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Discussion Starter · #1 ·
Trying to determine a generator transfer setup for a customer. Unless, I don't have enough knowledge of the options available, his current panel setups seem to be a little tricky.

His existing electrical:

400A Meter Base-->Two 200A Exterior Mounted Subpanels, one with AC circuits installed with main going to 200A subpanel in garage, other with Heat and Gas Pack circuits with main going to other 200A subpanel in garage-->Each subpanel in garage with random circuits


I'd like to give him the most options for powering circuits at the 2 subpanels, since I don't know of any transfer switch options at the meter and exterior panels (or that I imagine would be cost effective). So my consideration is this:

30A Generator Power Inlet Exterior Mounted-->10/3 wiring-->Watt Meter Box mounted between the 2 subpanels in garage-->10/3-->Junction box splicing and splitting 10/3 wiring to each panel-->Backfed 30A Breaker installed in each subpanel with Interlock installed.

Has anyone ever done this? Does anyone see any issues with it, either electrically or code related?

My theory is that with this setup, the customer will be able to choose whether to supply power to one or both panels, and be able to select which circuits he would like to power during an outage, while having the Watt Meter installed to allow him to monitor wattage levels on the main 10/3 head back to the generator.

Or if anyone knows of a better setup? With generator transfer setups, I try to give a customer the most power options, therefore I typically use interlock kits. Just not sure how to go about it with two panels, without having to use a transfer panel and moving wiring from both panels into the transfer panel, and then the customer only having 6-10 circuits worth of options anyway.
 

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Trying to determine a generator transfer setup for a customer. Unless, I don't have enough knowledge of the options available, his current panel setups seem to be a little tricky.

His existing electrical:

400A Meter Base-->Two 200A Exterior Mounted Subpanels, one with AC circuits installed with main going to 200A subpanel in garage, other with Heat and Gas Pack circuits with main going to other 200A subpanel in garage-->Each subpanel in garage with random circuits


I'd like to give him the most options for powering circuits at the 2 subpanels, since I don't know of any transfer switch options at the meter and exterior panels (or that I imagine would be cost effective). So my consideration is this:

30A Generator Power Inlet Exterior Mounted-->10/3 wiring-->Watt Meter Box mounted between the 2 subpanels in garage-->10/3-->Junction box splicing and splitting 10/3 wiring to each panel-->Backfed 30A Breaker installed in each subpanel with Interlock installed.

Has anyone ever done this? Does anyone see any issues with it, either electrically or code related?

My theory is that with this setup, the customer will be able to choose whether to supply power to one or both panels, and be able to select which circuits he would like to power during an outage, while having the Watt Meter installed to allow him to monitor wattage levels on the main 10/3 head back to the generator.

Or if anyone knows of a better setup? With generator transfer setups, I try to give a customer the most power options, therefore I typically use interlock kits. Just not sure how to go about it with two panels, without having to use a transfer panel and moving wiring from both panels into the transfer panel, and then the customer only having 6-10 circuits worth of options anyway.
Why not sell him a generator and transfer switch for the whole service?
 

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1) find out what loads the customer wants to run off the genset
2) figure the simplest way to power them, and size the genset (add new subpanel with the loads, run one of the 200a panels and have all the loads in that panel, or do the whole service
 

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Do a 20kw air cooled with two 200a SE rated switches (one on each 200a panel) in conjunction or one 400a SE rated switch and put some load shedding modules in there. This will give them full function of the house since the load sheds kick off the high demand items when needed to allow motor loads to start as needed. Gen, switches, and modules should be under $6k. If not, you need to call me and I can ship to you under that price! Interlocks and reliance / gentran small circuit switches are great for portables. But for a house this size 20kw air cooled is the smallest I would consider.

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Discussion Starter · #5 ·
Guess I should've mentioned that he already has a portable generator for use. An 8kw (10kw peak) with 30A receptacle. Hence why I am looking at best option for him to be able to swap between circuits, since he will only be able to use so many at a time.
 

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How do you feel about putting a double pole double throw safety switch after the meter before the panels? This will take care of the interlock and you would just need a power inlet hooked in with the switch. The customer should still have the option to run the selected circuits. However there wouldnt be a watt meter unless you put one in line as well. It would be a little more expensive but the one flip of the switch from utility to generator makes it worthwhile sometimes.

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Discussion Starter · #7 ·
I have used such transfer switches before (Zonk) and considered this, but I have only done such installations a few times, and on single subpanel installs. The existing service at this customer's home is a 400A Meter Only feeding two 200A Main Breaker Panels (one on each side of the Meter Box). I'm assuming a DPDT transfer switch would still only be able to be used in-line with 1/2 of the service correct? And if that is correct, then it would still require moving of any required circuits in the garage panels to the generator serviced panel, and not allow variation of powered circuits. At that point, I don't think there would be any positive benefit, not to mention much more cost.
 

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They do make a DPDT in 400a. Put double lugs in the new switch and split from there. Its just a matter of preference, this will be higher material cost but I'm sure less in labor.

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Sort of... you will still be feeding the line lugs on the safety switch with whatever kind of wire you are using rated for the 320 or 400 amps, but on the load lugs you will now use a double lug and run one to panel A and one to panel B etc. The split probably happens now in the meter by means of a double lug. You are just pushing that split a little further down the line. Eaton/Cutler Hammer number is a DT225URK, Siemens DTNF225R (although Siemens is usually highest, they actually buy theirs from Eaton!), SqD 92255R... Good luck!
 
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