Objectionable and multiple Generators

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I recently completed a design for a fire station. In that design I had an emergency panel fed from a generator. I used an automatic 3-pole transfer switch and bonded the system as a non-separately derived system(solidly connected neutrals, no bonding jumper or electrode at the generator). The client has now requested I make provisions so a portable generator can be brought in and back up the entire electrical system in addition to the on site generator. My initial reaction is to provide a manual 3-pole transfer switch and bond the system as a non-separately dervied system. Doing this leaves the neutrals of the 2-generator systems solidly connected, the only neutral to ground bonding jumper in the whole system is at the main service. Does any one know if this is an issue? Should I use a 4-pole transfer switch at the on site generator, to isolate the 2 generator systems all together?


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Re: Objectionable and multiple Generators

Will one generator carry the peak demand?

Do you plan to operate these units in parallel simultaneously?

Is the automatic transfer switch on the supply side of the service?

Check with the serving utility about switching the neutral. Some require this activity for protecting lineman during a power outage. A short circuit on the premises wiring can energize the utility MGN.

Customer system is also protected from the same thing occurring on the distribution system.
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