Omnistat surge protection

whumphrey

Member
I have lost three omnistat thermostats to electrical surges now. All three times the communications ability was damaged and one will not even power up. These events are usually a lighting strike in the area. AC surrge protectors and gfi outlets have protected other electronic equipment.
I am thinking the surge is coming in via the heat pump control wiring. I also have a leviton whole house surge protector.
Has anyone successfully put surge suppression on heat pump control wiring?
What did you use?

Thanks.
 
Look at your control voltages and find something that clamps just above that. Too high a clamp and you're going to still have issues.
 
You want to buy a M.O.V. (Metal Oxide Varistor) rated at 24V RMS, then connect this across the 24VAC power in the thermostat. (I beleive this is the red and black wires, but I could be wrong.)  This will clamp voltages at the correct levels. The Leviton protector is good, but probably isn't clamping enough.   This is a mini surge protector for your thermostat.  Just make sure you get one rated close to 24V RMS.
Something like the MOV-20D390KCT-ND from DigiKey will work. It will cost you $0.72 plus shipping.
 
I would suggest something other than a MOV. There's a lot of other events that would or could be damaging that they don't really protect or help with.
 
They're good for some applications but they usually have difficulty in suppressing surge events for longer than microseconds and they fail spectacularly....usually smoking or causing a small fire. There's a reason why NFPA has started specifically addressing their usage and failure mechanism.
 
I'd look into breaking the control cable as close as practicable to the heat pump if that's the suspect.
 
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