Just don't look right

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knot stable

Member
Location
Warren,RI
Residential setting single family home; 4/0 SEU cable to 200A meter socket with 200 main. GEC and grounding electrodes ok(this becomes your service) 4/0 SER cable to 200A MLO panel 42circuit. (factory single lugs removed,double lugs installed on site).From the double lug; another 4/0 SER to the original 42 circuit 200A panel.(with all homes electric heat connected to) Sub cable wired in properly. First panel has 2 ground bars connected with the jumper to each connected. Grounding and ground wires connected to each bar. (Wrong)

What if any is the ruling on doing this, 2-200A panel on one 200A main and the factory lugs removed and doulbles installed. Of coures the grounding and grounds must be seperated.
 

Volta

Senior Member
Location
Columbus, Ohio
Residential setting single family home; 4/0 SEU cable to 200A meter socket with 200 main. GEC and grounding electrodes ok(this becomes your service) 4/0 SER cable to 200A MLO panel 42circuit. (factory single lugs removed,double lugs installed on site).From the double lug; another 4/0 SER to the original 42 circuit 200A panel.(with all homes electric heat connected to) Sub cable wired in properly. First panel has 2 ground bars connected with the jumper to each connected. Grounding and ground wires connected to each bar. (Wrong)

What if any is the ruling on doing this, 2-200A panel on one 200A main and the factory lugs removed and doulbles installed. Of coures the grounding and grounds must be seperated.
Welcome.

You'd have to check the lug replacement with the panel labling, but otherwise:
The first SER should be ok per 310.15(B)(6) as a "main power feeder".

For 2008 code, the second SER would be too small 338.10(B)(4) > 334.80 > 60 deg C = 150 amp max (assuming aluminum).

Though the the 408.36 exceptions refer to "individual protection", the word "individual" was removed from the previous edition's positive text of 408.36. So as long as the OC protective device has "a rating not greater than that of the panelboard", it should be ok to protect multiple panels with one device.

And as you pointed out, separate grounding and grounded terminals at both panels.
 

electricmanscott

Senior Member
Location
Boston, MA
The first SER should be ok per 310.15(B)(6) as a "main power feeder".

For 2008 code, the second SER would be too small 338.10(B)(4) > 334.80 > 60 deg C = 150 amp max (assuming aluminum).

.

I don't think the feeders would be required to be larger than the service conductors.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector
I don't think the feeders would be required to be larger than the service conductors.
trouble-maker :grin:
(much debated situation)

my take would that the feeder "ampacity" would not need to be larger than the service "ampacity". If you had a 2/0 Cu service, does that mean a 2/0 AL feeder would be o.k. ?
If the amppacity of the 4/0 AL outisde is based on 75?, and the interior is based on 60?, same thing.
 
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Volta

Senior Member
Location
Columbus, Ohio
I don't think the feeders would be required to be larger than the service conductors.
Per 215.2(A)(3)?

I agree that the first feeder would comply, don't think the second would be considered "Feeder conductors for individual dwelling units . . .".

The conductor sizes listed in 310.15(B)(6) are for the total load of a dwelling unit, not partial loads.


In my not always humble opinion. :grin:
 

Smart $

Esteemed Member
Location
Ohio
trouble-maker :grin:
(much debated situation)

my take would that the feeder "ampacity" would not need to be larger than the service "ampacity". If you had a 2/0 Cu service, does that mean a 2/0 AL feeder would be o.k. ?
If the amppacity of the 4/0 AL outisde is based on 75?, and the interior is based on 60?, same thing.
double-trouble-maker :grin:
 

Smart $

Esteemed Member
Location
Ohio
Per 215.2(A)(3)?

I agree that the first feeder would comply, don't think the second would be considered "Feeder conductors for individual dwelling units . . .".

The conductor sizes listed in 310.15(B)(6) are for the total load of a dwelling unit, not partial loads.


In my not always humble opinion. :grin:
The double-lugs serve both as a splice and termination connector. The so-called second SER is a continuation of the same main feeder because they are the same size and type for one, not protected over its "debatable" ampacity rating for another.
 
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Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
I got lost on the third sentence. Where are the double lugs install? Which panel... Also all of this depends on the calculated loads. You mention all electric assumingly because you think the load is too great?????
 

Volta

Senior Member
Location
Columbus, Ohio
The double-lugs serve both as a splice and termination connector. The so-called second SER is a continuation of the same main feeder because they are the same size and type for one, not protected over its "debatable" ampacity rating for another.
I can accept that as either a splice and/or a termination. Good point. The continuation of the feeder still doesn't serve "individual dwelling units" 215.2(A)(3), which would have a great enough diversity (whole house) to be accepted under 310.15(B)(6), and seems to be interior feeder wiring 338.10(B)(4)(a).

Rather, it could feed a panel which contains 151 amps of fixed electric space heating equipment, which would exceed the ampacity of 338.10(B)(4)(a) > 334.80 > 60 deg C = 150 amps (assuming aluminum).

Where we can comply with either 215.2(A)(3) or 310.15(B)(6), then ampacity is of no concern as those sections essentially only refer to conductor sizes. I certainly accept that "The feeder conductors to a dwelling unit shall not be required to have an allowable ampacity rating greater than their service-entrance conductors". 310.15(B)(6). But at 150 amps for a 4/0, and not being conductors "to" the dwelling unit, it doesn't seem to work.
 

hurk27

Senior Member
I think I saw a post where Mike Holt got it changed back to the wording of the 2005, but I think this was for the 2011 cycle,

IMO it makes no sence to require any wires to be larger then the SEC's on the load side of the service:-?
 

knot stable

Member
Location
Warren,RI
I know this guy did not calculate the load of the second panel (where the SER AL finaly ends). So does this mean we can put 2 42 circuit panels on a 200A service if the load does not exceed the service rating? Yes the double lug does serve as a splice point BUT the real question here is does the calculated load of the last panel exceed the rating for the service with the first panel tied in with it's loads? I beleive what he should have done is bring the SER into the original panel and sub out with a 100A brkr to a second panel so all the feeders are protected.Also should have caculated the load of the panel with all the electric in it. Then he would have known how much he could feed out of that panel. Does this make any sense to anyone?
 

Smart $

Esteemed Member
Location
Ohio
I can accept that as either a splice and/or a termination. Good point. The continuation of the feeder still doesn't serve "individual dwelling units" 215.2(A)(3)...
I am of the impression the two panels are serving loads in one dwelling unit. They are supplied with one feeder. It makes no difference if there is a break in the feeder and tapped or spliced or otherwise terminated. The current of the feeder sections do not pass through any device between the service disconnecting means and the branch circuit OCPD's.

...which would have a great enough diversity (whole house) to be accepted under 310.15(B)(6)...
Correct.


...and seems to be interior feeder wiring 338.10(B)(4)(a).
I'm on the other side of the fence on this one. It qualifies as a main power feeder, no different than a service conductor. If the service disconnecting means were located in an interior panel, instead of outside, the SEC would also be interior wiring, but it is not subject to 338.10(B)(4)(a). Is there something magical that happens when the disconnect is outside that makes the main power feeder have different characteristics?

The rest of your post is moot from my point of view...
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector
the SEC would also be interior wiring, but it is not subject to 338.10(B)(4)(a). .

it isn't ??? there in lies the disagreement.....

suppose the exterior was SE, but the interior was FEB or TW. How would it be selected..by it's ampacity. The SE ampacity for interior wiring is 60?.
 

hurk27

Senior Member
I agree with Smart, as what is the difference if the main disconnect is out side with 2 breakers one for each panel or inside with a breaker for this sub panel, to me it makes no sense to require a larger wire size than the SEC's serving the whole service. I could see it this was a 200 amp panel serving a 100 amp breaker to a sub panel then one could say 310.15(B)(6) wouldn't apply, but even then I would think it should as this sub panel is serving branch circuits in a dwelling, so why allow a reduction of wire size for just the SEC's and main feeders, and not for the Sub feeders in any dwellings.

I remember back when Bennie would argue that there is no such thing as a sub panel, that all panels are service panels or a extension there of. I sure do miss him:) we used to chat forever in AOL
 

hurk27

Senior Member
I would say that 310.15(B)(6) should be extended to all feeders supplying any panel in a dwelling serving receptacle and lighting branch circuits. sounds like a good proposal to me, it would get rid of this confusion.;)
 

Smart $

Esteemed Member
Location
Ohio
it isn't ??? there in lies the disagreement.....
Not when the SEC qualifies under 310.15(B)(6). The ampere rating is given by size... period.

suppose the exterior was SE, but the interior was FEB or TW. How would it be selected..by it's ampacity. The SE ampacity for interior wiring is 60?.
Perhaps so... but that is because FEB (FEP?) and TW do not qualify as a permissable conductor type under 310.15(B)(6), whereas SE does.
 
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