As I understand, power surges can damage the AC boards, compressors and fan motors. Looking into hardwired surge protectors I found devices ranging in current, maximum protecting voltage and protection modes, whose prices also range from $20 to $800.

At the same time a 220V computer UPS cost is in the range of $100-400.

What should be considered when choosing a protection method for a 220V AC running off of a 30A breaker?

3 Answers 3


They are intended for different purposes:

Surge protectors are mostly designed to protect against lightning strikes, although more expensive models may include some kind of power conditioning (protecting against smaller surges).

A UPS, (Uninterruptible Power Supply), on the other hand, is designed to provide some amount of power to a computer during a power outage, helping to prevent data loss, etc. These also usually include a surge protector and power conditioning, of various qualities.

Motors, compressors, etc. generally draw a large amount of power on startup, unlike computers, which may cause problems. You probably also do not need your devices to keep running for a short amount of time during a power outage (if you do, a UPS would be the way to go).

Whatever you do choose, make sure that it is rated for the power and voltage being used, and that it is intended to be used in that manner.

As ThreePhaseEel stated above (beat me to it, it seems), a hardwired surge suppressor is probably your best bet.


You'll need a hardwired suppressor

You'd need several units of rackmount UPS in order to run an A/C off of it successfully, and the inverter on that thing is likely not going to be rated for motor starting duty anyway, so I'd just use a hardwired surge suppressor and be done with it.

  • I never intended for the UPS to run the AC for anywhere longer than a few seconds, but UPSs are rated for about 10kV of surge protection, compared to hardwired surge protectors, which are rated for 700-1000V at most. With the cost of labor alone to repair an AC unit in the hundreds of $$, I can get a LOT of UPS power for that much money.
    – ajeh
    Jul 4, 2018 at 17:11

I put in the commonly recommended Eaton whole house surge protector. EatonCHSPTULTRA which I got from HomeDepot. It is connected through a 50-A double pole circuit breaker. It attaches to the side of my exposed panel in an unfinished exposed stud wall in the garage. If the panel is in a finished wall, I think there is a box specially designed to receive it. Some new Eaton Cutler Hammer load centers have a knock-out in the dead front to receive this surge protector.

  • When l initially looked up hardwired surge protectors, my concern was that all of them were rated for up to 1000V maximum, which is nothing when dealing with a lightning strike. Home Depot does not even say for how much this one is rated.
    – ajeh
    Jul 4, 2018 at 17:10
  • @ajeh -- the surge energy in a lightning event manifests itself as current, not voltage... Jul 4, 2018 at 17:58
  • octopart.com/chspt2ultra-eaton-22917203 Whole-House Surge Protectors: Eaton Electrical Supplies Whole House Surge Protector CHSPT2ULTRA Home Depot Surge Protection Device,1 Phase,120/240V Zoro SPD Type 2 CHSP Service Entrance Surge P Farnell Eaton Surge Protection Device Jet.com SURGE PROTECTOR, 108KA, 50A; Series:CHSP; Suppressor Type:-; Outlet Type:-; Voltage Rating:600V; Output Current:50A; Peak Surge Current:108kA; Plug Type:(Not Available) Newark Jul 4, 2018 at 21:38

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