Hey I wanted to do this. Quick video on transformers transformers are something that we have to work with every day in air-conditioning equipment. There's a couple things I want to show you a couple things that will save you. Some, hopefully save you some heartache.

So I've got a transformer right here. This is a typical 40v, a transformer that you're gon na see in a lot of different pieces of air-conditioning equipment. This one is a multi-tap primary transformer, which just means that you can connect this primary. The input on the transformer to several different voltages, and if you look here on top, you can see for TV, a 50 or 60 Hertz with primary 120 volts, 208 or 240.

It says primary common is white, which means you always use white on the primary use. Black for 120 volts red for 208 and orange for 240 volts and the secondary is 24 volts, red and green. So what that means is for your secondary you're always going to use these to this. This transformer is only good for a single secondary voltage, 24 volts and then on your input side, your primary is what they call it.

That's what we call the input side on a transformer. That's where you would connect your white as one side and then you would choose one of these three colors, depending on if your 120 volts. That would be your black if your 208 volts, that would be your red and then, if your 240 volts that'd be your orange. Now these come in a lot of different configurations.

Some of them don't use wires, separate wires. They actually just have separate pins in them. On the primary, the one thing - and the first thing that I want you to know, is that you're only going to use the white and one other color you do not want to take the other two and then jumper them together. Obviously you need to cut them.

Cap them with a wire nut individually from one another rather than connecting them together. If you connect them together now you are shunting the primary of the transformer and you are going to burn it up. I've done that before so learn from my mistakes. What does it transformer do? A transformer is designed to change a voltage either step up or step down a step up.

Transformer takes a primary that is of a lower voltage and then the secondary goes up in voltage or step-down, where the primary of a higher voltage and it goes down to a lower voltage, which is what we have right here. This is a step-down transformer. If I was going to use this in a tip, gasps furnace, then it would be 120 volts, step down to 24 volts and a typical residential air handler would be 240 volts step down to 24 volts. The way this works is actually very simple.

There's two sets of windings in here. I actually did a separate video where I taught one apart, but you have to separate windings in here and depending on the number of raps it steps down, based on the number of raps primary to secondary. So, in the case of this one, if I was going from 120 volts down to 24 - that's five times less, so it has five times fewer raps on the secondary of wire than there would be on the primary side if 240 down to 24 that's ten times So 10 times more raps on the primary raps of wire on the inside of this transformer, then there is on the secondary. But what I wanted to talk about most of all is this rating.

On the transformer, this rating of VA, the VA rating stands for volt amps. I did a podcast on this as well short podcast episode, volt amps means volts times amps. So if you have a 40 V, a transformer like this one is that means 40 volts times amps. If it's a 24 volt primary, then you take 40.

You divide it by 24, 40 divided by 24 equals one point, six six right right in there, and so that means that the secondary of this transformer can handle one point: six, six amps at 24, volts 24 volts times. One point: six six equals forty VA. So, when you're, looking at how many loads, how many think different things this this transformer can power, you have to take that into account. How much amp draw is there going to be and for a typical air-conditioning system? This would be enough to power your you know.

Contactor coil, maybe you're, reversing valve it's a heat pump, your blue or relay just your control side, but using this one factory, transformer to also energize, say a UV light or other indoor, air quality products, or maybe say a zoning panel with damper actuators. Those sorts of things is probably not going to work. You're, probably gon na either have to upsize the factory transformer to a larger size. A 60 or 75 VA or add a second transformer to just power.

Those secondary devices, which is another popular thing that that people will do a couple things to know here, is that when you add a secondary transformer, you are adding additional load to the power, that's coming into the air handler or furnace, and so you have to think About that, when you're dealing with wire sizing, because now you are adding additional load to the system, but the main thing that I wanted to point out here is that VA may seem very much like wattage and they are very similar in fact, VA and wattage are The same number, if you have a power factor of one and power factor, just means how efficiently are the loads using the power anytime, we do not have a unity power factor which that's a power factor of one anytime. You have a number lower than that. Your VA will be higher than your wattage, meaning your VA usage will be higher than your wattage. We're talk about wattage versus VA, transformers tend to be sized in VA, because that's the total amount that they can handle, whereas your wattage may actually be slightly lower than that, depending on your power factor, you still have to take into account your volts times amps, which Is very simple to do all you do.

Is you just measure your voltage with a voltmeter? You measure your amperes with an amp clamp or an in series. Amp measurement. You multiply the two together, that's your VA and you just got to make sure not to go over the VA rating of your transformer yeah. No problem at that point which again in the field you can do this measurement run your different loads run.

Your blower run your heat run. Your air conditioning run your reversing valve if you're in air-conditioning mode and a heat pump, take those amperages multiply times the voltage and make sure that you're below the VA rating, if you're gon na add in additional loads, you have to do that same calculation. The VA rating is obviously rated at the voltage of the secondary side, so whatever the secondary side voltage is that's what you have to account for so that's it. It's actually quite simple.

Another interesting thing to do sometime is to measure your amperage on your secondary and your primary on a system that's running and what you're gon na notice, if it's a 24 volt step-down transformer like this for 240 down to 24 and let's say you're, reading one amp On the secondary you're, going to read one tenth as many amps on the primary because you have 10 times higher voltage. So as an example, if you're drawing one amp on the secondary, so I've got my clamp around the secondary red wire here with the thing running. One ampere, then, when I read on the primary put clamp here, I'm going to only read point one amp, because 0.1 times 10 equals one. If it was a 120 volt, so say it was a gas furnace.

Then it would be five times as much or five or five times divisor, so it'd be 0.2 on the primary and then 0.1 or one on the secondary. If it's a gas furnace and so now we're using black and white for 120 volts, we could put our clamp over either one of these wires and you would see that it's a five-time divisor instead of ten times. So if we have one amp on the secondary, then we would have 0.2 amps on the primary. Because again as that voltage decreases, the amperage increases.

That's just a basic function of Watts law, because, if we're keeping, if the watts are equal on both sides - or in this case more accurately, the VA, then, as we increase or decrease the voltage, we're going to change the amperage as well, which is why, with the Higher voltage, we see a lower amperage with the lower voltage. We see a higher amperage, which is why have you ever done? Anything like a car stereo, where you're dealing with 12 volts, lower voltage and you've got a 2000 watt. Amp you've noticed that you have to use enormous wire because at that lower voltage you have much higher amperage in order to drive the same wattage. Overall, some interesting things transformers are always about rated in V, a that's volt amps, and you have to make sure that you don't overload them.

Make sure that you don't connect two of the primary elites together and make sure that you're using the correct voltage a common mistake, that's made with these is people will take equipment, that's either 240 or 208. They'll put it on a 208 power supply and they won't retaliate. So you have to make sure that your primary setup for the correct voltage in order to get the correct, secondary voltage coming out the other side of it. Hopefully, you found that helpful.

We will talk to you again soon.