Honeywell HE360A Doesn't Shut off at Night - Nest 2nd Gen - Trane XV90

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Old 01-20-18, 12:37 PM
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Honeywell HE360A Doesn't Shut off at Night - Nest 2nd Gen - Trane XV90

Hi - I'm hoping someone can help me in diagnosing what appears to be an intermittent issue with my Honeywell HE360A humidifier (duct mounted and plugged into a wall outlet for power). It's mounted to a Trane XV90 two-stage heating, single-stage cooling furnace, and controlled by a 2nd generation Nest. A 6AZU2 relay is also used.

During the day, the humidifier runs only with the heat (as it's supposed to), but sometimes at night, after the thermostat automatically drops the temperature to 65 degrees for the night (11:00pm), the humidifier stays running (both water and fan) and I have to unplug it to get it to stop. Using the Nest app to turn off the humidifier doesn't work - the humidifier just keeps on running. After I plug the humidifier in again the morning, it works correctly, sometimes for a few days, before failing to shut off overnight.

Here is my setup which was performed by the HVAC company that installed the furnace in 2013. I had everything working correctly on my old furnace and they just moved the relay and wires over to the Trane XV90. I think it worked fine for the first three winters, but I started having this problem last winter (2016-2017).

My connections are as follows from the furnace panel:
BK (not used)
W2 --- Nest W2
W1 --- Nest W1
R --- Nest RH
G --- Nest G
BC -- Two connections: Relay Connector #1 (coil side) and white wire to outdoor A/C unit
Y --- Two connections: Nest Y1 and red wire to outdoor A/C unit
YLO (not used)
O (not used)

The * wire from the Nest goes to Relay Connector #3 (coil side).
The switch side of the Relay (Connectors #2 and #4) are connected to the two wires from the humidifier.

The Nest humidifier settings are as follows:
Type: Hum
Activate: Hum + Heat
Fan: Activate

Quiet Time: 11PM-4AM
Also, fan is set to run from 7AM-10PM every day.

So, my questions are as follows - I want the humidifier to run only when the heat is on (Stage 1 or Stage 2):
1. Are my Nest settings correct?
2. Is my wiring correct - especially with regards to the relay. Should I connect it to W1 instead of BC?
3. If #1 and #2 are correct, then how can I tell if the problem is with the Nest, the relay, or the humidifier? I'm assuming (maybe incorrectly) that if a wire was bad, the humidifier would have a problem turning on, not turning off.

Thanks to all who read this, and any thoughts/ideas would be appreciated!
 
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Old 01-20-18, 03:40 PM
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The wiring is correct.

I don't think the fan should be set to activate.... especially if that question is in the humidifier programming section. Turn that off first and see if that stops the humidifier when it should.

You basically want humidify with heat.
 
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Old 01-20-18, 06:30 PM
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Thanks for the quick reply! Iíll give it try.
 
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Old 01-25-18, 06:33 AM
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UPDATE: I still have an issue. The humidifier worked fine Saturday through Wednesday, but last night, it stayed on after the heat and fan were off for the night. Here's what I did:

- Unplugged the humidifier from the wall outlet last night to get it to stop.
- Every time the humidifier was plugged in this morning, it would start running again.
- Took the panel off the furnace to cut power, but the humidifier did not stop.
- The humidifier stopped only when I disconnected the wire that goes to the coil side of the relay and the BC connector on the furnace board.
- For now it is working correctly again. Even when the furnace is running this morning, the humidifier doesn't come on unless it's supposed to.

So, here's my layman's diagnosis, but please let me know if there is something else I should test, or if you see a more likely problem.

It appears that one of two things are happening:

1) There is still enough current running through the BD/Nest */Relay circuit to keep the relay switch closed even when the system is off. This would indicate a problem with furnace or Nest.

2) The relay switch has a problem getting stuck closed every 3-4 days, which is fixed by either unplugging the humidifier for a long enough time period or disconnecting the relay. This would indicate a problem with the relay.

There doesn't seem to be a problem with the humidifier, but rather a problem with the devices telling it when to turn off and on. There is never a problem with it not turning on when it's supposed to, only with turning off.

Being that replacing the relay appears to be the least expensive and simplest troubleshooting path, I've ordered a replacement relay and will install it over the weekend.

Does that make sense, or would a different path be recommended?

Thanks again for reading and any assistance anyone can provide!
 
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Old 01-25-18, 07:50 PM
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Is there a spare wire to the nest that you could use for a C connection ?
I think the nest may be drawing charging power thru the relay.

A different relay could address the problem especially if it needed more current to activate.
You could also try adding a resistor between B/C and W or B/C and *. Nest recommends 220 ohms at 5w. I use 240 ohms at 10w.
 
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Old 01-26-18, 05:49 AM
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Thanks again, for the quick reply! It's good to know that there are other options for me to try. I think I'll see if replacing the relay works, and then move on to running a C wire and/or trying a resistor. I'm planning to install the new relay on Saturday and post an update by end of next weekend if everything works fine (or earlier if the issue still isn't resolved).

I may be running new wires anyway as I want to move the thermostat to a new location and there is no extra cable length to spare. When the house was built, the thermostat was placed on a wall with a duct leading upstairs, so the wall itself is warmer than the air in the room. We have to set the thermostat 2-4 degrees warmer than we want in the winter (and 2-4 degrees cooler than in the summer). I'll get a cable with more wires if/when I do.
 
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Old 02-04-18, 07:00 AM
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I just wanted to report back to say that replacing the relay appears to have solved the issue. I have now gone 8 straight days with the humidifier shutting off correctly. If anything changes, Iíll update this thread. Thanks for the help, PJmax!
 
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Old 02-04-18, 09:55 AM
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Thanks for the update.

If the problem comes back.... connect both relay coils to the nest. Both will activate but only one will do the switching. The load of two coils will stop the problem.
 
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Old 02-07-18, 03:37 AM
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That’s a neat idea. Hope I don’t need it! Thanks again for helping me work through the issue.
 

Last edited by ajstan99; 02-07-18 at 03:57 AM.
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