# Run humidifier only when heat on?



## DarkBeer (Dec 10, 2016)

I have an American Standard Freedom 80 Comfort R furnace and a Honeywell bypass humidifier. I leave the fan on continuous run to keep the temp even throughout the house. Since the fan is always on, the humidifier runs all the time as well if the humidity is too low. I would prefer to only have it run when the furnace burner is on as well so that there is hot air to evaporate the water into. Is there a way to wire the humidifier to work that way or will it always run if the furnace blower is on?


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## user_12345a (Nov 23, 2014)

Yes. Trace the humidifier wires to the furnace control board and tell us what it's connected to.

you have a flow through humidifier, right?


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## DarkBeer (Dec 10, 2016)

There is a white wire that goes to neutral EAC and a black wire that goes to hot EAC. There is a neutral HUM that doesn't have anything hooked to it. Should I move the neutral EAC over to neutral HUM?


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## yuri (Nov 29, 2008)

The EAC terminals are for a electronic air cleaner/accessory and supply 120 volts when the fan runs.

Post the model # of the humidifier.

If it has a 24 volt transformer they probably put it on the EAC terminals.

The EAC neutral and other neutrals are all common and jumpered together so it makes no difference which are used.

If your circuit board has HUM terminals or one of them then check with a meter to see if it supplies 24 volts or 120 volts to ground when the burner is running. Need to hold the door switch in or duct tape it ON temporary.

If it is 120 then you can hook the transformer to it. If 24 volts then you can hook the low voltage wiring to the humidifier to it and the C on the board. The HUM only gets turned on with the heat.


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## DarkBeer (Dec 10, 2016)

Humidifier is a Honeywell HE225A 1006. Wires run to it from a transformer. There is a HUM terminal on the hot side, and it has a black wire connected to it that runs with other black wires to the power switch on the side of the furnace.


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## Bob Sanders (Nov 10, 2013)

Although running a humidifier without heat is less efficient than with heat, they are still capable of delivering humidity in just the fan mode only. If you think of those old floor standing humidifiers, they had no heat and could adequately humidify up to 3700 sq feet (they have a lot more surface area to them though).

Granted some bypass humidifiers work well with no heat and some don't so the choice is yours.... but if they are not running they can not do their job


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## Peeeeet (Mar 1, 2021)

Do folks agree that running bypass humidifier w house circulating fan is superior to only running it when furnace kicks on? I live in Colorado and it's pretty dry here. My house is reading 23% humidity and outdoor humidity is 20%. It is 48 degrees and 😎☀


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## beenthere (Oct 11, 2008)

Only if its connected to the hot water line at the water heater.

Other wise, its a waste of water.


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## Peeeeet (Mar 1, 2021)

Yes. Hot water. My humidifier is a HE265A honeywell. Pretty old now I guess. I will add an upstream to solenoid water flow restrictor since there isn't one and it's a flood hazard for me occasionally. Then, basically wire it backward to what the above gentleman did since mine only turns on with the furnace. Correct?


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## beenthere (Oct 11, 2008)

I don't know how yours is wired. Could be wired either way.


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## Bud9051 (Nov 11, 2015)

@*Peeeeet*

The outside humidity is much lower than that 20% indicates. RH changes with temperature so that outside air warmed up 70 degrees would be 9% RH. Mixing that with the air in your house you end up with the 23%. Your low humidity is due to air leakage. Air sealing has become a top priority for energy cost reduction and increased comfort.









Temperature, Dewpoint, and Relative Humidity Calculator


Brian McNoldy's T/Td/RH Calculator.




bmcnoldy.rsmas.miami.edu




Bud


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