# Humidifier on "HUM" or "EAC"?



## rayf01

Question for you everyone, trying to do a little research on this bit of information I was given before I make the swap.

I have an Armstrong Air 2 Stage Mid Efficient G2D80CT furnace in my house. There was a very old scaled up humidifier in place that I scrapped. I ended up installing myself a General Air 1042 ByPass Humidifier. Below is how I have it wired:











Everything is tested and working. I wired it per the diagrams matching both the furnace wiring diagram and the humidifer instructions.

The HUM contacts on the board put out 110V, and the transformer steps it down to 24V (meter reads 28V) as the Humidifer solenoid is a 24V solenoid.


Now here is where the questions comes in. I was talking to a local contractor who I am looking at having doing some duct work for me and he mentioned that they had issues with using the HUM contacts on the boards before (Specifically Lennox I think he mentioned) and the humidifers pulling to much power and frying the board. Instead he said, they have been instructed to us the EAC contacts on the board.

Thoughts on this? I am not even sure what the EAC terminal puts out for a voltage yet. I am thankful that he told me this before the heating season comes in to full swing and I possibly fry my board, but at the same time I am cautious, as the HUM terminals are there for a reason.


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## TJ_in_IL

EAC= Electronic Air Cleaner. HUM= Humidifier. 
If you want your humidifier to run with both the heat and cool cycles, then wire to EAC (not recommended).


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## rayf01

TJ_in_IL said:


> EAC= Electronic Air Cleaner. HUM= Humidifier.
> If you want your humidifier to run with both the heat and cool cycles, then wire to EAC (not recommended).


 
What about the way I have it configured then. Should there be any issues with this?


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## fabrk8r

You should have no electrical issues with the humidifier if it's wired the way your diagram shows.


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## Marty S.

As stated you're fine that way. The problem was with furnace control boards that supplied 24 volts to the humidifier, transformer wasn't big enough for the additional load. EAC would be used in heat pump applications or if you want the humidifier to come on with the fan.


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## TJ_in_IL

Thanks Marty, beat me to it.
I was going to say, I am in no way an expert, but from what I have heard, the bulk of the issues came from the stock 24vac transformer. My furnace installation guide specifically states not to use the low voltage for any other accessories. I installed mine the same way you did yours, and yet to have an issue (but then again, I have only used for one season).


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## hvaclover

TJ_in_IL said:


> EAC= Electronic Air Cleaner. HUM= Humidifier.
> If you want your humidifier to run with both the heat and cool cycles, then wire to EAC (not recommended).


what he said...in spades...


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## hvaclover

Yeah stay away from EAC cause the humid won't shut off automatically in ac mode.


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## beenthere

hvaclover said:


> Yeah stay away from EAC cause the humid won't shut off automatically in ac mode.


Unless your using a humidifier with an automatic control with an outdoor sensor.


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## hvaclover

don't think they are.


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## beenthere

OP may not be.

But Aprilaire has them.


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## yuri

Homeowner needs to shut the bypass damper for AC season anyway and should turn the humidistat to OFF. Then using the EAC term is no problema.


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## rayf01

Thanks for all the posts guys it makes me feel a bit better now, I'll leave it the way it is. I don't have an AC unit at all, strictly running the humidifier on the heat cycle is all I want. 

I gather since I am running it off the HUM terminal and that terminal supplies 110V then its not using the 24 volt transformer that comes with the board, however I am using the 24 volt transformer that came with the humidifier which I mounted on the side of the furnace. 

I don't have an outdoor sensor either, just a two wire humidistat which is mounted on the main floor next to my digital thermistat (seperate wiring). At this time I have the bypass damper closed and the humidistat turned all the way off. When the heating season comes in to full swing and the humidity in the house drops I will start opening thing up.

Sounds like I am ok then.


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## hvaclover

beenthere said:


> OP may not be.
> 
> But Aprilaire has them.


Be nice Been, I was working in my favorite job today..the Pit...Had a three ton evap fall on my head and that was the best part of the day.


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## kenmac

hvaclover said:


> ...Had a three ton evap fall on my head


 
For some reason. I don't think that's the 1 st time that's happened:laughing:


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## hvaclover

kenmac said:


> For some reason. I don't think that's the 1 st time that's happened:laughing:


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## beenthere

kenmac said:


> For some reason. I don't think that's the 1 st time that's happened:laughing:


LOL...:laughing:


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## hvaclover

the HO is a medical professional. she gave me two pills(they sure weren't aspirin) That made the pain go away.and that groovy feeling come back..then she put seven stitches in my bicep.

This is my best customer and I would go to the wall for her..but her furnace is in a cinder block room below grade and about five by ten.

The 13 SEER coil barely made it thru the door be cause a vertical round duct run blocks almost half the door way threshold.


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## carlb7

I am installing an Aprilaire 700 to a Ruud UHBK handler and I was going to come from the digital humidistat R&C to W1&C at the handler. I saw this wired on a Trane Humidifier that way. One of the diagrams for the Aprilaire showed this as the prefered method. Then I would plug the fan from the humidifier to an ac outlet nearby. Does this sound like the correct way to wire it for my installation?


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## hvaclover

carlb7 said:


> I am installing an Aprilaire 700 to a Ruud UHBK handler and I was going to come from the digital humidistat R&C to W1&C at the handler. I saw this wired on a Trane Humidifier that way. One of the diagrams for the Aprilaire showed this as the prefered method. Then I would plug the fan from the humidifier to an ac outlet nearby. Does this sound like the correct way to wire it for my installation?


Don't hi-jack other poster's threads. It's against forum rules and just plain rude.


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## carlb7

Sorry. I will submit new post.


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## beenthere

carlb7 said:


> Sorry. I will submit new post.



Its almost always better to start your own thread.

It keeps people from getting confused on who they are answering about what situation. While this thread is only 2 pages long. Some are more. And after a while. People start giving answers based on the original question/situation, and the answers are incorrect for the person asking the new question.


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## abasourdix

Marty S. said:


> EAC would be used in heat pump applications or if you want the humidifier to come on with the fan.


Shouldn't the humidifier come on only with the fan? In other words, if wired to HUM wouldn't the humidifier 24v transformer be powered all the time, and as a result over heating? Per your comment, if wired to EAC, then two conditions must be met for the humidifier to come on:
1. more humidity requested from the humidistat
2. furnace fan turns on (which is the reason humidifiers use a sail switch)

Can you please clarify?
Thanks.


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## hvaclover

EAC terminal are energized as soon as the fan starts blowing in both ac and heat.

The humidifier would still be energized even in cooling cycle. This is not a good idea as a lot of customers would neglect to turn off the water and turn the humidistat to off. This can cause problem...that story is too long to relate so I wont.


HUM terminal only energize when in heat cycle. This is advantageous because even with the humidistat turned up to maximum it still wont energize if in cooling. The water is normally left turned on but some customers turn it off just for peace of mind.

With out the advantage of HUM terminals the best way it to use isolating relay that will remain open in the cooling cycle an stop any voltage from reaching the humidifier.


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## Marty S.

abasourdix said:


> Shouldn't the humidifier come on only with the fan? In other words, if wired to HUM wouldn't the humidifier 24v transformer be powered all the time, and as a result over heating? Per your comment, if wired to EAC, then two conditions must be met for the humidifier to come on:
> 1. more humidity requested from the humidistat
> 2. furnace fan turns on (which is the reason humidifiers use a sail switch)
> 
> Can you please clarify?
> Thanks.


 Clover covered it but I'll add a bit to clarify my earlier statement. The HUM terminal only energizes with a call for heat from the furnace so since a heat pump is using the cooling speed HUM will not energize. Using EAC terminal energizes the humidifier transformer any time the blower comes on and the humidistat closes the circuit based on if humidity is needed or not. It's all in the circuit boards now so sail switches are not used.
Humidity levels should be set so the windows don't sweat, which is far less then the humidty in the house with the AC running in the summer so the humidifier won't run even if you forget to turn a manual humidistat off. I'm not sure how high the automatic humidistats go so if you have one of those with a heat pump then adding an isolation relay is cheap insurance.


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## abasourdix

One more thing: why do you recommend the HUM connection (or EAC if one manually turns the humidistat off and shuts the water in the summer), instead of the W-C connections on the 24V terminals of the furnace board?
Thanks.


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## hvaclover

abasourdix said:


> One more thing: why do you recommend the HUM connection (or EAC if one manually turns the humidistat off and shuts the water in the summer), instead of the W-C connections on the 24V terminals of the furnace board?
> Thanks.


Because the extra load of of the water valve solenoid would affect heating cycle. Might short cycle the heat or cause to fail completely.


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## beenthere

Yep. The thermostat is not rated to run both the heat and a humidifier off of its W terminal.


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