Service equipment upgrade

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mwm1752

Senior Member
Location
Aspen, Colo
Here I am getting more request to upgrade individual feeders in muti-dwelling units. Some instances are suggesting a service equipment upgrade. In general we are talking 1970's services with a main to a gutter tapping to feed the meter mains of each unit. Since the 70's it appears due to individual unit upgrades, the service conductors are not sized sufficiently to carry the load per 230.23, 230.31, & 230.42 (A).
Here is the conumdrum - my existing service conductors can handle 400 amps and have OCPD as a main disconnect rated at 400 amps which feed to such gutter & taps to some 15 units. The Building management wants to upgrade service equipment to say 800 amp rated main with meterstack assembly and fuse at 400 amps. This of course, open options to each dwelling for feeder replacement/upgrade/ load increase.
Though the existing condition have not cause over current tripping it leaves option for fuse replacement above the current carrying capacity of the service conductors if the fuses eventually start to open due to excess current draw. I keep landing on upgrade service comply with NEC 2014 230.23, 230.31, & 230.42 (A). Does anyone have a clear NEC code path otherwise in this type of situation?
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Why would you bother to upgrade the service conductors and not the service disconnect etc? Maybe I am misunderstanding but if all you are doing is upgrading the service conductors to 800 amps and leaving the 400 amp disconnect then I don't see an issue. If someone puts in larger fuses than that is their issue.

Everywhere we work someone can upsize a breaker for whatever reason and be or not be compliant. We can't help stupid.
 

kwired

Electron manager
Location
NE Nebraska
I'm lost as well. I read you have had individual unit upgrades over the years that maybe have pushed the original service to more then was originally there. Apparently still not over the original 400 amps yet though as no mention of blowing main fuses.

You then mention changing the service to 800 amp equipment with 800 amp supply conductors and 400 amp fuses - Unless I misunderstood something nothing is wrong with that even if someone later installs 800 amp fuses.
 

mwm1752

Senior Member
Location
Aspen, Colo
"The Building management wants to upgrade service equipment to say 800 amp rated main with meterstack assembly and fuse at 400 amps." They want to avoid upgrading the service conductors.
"I keep landing on upgrade service comply with NEC 2014 230.23, 230.31, & 230.42 (A)."I believe if they want to upgrade equipment then conductors should also be upgraded
 

kwired

Electron manager
Location
NE Nebraska
"The Building management wants to upgrade service equipment to say 800 amp rated main with meterstack assembly and fuse at 400 amps." They want to avoid upgrading the service conductors.
"I keep landing on upgrade service comply with NEC 2014 230.23, 230.31, & 230.42 (A)."I believe if they want to upgrade equipment then conductors should also be upgraded

Now you clarified it. That is no different then running 150 amp conductor to a 200 amp disconnect and installing 150 amp fuses in it.

If load calculation is 400 or less there is nothing wrong NEC wise with what they want to do.
 

mwm1752

Senior Member
Location
Aspen, Colo
Now you clarified it. That is no different then running 150 amp conductor to a 200 amp disconnect and installing 150 amp fuses in it.

If load calculation is 400 or less there is nothing wrong NEC wise with what they want to do.

ERGO - if the NEC calculation is greater than 400 the service conductors shall be upgraded
 
I thought when you used fused disconnects for a service you had to rate the wire for the size of the disconnect not the size of the fuse. Example: 200amp disco with 150amp fuses service wire still has to be rated for 200amps. Or is that just my POCO?
 

kwired

Electron manager
Location
NE Nebraska
I thought when you used fused disconnects for a service you had to rate the wire for the size of the disconnect not the size of the fuse. Example: 200amp disco with 150amp fuses service wire still has to be rated for 200amps. Or is that just my POCO?
60 HP 480 volt pump panel applications I have commonly installed - the pump panel is a service disconnecting means, it has a 200 amp fuse holder, we typically install 110 amp fuses and have 3 AWG (service) conductors as final connection to the pump panel.

Same pump panel also is rated for 75 and 100 HP but typically gets 1 AWG and 150 amp fuses for 75 HP and 2/0 AWG 175 amp fuses for 100 HP.

All is code compliant AFAIK, never failed an inspection anyway.
 
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