SPD at service disconnect vs loadcenter

Status
Not open for further replies.
M

makemenuconfig

Member
Location
Seattle, WA
Occupation
Journeyman
I'm doing a 200A residential service and panel upgrade. The meter is some distance from the panel. I'm using a 200A breaker in an outdoor enclosure to act as the service disconnecting means (2020 NEC), and running the load side to a MLO panel in the mech. room.

I need to use a SPD (also 2020 NEC). I am under the impression that they work better if they are closer to the service. Normally I put them in the main loadcenter because that's generally very close to the service. In this case there's 50' between the two. Also this panel is feeding another two subpanels, so my interpretation of 230.67(B)'s exception would mean I'd need a SPD at each subpanel unless I install one near the service disconnect.

So, my plan is to use a wireway for the load side of the main disconnect and tap the feeder to a 2 space outdoor panel (spa type kind of thing) to act as a disconnect for the SPD. Only the SPD would be attached to the load side of the breaker in this panel. This seemed a little unnecessarily complex. Three questions arose:

1: Does 230.67(B) actually require a SPD at each subpanel, or just the first subpanel?
2: Where will the SPD do more good?
3: Does having this extra outdoor panel make table 310.12 not apply, even though the SPD is a no-load device?
 
1. I agree with your interpretation..."at each next level of distribution" so yes at the sub-panels.
2. In my research... at every level of distribution downstream towards the load. Even a type 3 at the outlet would help.
3. I do not think your approach is warrented or maybe it is not clear to me. There is type a 1 SPD available I believe.

So best protection IMO...Type 1 at the service, Type 2 at each and every next level distribution, and type 3 at the receptacle outlet .
 
3. I do not think your approach is warrented or maybe it is not clear to me. There is type a 1 SPD available I believe.
Click to expand...

My question is about the type 1 SPD at/near the service and physically how to do that. Since the main loadcenter is technically a subpanel of the exterior main breaker enclosure, the only thing I could come up with was to tap the load conductors into a separate 2-space panel outside near the service.
 
Simplest thing might be to use a meter/main that also has loadcenter and subfeed lugs. Then you can either install a breaker just for the SPD or if you have say the AC or something like that originating at that meter/loadcenter it can possibly be doubled up on that breaker.

Probably cost less than a splice box or wireway, the small loadcenter, tap devices, and other necessary fittings and looks nicer as well.
 
makemenuconfig said:
Also this panel is feeding another two subpanels, so my interpretation of 230.67(B)'s exception would mean I'd need a SPD at each subpanel unless I install one near the service disconnect.
Click to expand...
If the service disconnect directly feeds only the indoor MLO panel, and the indoor MLO panel in turn feeds two other panels, then 230.67(B) would require the SPD to be at either the service disconnect, or the indoor MLO panel (under the exception). The two further downstream panels are not in play.

If the service disconnect directly feeds 3 different panels, then all three would need SPDs under the exception.

Cheers,
Wayne
 
Simplest thing might be to use a meter/main that also has loadcenter and subfeed lugs. Then you can either install a breaker just for the SPD or if you have say the AC or something like that originating at that meter/loadcenter it can possibly be doubled up on that breaker.
Click to expand...
They're not very common here, I'd have to ask the POCO if they accept that since it's not in their list of approved meter boxes. Mainly though I'm really trying to use table 310.12 so I can pull 4/0. 250MCM is about double the cost at my supply house at the moment, and I'm sure this arrangement would prevent that.

If the service disconnect directly feeds only the indoor MLO panel, and the indoor MLO panel in turn feeds two other panels, then 230.67(B) would require the SPD to be at either the service disconnect, or the indoor MLO panel (under the exception). The two further downstream panels are not in play.
Click to expand...
Ah, ok. This is the scenario. I misunderstood this. "...at each next level of distribution downstream..." seems ambiguous to me. That's what I'll do.

I was doing some digging. Section 225.42 (which did not make it into 2020 NEC) actually addresses this, noting that SPD should be installed at the distribution equipment containing OCPD's for cases like this where feeders are far away from the service.

1459-NFPA_70-2021.JPG
 
makemenuconfig said:
Ah, ok. This is the scenario. I misunderstood this. "...at each next level of distribution downstream..." seems ambiguous to me. That's what I'll do.
Click to expand...
Yeah, apparently it's ambiguous, but my interpretation obviously seems like the logical one to me. I read it as "at each (of the) next level of distribution downstream".

Cheers, Wayne
 
wwhitney said:
Yeah, apparently it's ambiguous, but my interpretation obviously seems like the logical one to me. I read it as "at each (of the) next level of distribution downstream".

Cheers, Wayne
Click to expand...
Here is where "interpretation" comes into play in the Code.

Because I interpret that it is needed at each next level downstream...which IMO includes sub-panels off of sub-panels, etc

Which coinsides with the highlighted information note above..."surge protection is most effective closest to the branch circuit"
 
shortcircuit2 said:
Because I interpret that it is needed at each next level downstream...which IMO includes sub-panels off of sub-panels, etc
Click to expand...
That idea would be much more simply expressed as "every downstream," there'd be no reason to bring levels into it. "Each next level downstream" is a pretty awkward construction, and I think much closer to "each of the next level downstream" than it is to "every downstream."

Cheers, Wayne
 
shortcircuit2 said:
Here is where "interpretation" comes into play in the Code.

Because I interpret that it is needed at each next level downstream...which IMO includes sub-panels off of sub-panels, etc

Which coinsides with the highlighted information note above..."surge protection is most effective closest to the branch circuit"
Click to expand...
How does a requirement in Chapter 230, apply to any equipment installed under 210, 215, and 225?
 
makemenuconfig said:
They're not very common here, I'd have to ask the POCO if they accept that since it's not in their list of approved meter boxes. Mainly though I'm really trying to use table 310.12 so I can pull 4/0. 250MCM is about double the cost at my supply house at the moment, and I'm sure this arrangement would prevent that.
Click to expand...
As long as load calculation is not over 180 amps 4/0 aluminum is still ok to be protected with a 200 amp OCPD. 310.12 where it can be used would happen to let you have 200 amp load calculation though.

Unless you have significant electric heat or instantaneous water heating, many 200 amp dwelling services maybe seldom if ever see more than a hundred amps.
 
Status
Not open for further replies.
Top