Side by side standby generators

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Rawls007

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I have a customer who's house I roughed in and have not built the service yet. She originally wanted to use a Generac automatic transfer switch/standby generator system to operate the whole house and detached garage. The load calculation on the house and garage is around 300 amps.

My original plan was to feed a 400A non-fused main disconnect from the meter can, and then from the disconnect to a 400A ATS. Generac does not sell a service rated 400A ATS, hence the main disconnect. The feeders from the ATS would then enter a trough and be tapped to feed two 150A outdoor breaker panels. I informed the customer that the 16kw generator she had would only be able to carry certain loads such as one A/C unit on cool and her lights and receptacles at one time.

Now she wants to buy another generator so she can carry the load of her 4 car garage/apartment. The garage has it's own a/c unit, water heater, dryer, and washing machine. It has it's own subpanel which will be fed from one of the main service panels.

Can these two generators be connected in parallel to one transfer switch or will each generator need it's own transfer switch fed from the main disconnect?
 
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Rawls007 said:
Can these two generators be connected in parallel to one transfer switch or will each generator need it's own transfer switch fed from the main disconnect?
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No you can not run them in parallel unless controls are in place to synchronize them. I doubt Genrac has such controls available for these units.

Also is there overcurrent protection at the meter can?

You need some ahead of the non-service rated transfer switch.
 
You could simply use a second generator and ATS for the garage/apartment panel. Since this feeder already has a disco, you won't need the second ATS to be service rated.
 
I will ditto Iwire's advice on syncing generators. Hard to do manually, nevermind automaticaly without expensive equipment that would not be compatible with Generac. I would say operating them seperately is your best bet. But for roughly the cost of two 16kw's, you might want to look into say a 30-50kw, with an ASCO transfer to a 'I want it on" panel. Maybe feed the rest of the house and garage on a "I might want it on" panel that would need to be manually switched. With a larger generator you can be more liberal with the loads and diversity. As well as have easier starting on the AC motors with a larger prime to drive them.
 
iwire said:
No you can not run them in parallel unless controls are in place to synchronize them. I doubt Genrac has such controls available for these units.

Also is there overcurrent protection at the meter can?

You need some ahead of the non-service rated transfer switch.
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So the 400A main disconnect should be fused? Also, the neutral to ground bonding would occur at the main disco, right?
 
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