60 amp circuit feeding a 200 amp main breaker

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DSCOTTD

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COCOA
Call me ignorant. I have a contractor that has a generator120v/240v, 3phase, 60 amp output. What he wants is to feed a 200 amp main breaker to only power a few lights while men complete the modular trailers. The panel has (2) 2 pole 60 amp breakers that we could back feed one of them and disconnect all loads except lights and maybe a receptacle. The guy buys a number 1 wire. Won't fit 60 amp and I explained why he can't hook up the way he thought, and that we can only use the 2 pole 60s. He argued and I told him find a different electrician to do it.
 

mopowr steve

Senior Member
Location
NW Ohio
Occupation
Electrical contractor
Why can’t you just hook up to the lugs of the 200 amp breaker? Your already protected by the 60 amp breaker at the generator, or does the generator not have a main output breaker?
 

norcal

Senior Member
If the generator has proper overcurrent protection the only problem would be if the breaker lugs were not rated for the conductor being used, but they do have a wide range allowed conductor sizes most of the time.
 

mopowr steve

Senior Member
Location
NW Ohio
Occupation
Electrical contractor
Never have seen anyone do that way. Only seen back feed a 60 amp breaker. The number 1 he bought was to go to the 200 amp main. He bought the wire based on his own theory.

Nothing wrong with doing it this way, your overcurrent protection is provided by the generators breaker. The 200 amp breaker at the panel is overkill but it only serves as a switch at this point.
I take it this is just a temporary hook-up and not a permanent back-up generator hook-up scenario in which case you would have used that 60 amp breaker and most likely a interlock kit.
 

480sparky

Senior Member
Location
Iowegia
Never have seen anyone do that way. Only seen back feed a 60 amp breaker. The number 1 he bought was to go to the 200 amp main. He bought the wire based on his own theory.

If 1.) the terminals in the breaker will accept the wire [if the wires won't fit, pigtail them onto something that will] and 2.) there's a 60a breaker on the gen-set, then hook it up. Even if it's a 4,000 a breaker in the panel, the wire will be properly protected by the 60.
 

DSCOTTD

Member
Location
COCOA
If 1.) the terminals in the breaker will accept the wire [if the wires won't fit, pigtail them onto something that will] and 2.) there's a 60a breaker on the gen-set, then hook it up. Even if it's a 4,000 a breaker in the panel, the wire will be properly protected by the 60.
I guess I am more worried than need be, would be more comfortable either to main lug only or back feeding the panel through the 2 pole 60's. Yes I understand the 200 being a switch at this point and the generators 60 protecting the wire. But if there happened to be an issue didn't want someone questioning why didn't you go to the 2 pole 60. Had several other electricians say the same thing that they wouldn't do it either.
 

iceworm

Curmudgeon still using printed IEEE Color Books
Location
North of the 65 parallel
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EE (Field - as little design as possible)
... But if there happened to be an issue didn't want someone questioning why didn't you go to the 2 pole 60. ...
Couple of questions:
What can you think of for an issue where the 200A panel main would even come up?
As already posted, the 200A in the panel is fine. However, do you have a backfeed clip for the 60A panel CB?

... ... Had several other electricians say the same thing that they wouldn't do it either.
Be interesting to ask them, "Why do they think that? Any code issue? Any safety issue?
 

ActionDave

Chief Moderator
Staff member
Location
Durango, CO, 10 h 20 min from the winged horses.
Occupation
Licensed Electrician
I guess I am more worried than need be, would be more comfortable either to main lug only or back feeding the panel through the 2 pole 60's. Yes I understand the 200 being a switch at this point and the generators 60 protecting the wire.
I think we all tie ourselves up in knots from time to time when we see something we are not used to seeing, or do something different than the way we were taught.
But if there happened to be an issue didn't want someone questioning why didn't you go to the 2 pole 60. Had several other electricians say the same thing that they wouldn't do it either.
There is no issue to be questioned. Electrically speaking the 200A breaker is no different than a main lug panel or a non fused switch.

One very good reason not to back feed the 60A breaker would be a lack of a breaker tie down in the panel. This would be both a code violation and a safety hazard. Even if there were a tie down I still might feel more comfortable using the 200A breaker since some of those tie down kits are so cheesy.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
As noted, either way is Code compliant but I think I would prefer to feed the 200 amp main simply because if someone needed to urn off power quickly they would tend to turn off the main, if present, before they looked for a back fed 60 even if it were identified.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
As noted, either way is Code compliant but I think I would prefer to feed the 200 amp main simply because if someone needed to urn off power quickly they would tend to turn off the main, if present, before they looked for a back fed 60 even if it were identified.
Plus, nothing else has to be bought.
 

DSCOTTD

Member
Location
COCOA
Couple of questions:
What can you think of for an issue where the 200A panel main would even come up?
As already posted, the 200A in the panel is fine. However, do you have a backfeed clip for the 60A panel CB?


Be interesting to ask them, "Why do they think that? Any code issue? Any safety issue?
it sounds like there issue would be if the 60amp generator breaker did not trip than the 200 amp breaker may allow more scc to flow, potential fire issue. Doesn't sound like code issue.
 

480sparky

Senior Member
Location
Iowegia
I guess I am more worried than need be, would be more comfortable either to main lug only or back feeding the panel through the 2 pole 60's. Yes I understand the 200 being a switch at this point and the generators 60 protecting the wire. But if there happened to be an issue didn't want someone questioning why didn't you go to the 2 pole 60. Had several other electricians say the same thing that they wouldn't do it either.

Why the need for two 60a breakers protecting the circuit? Is this something you always do? When you run your SABC to a resi kitchen, do you run them through two 20a breakers?
 

iceworm

Curmudgeon still using printed IEEE Color Books
Location
North of the 65 parallel
Occupation
EE (Field - as little design as possible)
it sounds like there issue would be if the 60amp generator breaker did not trip than the 200 amp breaker may allow more scc to flow, potential fire issue. Doesn't sound like code issue.

Yes as already said - no code issue.

Yes, it is true that if the OCP malfunctions, there can be an increase in fire danger. Of course that is true for most any case. I'd say they are stretching looking for a reason why they don't like it.
 
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