Random Trips when HVAC kicks on

[Baxter83]

I'm new to the site, so thanks for any help, and maybe I can pitch in here and there as well.

I'm in a dilemma. I've never had this happen before, but I just did a new construction and used a 200A Square D Homeline with plug in neutrals. For all of the 20A circuits I just used dual function AFCI/GFCI breakers. When the hvac kicks on it trips 1-5 random breakers, and 1-5 more every time it cycles. If all are reset at night by morning almost every 20A breaker will have been tripped.

Everything is grounded/bonded correctly, all terminations are tight, no shorts/grounds. I installed a generac backup generator, so the panel with all of the breakers is a subpanel, but I can't for the life of me figure it out. I'm not one to reach out for a lot of help online, but this one's got me stumped.

 

[tom baker]

Welcome to the forum. There is a lot of collective wisdom here, I have seen posts similar to this I am sure we can help out.

 

[synchro]

Have you used a built-in diagnostic test function on the breakers to determine if they tripped because of the AFCI, GFCI, or another reason?

Another suggestion is to disconnect the load hot and neutral conductors from at least some of the breakers and see if they still trip.

 

[Baxter83]

Have you used a built-in diagnostic test function on the breakers to determine if they tripped because of the AFCI, GFCI, or another reason?

Another suggestion is to disconnect the load hot and neutral conductors from at least some of the breakers and see if they still trip.

Good point. I'll have to check. I'm not sure how much detail I can get from the built in function other than the last trip condition, but that might give me some kind of baseline or pattern. Thanks

 

[hbiss]

After that I would temporarily replace some breakers with straight GFCIs and see how they behave. Many new A/C systems utilize VFD drives and GFCIs don't play nice with some VFDs. But I believe the problem there was when the VFD was supplied by a GFCI that kept tripping.

Ok, so lets say you have identified whether it's the AFCI or GFCI function that is causing the breakers to trip. What do you do about it? I can virtually guarantee that it's nothing that you did wrong as far as wiring or installation. The problem is either with the A/C equipment or the breakers, which in your case all of which are brand new. So that leaves you with contacting the manufacturers. Lots of luck with whoever the A/C manufacturer is but you could try. You could probably get Square D to send you new breakers to try also. It's possible that there was a new revision since the ones you got were made.

But get ready for it though, most of these cases don't end well and the only solution is to replace the breakers with regular breakers- which we are not allowed to do.

-Hal

 

[LarryFine]

A noise filter on the HVAC? And at whose cost?

 

[hbiss]

A noise filter on the HVAC? And at whose cost?

Not to mention obtaining and experimenting with various kinds or types to see if it will even work. And also not to mention it's not our job to modify or redesign equipment in an effort to make it work.

-Hal

 

[GFCI GUY]

Assuming you're using Class A gfci breakers? Maybe try elevated trip if possible?

 

[kwired]

Assuming you're using Class A gfci breakers? Maybe try elevated trip if possible?

Class A GFCI is only thing allowed by NEC where GFCI protection is required. Elevated trip in a dwelling - about only thing allowed is snow/ice melting equipment if you have any.

I second the noise filter approach on HVAC equipment that apparently is causing the tripping. About the only thing it can be is noise on the line if the trip is triggered by something on line side of the AFCI/GFCI.

 

[hbiss]

I second the noise filter approach on HVAC equipment that apparently is causing the tripping. About the only thing it can be is noise on the line if the trip is triggered by something on line side of the AFCI/GFCI.

Ahh baloney, noise filter. From where and what? I'm sick of this garbage! I wouldn't want to even get involved unless your time and materials are being charged as an extra. Talk to Square D, replace the breakers. That's all you are responsible for. You did your job. I would put it on the HVAC contractor to handle. Let him talk to the manufacturer. It's his equipment that's causing the problem. Let them send a rep to install noise filters if they will even admit that there is a problem and they will solve it. This is no different than somebody having a vacuum cleaner that trips the breakers. Get a different vacuum cleaner, not my job.

If you want to blame somebody blame the NEC!


-Hal

 

[Hv&Lv]

FWIW we fight this a little bit. I’m glad it’s the HVAC causing it quite honestly and not kicked back to the POCO..
these DFCIs are tested under ideal conditions. No PLC communications which cause noise, newer VFD HVAC units, etc..
its about time the breaker manuf. make sure their components work in the real world of imperfect power.

 

[Baxter83]

Lots of good info! Thanks to all. I'm going back to that site this Saturday to give it one more thorough look. How much would a noise filter cost for the hvac circuits, and where is the best place to get it? I've never had to use one. That is, if that is the route we have to go.

 

[kwired]

Ahh baloney, noise filter. From where and what? I'm sick of this garbage! I wouldn't want to even get involved unless your time and materials are being charged as an extra. Talk to Square D, replace the breakers. That's all you are responsible for. You did your job. I would put it on the HVAC contractor to handle. Let him talk to the manufacturer. It's his equipment that's causing the problem. Let them send a rep to install noise filters if they will even admit that there is a problem and they will solve it. This is no different than somebody having a vacuum cleaner that trips the breakers. Get a different vacuum cleaner, not my job.

If you want to blame somebody blame the NEC!


-Hal

Ok, I guess I wasn't intending to say a noise filter must be installed, my intended point was "noise" from the HVAC equipment is likely the cause for tripping. However OP wants to handle it is up to him. Filtering could be an option, should it be provided by HVAC manufacturer - IDK. Can bet they are not willing to look into it very hard on a typical residential install. One thing possibly gained is if enough people complain they may eventually change design to lessen this problem though. If a common enough problem that they have already addressed it, they might send HVAC tech replacement or add on components. Would likely need to be an item that has been in stock for a while though to have an update available. Lately according to my HVAC friends is they often are waiting for manufacturing of units they want to install.

 

[ptonsparky]

I think most of us would like to know the ’whys’ but we can’t afford to investigate continually at our own expense. Telling that to the customer who sees items we installed ’fail’ repeatedly is a PR nightmare.

 

[kwired]

I think most of us would like to know the ’whys’ but we can’t afford to investigate continually at our own expense. Telling that to the customer who sees items we installed ’fail’ repeatedly is a PR nightmare.

And if it is something caused by HVAC equipment, we have to convince the HVAC installer to get involved - that should be more on him than the EC if it is his equipment with a problem.

Bottom line is the EC's are the ones stuck in the middle on these AFCI problems and only reimbursement we are getting is in whatever markup we have put on the AFCI's we sell for the most part. Average single pole AFCI cost anywhere from 35-55 bucks or so depending on what pricing you may be able to get. Lets assume $45 average. 25% markup (kind of a minimal markup that no one should really go less than) you are making 11.25 extra off each. Say you average 20 AFCI's in a home that gives you $225 extra to use toward troubleshooting. Nothing wrong with the occasional item that gives you troubles, but these things seem to be repeat offenders with issues that are not so easy to find the cause of troubles. Most other troubleshooting I do I am able to find a definite cause and know what needs replaced. These stupid things often comes down to "try another one" and see if that works. I hate throwing parts at something and hoping it works, I want to know what is wrong and fix it so it won't happen again.

I'd rather get it right the first time regardless of what it might cost than to make customer think I am incompetent because I have to come back time and time again for what appears to be the same problem to them. Then on top of that telling them to replace or have an appliance repaired is not what they want to hear, you still become the bad guy. You had at least better be able to tell them and/or the repair guy exactly what is wrong or else you are blowing smoke at them, and they feel you are incompetent - not good for business. Sure you can replace that AFCI with standard breaker and it "works" without all the cost and troubles - now you put your liability at risk because you violated codes even though everyone is happy for now.

 

[Eddie702]

What about disconnecting the HVAC temporally?

I see your in TN. Are they using the AC now or is this a heat pump? Seeing it's winter and assuming this is a heat pump with back up electric strip heaters can you disconnect the compressor and run the strip heat for a few days just to absolutely prove it's the compressor (I am not doubting you or your work) just so you can prove it to the HVAC installer?


This might get you off the hook

 

[Baxter83]

So I went back to this jobsite this past Saturday. Spent 4-5 hours troubleshooting and narrowed it down to a breaker. It has passed final inspections and I can't get support from the hvac company or installer, so I swapped it for a standard 20A single pole. Problem solved...
Now for the fun stuff. This one breaker would trip and cause another one or three around it to trip ONLY when the heat would kick on. I kindof tore into the air handler unit after narrowing it down to that part of the split unit and luckily it was in the garage within sight of the panel. The moment I would flip on the breaker at its local disconnect "pop pop pop" go the 20A breakers. Sometimes one sometimes 3 or 4. They pulled a 2 conductor cable to the handler and I guess that's fine, but the circulating system which I assume is an add-on had a little control xformer that was P120V and S24vac. Well, seeing that they were using ground for their neutral I thought I'd just found the smoking gun, but it wasn't. So then I saw that one of the relays for the strip heaters wasn't connected to power, and a couple other, eh, questionable things, but even after isolating/disconnecting those it would still trip breakers every time power turned on to the unit or after it sat for a while and kicked back on. I'd already moved 20A breakers around to see if they'd trip in another slot, but it still was random, but I had one more that I hadn't moved yet after all that and it happened to halt the issues.

 

[Baxter83]

What about disconnecting the HVAC temporally?

I see your in TN. Are they using the AC now or is this a heat pump? Seeing it's winter and assuming this is a heat pump with back up electric strip heaters can you disconnect the compressor and run the strip heat for a few days just to absolutely prove it's the compressor (I am not doubting you or your work) just so you can prove it to the HVAC installer?


This might get you off the hook

I isolated the strip heaters and the pump. It's the moment that it gets power it looked like it goes through some kind of test cycle because the blower motor starts ramping the fan up slowly then stops, and it pulls in a relay that only had power to the coil and no 240 for the contacts. I'm no hvac guy, so I'm not sure of its purpose. I want to post pictures, but the files are too large, and I currently don't have a 3rd party photo thingy.

 

[kwired]

I isolated the strip heaters and the pump. It's the moment that it gets power it looked like it goes through some kind of test cycle because the blower motor starts ramping the fan up slowly then stops, and it pulls in a relay that only had power to the coil and no 240 for the contacts. I'm no hvac guy, so I'm not sure of its purpose. I want to post pictures, but the files are too large, and I currently don't have a 3rd party photo thingy.

Can you save your photos as lower resolution and then post them?

 

[ptonsparky]

Pictures taken with my Ipad can be edited before uploading. I edit the size of it to just include what I want. Still large, but they fit.