Gas Training - Fault Finding On A Combi Boiler - How Components Work

gas training fault finding on a combi boiler or any boiler really my name is alan hart and in today's video we're back at viva training academy and we've got roy who is the trainer aviva and roy's going to go through testing different components in a boiler we've got a lot of components here and it's going to give you some tips when when you're doing fault finding on boilers so this should be a really interesting video for new trainees into the industry we have done a series of videos so if you have a look at the if you look on the channel if you look at playlist and you look into the viva training academy one you'll see we've got a series of videos and these videos are trying to follow on from each other so some videos will cover the tb11a the surf isolation etcetera and then we'll cover fans in more detail gas files in more detail but this is this is a broad video this one to show you different components and how they work and i'm bubbling on now so what i'll do is i'll pass you over to i'll push over to roy hi hi guys it's roy fuegler here at the viva train academy over in halifax again and today we're gonna have a look at components inside boilers on a previous video we did a sequence of operation and from that you'll understand that it goes step by step by step so what we're going to look at is the components how a component interacts with other components what components do how they can go wrong and the basics of a little bit of fault finding on those components so before we start as always it's all about health and safety make sure you've got a set of instructions available when you're working on boilers make sure you've done your safe isolation obviously i'm working on the bench and that's why i haven't got any gloves on all the boilers sorry all the components are disconnected so there's no electricity there so when i talk about fault finding and i look into i try to simplify things and the way i look at components all components fall into one of three categories it's like the rule of three and so you've got a doer so what's to do with a do one actually does work a little bit like in my body i've got a hat and thankfully it's pumping away it's pumping blood around me so that's keeping me alive so obviously your boilers have got pumps in there so we've got a standard efficiency pump and then a few years ago we went on to erp pumped energy related pumps so we've got pumps in there so they're pumping water around the boiler around the plant heat exchanger around the system so they're doing a job next thing a little bit like you get inside me i've got my lungs there it's helping me breathe so we've got fans so again we've got a standard efficiency fan here and i've got a couple of uh high efficiency fans there how we know the high efficiency we've got a couple of connections very similar to on the pump but i'll come back to that very shortly so we've got gas valves again that's a doer that's letting gas come through that's opening up so we've got gas valves there and motorized heads so we've got the motorized head there on the diverters so they're doing they're actually allowing the water to go through the plate heat exchanger and to warm up so it's coming out the taps nice and hot or it diverts it around the system so there there you do us so that's a few doers in there so the next one we've got tellers so what's a teller well on our bodies we've got eyes they can see things we've got ears we hear things and we can smell things so there are sensors so the pcb is a little bit like our brain and i always refer to it as the brain so what it needs is information so the tellers are things like air pressure switch it tells us when the fan's not running and it tells us when the fan's running so then it allows the circuit call to make a decision to go on to the next stage which is the ignition stage so that's a teller things like floor switches this is a this is a read switch so this is this is allowing it to tell things it's telling the main circuit board if the tap's turned on or if the pump's running that's often old baxy bahama again we've got a floor switch here and when water's flowing across there it's operating a little paddle switch so again we know that that's operating so it's telling us it's working and we've got thermistors there's lots of different types of thermistors there's more thermistors that you shake a stick at they're telling the circuit board that certain temperatures hot water temperature floor temperature return temperature fluid temperature so we've got lots of thermistors in there so there you tell us now we've got some components which actually do both jobs so coming back to this high efficiency fan we've got the mains connection there so 240 volts going in it's got a circuit board on it and then we've got another connection that other connection is for pulse width modulation so that's communicating back to the circuit board the temperature sensors are telling the circuit board how warm the flow of the boiler is so when it's getting up towards 75 80 degrees it's getting up to its maximum temperature so that's the circuit board centered fan right we don't need as much gas so the fan's slowing down so that's what that's doing and again the energy related pumps we've got the two connections and again we've got the power wave modulation in there so that's allowing the pump as trv start to slow down to uh reduce its amount of speed it's running so it's using less energy so there are three types of components so you've got tellers doers and you've got some that do both so the next stage of three we've got switches so as we've already said we've got a read switch and a paddle switch there so there are two switches air pressure switches and over eight stars little over eight switches their switches so basically a switch is either open and becomes closed or it's closed and becomes open so let's take for instance an overheat stack so a little over eight stop there this one's got a manual reset on it so under normal temperatures that will be closed circuit and then if the boiler car temperature goes a little bit too high 100 and 510 degrees something like that that will go open circuit so it breaks circuits so it loses continuity so the circuit board knows that that's gone open circuit so it will shut the boiler down for safety so that's that's a simple switch the simplest switch that we will ever find on a boiler is and the reason i'm holding back you're all thinking about it so some of you might be thinking selector switch things like that we've got something even simpler the simple fuse it's a thermal switch that's the three ounce fuse which will be in the fuse spur or should be in the fuse and then we've got a little involved fuse they're varying in size dependent on the manufacturers of the boiler some are two amps or a three some can even be four amp and so a little fuse is a simple very very simple switch so they're switches so the next thing we've got is things with resistance in so things like your gas valves your motorized heads they've all got a stable resistance so when we test them with a multimeter i'm going to do that shortly what you will find is it will have a set resistance and if you refer to manufacturers instructions or their technical help lines they will give you resistance readings from most of the components and that will be a base reading based on average temperatures and things like that we did a video a few weeks ago looking at gas files and i went through some of the readings in there so that's your resistances so most of you doers will have a resistance in and then we've got the ones with a variable resistance so things like your thermistor this one's off a ruster that won't have a set resistance it'll have a scale so somewhere from 100 degrees maximum down to zero degrees minimum temperatures and depending on what thermistor and resistance range this one is and in the worster manufacturer's instructions there is a chart with those temperatures it will give you different temperatures at different ranges now the most common thermistor out there is probably this little one baxi have used it for care they've used it lots and lots of manufacture have used it and these are rated at 10 000 ohms at 25 degrees so 10 000 ohms 25 degrees so what that's saying is if i measured it in a room at 25 degrees i'd have a 10 000 ohm resistance and a lot of these are what are called ntc's negative temperature coefficients what that means is as the temperature goes up the resistance goes down so the higher the temperature the lower resistance and the circuit board understands that and that's what allows it to start to modulate and do things like that so we've got variable resistances so all these components can fail electronically and fail mechanically so this is more about the electronic side we could get a good resistance reading on a component but it could still not work properly something like this and for argument said we could get a really good resistance reading across the neutral but it could have seized it could be stuck so it's not going to circulate it's not going to draw fresh air in and put products of combustion out but we'd still get a good resistance reading so this is more about checking the electronic side of it obviously physical damage things like that flooding that can cause a lot of problems with them so when we look at electronic failures there's three ways that an electronic component can fail two of them are dead simple one of them is to go what's called open line so i'm just going to bring the multimeter in now so i've got the multimeter here and i'm just going to copy it onto arms now if we look at the display there with nothing connected i've got what's called ol open line open circuit so that means there's no connection between the live and the neutral connection or what whatever i'm testing with it so when i test the component so for instance this gas valve and i go across the two connections on there what i'm going to do is pick up a reading on that gas valve so the reading on there if i just check it there we go yeah i've got a reading so that's telling me i've got a resistance reading in that component now if i put my glasses on i'll be able to see what i'm actually doing with it so we'll just double check that one again so the reading on there is 4.1 or just over 4.1 k oh so 4 100. now if i check the manufacturer's instructions that will tell me that's a good reading for that gas valve so electronically it's fine mechanically it might not let gas through something could have seized up inside it could be blocked so that's a good reading so if i tested a component and got a well that means i've got no connection however much voltage i put into that component it's not going to work i'm not going to get it opening it's not it's not going to function correctly so the next one is a short circuit so a short circuit if i put the two leads together all i'm going to measure now is the resistance in my leads and there's very little resistance in these leads so if i look on that i've got around about 0.3 of an ohm so that's a short circuit anything less than 20 ohms in our industry is classed as a short circuit so what that means is potentially i'm going to blow the fuse if i put the power on to that boy what's going to blow the fuse so that's a short circuit and the last one which is the most difficult one is drifting what we mean by drifting is the resistance reading is there but it's not within the tolerance that the manufacturers have set so that gas valve we saw there that was around about four thousand one hundred ohms now most manufacturers give you a tolerance of about twenty percent so twenty percent above twenty percent below it should function to specification but again always check with the manufacturer's instructions they'll give you the specific details for that boiler that you're working on in those components i'm just using the rule of thumb again through the years of experience i've been in this industry but always double check with your manufacturer's instructions so drifting is outside that tolerance so if i was getting for argument circuit resistance reading on that gas valve of 6000 ohms it's too high it might not be opening fast enough if i was getting a resistance reading of let's say 2 000 ohms it's too low what they started to do something inside that that solenoid that coil in there is starting to fail so i've got three motorized valves here and i know for a fact that i've got some problems with them so i'm just going to check this black and white one now these motorized valves and they're used by lots and lots of manufacturers they've got three connections they've a neutral connection which is a black connection and two lives because the motor for heating motor for hot water so i'm just going to check this black and white one so i'm just going to go across black and white connections and i'm going to go up there and i've got a resistance reading of 5.8 or just over 5.8 k ohms so that's a good reading now across black and red i shouldn't have anything that should be oh well because it's in one position that one's actually in the heating position on the back seat so i've got a well on there so that's fine so you might get an oil reading but that's what it should be on that particular head so let's have a look at an old blackhead now a few weeks ago we did a video about blocks and i explained about the black and white heads so you you've probably seen that one so again this one's in the heating position so it should be between black and white so i'm just going to go on there yeah and i've got 9 000 or just over 9 000 ohms and then i've got oh well the reason for the difference in resistance is the different motors the black and white one has a different motor in there so the next one i'm going to pick up is another one of these all black heads i'm going to test this one so it looks as if it's in heating position because the pins up so i'm going to check across the heat inside oh dear i've got 0.4 ohms so that one i've got a short circuit on that particular side of it if i check the other i've got a well so that's definitely failed i've got a short circuit if i put that into a boiler and plug that boiler in as sure as eggs these eggs my fuse is going to blow so that has failed so the next one again an all black one this one the pins down so this is in hot water position so it should be across black and red if i go across black and red i've got a l so we'll check it across black and white i've got all well so that one has failed in the hot water position so the complaint from the customer with this one is going to be that they've got no central heating the hot water is fine but when it comes to central heating the boiler will fire but the pin won't come out and go around the heating circuit so that's what the complex going to be on there so let's just have a quick look at drifting i've got a couple of thermistors here in fact i've got three they all look very similar to each other so these thermistors are 10 000 ohms at 25 degree thermistors so i'm just going to check these this one here so what i've got now is 13 570 or 13.56 k so that's roughly where it should be now if i get a little pinky and touch the end of that what we're going to see is that thermistor my body is causing the resistance reading to go down because the temperature is increasing so if i now have a look at these two thermistors i know for a fact that these are faulty i know there's a problem with them so if i check this one i've got a reading of 21 000 ohms twenty one thousand on this thermistor ten thousand at twenty five degrees is about sixty degrees so that would be telling me the boilers at sixty degrees when actually it's more likely to be around about twenty three twenty four degrees so that's gonna throw out um the boilers adjustment so what it's going to do the water's not going to be getting hot enough because it's actually signaling it's hotter than it is now the next one if i test this one i'm getting 46 000 volts so a really high resistance so low temperature that's going to be telling the circuit board that the body was too cold and it could actually be coming in on frost protection so the customer might be complaining they can't turn the heating off the boilers on 24 hours a day and whatever they do other than turn the fuse spur off i'll turn a select to switch off if the boiler has one that the boiler is running 24 hours a day so that's that's what's happening with drifting we're getting a reading but it's not the correct reading so that's when we're looking at fault finding so you get to a point as we look through on sequence operation something doesn't activate so we can check that we're not getting the right information i've worked on boilers for a long long time i don't take things for granted one of the questions i always ask my students or my delegates when i'm doing fault finding courses what's the boiler telling you and again it's because i'm a simple yorkshire fellow that's how i interpret it i know the boiler cap taught me i've got i haven't got delusions of boilers talking to me i don't hear voices in the night what i mean is what information without touching that boiler can you get from it a lot of modern boilers now have screens on there which show you ten pictures now if that customers said to that boiler has not worked for two or three days and they've had no heating and hot water but it's telling you that the boiler temperatures are 80 degrees either the customer's not telling you the truth or that boiler is getting the wrong signal from the thermistor so it could be telling pointing you to the thermistor not being right error codes are brilliant to point you in the right direction what's causing a problem something gets to a stage for instance we expect the fan to run the fans running but we're not going to ignition we're not getting the spark generator coming up that could be the air pressure switch isn't operating correctly and a couple of weeks ago we looked at some air pressure switches so that's just been a quick um little tip my rule of three and doers tell us both how they fail how we test them in the future we're going to go more in depth on some live boilers about fault finding hopefully you've enjoyed today if you have leave a comment and have a like if there's any other videos you want us to do in the future any more specifics please please let us know we have got something planned i know some of you guys out there have sent some requests in me and alan are working on on hopefully getting those done for you and so until next time thanks very much for watching bye thank you very much for that roy and once again thank you to viva river training academy in halifax and viva's you know spending a lot of time in helping new recruits into the industry um it's really really good so so once again thank you to roy and thank you to viva training academy if you've got any questions please put me comments below and as i said at the start of the video have a look at the playlist for fever training academy there's lots of videos on there now with roy and with viva we've also got some with russ on there as well also richard we've had richard in some of the videos as well for the acs cash training so we've got lots and lots of videos now to help new new trainees into the industry our new gas engineers our new plumbers so yeah thanks for watching

Channel: Allen Hart

Views: 52,558

Keywords: gas training, viva training academy, boiler repair training, gas training videos, gas boiler, gas training course, gas training centre, gas course, boiler repair, gas engineer training, gas safe training, gas training tutorial, gas valve solenoid test, plumber training, plumbing training, how a combi boiler works, boiler fault finding, combi boiler, gas engineer, fault finding, gas boiler training courses, gas training principle, viva training, gas training uk

Id: Pxu_qyYCscE

Length: 21min 18sec (1278 seconds)

Published: Fri Apr 16 2021