1600 amp switchboard

xguard

Senior Member
Location
Baton Rouge, LA
I have a 1600 amp switchboard that was installed in the 1960's. We're installing an ATS upstream of the switchboard. The existing conductors are parallel (2 per phase) 1000 MCM copper. When we install the ATS I'm planning to replace these conductors.

The utility demand is 272 kw (838 amps, 208 VAC, 3 ph, 0.9 pf(assumed)).

220.87: 838 x 1.25 = 1049 amps. So my existing parallel 1000 MCM are okay load wise but I can't use the next size up breaker so I'm limited to 1000 amps, no good.

These conductors come in under ground through the building foundation in two 5" Conduits.

I'm wondering if I can penetrate the switch board in another location (legally) to bring in a different combination of conduits and conductors. I don't have any paperwork on the switch board. Can I come in the side of the same compartment the conduits currently enter but on one side?

I don't know how many conductors I can land on each of those bus angle pieces (not sure what they are called?). Any idea?

Thank you. (hopefully photo made it through)

1663880647907.jpeg
 
Last edited:

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Are you saying that you want to abandon the 5" conduits and run new ones? What size OCPD is ahead of this?
 

rambojoe

Wireman
Location
phoenix az
Occupation
Wireman
I have a 1600 amp switchboard that was installed in the 1960's. We're installing an ATS upstream of the switchboard. The existing conductors are parallel (2 per phase) 1000 MCM copper. When we install the ATS I'm planning to replace these conductors.

The utility demand is 272 kw (838 amps, 208 VAC, 3 ph, 0.9 pf(assumed)).

220.87: 838 x 1.25 = 1049 amps. So my existing parallel 1000 MCM are okay load wise but I can't use the next size up breaker so I'm limited to 1000 amps, no good.

These conductors come in under ground through the building foundation in two 5" Conduits.

I'm wondering if I can penetrate the switch board in another location (legally) to bring in a different combination of conduits and conductors. I don't have any paperwork on the switch board. Can I come in the side of the same compartment the conduits currently enter but on one side?

I don't know how many conductors I can land on each of those bus angle pieces (not sure what they are called?). Any idea?

Thank you. (hopefully photo made it through)

View attachment 2562210
Will ya look at that? Still conducting and looks great... And just one simple piece of tape per. Beautiful. Those busses must be huge to make them look like 500's...
Let me also say, they better be big busses....
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired) DINOSAUR
IMO, you can bring new conduits in keeping 312.6 in mind (deflection)

(There might be other options dependent on the size of your ATS OCP as mentiiond in in Post #2)
 
What size OCPD is ahead of this?
Yeah we need to know this, impossible to answer without.

As to the specific question, I would have no issue with stacking a lug on each side of the bus bar. If those aren't nema hole centers, you can just use one mounting hole lug or they do even make ones that are do not have holes and are field drilled. Check out the burndy compression lug catalog.
 

xguard

Senior Member
Location
Baton Rouge, LA
Are you saying that you want to abandon the 5" conduits and run new ones? What size OCPD is ahead of this?
Yea I was thinking to abandon the 5" conduits. I would need 1500 kcmil conductors. For 4-1500 kcmil and one 3/0 ground I would need six inch conduit. There's not an OCPD ahead of it right now, looking at 1200 amp ocpd though based off the 1049 amps from 220.87.

That said I haven't seen much on any websites of and for 1500 kcmil conductors, I just see it listed in the code book, so maybe it's not a practical choice and some other combination would be better.
 
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infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
I would need 1500 kcmil conductors. For 4-1500 kcmil and one 3/0 ground I would need six inch conduit. There's not an OCPD ahead of it right now, looking at 1200 amp ocpd though based off the 1049 amps from 220.87.

There are much better ways to do this with parallel conductors. If you can reuse the 5" raceways EF has a good suggestion. I'm sure that he ran the derating numbers.
 

xguard

Senior Member
Location
Baton Rouge, LA
Why not just keep the two 5" conduits and run two sets of 400kcmil in each?
My only hesitation with that was I didn't know for certain if I could terminate multiple conductors on each bar. It sounds like I can based on the responses here. I'm assuming you aren't counting the neutral as a CCC for the ampacity adjustment?
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Yea I was thinking to abandon the 5" conduits. I would need 1500 kcmil conductors. For 4-1500 kcmil and one 3/0 ground I would need six inch conduit. There's not an OCPD ahead of it right now, looking at 1200 amp ocpd though based off the 1049 amps from 220.87.

That said I haven't seen much on any websites of and for 1500 kcmil conductors, I just see it listed in the code book, so maybe it's not a practical choice and some other combination would be better.
If there is no upstream OCPD, that will require a 750 kcmil supply side bonding jumper.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
My only hesitation with that was I didn't know for certain if I could terminate multiple conductors on each bar. It sounds like I can based on the responses here. I'm assuming you aren't counting the neutral as a CCC for the ampacity adjustment?
There would be no issue installing lugs on both sides of the bus, giving you four termination points for each phase. You could also use offset lugs that permit "stacking" and have even more than four termination points per phase.
 

rambojoe

Wireman
Location
phoenix az
Occupation
Wireman
There would be no issue installing lugs on both sides of the bus, giving you four termination points for each phase. You could also use offset lugs that permit "stacking" and have even more than four termination points per phase.
As it is, the busses and terms already look modified. The mushroom head bolts look a bit grade 3 too. Use bellevue (?) washers and grade 8, lugs front and back is the normal setup...
With that size conductors its very easy to destroy the gear during the pull...beware.are you trying to keep shut down to a minimum?
With that size wire and the cost involved, i would suggest disassembling as much of the gear as possible.
 
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