Humidifier only runs with furnace, not HP

[moonman]

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? Any thoughts?

[heaterman]

Not enough heat off of the HP for the by-pass to work effectively. Probably wired correctly.

[moonman]

Is that true even if it's hooked up to the hot water line?

The installer has the IAQ set up to force the fan on during a call for humidification.

I don't think he would set it up like that if he thought it would not humidify with only the fan running.

[RyanHughes]

Not enough heat off of the HP for the by-pass to work effectively. Probably wired correctly.

Are you sure about that? By-pass humidifiers aren't uncommon.

[beenthere]

He may have a slight miswire at teh furnace.

[heaterman]

We've never had alot of luck with by-pass humidifiers used in conjuction with HPs. That's not to say you can't get some moisture into the air, just not optimum. We use steam generating hunidifiers with heat pumps and powered humidifiers with fossil fuel units. We use by-pass models in conjuction with fossil fuel units if pricing is the issue. In our area adding humidity to the air is not normally even required in most of our customers homes until late December or early January which is usually when the aux. heat is the main source anyway.

[moonman]

In our area adding humidity to the air is not normally even required in most of our customers homes until late December or early January which is usually when the aux. heat is the main source anyway.

I'm located just outside of Pittsburgh and I agree with you that humidity probably shouldn't be needed till later in the season but since the humidifier was never tested when installed I was only checking it to make sure it worked. Had to wait till nighttime temps got low enough to force the Aux heat on.

Still if it is setup to force the fan on during a call for humidification it should work even when the HP is on if needed. By the way it does force the fan on during a call for humidification (at any outside temp) but it won't run the humidifier unless the outside temp is 35 degrees or colder and the IAQ forces the Aux heat to come on. My balance point is set at 35 degrees.

I have new double pane windows now so all of my previous experience with humidifiers was with single pane windows which would sweat even at relatively low humidity. My old humidifier was manual and I tended to just set it low and forget about it. Otherwise I'd always be trying to stay one step ahead of the weatherman or else the windows would be dripping with condensation.

Since this is a new system I'm having to set up the humidifier by trial and error. Need to find the correct percent humidity for the house and then adjust the "frost" setting so the windows don't sweat when the temps do dip colder.

Anyone know what a good winter humidity percent should be? Let's say at 35 degrees. Should the indoor humidity be 40% at 35 degrees if the house can handle it? Since the IAQ has a "frost" setting I know it will adjust the humidity level up or down based on outside temperature but first I could use a baseline to go from.