Aube rc840t-120 tripping GFCI breaker


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Old 10-06-21, 08:37 PM
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Aube rc840t-120 tripping GFCI breaker

Hi all,
Just a dumb homeowner here and not a pro, so I'll try and provide as many details as I can.
I've turned a shed into an office and plan to have electric heat. I picked up a Wexstar infrared panel rated for over 200 sq ft depite only having 108 sq ft in the shed /office. It's only 600 watts so I figured take a step up in case it doesn't heat as well as advertised. The best perk is that I can ceiling mount it, which I plan to do.
The unit itself is simple. Plug it in to turn it on. Unplug to turn off.
I have a dedicated circuit with 15A receptacle in the ceiling.
I have an Aube rc840t-120 connected to a Nest Thermostat and controlling whether the receptacle is powered.
The circuit is running on a 15A GFCI breaker.

(For those if you concerned, an electrician set up the circuits to the shed in proper conduit at proper depth. She is the one that insisted on the GFCI breaker for this. She installed the relay but hasn't come back after sheet rock).

As indicated by the title, when I wire in the Aube the breaker trips instantly every time. If I bypass the Aube and power the receptacle directly then the breaker doesn't trip. I'm assuming that helps indicate the receptacle isn't the problem.
Before going any further.. Is this setup a pipe dream? Am I missing some fundamental requirement when using a relay?

I'll draw up a diagram later, but the Aube is wired as follows:

(From breaker) Hot connected to Aube black wire.
(From breaker) Neutral connected to Aube white and neutral (white) from receptacle.
Red from Aube connected to hot (black) to receptacle.

The Nest from the transformer is wired C to C, R to R and W to W.


This setup trips the breaker instantly every time.

I went out on a limb and tried an alternate wiring configuration, as if it was a regular 840 plus an external 24v transformer. (I disconnected and put a wire nut on the Aube white and C wires). Same result. I understand that was probably dumb /risky.

If you have any thoughts on this I'd really appreciate it. This whole shed project has gone way over budget and is so close to the finish line. If I can DIY this without burning down the shed that would be ideal.

Part of me is wondering if I just have a bad relay.

Thanks!




 
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Old 10-06-21, 08:50 PM
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Welcome to the forums.

Part of me is wondering if I just have a bad relay.
I would agree with that.

You've confirmed the supply wiring is ok by connecting the heater directly to the incoming line. That would indicate the GFI is wired correctly.

Try this..... connect just the white and black from the 840T to power and see what happens without the heater connected. I've never seen any leakage problem with the 840T and thought the case was plastic which would mean it can't leak to ground.



Just FYI..... the Nest is the only wifi stat the 840T will power.
It doesn't have enough output to run most of the other available wifi stats.
 
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Old 10-07-21, 02:36 AM
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Thank you for the quick response! I'll give that a shot today and let you know how it goes.

Quick note: The heater is currently not plugged in. I was wondering if having no load (just a receptacle with nothing plugged in) on the heating circuit after the relay could be throwing this off. I suppose the relay bypass test I did clears that possibility as a flaw though.

Thank you for your help!
 
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Old 10-07-21, 05:52 AM
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Hi,
I just did the test. Source hot to Aube black, source neutral to Aube white. Disconnected and capped the Aube red. The receptacle is disconnected entirely.
Breaker still trips as soon as I turn it on.

​​​​​​Think this points to a bad relay?

Thanks!
 
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Old 10-07-21, 09:20 AM
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Is the 840T mounted to a metal box ?
If yes.....and the box is grounded.... unmount it.

Connecting just the white and black wire cannot cause any problem.
A leak (minor short) from white or black to ground is what causes the trip.
No load can not cause any problems.
 
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Old 10-07-21, 09:35 AM
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It is mounted to a metal box and yes the box is grounded.

This definitely makes sense as a potential culprit! It may take a bit of time for me to plan and execute this change but I'll keep you posted. If I can safely do a test with the aube unmounted and just hanging off I'll also let you know.

Thanks!
 
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Old 10-09-21, 07:08 AM
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Hi,
I just ran the test with the Aube unmounted. The breaker still trips every time.

​​​​​
A picture to make sure I'm not crazy. Red is hot from the conduit.
Uncapped white/black to right are to the receptacle so no risk there.


Yes, I had the relay mounted to the outside of the junction box inside the wall. I figured I'd never need to access it and it doesn't generate heat like a solid state relay.
 
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Old 10-09-21, 09:37 AM
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when I wire in the Aube the breaker trips instantly every time. If I bypass the Aube and power the receptacle directly then the breaker doesn't trip
This is not making any sense.

Are you saying that you put a receptacle on the red and white wires that are currently feeding the 840T and plug the heater in that the circuit does not trip ?

Above all you need to make sure that white wire is the match to the red wire. With a GFI or AFCI breaker.... the white wire connects to the breaker and must match the hot wire.
 
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Old 10-09-21, 11:15 AM
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I figured it out and everything is working as expected.

While tracing the circuit back to the breaker looking for problems I disconnected the heater's hot and neutral before they fed into the conduit to the shed.
I went back into the shed for a tool and noticed the lights were out. I didn't touch that circuit! Voltage tester indicated lights supply wire still hot but the lights were not working. Turned off the breakers again, connected the heater's neutral (only) and turned on the breaker for the lights. They now worked.
It looks like the neutrals for the heat and lights got mixed up when they came out of the conduit. The breaker for the lights was ok with this apparently but the GFCI breaker for the heat was having none of it.
I swapped the neutrals and both circuits are good. I have no idea how my test to the receptacle worked last time. Today I tried it again and it failed which led me down the path to finding the issue.
Thank you for all your responses! I don't know if I would have gotten this far without your input.

This Wexstar heater better work!
 
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Old 10-09-21, 11:49 AM
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Awesome job. You stuck with the project.
 
 

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