Question on wiring - Model 62 control with Aprilaire 800 humidifier


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Old 03-08-21, 07:18 AM
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Question Question on wiring - Model 62 control with Aprilaire 800 humidifier

First time posting. Need some advice on 800 + 62 installation.
We have Heil two-stage gas furnace controlled by Nest E. Would like to add the 800.
Would like 800 controlled by supplied 62 digital control, no separate humidistat.

Looking at the schematic in the installation manual (see below), it shows G terminal (fan control) on the thermostat connected to the G input on the 62, and the Gf output from the 62 connected to the G input on the furnace. I am assuming this is to let the 62 run the furnace fan whenever the steam is on.

My question is this - if I never want the humidifier to run without the heat on, and therefore never need the 62 to control the fan, just to switch the 800 on when both the heat and the fan are on, can I leave the existing G terminal wire from the thermostat to the furnace in place, connect the G terminal from the furnace to the G terminal on the 62, and leave the Gf on the 62 unconnected (as shown below in red)?

That way, should the 62 ever break, my heating system would never notice, since all connections will still be as they are right now.

Thanks in advance!


 
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Old 03-08-21, 08:43 PM
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Welcome to the forums.

Typically a humidifier won't deliver enough humidity unless the burner is running. So I never use the G wiring. In your case you have a steam humidifier that could run and deliver humidity without the burner.

If you don't want the humidistat to control the blower.... don't connect any wiring to the G terminals.
The W terminal is what activates the humidifier.

If you have a thermostat wire on W1 and W2..... you may want to connect the W wire to the HUM terminal.
If you are interested in that.... post the part number off the control board.
It needs to be determined if your board provides 24v or 120v HUM power.



 
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Old 03-17-21, 09:22 AM
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Thanks for your reply.
Planning to work on the installation this weekend, so time to make some decisions.
I get it that the steam humidifier can run and provide humidity without the burner, but am really worried about possible condensation inside the ducts, or even inside the furnace. Do you have any opinion on that?
If what activates the humidifier is the W terminal, then why does the 62 manual even asks for G from the thermostat to be connected to the humidistat? You are saying this input is never used?
Finally, the control board is Honeywell ST9162A1040. The W1 and W2 wires are indeed connected, I believe that is because the furnace is two-stage. I don't see any HUM terminal anywhere, so not sure what you mean.
 
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Old 03-17-21, 04:15 PM
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asks for G from the thermostat to be connected to the humidistat?
The 62 forms a series loop in the blower line. You would connect the G wire from the thermostat to G on the 62 and another wire from Gf on the 62 to the G terminal on the furnace. This is only done if you want the h'stat to be able to turn on the blower and humidify with the burner not running. So you don't need the G wiring.

When you apply 24v to the W line.... the humidistat starts the humidifier.

Your HUM terminal is 120v. You would need to use a 24v transformer connected to HUM and any available neutral terminal to supply 24v to the W line on the h'stat. Using this method would allow the humidifier to run in W1 or W2 heating modes. Otherwise you'll be forced to use W1..... low fire terminal.
 
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Old 03-19-21, 12:11 PM
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Oh boy... This little project that seemed like it would be relatively simple, grows more complex by the minute...
Pete - I am very grateful for your help so far, but sounds like I need more, please:
- Did I understand correctly that when the thermostat calls for 2-stage (high) heat, there is no signal on W1?
- Signal between HUM and neutral is 120 V AC?
- Can you please explain how to connect the 24 V transformer output to the 62 humidistat? One wire to W, and the other wire to what? Also, is 62 expecting 24 V DC? Meaning, do I need some kind of rectifier after the transformer?

Thanks in advance!
 
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Old 03-23-21, 07:35 PM
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Excellent question on two stage operation. I can't answer it off the top of my head. I always thought either W1 or W2 was energized. Now I'm seeing both can be energized during stage 2 operation.

Do you have a meter ?
Clip your meter on W1 and C. Set the stat up at least 10 degrees.
When unit shifts to stage 2...... see if there is still power on W1.
If there is..... you can use W1 and C for your humidistat.

If not..... then you'll need the transformer. The output of the transformer would connect to the W of the h'stat and C on the furnace board. ALL voltages involved in HVAC are 24vAC. No DC is used.


 
 

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