I found this curious item in my main load center (circuit breaker box), marked "SQUARE D COMPANY / SECONDARY SURGE ARRESTER / J9200-10". It has been there for at least 20 years, attached to the ground/neutral bar and the load side of the main breakers, and dangling free inside the load center. At Schneider's site (apparently bought Square D), "the J9200-10 was a 175Vac to neutral/ground maximum, single-phase arrestor". So I assume it was installed in my panel with the intention of offering whole-house surge protection.
Questions:
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Should I keep it installed ?
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Should I replace it, since it's so old, that is, do surge arrestors "wear out" ?
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Not visible in this image, but it has a round threaded protrusion and locknut, obviously meant to be installed in a 1/2" knockout. Seems like the body of the thing is meant to be on the outside of an enclosure (as opposed to the inside), since loose wires come out the other side. Perhaps it was simply left dangling inside the box due to laziness. Should I install it in a knockout (of the load center) ? I imagine this is a metal-oxide varistor (MOV) and these things dissipate surges as heat, which gives me pause in having it outside any enclosure.
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If I install it in a knockout (with the body outside), the wires will not reach. Is it ok to extend them with soldered THWN and heat-shrink insulation ? I prefer to avoid the clutter of 3 add'l wire nuts. I believe solder is considered satisfactory electrically, but not mechanically; but since the solder joint and both ends of wire are within the same enclosure, I don't think the mechanical thing is of concern.
Here is the backside of it.
Best Answer
They are intended to be mounted outside the box...
You are correct that they are intended to be mounted to a KO (usually on the breaker box), instead of being left inside, all flop-a-dop, as yours was. You can use this unit still, although you will probably want to leave some space around it, as its further lifespan is unknown. (All MOV-based suppressors have a finite life; a MOV that's seen too much will break down under normal mains voltage, which on good suppressors will cause a thermal fuse to blow and take it out of the picture.)
...and not double-tapped either
While you're in there, you'll want to clean up the "double tap" on your main breaker's lugs and move the surge suppressor wiring to its own two-pole breaker of an appropriate ampere rating, or use wirenuts and appropriate-gauge pigtails to add it to an existing 240V circuit of a suitable ampere rating. Note that Siemens breakers (unlike Square-D QO and HOM and Eaton CH) are not rated for two wires under a branch breaker lug, by the way.