standby generator installation

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mark480

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Hello, we have a700kw generator that will provide 480 volts to transfer switch with a ground and neutral at the distribution/ mcc. The transfer switch has a neutral and ground bonded at the same potential.My question is some guys take the neutral and ground and seperate them at the generator and run a ground , neutral & 3 hots to the transfer switch.Some guys tie the neutral from the gen to the ground and run 3 hots 1 neutral. And other run 3 hots 1 neutral 1 ground from gen to transfer switch. The building is 480volt 3 phase 4 wire. when running 3 hots 1 n 1 ground will the main breaker at the generator trip on fault or the main breaker at the load equipement trip.And what is the best RIGHT WAY to connect this generator, i have my own view what is yours thanks
 
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Joethemechanic

Joethemechanic

Senior Member
Location
Hazleton Pa
Occupation
Electro-Mechanical Technician. Industrial machinery
mark480 said:
Hello, we have a700kw generator that will provide 480 volts to transfer switch with a ground and neutral at the distribution/ mcc. The transfer switch has a neutral and ground bonded at the same potential.My question is some guys take the neutral and ground and seperate them at the generator and run a ground , neutral & 3 hots to the transfer switch.Some guys tie the neutral from the gen to the ground and run 3 hots 1 neutral. And other run 3 hots 1 neutral 1 ground from gen to transfer switch. The building is 480volt 3 phase 4 wire. when running 3 hots 1 n 1 ground will the main breaker at the generator trip on fault or the main breaker at the load equipement trip.And what is the best RIGHT WAY to connect this generator, i have my own view what is yours thanks
Click to expand...


So is this a N-G Bond question?

In either transfer switch position, is there ever more than one NG bond?
 
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mark480

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i guess what i am asking is, if the load neutral and ground are together at the transfer switch after the main breaker, does the standby generator neutral and ground have to be together even though indirectly they are in the transfer switch.Will the standby gen breaker that feeds the load trip and protect the load or will the main on load side trip? sorry if i am not explaining this properly
 
Joethemechanic

Joethemechanic

Senior Member
Location
Hazleton Pa
Occupation
Electro-Mechanical Technician. Industrial machinery
If you have a N-G bond on the load side of the transfer switch, you should not have a N-G bond at the Generator.
 
jwelectric

jwelectric

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Location
North Carolina
I am not too sure I understand the questions being asked.
First we must establish that the transfer switch is on the load side of the utility disconnect and the service is bonded there and the neutral is not being switched in the transfer switch. In this case the neutral bond is lifted in the generator.

If the transfer switch is ahead of the service disconnect then it becomes the service disconnect and the bonding will take place in the transfer switch with the conductors going to the building panel being feeders. The transfer switch will be required to be service rated with the ability to open both the utility power and the generator power at the same time and contain overcurrent protection. Again the neutral will go unbonded at the generator.

If the transfer switch is on the load side of the service disconnect and switches the neutral then the neutral will need to be established at the generator and a grounding electrode system established at the generator.

Which one of these applies?
 
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maghazadeh

Senior Member
Location
Campbell CA
jwelectric said:
I am not too sure I understand the questions being asked.
First we must establish that the transfer switch is on the load side of the utility disconnect and the service is bonded there and the neutral is not being switched in the transfer switch. In this case the neutral bond is lifted in the generator.

If the transfer switch is ahead of the service disconnect then it becomes the service disconnect and the bonding will take place in the transfer switch with the conductors going to the building panel being feeders. The transfer switch will be required to be service rated with the ability to open both the utility power and the generator power at the same time and contain overcurrent protection. Again the neutral will go unbonded at the generator.

If the transfer switch is on the load side of the service disconnect and switches the neutral then the neutral will need to be established at the generator and a grounding electrode system established at the generator.

Which one of these applies?
Click to expand...

I think he got 3 pole non-service rated ATS. he also said that there is neutral and ground at the
distribution / MCC without saying if N & G bonded there. As many of us know by now there are many guys that they have problem undrestanding grounded vs. grounding and the relation in between, service equipment vs. non service. and so on...........
Not enough info get posted in order to visualize things he sees and we don't.
 
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maghazadeh

Senior Member
Location
Campbell CA
Joethemechanic said:
If you have a N-G bond on the load side of the transfer switch, you should not have a N-G bond at the Generator.
Click to expand...

I agree with you Joe, But we don't know if he has a sevice rated ATS or not.
All we know he has a 3 pole ATS, then assuming ATS is not service rated then bonding (main bonding jumper) between N & G must be at main disconnect switch. Do you agree?
 
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Pete Hall

Member
Location
Pennsylvania
seprately versus non separately derived

seprately versus non separately derived

if you have a 3-pole switch, you should most likely configure this distribution system as non-separately derived, meaning the n-g bond is made at the normal source feeding the switch only and you can have any kind of neutral (through,overlapping) to this switch, because theres only one NG bond made upstream on the normal side.

If you have a 4-pole switch, you would have a separately derived system in which there would be a NG bond on both the normal and emergency sources to the switch.

If the switch is serving the entire building or infrastructure, it needs to be service entrance rated, meaning it has a neutral link capable of being disconnected, beefier construction, withstand etc....with the assumption that the NG bond is still going to be made upstream in the distribution system at either/or normal or emergency sources depending upon the switch type and separately/nonseparately derived system configuration listed above.
 
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mark480

Member
not sevice rated , neutral and ground at the transfer switch are seperated and at the main before the transfer switch the ground and neutral are together.I feel you would run five wires from gen n/g/three hots to transfer switch, and do not bond neutral and ground together at standby generator.question is will the generator main breaker trip on fault or the main in the mcc trip on fault is all equipement was the same? o bye the way this system is 480/3phase 4 wire thanks mark
 
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mark480

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i just read petes reply and understand it, sorry for not posting a reply, i had hernia surgery. getting old still think a can life those large motors :)
 
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