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bookert · Oct 24, 2009, 12:56 PM

Here’s my shop and home power configuration.

Power is fed from the grid into a 200 amp box in the shop.
The shop box feeds:
100 amp breaker (heavy gage feed wires out of breaker) feeding 240V to the houses 100 amp panel
30 amp 240V to the water pump
15 amp to a monitor heater to keep the water system from freezing (located in shop)
15 amp for lights in shop.

I need to install a transfer switch in the shop panel and send power to the house panel in addition to the water pump, heater and lights located in the shop. I’ll control the house draw by use of the breakers in the house panel.

What type of transfer switch is required and how would it be wired to split the load and distribution?

Thanks

KISS · Oct 24, 2009, 01:29 PM

If we are dealing with a small generator, then purchase an interlock kit at Generator InterLock Kit for the main panel. This would mechanically interlock the 200 A main breaker with the back fed generator breaker (say double pole 30 A), so they can't be on at the same time.

Then you can use all the breakers to distribute the load. It would require two trips.

House: Turn off main breaker
Garage:
Turn off all loads.
Turn off main
Turn off Gen input
Start generator
Turn off all loads in garage
Turn on Gen breaker

Select loads in both loacation that you want powered.

If you want an automatic transfer switch, then there are different issues to talk about.

bookert · Oct 24, 2009, 01:52 PM

K.I.S.S

Before I really thought it out I was in Lowe's and saw the Reliance 30216 kit 6 circuit 30 amp kit and purchased it. After creating a diagram, I figured I had better ask the experts if this kit could be incorporated (maybe tying some of the transfer switch circuits together to feed the 100 amp circuit to the house and using others to feed the shop). If that is undoable or dangerous then the interlock kit will probably be the way to go. BTW the generator is a Rigid 8k.

Thanks and I'll check out the Generator Interlock kit

KISS · Oct 24, 2009, 02:06 PM

Now, usually 100-125 A breakers are the max available at the panels.

If this generator was connected to an automatic transfer switch then you might do something like load shedding, where, for instance, the AC unit would not be allowed to turn on when the generator is running.

Since, say 40 A * 240 is 9600 W for a typical AC unit, this would exceed your capacity so you don't let it come on.

Stratmando · Oct 24, 2009, 04:26 PM

Much easier if Interlockkit or Transfer switch was at the Main Panel.
If Generator is at the Garage, then
How far and is it possible to run an additional conduit to handle 30, 50 or ever how many Amps you need back at the house, then you would need 2 Interlockkits, 1 at house and 1 at garage.

bookert · Oct 24, 2009, 05:26 PM

Stratman
The shop panel is approx 140ft from the house panel and yes, my plan is to put the generator in the shop near the panel.
There may be room in the existing conduit to the house for the additional wires.
Would the interlock on the house box be required if all unused breakers in the shop are off?

At this point I'm thinking K.I.S.S. 's first suggestion will be the most practical, using a single interlock at the shop panel, backfeeding the generator in through a 30 amp double pole breaker and just manage the load through the breakers in both boxes .

Thanks

KISS · Oct 24, 2009, 06:25 PM

No additional wires are required back to the house.

An interlock kit in the house panel is not even required, because it's fed from the main panel.

It's just that you might have a few 140 foot trips or two in the rain, but it looks as if the garage circuits have to be on anyway.

There are some nuance that I forgot to mention and that the fact that you have two phases of 120, so you may have to reserve one of those for the garage to maximize the house stuff assuming no 240 V loads in the house.

Stratmando · Oct 25, 2009, 08:34 AM

I was thinking an Interlockkit at the house to prevent Backfeeding. Without the additionals wiring for a breaker at house, how can it be done without additional wiring?

KISS · Oct 25, 2009, 08:39 AM

Power is fed from the grid into a 200 amp box in the shop.

Power is fed TO the shop first and the generator input is IN THE SHOP PANEL. Generator input and utility input are in the same panel, therefore only one interlock kit is required. The HOUSE is a sub-panel to the shop.

It's NOT the shop is fed from the house and the generator is fed from the shop.

Stratmando · Oct 25, 2009, 08:50 AM

AH, My Mistake. Just Rarely/Never see House fed from Shop, Usually the other way.
Kiss you are correct, A Kit in the Garage is all that is needed.