Nest 2nd Gen + Generalaire 1042 + Lennox ML193UH

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Old 01-07-17, 09:09 PM
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Nest 2nd Gen + Generalaire 1042 + Lennox ML193UH

Hi there,

Newbie here. I was wondering if i could get some help connecting my Generalaire 1042 humidifier to my existing Nest 2nd Gen thermostat. It is a bypass humidifier, i guess, as per the internet. :-)

Here's how it is currently connected.

Starting from the solenoid valve of the 1042 humidifier, there are 2 wires...
- first wire connects directly to the "NO" terminal of the humidistat.
- 2nd wire connects to a transformer and from there it connects to the "C" terminal of the humidistat. The transformer have 2 more wires which connects to the "EAC" and "Neutral" terminal of the Lennox furnace. So in total, there are 4 wires on the transformer.

With the above connection, the humidifier works when the thermostat calls for heat. It also works by just turning on the fan through the nest app without calling for heat.

Is a relay needed for this to work properly? Can i remove the transformer and use the C terminal of the furnace instead?

Any help would be greatly appreciated.

Thanks in advance!
 
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Old 01-07-17, 09:36 PM
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Welcome to the forums.

You can connect one of the solenoid wires to the C terminal on the furnace.
The other solenoid wire connects to the * terminal on the nest.

No additional transformer or humidistat is needed.
 
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Old 01-07-17, 11:13 PM
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Thanks PJmax. So i guess i don't need a relay as well? Just want to confirm as the Nest site mentioned "relay" multiple times when dealing with humidifiers.
 
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Old 01-07-17, 11:18 PM
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You can use a relay if you like. Then the nest would trigger the relay. You'd use a separate power supply to run the humidifier.

Most people don't use a relay.
 
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Old 01-07-17, 11:35 PM
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That sounds a bit more complicated :-)

Is there an advantage/disadvantage of using a relay? What is the difference? If you don't mind me asking.

Thanks!
 
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Old 01-09-17, 05:37 PM
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Hi Pjmax, i rewired the humidifier as per your instruction and it is working now. Thanks much for your help. However, it seems like the humidifier doesn't engage anymore when i turn on the fan of the furnace, is this what's expected with this connection? When you get a chance. Thanks.
 
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Old 01-09-17, 06:22 PM
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Since you are using the nest..... you have to program it to do what you want.

I recommend "heat and humidify".
What you are asking about is "blower and humidify with no heat".
 
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Old 01-14-17, 12:22 PM
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Thanks PJmax, appreciate your help.
 
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