A simple (I hope!) back-up generator question

[ScottG]

I'll apologize in advance if this has been asked before but my eyes were crossing looking through all of the existing generator-related threads.

I'd like to purchase a small, gas-powered generator and a simple manual transfer switch (like a Reliance, etc.) to power a few essentials during a power outage. However, all of the circuits that I consider essential (120V well pump, furnace blower, septic pump, refrig and microwave) are located in a sub panel about 70 feet distant from my main service panel. Can I hook-up the transfer switch safely to the subpanel circuits? I don't want to create a situation where I'm back-feeding the main.

If it matters, the sub is powered by an 80A breaker via three #4AWG CU with a #8AWG ground. The neutral and ground busses are isolated and the ground bus is bonded to the panel...so it looks like an OK install.

Again if this question is redundant, please point me to the appropriate thread.

Thanks in advance!

 

[pattenp]

There is no issue with the transfer switch switching the circuits in the sub-panel to the gen. Its no different than switching circuits in the main panel to a gen.

 

[Stuart in MN]

This actually makes the job easier, as all the essential circuits are already powered from a separate panel. The transfer switch will connect the subpanel to either the main panel, or to the generator plug.

 

[Jagmandave]

Just remember to open the main breaker on the main panel so you don't try and backfeed the rest of the world!

 

[pattenp]

Just remember to open the main breaker on the main panel so you don't try and backfeed the rest of the world!

That's the purpose of a transfer switch.

 

[aandpdan]

Another option, on your subpanel, is to put in an interlock breaker.

Basically, your subpanel becomes a transfer panel.

IF the panel manufacturer makes one it's a h*ll of a lot cheaper than the aftermarket and it is MUCH cheaper than the Reliance transfer switch you're talking about. I have one on my house, $45. I can select ANY circuit and not worry about the possibility of backfeeding.

 

[ScottG]

Another option, on your subpanel, is to put in an interlock breaker.

Basically, your subpanel becomes a transfer panel.

I don't think an interlock will work as the sub is just a main lug and doesn't have a main breaker to disconnect.

Although, your comment makes me wonder...would a manual transfer switch designed to switch the entire sub panel from main feed to generator feed (such as the Reliance 100A Utility Gen Sw.) be a simpler option than one of the multi-circuit switches?

 

[pattenp]

I don't think an interlock will work as the sub is just a main lug and doesn't have a main breaker to disconnect.

Although, your comment makes me wonder...would a manual transfer switch designed to switch the entire sub panel from main feed to generator feed (such as the Reliance 100A Utility Gen Sw.) be a simpler option than one of the multi-circuit switches?

I'd lean towards that option.

 

[ScottG]

I'd lean towards that option.

To which option are you referring?

 

[pattenp]

To which option are you referring?

You can't read my mind? This..

manual transfer switch designed to switch the entire sub panel from main feed to generator feed (such as the Reliance 100A Utility Gen Sw.)

 

[ScottG]

Thanks, my ESP isn't fine-tuned.

I'll have to see if I have enough room between the sub and the furnace to squeeze in the switch. Does anyone know off the top of their head what the clearance requirements are for a service panel? (or a code reference?) It's pretty tight in there and I'm guessing it's isn't going to work out.

And, yes, I could go to the other side of the panel but I'd be getting into splicing the feeder to make it reach which I'd rather not mess with...

 

[Stuart in MN]

You need a 30" wide clear space in front of the panel, but note that the panel doesn't have to be centered in that space. Also, two panels (or in this case a panel and a transfer switch) can share the same space. This article explains it pretty well: http://ecmweb.com/code-basics/how-much-working-space-enough