New SPD Model

[niel]

yes, one can go spd crazy between all wires for added protection. the point you brought up is 100% accurate.

"The situation that the SPD tries to prevent is to keep that current from going through
the sensitive non-ground circuitry on its way back to real ground. "

this is better done to ground rather than through neutral as the surge through the neutral could induce voltage into the other wires as it often is running parallel to them. unfortunately, if the ground lead also parallels the other wires (as mr wiles insists) the same scenario can be made. sometimes you can't win no matter what you try to do, but now you can see my logic in sending it off to that ground rod.

[niel]

in rereading this it occurs to me that many may be misunderstanding what i said. i do for the record fully agree with kento's assessment. my argument was that with the present 2 legged spd only that it should not ground out to the neutral, but rather to the ground rod at that remote location as the neutral could be above ground potential and present a longer path to the actual ground while it could also induce that surge into the other wires. going to the ground rod there at the building will at least put the 2 hots to ground surge wise, but i acknowledge there is still the problem of the neutral being above ground and picking up the same energy the hots picked up and the reason 3 spd legs to ground are needed. yes, neutral does eventually go to ground, but long distance grounds are really a no no when it comes to surges from lightning emp. i recommend kento's 3rd pick to that ground rod at the remote building. that's the proper scenario.

now referring to the separate issue of ground rods if the buildings are close together then go ahead and tie the ground rods together via heavy gauge bare copper wire buried underground, but if spaced apart like typical telephone poles are then it isn't necessary to tie tied then as the ground resistance is then high enough to quell a surge potential or loop between the rods. ideally they should be tied though, but if it's good enough for utilities then it's good enough for us at those distances.

[Kent0]

Any news on the four-wire SPD for three-phase or 120/240 subpanels where the neutral should be protected?

[beechhigby]

 I am looking to quote a 10Kw Enphase 3 phase 120/208 system and want to use your MNSPD
what model and when ready?