Re: Whole house surge protectors

Ignoramus wrote:

> Is a WHSP something that is much more than
> a (hopefully) beefy MOV in a steel box?

They are typically two beefy MOV's (hot1-to-ground and hot2-to-ground)
or three beefy MOV's (above plus hot1-to-hot2) in a sand-filled metal
box. Most also have a little LED telling you that you're "protected" (I
think this works on a few mA leakage current through the MOV when the
MOV has not yet failed open.)

These are typically installed behind 15 or 20A breakers (at least the
smaller ones designed for say 200A panels).

> 2. Can I, instead of buying a WHSP, just
> buy properly rated MOVs and install them at the
> service panel? (from each power leg to ground,
> I suppose).

You could, but you'd then face the never-ending battle of getting your
local electrical inspector to approve something that isn't UL listed.
MOV's hit with a big surge really do explode into tiny little pieces,
having those pieces flying about inside your panel isn't the most
desirable thing. Sometimes they fail shorted, other times they fail
open.

> Any thoughts?

Putting the protection at the service panel (where presumably you've
got a nice good low-impedance path to ground) is generally a better
idea than installing it far away from ground.

Tim.

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