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Discussion Starter · #1 ·
Greetings eveeryone.

I am installing an Aprilaire model 400 humidifier into my old Carrier air handler, running off the Carrier heat pump. I have a Honeywell TH8320 thermostat.

There is a small transformer (0.42A - 10W) included to convert 120V to 24V. This 24V is simply used to operate the little solenoid which turns the water on and off. Apparently nothing else.

Unfortunately, 110V is not available anywhere near the 220V air handler and the main electrical panel is far anyway.

Hee is the link to the installation sheet: http://www.aprilairepartners.com/products/category/humidifiers/83218.pdf

As you probably know, there is a transformer in the Carrier air handler which supplies 24V to the thermostat connection & motor control boards.

I would like to take the 24V off of the internal transformer. I asked AprilAire tech support if that was permissible. Here is her answer:


There would be too much draw. It would create electrical problems.

We would not recommend using the same 24V source for both the R and C as well as the solenoid valve. Perhaps you could get the power from somewhere else, like an outlet? Or even if you had a 24V something like a door bell circuit that could also power up the solenoid valve. But, it is best to not connect both the R and C and the solenoid to the same 24V from the furnace.​

Doesn't really say why. Sounds a little like a C.Y.A. answer to me. They don't know the size of the internal transformer (appears to be a 60VA) and how much power might be available.

What do you think? Should I hire an electrician to wire in 110V for me? Probably cost $300+

Thanks


Thanks!

Murph
 

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AKA HVACTECHFW
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I ALWAYS put a separate transformer on the humidifier circuit incase of a humidifier circuit malfunction it won't take out the heating transformer.

Instead of hiring an electrician you could purchase a 240V to 24V transformer and do it yourself.
 

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Roofmaster
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Why cant you just pick 110 off one of the two hot legs that run to the unit to supply 220V? There should be a black and a red which are 110 each, a white neutral, and a bare ground wire.
 

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AKA HVACTECHFW
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Neutral is not typically run with 240V supply. And, NO!, do not pull 120V between 1 leg of the 240 and ground; that is against code.
 

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Neutral is not typically run with 240V supply. And, NO!, do not pull 120V between 1 leg of the 240 and ground; that is against code.
Yep, just 2 hots and a ground. Neutral isn't ran to an 240 volt air handler normally.

I also wouldn't put an Aprilaire 400 on a heat pump. They don't work too good cause the air temp is too low unless the aux heat is on.

The 600 works much better cause you can use hot water to feed it.
 
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Roofmaster
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Can you explain this to me? I know that the neutral goes to the same bus bar as the ground with 110V AC.

And I know that most generators with a 220 4 prong plug that gets one black hot, one red hot, one bare ground (Green screw) One white neutral (Chrome screw)

And why is it against code to have a neutral? Thank You in advance
 

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AKA HVACTECHFW
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It is not against code to have a neutral. It is against code to use the bare ground wire as a neutral connection. Explain your question more thoroughly.
 

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Roofmaster
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OK, well that makes sense. Im talking about three insulated wires and an equipment ground. Red-110, Black-110, White-Neutral, Bare wire, Ground.
 

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Discussion Starter · #9 ·
Why cant you just pick 110 off one of the two hot legs that run to the unit to supply 220V? There should be a black and a red which are 110 each, a white neutral, and a bare ground wire.
Unfortunately, this unit doesn't have a neutral.
 

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Discussion Starter · #10 ·
Yep, just 2 hots and a ground. Neutral isn't ran to an 240 volt air handler normally.

I also wouldn't put an Aprilaire 400 on a heat pump. They don't work too good cause the air temp is too low unless the aux heat is on.

The 600 works much better cause you can use hot water to feed it.
Well, I already have it installed, but I did plumb hot water to it. I got the 400 because I didn't want to have to deal with the excess drain water.

I have hooked up the 24V transformer with an extension cord, just to get it running, and it seems to be working pretty well. Now I just need to ditch the extension cord and wire it right.

I did find the doorbell xformer, but it measured 19.5 VAC. I wonder if that would work?

Murph
 

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Roofmaster
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Sounds like 126 has the best solution. Or, simply pull a 110 circuit over there.
 
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