HVAC

Heat

How a thermostat calls for heat on a heat pump and straight electric heat system.
Preventative Maintenance
Thermostat
Diagnostic
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Transcript

 Right now this is working. We have, it's 57 degrees. I'm trying to heat it to 64, so the way this is working, my condenser, my heat pump is outside running. Here's my condensing fan motor. Here's my compressor, my indoor fan, my evaporator is working because I've got the temperature set to such a difference here.

I'm getting some extra help for my heat strips. So all of these things are receiving power at the moment. The major difference, well two major differences between this mode and AC mode on a heat pump is in a heat pump. This would not be on, and I would also be getting power to my orange wire, which would kick this reversing valve on.

This is a Goodman Defrost controls system, so. This is wired up as a Goodman. So Goodman reversing valves are powered in ac, so because the AC is not on, the reversing valve is not energized, so there is no power going to the orange wire. There's only going, there's only power. We've got our 24 volts, our red wire, it's sending power to our yellow, which is outside.

We have green. Wire right here, which is our fan motor, evaporator fan. And then we're also supplying power to this white wire, which is our electric heat strips. In heat mode, you have your 24 volt red supplying your condenser yellow wire. Your indoor fan green wire, your white wire heat strips. What's really cool about heat mode on a heat pump is you have this function called emergency heat.

So if we flip this switch right here from normal heat over to electric or emergency heat, your condenser, your everything outside shuts off, and it is strictly relying on your indoor heat strips, even if you have straight. AC or so, which means you do not have a heat pump if you just have a straight ac uh, outside, you have an electric heat inside.

So at this point, this is strictly electric heat. You've got your heat strips on and you've got your fan on. Now, what happens when you satisfy the temperature is your heat strips. This piece right here. Uh, so I've got it set below the temperature now. So it'll take a second for that sequencer to cool down.

But what'll happen is your heating element will kick off. Then after the fan relay cools down, your indoor blower motor will kick off because it's receiving no power. But what's happened is this, this, this relay right here, this peg on the inside. The 24 volts have heated up a little coil, a little disc, and that disc expands and it shoots a rod up to make this connection.

This connection is what powers this fan. So as that little coil, that little metal disc no longer receives power. It's flexed at the moment like this, and, but as it starts to cool down, it'll straighten out and it'll pull a post down. And as it disconnects this power. It turns this off, and that is how the heat side of a heat pump works.