Portable Generator - Manual Transfer Switch and Capacity

Old 08-20-14, 04:03 PM
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Portable Generator - Manual Transfer Switch and Capacity


The plan is to buy a 8kW Generac portable generator, to feed a Generac manual transfer switch (10-16 circuits, 30A).

The manual transfer switch is fed from the main panel via a 60A feed. The generator puts out 8kW through a 30A outlet and appropriate wiring to the transfer switch.

I want to back up the following circuits:

1. 2 Air handlers, 240x15A each. These are only used for AC, not heat. BUT, the 24VAC source that powers my Honeywell thermostats comes from these air handlers. The same thermostats also run the oil burner. That said, in winter, with power outage, the air handlers will need power to power the thermostats so that the heat will work. I know, inefficient but the total draw would be next to nothing on these two circuits in a back up mode. Only used for heat, not for AC in a power outage.

2. Well Pump. 240x20A

3. Fridge - 120x20A

4. Oil Boiler - 120x15A

5. Outlets to Family Room - 120x15A

6. Lights to Family Room - 120x15A

7. Lights to Bathroom - 120x15A

8 Heat Pump Water Heater - 240x30A Only uses about 0.7kW in heat pump mode. We only use the heat pump mode, and never the resistive elements...

So, if we add all the above, it is clearly over the 60A feed to the switch panel from the service. I can live without the water heater being powered by generator (though it would be nice), but would like to have the other circuits powered.

That said, will this work? The reality is that all these device are unlikely to be on at the same time, and hence shouldn't break the 60A feed under normal day to day conditions, as they draw nowhere near the peak current of the individual branch circuits.



Old 08-20-14, 06:56 PM
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It's looking like to much load on this disconnect panel. True.... you won't use the A/C air handlers when in genny mode but how about when in normal power ?

Your normal loads on that transfer panel could be over 60A.

Your well pump may require a lightly loaded panel to be able to start. That means you may have to shut off some loads when the pump needs to start. It needs a lot more power to start than run.

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