Down sizing generator breaker

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sjcj

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Currently, I have a Kohler generator that I would like to utilize at a lift station for back up emergency power. It is a 120/240 3 phase 60kw 180 amp generator with a 175 amp breaker. I would like to know if I could safely downsize the breaker to 100 amps at the generator. The reason is cost effectiveness. I have cabling available that would effectively run the 100amp manual transfer without having to run new wiring/sub panel...etc. Cross reference to Kohlers tech support and awaiting their thoughts. But I value the input here.
 
Well if all of this feeder is outside you might be able to use the rules for outside taps of unlimited length and never change the breaker at the generator.

Another route would be to install a 100 amp fusable disconnect right at the generator.

Changing the breaker on the generator itself might become a listing issue unless you get the new breaker from the generator maker.
 
sjcj said:
Currently, I have a Kohler generator that I would like to utilize at a lift station for back up emergency power. It is a 120/240 3 phase 60kw 180 amp generator with a 175 amp breaker. I would like to know if I could safely downsize the breaker to 100 amps at the generator. The reason is cost effectiveness. I have cabling available that would effectively run the 100amp manual transfer without having to run new wiring/sub panel...etc. Cross reference to Kohlers tech support and awaiting their thoughts. But I value the input here.
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If I were Kohler support I would be somewhat intregued at your request. If I were to understand your concern correctly I would as what is the issue?
It is somewhat difficult to address your question. Should it be assumed that the generator is way oversized for the load to be served ?
Think of the generator as if it were a utility. A utility has a tremendous capability of delivering power and yet we size a service and conductors to serve the load.
So what if a generator is oversized. I'm sure that so have sized you conductors to serve you load and then protected the conductors with the suggested 100a breaker Other that the generator being needlessly oversized and more expensive that a generator sized to serve you load I do not see an issuer.
 
If he has a 100 amp transfer switch can he even hook the 175 amp breaker to it? I wouldn't think so.
 
iwire said:
If you change it to a disconnect switch would you feel that way?
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Fused or unfused? If it was fused at 100 amps I would have no problem with it.
And what is behind the ATS another 100 amp panel or something smaller than 100 or larger than 100.
 
qcroanoke said:
If he has a 100 amp transfer switch can he even hook the 175 amp breaker to it? I wouldn't think so.
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You have to be more specific as you have now changed the question from being a 100at breaker to a TS.
Then the question is, you appear to be assumng a contactor type TS or should it be more appropriately a breaker type TS with TM breakers?
If it is as 100a TS with 100at breakers thern it is a none issue.
 
templdl said:
You have to be more specific as you have now changed the question from being a 100at breaker to a TS.
Then the question is, you appear to be assumng a contactor type TS or should it be more appropriately a breaker type TS with TM breakers?
If it is as 100a TS with 100at breakers thern it is a none issue.
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The OP specifically states a 100 amp manual transfer switch. The generator output breaker is 175 amps.
You seem to be the one assuming.
 
qcroanoke said:
The OP specifically states a 100 amp manual transfer switch. The generator output breaker is 175 amps.
You seem to be the one assuming.
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My response was directed toward " I would like to know if I could safely downsize the breaker to 100 amps at the generator.."
I guess that is fairly specific. Then why the following post regarding a TS if a100at breaker has been provided to feed it?
I am somewhat intregued as to where this discussion is going.100at breaker being feed by a genset feeding an 100TS. Since it wasn't specified what type a TSwas being proposed a breaker type 100a TS with100at TM breakers would be a good solutiiom.
 
templdl said:
My response was directed toward " I would like to know if I could safely downsize the breaker to 100 amps at the generator.."
I guess that is fairly specific. Then why the following post regarding a TS if a100at breaker has been provided to feed it?
I am somewhat intregued as to where this discussion is going.100at breaker being feed by a genset feeding an 100TS. Since it wasn't specified what type a TSwas being proposed a breaker type 100a TS with100at TM breakers would be a good solutiiom.
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You quoted me. Not the OP. So, no. You were not fairly specific.
He wanted to know if he could downsize to 100 amp breaker in the generator. Iwire pointed out he could use a 100 amp fused disconnect right at the generator and be fine.
And that would leave out the UL listing being voided by changing the factory installed breaker.
 
qcroanoke said:
You quoted me. Not the OP. So, no. You were not fairly specific.
He wanted to know if he could downsize to 100 amp breaker in the generator. Iwire pointed out he could use a 100 amp fused disconnect right at the generator and be fine.
And that would leave out the UL listing being voided by changing the factory installed breaker.
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This is the problem with multiple replies to an OP that could have been responded too with a singe post. It ends up to be a who is on first thing trying to make sense out out the string. When I looked at the OP I thought it would be an elementary issue. 175a output genset, simply using a 100at breaker feeding a 100a TS even if though the genset is capable of putting out 175a.
I may have missed the reason as to why that would be that complicated.
 
qcroanoke said:
Fused or unfused?
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As far as I know and I am willing to be shown otherwise switches do not have to be protected at their rating only used within their ratings.

The same as using a 15 amp snap switch on a 20 amp circuit.


templdl said:
This is the problem with multiple replies to an OP that could have been responded too with a singe post. It ends up to be a who is on first thing trying to make sense out out the string.
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Here is a thought, if you are not happy with the way a question is asked just ignore it and move on instead of always complaining the questions are not worded to your liking.
 
templdl said:
This is the problem with multiple replies to an OP that could have been responded too with a singe post. It ends up to be a who is on first thing trying to make sense out out the string. When I looked at the OP I thought it would be an elementary issue. 175a output genset, simply using a 100at breaker feeding a 100a TS even if though the genset is capable of putting out 175a.
I may have missed the reason as to why that would be that complicated.
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I'm sorry. I guess Iwire and I should have waited for you to answer the question.
 
iwire said:
As far as I know and I am willing to be shown otherwise switches do not have to be protected at their rating only used within their ratings.

The same as using a 15 amp snap switch on a 20 amp circuit.
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Ok, so you're saying it's ok to protect a 100 amp MTS with a 175 amp breaker as long as the load is less than the rating of the switch?
Please show me where that is in the NEC. If it's ok I need to know because we as a company will not do that. I understand the 15 amp switch on a 20 amp circuit.
What if there is a larger than 100 amp breaker behind the MTS?
 
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