Electric Expansion Valve (EEV) Operation and Testing! HVAC Metering Device Training!

in this hvacr training video we're going over the eev the electric expansion valves operation the wiring and the testing so an eev is typically found on inverter systems and other high efficiency HVAC units and make sure to check out our new book on inverter Mini Splits and we go over the electrical operation of all the components inside we go over the refrigerant related practices and a lot of the questions that you may have concerning these systems so check this out in the full outline over at ecservicestate.com in the mini split tab an eev is an electric expansion valve that has a adjustable pin on the inside of the eev to regulate the refrigerant flow going through it so if you have high pressure high temperature liquid refrigerant heading through on this side you'll have low pressure low temperature liquid over here and likewise if you are in heating mode or an air conditioning mode basically you change the direction of the refrigerant you'll have high pressure high temperature liquid coming here and then you'll have low pressure low temperature liquid coming over here and so it's a pressure reduction device and it's electrically driven with 12 volt pulses so 12 volt DC pulses of electricity and you're going to see in the inside of here there's little teeth and there's actually in this one there's 40 teeth total and I cut the the end cap off the top it typically looks like this where you have a end cap that's sealed and I I cut the end cap off so that we could see as well you'll you don't have access to the magnet right here it's always in a sealed stainless steel shell and so I cut this off so that you could see it and we could also Mark it but basically this is a permanent magnet with 10 North Poles and 10 South poles and they're offset from each other so I just want to show you this right here we can remove this completely because we cut the stainless steel shell out and so you can see there's our pin and so it rides up and down you have our stainless steel shell separating our permanent magnet with in this case it's going to have 10 North Poles and 10 South Poles so you'll have a north and a South and a north and a South and a north and a South all the way around this even though it looks like just one one magnet section so we can take this magnet right here and you can see we have just slight control over it and what I want to show you is so I just want to count here so we're going to start right here one two three four five six seven eight nine ten and that would make 11. so you have 10 North and then you have 10 South one two three four five six seven eight nine ten eleven so we have 10 North and 10 South and so you can see we have slate control over it right here but not a whole lot so if you try to add a regular magnet on here you have no control but if you concentrate that onto the teeth then you have say in this case 10 North teeth and so you have 10 spots and where you're going to be grabbing at in order to to turn this and so these little teeth are going to line up with the permanent magnets right here on the inside a question I get asked a lot is can a solenoid tester that has these two little magnets inside can that be used to turn the inner permanent magnet of the eev and the answer is no it can't so as you can see it's not turning but if you project that magnetic force onto 10 teeth and you put that around the eev then you have enough grip on the inner permanent magnet in order to turn it but really what you want is you want 20 magnetic forces so 10 North and 10 South that will really grab a hold of that magnet in order to turn it even when you have the stainless steel shell on the outside so right now we're applying 12 volt power to one of the two sets of coils inside this section of iron casing so we have 10 North teeth and 10 South teeth and so we have 20 magnetic forces and so you can see that it's able to grab a hold of that magnet really well in order to be able to turn it so right now we're riding on the outside of the stainless steel show and so that's the the upper part right there and so it's still able to turn it no problem now you don't want to have this powered by itself for a long period of time it's just going to be or even a short period really it's already heating up so you don't want to burn out the coils so we're going to turn this power off so in this head there's 40 iron teeth so there's four sets of 10 this is what the head looks like when you don't have it covered in plastic like that and then we go a step further and this is what it looks like when you take it apart and so what's actually happening here is you do have four sets of 10 iron teeth so you got one right here and you got one on this side and then you got one here and one here and so really what's happening is when you power between here and common we'll say this is north and this is south and then when you power this one this is north and this is south then when you power this one this is north and this is south and you power that one and that's North and that South so basically you have these teeth right here on the inside in a manner where they're all offset from each other so you have just like this rotating magnetic field that is just going to be turning this permanent magnet with 20 so 10 North and 10 South at a time magnetic forces so it's just a rotating magnetic force essentially what's happening every time that you you take your 12 volts across each of these so you have to have say negative here and then you're going to have positive here and so that's what's happening so then it's a matter of finding the right sequence so in this case we have a six wire eev so we have our 12 volt power supply over here you could just use a 12 volt battery if you're going to do this in the classroom but you have a negative polarity on these two wires and these two are your common wires and so one common is to the lower sets of coils and the other common is to the upper sets of coils and so you have two coils in the top and so you got two wires coming out and then you got two wires in the bottom two wires coming out now you're not going to be able to tell which ones are what until you take electrical resistance readings with a multimeter or using the manufacturer's literature but I'll check the electrical resistance values of each of these when we're done in order to show you what's going on but the whole point is you are going to need a certain sequence to apply your 12 volt power in order to get this to move and so the eev Works on 12 volt direct current pulses to each one of these wires and if you want to change the direction then all you need to do is just change the direction in which the Tabs are being powered and so you can see we're going from the top down here and when we do that we're rotating say clockwise but if we go from the bottom up it's going to move the inner permanent magnet counterclockwise and so all we're doing is we're just doing this really quickly when we're going across all of these tabs so all four and so if you were to hit these in say the wrong sequence see how we're moving steady right now but if we went from here to here you see we're just kind of jogging back and forth but if you were to go from say like here to there or here to there you got to make sure that you have the right sequence it's very easy how the electrical circuit board is opening the pathway down here very precisely it's using a set number of pulses so maybe it's 16 pulses would be one two three four so four times four is 16 pulses it just made a refrigerant adjustment down here at the pin that's how it works and so anytime a mini split system starts up You're Going to Hear It Go click click click click and then after it fully closes you're going to hear another set of clicks and so that is the eev on a mini split system making that noise and it's because the circuit board in the mini split is trying to determine what position the pin is at and so it fully seats it upwards and then fully seats it downwards in order to know where the pin location is now let's see how many individual pulses it takes to fully open the eev so I just did 80 times 4 so you got 160 so you got 320 pulses total in order to fully open that up now sometimes I was accidentally hitting one of the wrong Terminals and so this eev may end up supplying say 400 pulses even if it only needs say 280 or something like that but that's how it works it's going to supply more pulses in it than it needs and it's not going to do any damage as you can see it's not going to get stuck it's not going to get stuck at all and you can just go ahead and start re-closing it back down again it's important to realize that when this head is powered in sequence with 12 volt pulses across the wires it's going to be turning this permanent magnet but after it does that there's no longer power that's sent to the head and so this pin is naturally going to just stay in this position and so it's not going to move again until this eev head is powered with a certain amount of 12 volt pulses and it's going to turn this magnet again in order to adjust the pin and then after that it's no longer powered the pin stays right at that location so it's pretty simple now let's go ahead and turn the power off and we're going to take some electric resistance value measurements so we're going to clamp down here on our common wires and then we're going to take our other clamp put it onto the white so the whole point is that a six wire functions very similarly to a five wire and so this one right here is a five wire as you can see right there whereas this one is a six wire so the two Commons basically at the indoor PCB the printed circuit board these two May connect or they may be separate depending on the circuit board but as far as testing goes you could just connect these together in order to check your resistance values or you could do them separately in this case we're just going to do them separately so that you can see what's going on here so we have from red to White we have nothing from red to blue we do have a electrical resistance value so we have 45 ohms so that's red to blue red to orange nothing and red to Yellow we have very close to 45 ohms so 44.7 so if we were to go from yellow to Blue we're going to have double the electrical resistance value and that's because the common wire is basically splitting up the two coils and so that's why you see 90 there so now if we're going to check Brown we go from brown to White you got 45 ohms now this one is not going to be touching to our blue because that was on our last set of coils so you do see our electrical resistance value here 45.6 and so if you were to go from Orange to White you're going to have double the electrical resistance value which is correct and so in this case that electrical coil is intact and so what you could do is if you knew your two common wires you could just have those connected but a lot of times they're going to be in a connector such as this right here which you're going to be testing and so you're not going to have just the the wire sticking out so you may need smaller probes so in this case we can just check right here on the back so you know that's not your common we gotta find where we are measuring a lower electrical resistance value such as 45 so right there so blue so it looks like blue is our common on this one I don't know if you can see that so Blue's right there if we put our one Probe on blue and we come right down the line we're going to get 45 ohms or something close to that say 46 on each one of these terminals you want to make sure to not accidentally open up the the terminals by trying to jam the probe if it's like a large probe into an area where it's not supposed to be at so as you can see right here 46 and if we were to go from here to here you're going to measure basically double on every single one of these and that's because they have a shared common so that eev is electrically good but the problem often is that you have rust forming on the inside of this so something that looks like this it's not good uh sometimes you can't even get the head off or actually a lot of times you can't even get the head off and the whole point is that you want to have this fully insulated you want to have this all insulated including the head on a system because you don't want any condensate forming up in here which ends up producing this rust and so this you got to remember that this whole cavity this whole cavity is going to have low pressure liquid and so if there's any humidity in the air so outside of the eev even if this is in the outdoor unit any humidity is going to get attracted onto here and condense because it's a low temperature liquid area so it's got to be insulated in order to protect this from rust between here and the iron teeth which can cause a problem with the magnetic force that you're trying to apply and so it it may not function anymore properly because of that so some of the problems that you may run into is rust at the eev head you could have a problem with the threading getting internally stuck due to over pressurization during a nitrogen pressure test that is a possibility but normally the body of the eev is pretty Hardy and usually doesn't have any problems you could have a wire that has rubbed and chafed and basically broken off and now you're not able to send your 12 volt Pulses from the circuit board to the eev head you could have a problem with the PCB itself maybe the PCB is malfunctioning and it's not sending the 12 volt pulses to the head you could also have a loose connection right here maybe that has just wiggled free or it's just not making good contact so that's several things to look for when troubleshooting on an eev and if you want to learn more about mini split systems and all the electrical components inside make sure to check out our inverter mini sport operation and service procedures book this is available over our website at acservicestate.com and the mini split tab also make sure to check out some of the mini split install and service videos linked down in the description section below and hope you enjoyed yourself we'll see you next time at ac service tech Channel

Channel: AC Service Tech LLC

Views: 1,691,321

Keywords: acservicetech, repair, maintenance, how to, fix, hvac, hvacr, how do you, test, ac, service, tech, check, measure, read, superheat, subcooling, refrigerant, procedure, voltage, charging, temp, multimeter, freon, hvac class, hvac school, hvac training, hvac course, replace, troubleshoot, diagnose, EEV, Elet, Expansion Valve, Minisplit, Mini Split, magnet, pole, steel, temperature, pressure, magnetic pole, operation, testing, solenoid, inner, magnetic force, teeth, grip, south, north, volt, power, coil

Id: LzvVjvUpOVM

Length: 16min 34sec (994 seconds)

Published: Sat Jan 07 2023