Transient Voltage Suppressors: Breaker line side or load side?

[mgookin]

I have to admit: it is a little bit confusing. If "overcurrent device" is a circuit breaker [low voltage system] then "the load side of overcurrent device" will be downstream of breaker [Pos.1].
However on medium voltage systems the current transformer could be located at line side of the breaker [Pos.2] I think.View attachment 11884:?

Type I is between your main OCPD and POCO tranny.

 

[Besoeker]

To do their job and stop a surge, MOVs tend to sacrifice themselves in the process. If they are on the line side, how do you replace them? Shut down the feeder in the panelboard?

I would put them behind the main, or better yet, behind their own disconnect. That way if you have to replace them, you do your LO/TO right there.

I agree with that. I don't like the idea of anything connected to the live side of a breaker even if permitted by code.

 

[LMAO]

OK, so I am adding these type II TVSSs (SPDs) in VFD enclosures. They're tapped off main breaker load side and power cables run maybe 10" to TVSS. I am using 10AWG which is less than breaker rating. I am sure I am following NEC tap rule, so I should be OK, right? I am not finding anything in UL about TVSS field wiring (UL 508 or UL 1449)...