Humidifier won't turn on with furnace fan set to Auto.
I live in western NY and we've had the furnace on for weeks now. Lately, highs are near 30 degrees and lows around 20.
My (Trane) thermostat has two fan settings - Auto and On. In On mode, the fan runs 24/7 at very low speed. In the winter, with the heat on, I prefer Auto mode which is where I have the Thermostat set.
I had a feeling my new Aprilaire 600 wasn't working since the RH was slowly dropping (over a few days) down to 30%. I was looking for 40% so I had been slowly moving the adjustment dial up to 7 with no corresponding increase in RH.
I also noticed that when the heat kicked on, nothing happened at the humidifier control panel - i.e. no green light, no water. However, the humidifier did work properly in Test mode.
So I checked around the Internet and found a post that suggested switching the Thermostat fan setting from Auto to On. Bingo! The next time the furnace kicked on the green light on the humidifier panel came on and the water flowed. It now continues to work "properly."
The bad news, as I mentioned above, is that I prefer to have the Thermostat (fan) setting on Auto, not On. So my questions:
1) Is this normal? 2) If not, which device is probably at fault? 3) Can the thermostat and/or the humidifier control panel be rewired by my service rep to "fix" this?
Re: Humidifier won't turn on with furnace fan set to...
There is a devise called a current sensing relay (a little black box that hangs on a blower motor wire that senses current from that wire) If you have such a devise it should hang from the white (common) wire. Loop the wire through twice.
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Hope this helps, check and see if humidistat is set to 35% humidity and that bypass damper on humidifier is in the open position or winter position.(humidistat is usually located on cold air return duct near furnace). Next, replace humidifier media pad, remember to replace media pad (filter) annually, you also may want to clean any lime deposit out of humidifier housing with a solution of warm water and white vinegar before installing your new media filter.Remember to turn power off at side of furnace when cleaning humidifier and replacing media. Before installing new media turn power back on to furnace, set humidistat to the on position, turn furnace thermostat above room temp., and inspect humidifier to see if water is running from top,(you may want to have a bucket under humidifier when checking for water), if you see water running, turn power back off to furnace, properly install new media filter, reconnect humidifier cover & set humidistat to 35%. If you do not see water present, check water supply valve to humidifier and make sure its turned on. If water supply valve is open, then check water supply tubing for blockage.And the last things to check is to make sure all registers through out your home are open and not blocked by any objects, also make sure furnace filter is cleaned, if none of this works refer to installation manual to see if humidifier was sized and installed properly, Good luck.
Is the furnace fan set on auto or on. You will get better humidity if you keep the fan on. It won't add much to your electric bill because many of the newer furnaces operate the fan on DC voltage. Try it!
The furnace should be equipped with a #50 relay to turn the Humidifier on and off when only when the furnace blower is on. You should have a test mode on your humidistat. Do you have water coming up to the solenoid valve? Make sure that the saddle valve is turned on to supply the water to the humidifier. Is your humidistat set high enough to turn the humidifier on? Is it plugged in?
It sounds like the humidifier may be improperly wired.
It's hard to solve without checking the wiring, but it seems like the humidistat is wired so that as the dial is advanced, it incorrectly turns on the fan, or furnace, or both. The contacts of the humidistat should be wired so that they turn on the solenoid only. Also, the power to the humidistat, to turn on the solenoid, should come on only when the fan is on.
Hope this helps!
This may not be a solution, but a couple things you might want to look at. First, the humidifier may not be big enough for your house - just because a contractor installed it doesn't mean he sized it right. Second, humidity may only be 30% locally by the humidistat, but higher in other parts of the house - it depends where the humidistat is located. Finally, look at your hot water line - I'm surprised he ran it off hot water and not cold - seems like a waste of energy to me, but the feed line may be clogged by sediment from the water heater
I had this problem several years ago. In order for the water to flow, the outside temperature sending unit must indicate to the controller that it is less than 60F. If not, the unit will not operate outside of test mode. Check the temp outside where your sending unit is (could the sun be heating that side of the house?) and ensure that the circuit to the sending unit is working. I had a bad wire splice inside a wire nut stopping the circuit. Took me a long while to figure it out.
If the outside temp and your sending unit circuit is ok, I wish you luck on your troubleshooting.
I would guess from the info provided that you only have two wires going to your thermostat which would explain why the fan switch doesn't work on the thermostat. You can bypass the thermostat as a first step in troubleshooting. After that it depends on the type of furnace, standing pilot or electronic ignition...