1 and w1 are the same right what does a heat pump do when you need to run first stage heat it calls y with no reversing valve what does it do when it runs first stage cooling it calls y with a reversing valve right so in older thermostats you didn't used to have an installer set up we're used to this now as a standard thing every thermostat has an installer set up you go in you tell it what kind of equipment it is but on older thermostats all the way back to mercury bulb thermostats which are actually the standard when i started in the trade not that long ago in 2000 people had mercury above thermostats everywhere isn't that wild kind of throws me off doesn't seem like 2000 should have been should be 21 years ago but it was um yeah so in those types of thermostats you didn't have internal logic so the only way you could tell it what kind of system it was was by putting jumpers in place and you'll still see some of these you'll actually have physical jumpers in place and so you had to jumper uh y1 to w1 nowadays you tell the thermostat that is a heat pump and it automatically does that it automatically just energizes y in both heat and cool testing heat strip current so 5 kilowatts it's about 20 amps but we talked about why it changes if you're hooked up like we are here because this is a 208 facility quick question why is this a 208 facility what does it mean for something to be 208 say it again it's going to be generally commercial commercial but why are commercial buildings off in 208 why is that because if i measure if i measure the outlets here what voltage am i going to get out of these outlets you're going to get 120 right but it's three-phase right and so you're going to get 120 on these yeah yeah no you get 120 still because from leg to neutral it's the same it's from leg to leg the two legs are no longer uh 180 degrees out of phase like they once were so 180 degrees out of phase means that they're you know like this it would be what would it be if it would if it's thirds it would be 90 uh why am i all of a sudden having uh be like this 120 degrees out of face yeah wow that was really weird so so because they're not because they're not the faces aren't lined up now you have a lower voltage between phases so that's why you have two way the point being that you're gonna see 208 when the building is a three-phase building and you're only using two legs and that's what this is this is single-phase equipment hooked up to two legs of three-phase so when that happens you're gonna see lower output which means you're gonna see lower current so just because you were to measure you know 18 amps on this you wouldn't because you might think oh this heat strip's not working properly no it's just that the input voltage is lower so input load input voltage lower equals lower output lower current 10 kilowatts is around 40 amps but it's still 20 amps per strip so if you imagine this was this is 10kw this is actually a 9kw strip but if it was a 10kw strip you'd have five and five so you could still measure them individually you put your amp clamp on the black wire that feeds the strips one side of the strips put your clamp on it'd be 20 each if you went to the main leg that feeds it your main input or you put it under both wires at once then you would measure 40. make sense cool but it's still going to generally be maximum of 5 kilowatts per strip and this is just showing this so if you look a nap draw on both here at once yep as long as you're not opposite phases they're on the same phase then you'll measure the same and these would be if you took both blacks and put a clamp over both you'd measure the cumulative amount so this guy right here what is this 5 kilowatt or 10 kilowatt it actually that was a trick question because this is the same one we just looked at it's actually nine but it's two separate strips so yeah it says it right there this one right here is this a 10 kilowatt or a 5. it's a 10. you see two separate strips right this guy right here you can tell it's a five because there's only one it's in the center that's a five now it isn't necessarily what i'm saying this that could be a 3.5 it's but it's a single strip all right heat strip thermal limits i'm going to pass this bad boy around so you can take a look at the thermal limits this one's interesting because it's got thermal limits thermodiscs on the high voltage side on each strip and then it also has a low voltage thermodisc too which also protects it so it's got double double the protection huh pass it around it's fun we're having a good time here everybody's enjoying themselves you know um so if you look at oh that's right he was in the last class wasn't he he was in your uh hashtag class yeah hashtag class yeah that other class that happened a couple different types here we've got a fusible link which i want to mention quickly because you will see these sometimes this is a single this is a single fail um so is the one with the orange wires thermal overload this one here is that's what eric told me he what why he says he's pretty sure it's a single fail i don't think so there's a button right in the middle of it you can click it no i didn't just reset it but if there's not then auto reset i still think it's not a reset but whatever the other thing you're going to notice here is they actually have temperature ratings right on them so 150 degrees and then it resets at 55 degrees less than that is what i think that means not that that really matters that much this got this little guy here's 180 degree trip so you can if you pay attention you'll notice a lot of interesting information but if you see one of these and one of these is open you have to replace it now how would you know if one of these is open or any of these how would you know if they're open open out be the easiest way right so take the wires off take your own meter obviously shut the power off first measure across it what are you going to measure if it's open oh well infinite ohms no path right if it's closed maybe if your meter has that setting on it but a lot of times i see text don't have their meter on there like it's not ringing out and as you look down the meter it's reading zero right or point one or something like that look it's reading point one is that good or bad low ohms means good path infinite ohms means bad path infinite almost means open low ohms means closed right all these are switches so they don't consume energy they just open and close in order to protect the circuit all right what can we use to control a heat strip the top the two top ones here we show a heat sequencer and we show a contactor so when we talk about control i'm talking about the actual line voltage control what actually turns the heat strips on and off there are certain types of i'm telling you it's the thermostat or something's wrong so you have uh relays or they actually wouldn't call them relays they would call it a contactor um that are rated for the current that a heat strip uses come on in have a seat come on in come on in come on in it's okay it's good we're having a good time um you have contactors some brands will use a big old contactor in there to turn it on and off and some will use what's called a sequencer or sequencing relay the only thing to know about a sequencer that makes it different is that a sequencer the contacts close at different times because it actually uses a heater so rather than an electromagnet down here it has a heater and that heat causes these little round thermodiscs to snap at different times in order to make or break the circuits so basically when you see a sequencer it's generally there because you're running things at a different sequence you talked to them bert yeah that might be just disrespectful right right it could be just a few seconds it doesn't all come on at once could be or it could be so that you have a fan off or on delay too so you get the point so sequencer brings things on at potentially different times and they're generally designed to handle the current that a heat strip is going to have and again depends on what type of sequencer it is but what you don't want to use to control heat strips line duty is a regular relay like a 93 40 or 93 80. so quick pause yeah quick pause i'm just going to address this again why do you not use a 9340 or 9380 to directly control the line voltage of a heat strip why it can't handle the amperage can't handle it you know it can't handle the heat so it needs to get out the kitchen am i right it's like tom cruise from a few good men it cannot handle the truth you know what i'm saying all right 15 amps that's all it can handle 15 amps so if it were a three kilowatt heater it could maybe barely handle it but that's not what we're gonna that's not what we're gonna use for that so this is for uh fans blowers condenser fans that sort of thing and then controls isolation whatever it's not for heat strips but what's interesting is we actually use it in conjunction with heat strips for a fan interlock sometimes and this is where it gets a little tricky and they may not always use a 9340 but they're going to use some sort of similar control we're going to talk about that in a second all right let's talk about heat strip staging why would we stage heat strips if you had more than one so that way they don't come on at the same time you're especially going to see this in other markets where they have 15 and 20 kilowatt heat less current yeah that's it's brilliant brilliant where'd you get that from what else what else there's one other thing um the less electric the better the better yeah it's a good you make a good point less electric heat the better so if you only need five kilowatts in order to keep up then only run five kilowatts and let the heat pump do the rest right because the heat pump is far more efficient than the electric heat the other reason is if you bring on 20 kilowatts of electric heat all at once how much current is that it's not hard math 20 20 20 20 80. people count on their fingers pull off your shoes use your toes 80 amps 80 amps all at once amps all at once i was struggling with that yeah and again i mean whether you run 80 amps all at once or you run it slowly it's not it's not like it's that big of a difference but if you don't need 80 amps it comes down to the staging if you don't need it then don't run it basically if it were 20 kilowatt any questions about that i said we're only going to go an hour already over an hour so i'm going to finish up this class and we're just gonna leave all right how's that sound sounds fun to me i like going home where did you get that diagram that is so nice yeah sure is it's right in my site if you google 9340 or any of this stuff you know i have a website it's got some good resources on it it's a great place to prepare if you're going to give a class last class okay so um this just illustrates oh boy some money somebody's gonna get it ballsy you'll notice that these two actually kind of look the same so this shows the coil so that's these points here so that's actually the electromagnet that switches its position this is the normal position normally closed between one and two normally open between one and three and you'll see they have this same diagram drawn on here that's this guy right here one and two are closed one and three are open right if you energize it what happens from here to here it goes open from here to here it goes closed so and this guy same thing same same time make sense yep all right cool so here's how interlock is wired we're just going to talk through this circuit very quickly and then i'll show you how to think about this circuit if you ever have to wire it because it's a it's an opportunity for a big mistake if we wire up this interlock in such a way that the heat strip current is being carried through the relay we're going to melt the relay and make a big fire right big stinky plasticky mess so we don't want to do that we have to make sure that it's set up in such a way again back up what's the purpose of the interlock again anybody remember make sure the fan comes off blower comes on with the heat strips he strips her on blowers on at the same time that's the reason that it's there now again they're not always going to look like this relay but the interlock's almost always going to be wired if it's line voltage it's almost always going to be wired in this same general way we don't want every time the blower is on for the heat strips to come on right that would be bad there's a lot of ways you could wire it so that every time the blower comes on the heat strips come on that would be easy to do to make them both come on at the same time but we don't want that that would because very high power bills right don't want that we also don't want the heat strip current to be carried through any of these contacts kind of tricky so here's how this works and this shows the terminal numbers on it so if the heat strips go on so this contact for the heat strip closes both of these clothes right imagine these clothes you have voltage coming through here this relay is already regardless of whether the blower was previously calling is closed which brings on the fan right current for the heat strips isn't being isn't being taken through any of these let's say that the that this relay is already on so the blower was already on well does that hurt anything no because the blower is already on these clothes it doesn't make it through to the blower but the blower is already on so who cares right either way if these heat strips are on the blower is also going to be on so rather than your heat your blower relay back feeding your heat strips your heat strip relay is back feeding your blower through a relay that prevents the opposite from occurring right we don't want every time your blower is on for your heat stress to be fed so let's look at it the other way let's say that we have our you know we have a g call so when it calls on this closes and this opens for our blower to run right so now our blower is running can it back feed our heat strips nope because this is now open because you have a g call right so you get this this is when you don't have a g call this is what it's like and when you switch it it goes the other direction one three two one three two kind of complicated but we're gonna skip that here we go so this is how you do it because this is where when people are given one they do it wrong even if i give you the exact diagram to do it because it just is counterintuitive so you follow the ladder diagram closely to wiring a fan interlock this is the very same thing that we just showed don't think about the relay right side up flip it upside down so now you're connecting power in because when we think of power in we always want to go to terminal one with power n right but does this show going to terminal one with power n nope power n goes to terminal three powering goes to terminal three blower speed tap goes to one and then the load side of the heat sequencer relay this is the most confusing part because it's not the power in to your heat strip relay or heat strip control it's the power out of your heat strip control between your heat strip control and the actual strip itself right so two will only ever be energized if the heat strips are falling two will only okay let's say that again so two will only ever be energized if the heat strips are already calling correct correct yeah terminal 2 cannot be energized otherwise because if the blower is not running then there's not going to be any potential there if the blower is running then that relay is going to be the opposite position and this guy here is going to go open which prevents it from back feeding make sense that's a standard heat interlock now there are other control strategies that just rely on the 24 volt call and it just uses a board you know it doesn't use this sort of high voltage strategy but this is the most common typical long-term way that this is done and this just shows you know how you would actually wire that up in real life with a with a sequencer a lot of trains go through the same 93 490 340 relay with low voltage so you have the high voltage on the top low voltage on the middle high voltage for the blower voltage so they break common to the contactor going to the e-strips yes yes that is correct it also has that time delay relay on there as well to run the blower that's that old school way of doing it in 93 40. these are some standard things that you need to know how to do you need to measure heat strip amps to make sure heat strips are running that's how we can tell if they're running you're not going to look at them so you just clamp onto the black wire that feeds each individual strip clamp you're going to measure the current right you're also going to test it on and off so it's not just a matter of saying yep i've got 20 amps it's good leave yep i've got 20 amps that's good now shut it off make sure that i know i don't mean shut it up with a breaker i mean shut off whatever jumper you put in or whatever installer setting you put into the thermostat and make sure that that 20 amps goes away so test it on test it off force the system into defrost and test the heat strip amps that's a more complicated test but if you ever have a system that's having an issue especially in heat if we get a cold snap which happens sometimes and you have a customer that's not keeping up or having challenges that's something you want to check make sure that the um that the defrost board is bringing heat straps on when it's in defrost like we talked about last class all right now this is a this is a quick this is our final little little thing here and i'm going to have our this is a good one for our senior techs here so we're gonna actually bring the white board up here okay so anybody who considers himself to be a senior tech where'd ronnie go he said he had to go i just had to go huh kid stuff yeah sure i don't know what that's like all right so this is actually a code in a lot of places i couldn't find it in the florida code but i thought it was here at one point like nobody does it in florida but heat pumps having supplementary electric resistance heat she'll have controls that except during defrost prevent supplemental heat operation when the heat pump compressor can meet the heating load a heat strip outdoor temperature lockout shall be provided to prevent supplemental heat operation in response to the thermostat being changed to a warmer setting the lockout shall be no lower than 35 degrees and no higher than 40 degrees so typically be 40 degrees you set up a thermostat outside a control that unless it is below 40 degrees outside your heat strips can't run now they're saying except in the case of defrost but i'm going to ignore that part how would you wire up a device like this it's just simple we're going to imagine it's open and closed so it closes when it gets it closes when the temperature is below 40 degrees and it opens when the temperature is above 40 degrees how would you wire it in order to accomplish that mission wire anyway i want your writer the best way what is the best way to do it to prevent from energizing unless the temperature drops below 40 degrees outside yes this is actually a fairly good puzzle got it okay show me uh doctor use that though can i just write something different what no no you don't have to use this thing just again this is just this is just what an outdoor thermostat looks like generally who cares you know the open and closed whatever it doesn't it doesn't matter okay so in many cases you're going to use a universal control that you just set the dial and sometimes just give me a snap action disc that's automatically set to 40 degrees but the general idea is when it gets below 40 degrees it's going to close and allow the heat strips to come on okay [Applause] okay okay all right so there's our heat strips they just have a name okay okay all right so the thermostat wants to turn on our e-strip so it says the w all the way to our condensing unit okay via one of our thermostat wires okay now this is a close on fall aka the 40 degrees okay and when it does that it closes and it actually sends the voltage all the way back to our air handler which energizes our heatstrip relay how is that different than how we wire things now what do you mean how's that different than how we wire up units now well units now go stretch directly from the thermostat to our heat strips so does that mean we have to run a separate wire from our thermostat all the way to our condenser no you have spare wires for that i think you have two extras you just take you just run it out the w that goes into the defrost board and you would still need to bring it you just bring it back sometime hey i was right that's all there is to it [Music] you still need to bring it back yeah and so this isn't this this is not incorrect it's just not really explaining it exactly how you would do it so one way the way that a lot of people would do it is they would use two separate wires and they would actually run those out and then they would make and break inside the air handler but that's that's that's a waste of a wire you do need right what's that like a safety switch would right on the inside yeah but you're but you have to use two wires in order to do that all the way to the outside so in sam's way you know i think what he's saying here on this very well-drawn diagram is that rather than taking your white rather than taking your white and connecting it to the white terminal of the white wire inside your air handler you're just connecting your thermostat white and your condenser white together in the air handler then that's going out and then you're running another wire black brown green whatever extra you want to use and you're running that back from the condenser to the air handler and then that one is what you're connecting to the air handler white so the air handler white is only being connected from that wire coming from the outside and so what that means is is that unless that bad boy closes it's not going to allow and in fact let's think here you could actually do it you could actually wire it in such a way that it would work the way that this code says because this is saying that if defrost runs it will still turn the heat strips on and so it would just it's a matter of where you break it so you would connect this rather than breaking it after in the in the wire coming back you would break it in the wire going in and then the defrost board could still send the white signal even if this was open so in this case even if this was open if we did it on the wire end the defrost board could still route it back to white yeah it's kind of a hard diagram to draw because there's a lot to that but they're black correct and then you feed back black back yeah yeah what's the other way of doing it the other the other way of doing it no what do you mean that is the way this is your way what i just said yes what i just said is your way isn't it so here we'll draw look i'm going to actually try to draw it in a way that is visually correct correct so the typical if you were going to do this with an ecobee how would you do it the eaglebeat does this already through weather app correct so the ecobee you just tell it what temperature you you know to lock it out at and it just does does it with a weather app piece of cake how would you do it with the carrier infiniti well the carrier infinity weather app sometimes experience crashes yeah no that's not what i'm talking about the carrier infiniti has an outdoor temperature sensor right so it doesn't need a weather app it has an outdoor temperature sensor right not anymore carrier no it it from the factory it has one well they still use the weather app they do oh okay well anyway all right i can't get this tape off so we're going to go air handler is going to be in the center no so air handler is going to have a w terminal here our thermostat's going to be here we're only going to focus on our we'll do a w2 we're only going to focus on this circuit this is our t-stat w2 and then our defrost board so normally we would take this and connect it here and then here but now what we're going to do is we're going to go into our air handler and we're going to wire not together a wire that goes out to here we're going to break with our with that outdoor thermostat control we're going to break it here and let's actually draw this properly so you're welcome so it's a single pole single throw close on fall thermal switch buma sorry sorry that was a little too much there so then that feeds into our defrost board right and then from here we would run a different wire back and this would probably be our black or brown probably black if we have that extra so our defrost board could still send a signal to bring on the heat strips by itself even if this was open but in order for the thermostat to do it this has to be closed in order to send it back but another way you could do it which would be the way that you would immediately think to do it would be to take your you guys have something to share with the entire class jacob called you dog did he really i had to grab pizzas on this would be to take two would be to take two wires yeah thanks would be to take two wires from the outside and then when you bring uh you would go in here and you would go here like that but now you have to use two separate wires from inside the outside so it's just a waste of an extra wire so if you were let's say that you were at a two stage and you were using black for the second stage then what color then you could use say green that would be a possibility um if you have a wire that's fuchsia plaid you could use that one you know maybe if you had a chartreuse wire use that you know light tan what color structures most of the closest to it i have no idea all i know is the ground wire that is going with your high voltage i have a question breaker no you cannot i have a question for you encarnacion what is her favorite color what is her favorite animal puppies [Music] what's your favorite hobby volleyball and serving and serving the lord boom all right i think this class is done okay is this really mandatory it says mandatory requirement this is from i don't know which code this is from this isn't from the um this isn't from the unified mechanical code but this is a code that is a lot of places i don't i'm pretty sure this was in the florida code or is i just couldn't find it in a quick look um but it does exist everywhere and it actually is a kind of a good idea in terms of energy savings it's actually a pretty good idea because you really don't need to run heat strips when it's warmer than 40 degrees outside uh and heat strips really do run up power bills pretty quick and it's actually kind of nice too because it's another thing that prevents your stupid thermostat from doing something stupid and running your heat strips stupidly stupid stupid stupid did i mention stupid i made elise laugh that was good isn't isn't elise just the best wow oh man yay any questions anything else no great thank you god bless america bald eagle thanks for watching our video if you enjoyed it and got something out of it if you wouldn't mind hitting the thumbs up button to like the video subscribe to the channel and click the notifications bell to be notified when new videos come out hvac school is far more than a youtube channel you can find out more by going to hvacrschool.com which is our website and hub for all of our content including tech tips videos podcasts and so much more you can also subscribe to the podcast on any podcast app of your choosing you can also join our facebook group if you want to weigh in on the conversation yourself thanks again for watching [Music] you

Channel: HVAC School

Views: 205,325

Keywords: hvac, hvac school, electric heat troubleshooting, hvac math, hvac math examples, hvac classes, hvac education, BTUs, heat pump, electric heat, ampacity, contactor sequencing, air conditioning, hvac training, air conditioner, heat pump troubleshooting, heat pump wiring, air conditioning system, air conditioning unit, hvac classes online free, heat pumps explained, air handler, heat strips, hvac training basics, hvac heat strips, hvac heater, heat strip amp, Hvac commercial

Id: AqQx-YJVYjI

Length: 67min 35sec (4055 seconds)

Published: Thu Oct 28 2021