Humidifier only runs with furnace, not HP

[moony]

About a month ago I had a Trane dual fuel system installed along with a Honeywell by-pass humidifier and IAQ thermostat. Because the humidity was too high in the house during the install the humidifier couldn't be tested. The installer assured me it was wired correctly and everything should work fine.

Now that the humidity is down in the house I've noticed that the humidifier only runs when there is a call for humidification and the IAQ shows "AUX Heat On" (furnace). The humidifier does not run when there is a call for humidification and the IAQ shows "Heat On" (HP).

I noticed that the installer did not wire the humidifier according to the IAQ wiring diagram. He wired one side of the humidifier directly to HUM1 on the IAQ. The other side he ran to a transformer located in the furnace and then back up to HUM2 on the IAQ. Could the way it's wired cause the humidifier to only be energized when the furnace is on?

[David Bross]

The Humidifier should operate in either furnace or Heat pump mode. Since you have both systems for the most efficy. They should have connected the Humidfier to come on via the Humid stat energized of of the indoor fan which is common to both the furnace and Heat pumpo. This may require the additional devices such as a relay on the fan switch in the system.

[moony]

Agreed that the humidifier should run during both furnace and HP. Not really sure why they wired it the way they did. I think they got their wires crossed, literally and figuratively. The tech who installed the humidifier didn't know it was going to be controlled by the IAQ until after he had installed the transformer and it was time to wire up the humidistat and then he realized that he didn't need it. I guess my question is should I just wire it up according to the wiring diagram from the IAQ or is there something I can do with the way it's wired now that will make it work? I haven't opened the wiring box in the furnace to see how the tranformer is connected but I'm guessing it is hooked up wrong in the box. Any suggestions?

[Jay11J]

Is your transformer wired up like this?


If so, then it's wired up right on the low voltage side... On the other side (Line voltage) it is wired up on HUM wire that is in the box. So the wire needs to be switched over to the EAC wire.

HUM will only power up when the furnace runs, the EAC will power up any time the blower is running.

[moony]

Wired up just like your picture. I think you solved my problem. Haven't looked in the wiring box yet but can be pretty sure the transformer is hooked up to the HUM leads like you say.

Sometimes when things don't work the way you think they should you get worried. Now that I know that nothing is technically wrong with the system I feel better.

Wire from the EAC enters the wiring box through the side of the furnace. I'm guessing my EAC is already connected to the EAC lead. Furnace wiring diagram says max. load for EAC lead is 1.0 amp. Would there be a problem having both the EAC and humidifier transformer both connected to the EAC lead.

Also is there any reason not to just leave it connected the way it is now. Only works when the furnace is on but with balance point set at 35 degrees the humidity in the house shouldn't be as big an issue when the HP is operating.

[Jay11J]

Originally Posted by moony

Wire from the EAC enters the wiring box through the side of the furnace. I'm guessing my EAC is already connected to the EAC lead. Furnace wiring diagram says max. load for EAC lead is 1.0 amp. Would there be a problem having both the EAC and humidifier transformer both connected to the EAC lead.

I wouldn't advise doing it.. I would then wire the transformer right to the incoming house power that powers the furnace.

Then the IAQ/EIM will turn on the humidifer as needed on set up #374 to 2.

Only works when the furnace is on but with balance point set at 35 degrees

You still got a lot of heat in the air outside, bump it down to 25˚, and if you feel that you are cool with that temp bump it to 30˚

Is the furnace a two stage?

[moony]

Won't hook it up to the EAC lead then, thanks.

My installer originally had 374 set to 1 (force fan on). It did force the fan on like it should but since the humidifier didn't run when the HP was on I changed it to 2.

Some say shouldn't use humidifier with HP cause the air temps are not high enough to get much humidity. My humidifier is hooked up to hot water line. If it were set on 1 (force fan on) would the humidifier work ok?

Furnace is a Trane XV95, 2 stage, variable speed.

I could try lowering the balance point to 25 but I think my heat loss is greater than the HP can provide at that temp.

I have IAQ setup with a 2 degree droop and have temp set at 70 degrees. Tried to set the balance point so wouldn't have to droop 2 degrees unless extreme heat loss (door left open, etc)

[Jay11J]

I'll get back to you tonight some time, I have to work till 8 tonight.