All right, so this video is about a common problem that exists when technicians in the field replace a higher-end thermostat that has dehumidification type controls in it, especially specifically the unification with a typical truck stock thermostat that doesn't have these types of settings. So what a technician would do is, it would say: okay, ma'am, your thermostats failed. I've got one on the truck here that I can replace it with and it'll work. Just fine okay, great customer accepts that until they go and they go to wire it up and of course they know all these wires.

What they all do. This is a heat pump, so we've got orange for the reversing valve auxiliary heat for our heat, strips yy1. For a contactor G for a blower and then we have our common in our hot, then we've got these a/c scenes. We've got this AC C plus.

Well, what is that? And so the technician says: well, this new thermostat doesn't support that, so they unhook it and they just push it back in the wall with wire nut or whatever, and figure that it's all fine and dandy. But we've got a couple problems here. So what happens here is in order for this system to D humidify properly, when it's setup, they're gon na remove this jumper, and so you can see this jump are still there, but it's just only connected to one side versus being connected to both pins see. If we can see that there yeah it's only connected to one half, and so what that does is now D H is not connected directly to our on this system.

If you don't have a 24 volt call 24 volts present at D H, then the system will run in to humidify mode, which is essentially just a slower, blower speed. And so if we wanted to blower to always run at full speed and not at that slower speed, then we'd have to put this jumper back and all brands are the same. Trane Lennox, Ruud ream. They all have some version of doing this and you have analog type controls.

Do you know 24 volt controls instead of communicating controls, which is what we've got here. This is a carrier F, V air handler performance series, air handler, so it's still 24 volt controls. But these 24 volts signals then impact the board, which then changes the calls that it's going to send to the blower to change, blower, speed and one of the main ones. Is this the H call? So when we have 24 volts present on D H, it will run at full speed and when we do not have 24 volts present at D H, it will run and Douce dehumidification speed.

So if we pull this number set off the wall and cap, this wire, what's gon na happen, is we're never going to have any 24 volts at D H, because there's no jumper and now this wires connected to nothing on the other end, and so we're always Going to run at reduced speed blower, which means we're always going to run a cold order of Aperta coil, we're always going to run closer to freezing and in a lot of cases, that's not a desired circumstance. So what we would have to do, if you replace the thermostat like this with a typical thermostat that does not have these controls, which again you got to talk to the customer about that see if that's what they want. But if you do that, yes, you are gon na lose your D modification, but you want to run at full speed, which means you got to take this jumper or whatever factory jumper was originally in there. That was cut or whatever and place it back in place.

So that would be just a matter of pulling this out pushing it back in place there. So now that's gon na stay running at full speed by one dehumidification, and I that I reconnect it. It's the only one pin so that way it's not connected across there. So most of them are gon na go between R and D H with this jumper.

If you want the humidification mode, you have to remove the jumper connect it back to a control that will purposefully de-energize a wire. In this case. This is a core which is you know, made by ecobee and so you'll see similar setups in nikko B. That's the accessory plus.

So when it D, energizes acessory, plus it's gon na go into the mid ofin mode and when it energizes it, it's gon na run full speed. Alright, thanks for watching. Hopefully that helps talk to you next time.