Journeyman HVAC question from Electrician

[Braapdaddy]

Hello friends electrical contractor here working on my personal home

Direct lightning strike to roof peak got thermostat wire in turn took out my

Carrier thermostat totally visible arc flashed

Carrier circuit board in attic unit totaly visible
arc flashed

Circuit board on outdoor unit barley a spot on the board but absolutely took it out ( I noticed this last after replacing the 18-8 and and the attic unit and new t stat )

I am a 27th year electrical contractor and I hooked up more units than I can count but never got into the specific internals other than the main breaker connections and my late father in law was a HVAC/R contractor Carrier authorized installer ...... he and I installed the unit when brand new on the new build

Here is where it went sideways !

I hooked every wire back 100% just like they were on the old circuit board In attic and T stat ....... I double checked everything just to be sure comparing the old photos and the old actual pieces with the old T stat wires left in their original locations as not to get anything mis wired ( I know all my electric wire colors by heart but not thermostat wire colors)

Ok so I turn on the outdoor unit 40 Amp breaker go up in attic ready to turn on the two two pole 60 Amp breakers to the heat strips and control circuits........after the short time delay the heat strips come on to my absolute horror WHITHOUT THE FAN ON !

lucky I was up there full tool setup ready to go because it got so hot scared the wee out of me melted the plastic inner on my very nearest duct and this is only about 10 seconds from double pole 60 breakers being turned on !?!?

So my son who had helped my father in law a few times on the job said we better remove the circuit board on the outdoor unit and look it over since it didn't pull the contactor in at all ........we removed it and sure enough very small flash on back side of board

Manual making the contactor briefly still engages the compressor however I only dud it just long enough to see if it fires off

What happened to allow the strips to come on with no fan ?

Was it the outer board that allowed it to call for heat ?

My new thermostat is ever so slightly different by one wire or so it seems was this the issue

I have a new outer circuit board on the way now

I disconnected every thing to do with the heat circuits for now and only left the 240v going into the large VA transformer witch controls my thermostat and blower motor ....I have full operation of the blower ON/ OFF/AUTO so we can circulate air with a few window units going and that's helping a lot especially for the Cats on the 100 degree heat

Any ideas on what I should replace ??
......possibly the whole heat strip insert or possibly a sequencer on that kit ??

Hopeful on Monday when the new outer circuit board gets here it's plug and play and back to AC forget the heat issue until winter I'm thinking

Thanks in advance to the HVAC wizards on here who may be able to shed some light on my issue

Mike

 

[Lubener]

Lightning damage is too unpredictable. The whole system should have been scrapped out and an insurance claim filed.

 

[CDX825]

I'm assuming the outdoor unit is a heat pump? If so It will be wired to send power to the W on the indoor unit to turn on the heat during a defrost cycle. The blower not coming is an issue for sure. Depending on the wiring in the indoor unit the blower will be either powered by the sequencers in heat mode or the control board will send power to the blower.

 

[SC Maintenance]

Does your fan function at all ever. There is an interlock somewhere that won't let the heat strip come on without the fan on. There might even be a sail switch somewhere for proof of airflow, so it could even be that, not the board.

I would pull the manual if you can find it - it should say exactly how in the installation guide - that would be part of the new install test since its a fire hazard.

 

[DBMaster]

I used to manage heat strip inventory for Lennox. What brand is your system? There was one point at which, in a rush, Lennox chose not to complete full development testing on models that were updated to comply with newly adopted UL guidelines. The result was that some models would not turn off. The "fix" was a sequencer kit. This would have been around the 2013-2015 time frame.

Managing heat strips left me feeling very reluctant to ever get a heat pump system that uses them. I would probably seek a system with gas furnace, or perhaps dual fuel.

 

[Braapdaddy]

Does your fan function at all ever. There is an interlock somewhere that won't let the heat strip come on without the fan on. There might even be a sail switch somewhere for proof of airflow, so it could even be that, not the board.

I would pull the manual if you can find it - it should say exactly how in the installation guide - that would be part of the new install test since its a fire hazard.

Fan functioning as it should with the switch on t stat .....I have it going right now to circulate the air the 2 temporary small window units

I did find a few install manuals for Carrier units online looking over the wiring sequence now

I suspect something on the heat kit insert commands the fan to come on when the heat strips go on ...... and it may have melted the circuit closed when it fried it

The outer circuit board called the " defrost comtrol board " is on the way will be here tomorrow

Thanks for the response

 

[Braapdaddy]

I used to manage heat strip inventory for Lennox. What brand is your system? There was one point at which, in a rush, Lennox chose not to complete full development testing on models that were updated to comply with newly adopted UL guidelines. The result was that some models would not turn off. The "fix" was a sequencer kit. This would have been around the 2013-2015 time frame.

Managing heat strips left me feeling very reluctant to ever get a heat pump system that uses them. I would probably seek a system with gas furnace, or perhaps dual fuel.

It a Carrier 2.5 ton heat pump from 2010
Two 60 Amp heat strip circuits
One 40 Amp circuit to outdoor unit

After tomorrow every circuit board will have been replaced

I have disabled the whole heat strip kit for now to allow me to run the blower fan to circulate the window unit air temporarily

 

[Braapdaddy]

I'm assuming the outdoor unit is a heat pump? If so It will be wired to send power to the W on the indoor unit to turn on the heat during a defrost cycle. The blower not coming is an issue for sure. Depending on the wiring in the indoor unit the blower will be either powered by the sequencers in heat mode or the control board will send power to the blower.

Thank you for the response

I suspect it took a hit and melted a circuit or sequencer closed on that heat strip kit

 

[Braapdaddy]

Lightning damage is too unpredictable. The whole system should have been scrapped out and an insurance claim filed.

$20.000 deductible ......plus I fix everything myself that way there is only one person to blame

Sure wish my father in law was still alive he did the original install with me helping him
When he would ramble on about this stuff I should have listened closer

 

[mk378]

If the house took a direct lightning hit that blew wires out of the wall, I doubt anything electronic or even just electric is any good.

The heat strips should have a limit switch to shut them down no matter what sort of overheat. There is likely a requirement not to use plastic duct close to the unit which was not followed.

 

[Braapdaddy]

Agreed upon further inspection I removed the heat strip kit and did find a section with evidence of damage

When I manually push in my contactor on the outside unit fires up the compressor and gets the line cold after a few seconds that is all I have let it run

I am hopeful when the new circuit board arrives tomorrow it will function normally except of course for the removed heat strip section

As for the plastic ducts I may have overstated caught fire whereas it definitely got extremely hot

Looking into a new unit to match my plenum openings and deminsions now

 

[Fitter30]

Lightning strikes on equipment and all the copper turns bright green including the ends of wire.

 

[Braapdaddy]

Update the inside unit did sustain to much damage to keep spending money on it

Sadly it was a Carrrier Puron 410 setup

I got a new 3 ton system not as high end as my old one and the plenums matched up in every dimension but one and I can make a sheetmetal adapter plate simple

So far I'm into about 300 on trying to fix the old unit

New 3 ton Allied/Concord/ Armstrong indoor and outdoor unit $3.589