Wiring a system with two meters, two transfer switches, and one generator

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I have a customer with one power company feed split at the house to go through two meters: one meter for general household electric, and a second meter for his geothermal system (power provided at a discount rate). He needs a generator to provide backup power for both "systems."

I'm using a 20 kW Generac generator, and two Generac transfer switches.

My question is how to wire the 24V and the 120/240V cables that send the signals to the transfer switch mechanisms in each unit. I'm guessing that to isolate the 240V power between the two systems, I should (a) connect the signal wires between the generator and Transfer Switch #1 normally, (b) connect the 24V signal wires in parallel, but (c) use a 240V relay switch for the N1 and N2 wires between Transfer Switch #1 and Transfer Switch #2. Do I need a relay switch for the Load wire too? Does it matter which transfer switch unit I use to connect the signal wires for load shedding?

Does anyone have experience doing this?
 

ceb58

Senior Member
Location
Raeford, NC
I have a customer with one power company feed split at the house to go through two meters: one meter for general household electric, and a second meter for his geothermal system (power provided at a discount rate). He needs a generator to provide backup power for both "systems."

I'm using a 20 kW Generac generator, and two Generac transfer switches.

My question is how to wire the 24V and the 120/240V cables that send the signals to the transfer switch mechanisms in each unit. I'm guessing that to isolate the 240V power between the two systems, I should (a) connect the signal wires between the generator and Transfer Switch #1 normally, (b) connect the 24V signal wires in parallel, but (c) use a 240V relay switch for the N1 and N2 wires between Transfer Switch #1 and Transfer Switch #2. Do I need a relay switch for the Load wire too? Does it matter which transfer switch unit I use to connect the signal wires for load shedding?

Does anyone have experience doing this?

You can just use N1 N2 ( utility sensing ) and the T1 ( batt charger) to the gen. from your "master" ATS. then bring 0,194 & 23 back to the master and then jump them to the slave ATS. There should be no need to connect N1 N2 & T1 from the slave. You will need to do your shedding from the master.
I hope that both are service rated unless you have a disconnect after the meters and that even with the load shedding the 20 kw can handle the geotherm. unit.
 
Thanks for the information

Thanks for the information

Thanks for the information.

The disconnects are already in place after both meters and before the service feeds to the breaker boxes. I'll put the ATFs between those disconnects and the breaker boxes.

The heat pump and fan will draw a maximum of 27 amps, and the pump for the well requires an additional 9 amps (open loop groundwater system). The backup electrical resistance heat and electric water heater will be shed from the geothermal side, and I'll shed the electric dryer and range on the general household side. The remaining circuits power lights, TV, microwave, dishwasher and computer.
 
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