HVAC Training Board: How To Troubleshoot A Transformer (How To Check A HVAC Step Down Transformer)

hello everyone and welcome to jumperman tech where we specialize in hvac but do everything diy and today we're going to be going over how to troubleshoot a step down transformer thank you to everyone tuning in to jumper man tech today we're going to be going over how to troubleshoot a step down transformer if you find this video interesting or helpful please drop a like comment and subscribe as i come up with new videos every week and let's get straight into it before we can begin troubleshooting it's important to understand what is a step down transformer and how it actually works essentially a step down transformer is an electrical component that steps down the voltage so your transformer consists of two coils a primary coil and a secondary coil your primary coil is always going to have the higher rated voltage and then we step down the voltage to our secondary coil which is going to be lower in this case this transformer can either be 120 208 or 240 volts as your incoming power as your primary coil and then it steps it down to 24 volts some of the best advice that i can give is pay attention to detail your attention to detail not only as a technician but in life will take you very far so let's see what's going on here we see some bold lettering here that's going to be our model number underneath it says cat number i believe that's catalog number and again it's referencing this model number we have a primary and secondary let's go into detail here so your primary coil is going to have a common which is your white color and then we have three other voltages with three other colors so 120 is going to represent the black wire 208 volts is going to represent the red wire and 240 volts is going to represent the orange wire so depending on what the incoming voltage is that's what you're going to see connected in this case we have 120 volts so white and black is going to be connected here if we had 208 volts you're going to notice the white and red is connected if we had 240 volts we're going to notice the white and the orange is connected from there we have a secondary coil where we're going to step down the voltage from either 120 to 24 to a weight to 24 or 240 to 24. so your secondary is red and green all right so those are the colors of our wires those cannot be changed it is what it is it says 40 va 40 volt amps this is a class b insulated transformer and it says it's a class 2 transformer now we have some lettering here not exactly important what's important is understanding your primary voltage and your secondary voltage and colors are important in this case this is an electrical training board that i designed and created and what we're actually looking at is an air conditioner the way we're going to troubleshoot this transformer is by first identifying what we're working with if there's a label definitely pay attention read what you can a lot of times you're not going to be able to read what you can so a good way to find out what is your primary voltage look at the voltage of the system you're working on if this happens to be a 208 volt system chances are 208 volts is going to be your primary voltage if you have a 120 volt system your 120 volts is going to be the voltage you're looking for at your primary i'm going to start off with what's the easiest and fastest way to check if your transformer is operating the way to check that is to make sure you have your secondary voltage the easiest place i would say to check for that is behind your thermostat you're going to have a constant 24 volt supply between your r and c terminal instead of climbing into crazy places going into attics running outside and you know taking off all these panels the easiest and fastest way would be to go straight for your thermostat [Applause] we're going to pop off the face plate for our thermostat and we're going to go between r and c with our voltage meter when the system has all the power on the fastest and easiest place is definitely going to be your thermostat you don't have to run around taking off panels climbing into who knows where setting up ladders and all those things where you know you have a constant 24 volt supply at your thermostat your c wire stands for common and your r stands for your 24 volts your power wire and this is all coming directly from your transformer so between r and c you should have 24 volts i have my multimeter set to volts ac and we're simply going to check between r and c right there we have 28 volts there's no such thing as a perfect world you're going to have a voltage close to 24 volts this indicates that our transformer is good because we have our secondary voltage the reason i go with this first is because if we have our secondary voltage then we know we have the proper voltage on our primary and we have incoming power and this saves the most time in this case our transformer is good if between r and c we didn't have 24 volts now we have to further look into what's going on now we need to make sure do we have voltage at our primary before we can actually say that this transformer is bad no matter what kind of transformer you have you're gonna have two wires connected at your primary and you're gonna have two wires connected at your secondary your secondary you don't really have an option it's gonna be your red and green and this is always going to be your 24 volts but if you look at our primary you notice we have a few multiple readings with a few multiple colors this indicates to us that we could have any one of these voltages but it's always going to be between two wires one wire that's always going to be connected is your common and that's going to be your white wire so what is this actually telling us that means between white and black we should have 120 between white and red we should have 208 and between white and orange we should have 240. so now let's trace out the wires okay coming out here i see my white this is my common but what do we have here the red and the orange is capped off so that means we're not using that the red is 208 and the orange is 240 so now we know we're using our 120 volt circuit because if i follow this again here's my black wire so between black and white we should have 120 volts all right so we have our meter set to volt ac and turn the power on between black and white we should have 120 right there as you can see we have a 122 volts indicating we have our 120 so let's say if we had any of these primary voltages and we didn't have 24 volts then your transformer is bad but before you say that pay attention to your transformer sometimes there's a built-in breaker inside and sometimes there is an inline fuse connected so we have 120 volts at our primary and then we checked at our thermostat we had our secondary of course in this case everything is good so here's our 120 right we're going to make sure that we have our primary voltage and then we're going to make sure we have our secondary you can follow the wires so it's going to be your red and green and i can see the red and it comes here and the green comes here this is a low voltage terminal block so between red and the green wire right there we have our 28 volts so that is a good transformer to keep things simple the way to check a transformer is to first identify if you can what is your primary voltage see which colors they are and make sure you have your primary voltage check your secondary voltage and make sure you have your secondary voltage if you do then of course your transformer is good i'm going to end off this video with a couple tips if you have your incoming voltage and you have no secondary voltage right away your transformer is bad but before you can make that decision make sure that there's no reset button or little breaker any type of switch that you see on the transformer because if that trips you wouldn't have a secondary voltage a lot of times they do have this protection in this case we do not have one but if you follow the wiring we do have an inline fuse so you would turn off the power and make sure that your fuse is actually not blown so if you have your incoming power you don't have a switch here that tripped and in this case we have a fuse and the fuse is good and you still don't have 24 volts your transformer is bad it's all about making sure if you have your primary and secondary voltage so if you don't have voltage at your primary you need to stop what you're doing has nothing to do with the transformer you need to look into the incoming power to the system that means you're not getting incoming power you got to follow those wires so those are a couple tips but pretty much that's what it is make sure you got your primary make sure you got your secondary if so you have to go about things with the clues that the control circuit gives you if anyone found this video interesting or helpful please drop a like comment and subscribe as i come out with new videos every week and i'll catch you all next time [Music] you

Channel: Jumper man Tech

Views: 187,375

Keywords: hvac training videos, hvac troubleshooting, hvac training, hvac transformer, electrical transformer, power transformer, hvac, hvacr, transformer principle, how to wire a transformer hvac, hvac step down transformer, hvac transformer troubleshooting, hvac transformer wiring, hvac transformer 24v, hvac transformer keeps tripping, hvac transformer test, hvac training videos troubleshooting, transformer testing, transformer, step down transformer

Id: SMTINB0Xfrk

Length: 10min 50sec (650 seconds)

Published: Sun Jan 02 2022