Floor Heat Ground Fault


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Old 05-03-21, 10:35 AM
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Floor Heat Ground Fault

I am troubleshooting a ground fault error on a set of electrical floor heat mats and I'm getting stumped. The system that is installed is a 120v QuietWarmth Film Heat (4 mats, all model QWARM3X10F120 ) on a programmable thermostat (OJ Microline UTN4-4999). The installation is on a concrete basemen floor, with LVP flooring.

Troubleshooting I've Done:
-Confirmed that the thermostat was rated for the wattage being used.
-Swapped the thermostat with a confirmed functional thermostat. Still received the error.
-Checked proper voltage for the system, voltage was good. Still received the error.
-Disconnected floor sensor and switched to room temperature control. Still received the error.
-Disconnected all the mats from the 3 junction boxes that tie back into the thermostat. With no mats connected, the system will stay active, which leads me to believe it's an issue with the mats.
-Here's where I'm getting baffled. I tried to connect the mats one at a time to find the "bad mat". Individually, and of the mat's will run without a ground fault. With 2 mats connected, the mats will run without a ground fault. If I connect 3 or more mats, there is a ground fault error.

I'm trying figure out why there is only a ground fault when 3 or more mats are connected, here are my current speculations:
-The romex jumpers from the thermostat to the junction boxes where the leads from the mats tie in, when under load, are having a weird interaction that triggers the GFCI.
-The flooring installers who installed the mats and have not been very responsive, overlapped something somewhere.
-There is minor damage to multiple mats that doesn't create enough fault current to trip the GFCI until the load is high enough.
-The vapor barrier was not properly installed and moisture has gotten into the system, but doesn't create enough fault current to trip the GFCI until the load is high enough.

Any thoughts, insights, similar experiences that anyone could share would be very helpful.

Thanks,
-John
 

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05-03-21, 01:59 PM
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Each mat may have a slight leak. You'll need to use an ohmmeter set to a very high scale.... 100k or higher to check each met. Technically there should be no continuity from any mat wire to ground.
 
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Old 05-03-21, 11:56 AM
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Hi, where are you seeing this GF error?
Geo 🇺🇸
 
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Old 05-03-21, 01:59 PM
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Each mat may have a slight leak. You'll need to use an ohmmeter set to a very high scale.... 100k or higher to check each met. Technically there should be no continuity from any mat wire to ground.
 
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Old 05-03-21, 02:10 PM
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Thanks for the responses, I really appreciate the help here guys.

Geochurchi, the thermostats for the floor heat system have built in GFCI protection and when 3 or more mats are connected, a Ground fault detected message flashes on the LCD screen of the thermostat and the red fault light on the side of the unit blinks.

PJmax, my multimeter is showing very small reading to ground on the leads for all four mats, I believe it cycles down to fractions of milli-ohms before it it displays anything. I thought it unlikely that all four mats could have been damaged, so that there may have been something going on with my meter.
 
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Old 05-03-21, 03:03 PM
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It's not milli ohms you're looking for.
You're looking for very high leakage resistances.... in the order of 20k ohms or better from white or black to ground.

Are your four mats wired separately ?
It would be extremely rare for more than one mat to have a problem.
 
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Old 05-03-21, 03:49 PM
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The mat's are wired together (I have 2 separate junction boxes that each have 2 mats into a new romex wire, that then runs to the thermostat location, because the mat installers chose not to run the leads back to a single point) but I separated all the leads from one another to check the them all individually. I did get a similar reading to ground on each of the 4 mats though, and registered no continuity to ground to each of the conductors on the romex jumpers when I had them isolated. I may be getting my "m" and "M" mixed up for the resistance reading though and that's quite a difference.
 
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Old 12-02-21, 07:50 PM
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Have you figured out what the issue is? I am having the identical issue with an installation of the same description.
 
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Old 12-02-21, 07:59 PM
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Welcome to the forums.

I troubleshoot floor heating systems. I disconnect the floor loops from the controllers and check from each wire to ground. You need to use a fairly good meter with high resistance scales. You are looking for any continuity from each wire to a known ground. There should be no continuity measured, If there is..... there is a leak.

What's a leak..... damaged jacket, nail or screw thru cable.

I'm horrified by some of the laid back (careless) installations I've seen.
The longevity of the system is all in the installation.
 
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Old 12-02-21, 08:21 PM
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If it is Ditra Heat, consult their installation instructions. There are lots of things that can go wrong with the installation and the resistance and continuity is supposed to be measured multiple times- after each step of the process (before installation, after installation and after tile), compared with the factory specs, and a written record made. (See record log)This is the sort of thing that seperates a trained installer who follows installation instructions from your run of the mill, fly by the seat of your pants installer.

Link
 
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Old 12-02-21, 08:51 PM
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My issue is with Quiet Warm. I've installed Ditra Heat and it works without issue. It seems like the Quiet Warm mats are overheating. I took up the laminate floor and checked the cold leads for abrasions and such. I reinstalled giving extra care that wires didn't overlap under the laminate floor. I have the same issue as JC. I get a ground fault when I hook more than 3 heat mats to the thermostat. Even with 3 heat mats installed, the system heats for about 5 or 6 hours and then I get the ground fault notification again. At the time I took up the floor, it seemed that where the cold leads attached to the heat mats that the insulation tape had moved significantly from it's original installation placement. I repositioned it and added duct tape to stabilize it's position. Still, the mats are suspect. I'm looking for the resolution from someone having a similar problem before I buy all new mats.
 
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Old 12-06-21, 05:46 AM
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I have an exact problem with QuietWarmth mat. Each connected separately works just fine but if I combine two or more I get a ground fault issue. It comes up within seconds so it doesn't need to heat up before it's triggered. It happens in every room so chances of a bad mat or damaged mats are small. Could it be a thermostat that cant handle it? I use recommended OJMicroline UDG-4999. Was anyone able to find a solution? Thank you for your help.
 
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Old 12-06-21, 09:38 AM
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Question.... are these mats two wire...... hot and neutral.... or is there also a ground wire ?
 
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Old 12-07-21, 05:22 AM
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Pjmax, Quietwarmth mats do not have ground wires.
 
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Old 12-07-21, 10:37 AM
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Ok..... so then we need to figure out where the ground fault is coming in.
A ground fault is a leak from either supply wire to ground.

Are there mats over a masonry floor ? If yes.... the floor must be sweating.
 
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Old 12-10-21, 06:05 PM
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Pjmax, per the Quietwarmth instructions, the concrete floor is first covered with an underlayment pad of their manufacture. The heat element mats are laid on top of they underlayment and channels are cut in the underlayment where the wires run. The instructions did not call for it but I put down a layer of tape to insulate the wire from direct contact with the concrete. I have also taped the wires parallel so that they do not cross and get pinched between the laminate floor and the concrete when the weight of foot traffic is directly on top.
 
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Old 12-10-21, 07:35 PM
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The wires crossing will not cause a ground fault.
As I've mentioned.... a leak between hot or neutral to ground is what causes the fault.
 
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Old 12-13-21, 06:19 AM
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Did you have any luck narrowing this down? I have a '10 mat' system that was installed a few months ago in a new construction commercial building over LVP flooring. It seemed to work ok, initially. Didn't turn the system on again for at least a month after baseboard was installed. My initial thought was that the guy installing the baseboard put a fastener through the wiring. However, I've tested every mat and they are all showing continuity of around 150-180 ohms. It doesn't matter which set of 3 mats I connect, the system works fine. But as soon as I add ANY 4th mat on, the GFI on the t-stat trips. The system is running a 30 amp dedicated 208 circuit.

I've spent about 7 hours troubleshooting so far. I'm getting the full 208 volts at the line side.

Much like one of the other responses above, one of the rooms has 4 mats that collect into a junction box an then hop over to the tstat. The other half of the room has 6 mats collect into a different junction box (along with the tstat sensor wire) and then hop up to the tstat.

If I test the jumper wires (where they come into the tstat junction box), it comes back at 50(ish) ohms (going on memory, but I wanted to make sure there wasn't a break in the jumper wires and cluster). If I nut the jumper wire in the collection junction box and test for continuity at the tstat junction box, I do show continuity but can't remember how many ohms (it was considerably less, but I attributed that to the fact that it was just wire in a loop).

For what it's worth, the tstat IS picking up a floor temp of 58 degrees...so I don't think that wire is the problem either.

Need help, this is for my wife's yoga studio and the floor is 58 degrees!!!!
 
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Old 12-13-21, 06:19 AM
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Exact same issue

I have 4 Quietwarmth mats installed over vapor barrier underlayment on concrete. Everything was installed exactly per the instruction manual testing each mat's ohm readings multiple times before, during, and after floor installation - all within specs. The breaker is a non-GFCI on a dedicated 20 amp circuit. I also use the recommended OJ Microline UDG 4999 GFCI programmable thermostat. The floor worked properly for about six months but is now tripping the gfci on the thermostat immediately when the thermostat switches on to heat the floor. I have disconnected all mats at the junction box and taken ohm readings for each which all still match the installation readings. Each mat connected individually will heat without issue. I can connect any 3 of the mats and heat without tripping the GFCI but as soon as I connect the 4th, no matter which one, the GFCI immediately trips. I was thinking it has to be a faulty thermostat but you're saying you switched to a known working thermostat and it tripped as well. I don't know what to do at this point but I really don't want to have to clear out the room and take up the floor. Has anyone else figured it out?
 
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Old 12-13-21, 06:19 AM
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over the weekend I installed a different thermostat, the simplest I could find just to try to see if it works. I used it in three different rooms with heating areas between 30sq (2 -10 ft x 18-inch mats) and 150 sq ( 5 mats of 10ft x3 ft) and it works great. It takes much longer to heat up a large room. The thermostat I used does not have build-in GFI and is not even in Farenthight but as a test I think it proved to me that the problem is with my OJ microline UDG-4999 Thermostat. I am not good with all of this so let me know what do you think. below is the link to the one I have tried. https://www.amazon.com/dp/B091NW1H7B...roduct_details
 
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Old 12-13-21, 06:27 AM
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forgot to mention that in my case I was only able to heat one mat. The moment I connected the second one it would give me ground fault. No matter what room or square footage.
 
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Old 12-13-21, 06:53 AM
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Non-GFCI thermostat

I'm not sure that you accomplished anything by hooking up and heating your mats with a non-GFCI thermostat.
 
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Old 12-13-21, 09:34 AM
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The units come with GFI protection in case water leaks thru the floor and gets to the mat.
That could prove to be a shock hazard if someone where to stand in the water and touch ground.

It appears that all the problems are with QuietWarmth mats and are on some type of masonry floor.
Anyone's problem not match this description ?
 
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Old 12-13-21, 07:59 PM
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I have had my laminate floor up looking for anything to cause this problem. There are no compromises in the wire and no moisture. As I hear more people with the identical issue I am growing in the suspicion that there is a defect in the product that shows up after it has been in use for a time.
 
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Old 12-14-21, 06:14 PM
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I originally contacted Quietwarmth customer serivce but they would not help me because the thermostat was an OJ Microline. I subsequently changed it out for an OEM thermostat from Quietwarmth. I got the same ground fault result. In the time since I stumbled upon this forum and additional people are joining in the conversation, each with the same issue, I have sent a request for assistance to MP Global, the distribution company for Quietwarmth, Ditra and others. I included a link to this page in my message. I will advise here, when and what if they respond.
 
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Old 12-15-21, 12:24 PM
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The part that makes this so confusing is that a ground fault is a fault between hot and ground or neutral and ground. I can see this happening on a masonry floor. I can't see a fault happening on a wood floor. It's hard to blame the product because even if it was defective..... how is it getting a fault to ground ? Putting the product in a pail of water wouldn't cause a ground fault if the water wasn't grounded. A short in the product would not cause a ground fault either.

Question.... you aren't using a GFI breaker or receptacle to protect the mats....are you ?
The GFI in the thermostat should be the only protection inline.

Does the wiring down to the mats have a ground wire or shield in it ?
 
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Old 12-15-21, 03:31 PM
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Pjmax, the only GFCI in the circuit is in the thermostat. The breaker in the panel is neither GFCI nor AFCI.

The cold leads to the mats do not include a ground in any form. Neither a third wire, nor a braided shield.

I believe that given 5 different installers encountering this anomaly where one or any combination of two or three mats work but adding a forth causes the Ground Fault notice, that it is increasingly less likely an installer issue. I've been doing construction management for 40 years and I understand that 99 44/100 % of issues of this sort are installer issues. I am growing to believe that some condition in common with these installations, not a ground fault, is causing the electronics to interpret the condition as a ground fault.

I am still waiting for a reply from MP Global but am anticipating that the issue lies within the components and not a matter of installers not following directions or poor workmanship.

I am wondering if the use of a power module and splitting up the number of mats between the thermostat and the power module would circumvent the issue. My installation is not supposed to need one as the combined draw of the 5 mats is only 9 amps of the 15 allowed on the 20 amp circuit. While I'm not anxious to spend another $125 on a power module nor another 20 amp breaker, run wire and cut in another box, it just might get past all this. That's not to say I don't still want Quietwarmth/MP Global to make good. There just reaches a point when waiting on the manufacturer's customer service becomes unreasonable for the customer.
 
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Old 12-26-21, 05:43 AM
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After having several conversations with a rep, at least in my situation, it appears that each mat is producing a small amount of fault current; and at a certain number of mats, the total fault current exceeds the level on the thermostat, causing it to trip. The standard OJ Microline and OEM thermostats monitor for 5mA of fault current, the solution recommended to me was to split the loads into multiple thermostats or to purchase a thermostat with a higher fault tolerance (I know they produce a 15mA thermostat). At the job that I was having the issues on, I installed an additional thermostat and floor sensor, and it resolved the issue for a while, but recently has started tripping the GFCI again...

That all being said, that was my first (and only) encounter with a film floor heating system, and I've never worked with a floor heating product before that had any sort of fault in the mats that was acceptable.
 
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Old 12-26-21, 01:59 PM
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it appears that each mat is producing a small amount of fault current;
How ?!!?!?!!?

It's called ground fault. There cannot be any ground fault if there is no ground.
You cannot have a ground fault on only two wires. You can have an open or a short.
I'm thinking these GFI type floor control thermostats have an internal fault. A design fault.

It sounds like the ground fault coil is registering mat load. That would be a design fault.
 
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Old 12-26-21, 07:10 PM
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JC Madison, why, if you have purchased and installed components according to their directions, is their solution at your expense? That was actually rhetorical, but did you try to hold them to their warranty?
 
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Old 12-26-21, 11:45 PM
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JCMadison I am not trying to steal your thread but I am in a very similar situation.

I installed a TEC heat mat I my basement bath, the TEC which seems to be Lowe's QuietWarmth and initially I had a problem with the GFCI tripping after install. TEC directed me to but the 15ma GFCI (ADG-4999) instead of the 5ma GFCI (UDG-4999) thermostat and all was good. I was trying to save money and purchased the Class A therm online instead of getting the Class B from Lowe's but apparently the code allows for the system to be sold and is code compliant that way.

Fast forward 8 years and the original thermostat is throwing the ground fault error. Sometimes it will take a week to throw the fault and other times I reset it everyday, but it happily goes back to heating. I assumed an electronic error so I purchased a thermostat off the web and installed it today. It ran for a few hours and now throws the GFCI error on call for heat every time I reset it.

I am with PJmax that there is either a design issue in current drawn and ground resistance not taken into consideration or that they "burn" out after a time, which I doubt. I get a few mega-ohms of resistance when I check either wire to ground so there is some current leak but, really shouldn't register on a GFI circuit.
 
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Old 12-29-21, 04:58 AM
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PMStoddard, the mats that I connected were for a customer and installed by a flooring company, I merely hooked up the circuitry for it. The customer has gone after the installer and manufacturer for compensation but I'm not sure how much success she has had doing it.

PJmax It could be an issue with the T-Stat itself, the OJ Microline and the OEM look absolutely identical and you could have components swapped between them (Either the same design or manufactured by the same company and labeled differently). Maybe swapping the T-Stat out for a different style would resolve the issue. Also, could it be irregularities in the heating filament in the mat cause the issue?
 
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Old 01-10-22, 02:20 PM
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Same issue

Has anyone heard back from mpglobal yet?
 
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Old 02-05-22, 12:17 PM
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Not the thermostat

I purchased and installed a new thermostat albeit also a 5ma GFCI which also trips immediately with 4 mats connected but not 3. I cannot understand where a ground fault comes from. Again, I have a 20 amp dedicated circuit with a non fault-protected breaker and the ground wire of the 12-3 wire terminates at the thermostat box. It simply has to be the Quietwarmth mats. I guess I either go with a 15ma GFCI thermostat, leave one mat disconnected, or tear the Quietwarmth mats out and start over! How about going with a non-gfci thermostat and putting a gfci breaker in the panel?
 
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Old 02-07-22, 05:18 AM
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Possible resolution

Update: I spoke to the company... He seemed to know just what the problem was, leading me to believe this is an ongoing issue. He said it is the thermostat. The 5ma threshold is too sensitive for this application. And he said he was going to send me a 15ma GFCI thermostat that would take care of the issue. Fast forward a week and a thermostat arrived in the mail ... I swapped them out and voila! The same issue... It still trips when more than one mat is connected. Now I was starting to think maybe it is something I may have done.... Anyways I get ahold of the company rep again, and he eventually has me send a picture of the new thermostat to him... And wouldn't you know he says they"accidentally" sent another 5ma. Model. I compared the 2 units myself and cannot figure out what indicates the GFCI sensitivity, it must be in the serial number or something. So now as it stands, I am waiting for another thermostat from the company... I am supposed to return the original thermostat I purchased to him in place of the one he sends me, but I just may return it to the store for a refund of the$100 it cost. He said that we can just swap then out and he'll take the other one back so it doesn't cost anyone anything... But this is costing me money. Time=money and I've now spent many additional hours on this product, using it the exact way they tell me to. Why should it not cost them anything to solve their issue? They should be glad they don't get sued for time and labor of ripping their product back out and putting in one that doesn't have an issue.
 
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Old 02-07-22, 04:59 PM
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Botto2193, Zdc1992: Have you tried reversing the wires on from the panels to the therm? My system doesn't specify hot or neutral and shouldn't matter since it is a resistive load.

Zdc1992: If it is a OJ Microline therm it will likely be an ADG(5ma) or UDG(15ma).

To update my situation: I swapped the wires going to the mat and my original thermostat hasn't tripped since. I have no explanation for why this works other than it seems to be bringing the voltage difference on the phases back into the no-trip zone. Might be something to try instead of buying 3 thermostats like I did...
 
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Old 02-09-22, 07:20 PM
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Update

MP Global finally responded through their social media portal. I was referred to Chase in sales who indicated that he is aware of this thread in the DIY forum. He sent a 15 mA non-programable thermostat (at his expense) and I have swapped it out and reconnected all the mats.
I will leave the installation in this state for the balance of the season to verify that this takes care of the problem and that it doesn't start tripping again.
Once I'm satisfied I will ask Chase for a replacement of the wifi programmable thermostat face, which will interchange with the non-programable face. The GFCI is in the base.
 
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Old 02-09-22, 08:12 PM
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Good news. Thanks for the update and thanks to Chase for his help.
 
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Old 02-12-22, 12:40 AM
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PMStoddard, if they are OJM therms I have 2 extra programmable faces. They might fit. PM me
 
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Old 03-28-22, 04:56 PM
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Same issue

Iím having the same issue. Just installed the quiet warmth 2 mat system with the et-72g thermostat from the manufacturer and it just trips gfci every time.
 
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Old 03-28-22, 07:53 PM
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Welcome to the forums.

There are a lot of ideas and things to try in this thread. It seems to be experimental.
I always start by using a digital meter and checking between the wiring and ground or the wiring and shield if there is one. You should not see any continuity.
 
 

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