Lightning strike killed AC

[AntonLargiader]

We have a Trane system with Honeywell Prestige IAQ stat. Today there was a nearby strike that took out a few things at our house and our neighbor's including our downstairs HVAC. The stat is calling for cool but the IAQ board is power cycling. Green power light, then cool light and a buzzing sound, then all goes dark. A few seconds later it resets. When it buzzes, the power at the terminals from the transformer drops very briefly from about 26VAC to somewhere in the teens, but it's so fast my meter can't lock onto it. There are some micro relays on the board and it could be that the output of one of them is shorted (reversing valve, etc).

Anyone with IAQ experience have an idea what I should check next? I'm going to call a service tech tomorrow but it could be a while before he can get here.

 

[Marctrees]

I seriously hope you can find a truly smart tech for this problem.

Not the average joe that'll just start throwing your $ at it.

I'm sure you'll be present to discern that, you know more than enough to be able to figure if the guy knows his stuff.

Could be multiple damaged components.

Let us know how it goes.

Marc

 

[brewchief]

I would disconnect the Y and O wires leading to the outdoor unit and see if it stays on, this will remove the contactor and reversing valve from the circuit.

It sounds like a short somewhere in the low voltage wiring or components, power can travel through some weird places during a strike.

 

[AntonLargiader]

Thank you Brewchief for jump starting my brain on this. I did what you suggested, and the resets stopped. I also got a fan light which I don't remember having before but I could have spaced out on that. I reconnected the O and it stayed alive. I reconnected the Y and the resets resumed. So, I guess there's a chance it's just a shorted contactor coil which seems like a pretty simple repair to me. Could be other stuff as well, I'm sure, but that looks like a good start.

We also lost our range hood fan control, modem, and apparently the ballast in the upstairs vanity light. So far. Maybe we need to beef up our grounding? We probably have only one rod.

 

[DC73]

Maybe we need to beef up our grounding? We probably have only one rod.

At the very least, you need to inspect your grounding and make sure it's okay. Proper grounding is the first step in preventing damage by lightning.

I had a similar incident happen to me years ago in a house I had built. As it turned out, the ***** electrician connected my copper ground wire to my copper ground rod with an aluminum clamp which was buried beneath the soil. That aluminum clamp had corroded into powder and so I had no ground when the lighting struck nearby.

DC

 

[tab2]

Wow I was talking about this with a coworker today. Our homes were both struck directly at one point and pretty much anything that converted anything to DC or had a control board was fried. 15 years ago that was a lot less things than it is now. We both filed an insurance claim. It killed 1 tv, all the cordless phones, microwave, wall oven, computer that was on etc. so an insurance claim was made. It looks like you might be under the deductible though. Good luck!

 

[Fueler]

I get power surges and the on/off/on thing during severe storms and have gotten bit by them on occasion.
I installed these surge protectors on my mini split units.
Hopefully I will never find out how well they work.....or not.
https://www.amazon.com/dp/B00DGABTRO/?tag=atomicindus08-20

 

[brewchief]

If you disconnect the Y at the outdoor unit you can rule out a shorted wire pretty quick, it could be a contactor or a defrost board, contactor is cheap enough to throw on if you can DIY it, if it doesn't cure it it's not a big deal as it's nice to have a spare on hand anyway.


We had a customer get a bad hit a few years ago, killed practically everything electronic in the house, when all was said and done the well needed to be replaced including the wire feeding it from the house underground, the complete electrical service including the meter can, panel and every single inch of wire in the whole house. They had an electrician there for weeks fishing new wire. Furnace was only a year old but needed control board, thermostat, motors and complete wiring harness, we also found where the voltage had arced from the A/C lineset to the cabinet burning a hole in it, replaced A/C as well. I believe they were out of the house for 6 months or so while repairs were made, IIRC it was $150k total or so.

 

[kj_mustang]

I believe they were out of the house for 6 months or so while repairs were made, IIRC it was $150k total or so.

Wow!

 

[LS6 Tommy]

Once again, I'm on board with brewchief's diagnosis...

Tommy

 

[AntonLargiader]

Writing on the iPad because we still have no internet...

FWIW when I went out to check the contactor I had turned off the control power but not the pull-out. The yellow line from the contactor hit something at the defrost board and I got a huge spark which apparently killed the stat which had seemed to be OK before. Just some background...

So, I explained all of that to the tech and we agreed he would install a new Trane stat and figure out what the underlying problem was. He left with the system running (I'd gone back to work) but later on my wife reported that the stat was blank and there was no cooling. We got the tech back and he dug a bit deeper.

He had found a burned out 24V transformer and replaced it, along with the stat. Now it was dead again. His updated conclusion is that the 1st/2nd stage changeover valve in the compressor is bad and actually sends line voltage (120 or 240) back on the 24V lines when the compressor gets the 2nd cool call. He had tested on 1st but not 2nd on the first visit, and when it kicked to 2nd later on it fried stuff again. He was able to recreate that problem. Something like that is why I got such a big spark when the yellow (should be 24V) grounded out. I explained to him that the control power was off at the time so there should have been no 2nd cool call, which was a hmmm moment, but that is basically where we are. He disabled 2nd cool and everything has been running fine all evening but the system has yet to shut off.

We are thinking there is extensive damage in the outdoor unit at this point, because the defrost board is zapped, the compressor is bad, and we don't know about the heating components yet. Weighing options that involve warranty and homeowners insurance.

The other stuff is easier. CenturyLink is sending a new modem. I need to buy a small ballast or something like that for the bath light. I have to replace a bulb in the upstairs hallway. And I need to see about a replacement control board for the range hood, but that can't cost more than the hood itself.

 

[brewchief]

Lightning strikes and power surges are normally not under warranty, an uncommon issue like this may have the factory looking for any parts back and they can deny all coverage. I would be contacting your insurance company.

Certainly an uncommon problem, it's amazing what can happen with a lightning strike or big power surge.

One of the whole house power surge suppressors that mount at the service panel might have helped, hard to say for sure.

 

[AntonLargiader]

I'm going to push for a OU replacement. I don't think I'll really have to push; the quote is just under $3k for the known repairs (including some warranty that may not happen, and the risk of finding new problems in heating season) and around $4400 for replacement.

I think I like this new Trane stat. When the system was installed three years ago I didn't go with the Trane smart stat because it was ugly, expensive and dumb. I went with the bare-bones one and replaced it last year with a Honeywell Prestige IAQ which I liked, but only the Trane stats can utilize the variable speed blower functionality.

Now there's one that's better on all counts and we have it. The system seems to (and should) dehumidify better because it can slow the blower down more, and that also reduces the sound a bit. It isn't quite as clean-looking as the IAQ, though, and it won't show outside humidity. Also, there is a tiny bit of relay clicking that you won't hear with the IAQ because it has no relays in the head unit.

 

[ctfjr]

. . .

He had found a burned out 24V transformer and replaced it, along with the stat. Now it was dead again. His updated conclusion is that the 1st/2nd stage changeover valve in the compressor is bad and actually sends line voltage (120 or 240) back on the 24V lines when the compressor gets the 2nd cool call. He had tested on 1st but not 2nd on the first visit, and when it kicked to 2nd later on it fried stuff again. He was able to recreate that problem. Something like that is why I got such a big spark when the yellow (should be 24V) grounded out. I explained to him that the control power was off at the time so there should have been no 2nd cool call, which was a hmmm moment, but that is basically where we are. He disabled 2nd cool and everything has been running fine all evening but the system has yet to shut off. . .

fwiw get your insurance company involved right away - at least notify them what happened. About 1-1/2 years ago an excavator pulled out our neutral wire of our service. One of the issues was our oven. We ended up spending over $1900 on just repairing that with all the calls/recalls to the service company. Should have pulled it immediately and replaced it.

 

[AntonLargiader]

I did. Talked to them last week; I'm having the HVAC people back out this week to check out the other system (one foot away from the unit that got fried) and then I'll file the claim.

Oddly enough, the range fan control has mysteriously healed itself which is pretty rare for electronics.

 

[jdieter]

If lighting strikes are frequent in your area a whole house surge suppressor is a good investment as well as quality surge suppressor strips are your electronics and confirm the integrity of your service grounding system and just in case add a second ground rod 8ft from the primary ground rod.