Breaker Decisions - GFCI?

[glenn bradley]

I'm going through the prep-work for my sub panel. I'll need 4 - 220v (dedicated to machines) and 4 or so 110v breakers ( a couple for lights and some for outlets). It seems it would make sense to have the GFCI function at the breaker as opposed to in the line. If I haven't already made it obvious, I know nothing about this I haven't read in a book.

It may be from my own ignorance but I think I'd sleep better with a master switch for the sub panel that "kills" the shop when I'm done for the day.

Opinions?

[Rob Russell]

Glenn,

For the 220/230/240v circuits, you'd need to have GFI breakers.

For the 110/120v circuits, using a GFI receptacle is probably cheaper, but the breaker is easier to find.

If you want to kill and lock the subpanel, a locking disconnect switch is the easiest way to do that. It would sit between your main panel and the subpanel.

A fancier way to lock the subpanel is to use a contactor (probably a 100 amp) and have a key switch in the control circuit. Put in the key, turn it on and your subpanel is live. Turn off and remove the key and the subpanel is killed. If I were doing that, I'd have 2 subpanels - 1 for lighting only and the other for machinery. That way you can have lights on without energizing the whole panel. Another way to accomplish the lighting is to feed the shop lights from your main panel - that way all that's in your suspanel are the machinery and "tool" outlets.

Rob

[Jim Becker]

The kill switch is an excellent idea. If I were doing over my shop electric again, I would have put in a separate sub-panel strictly for tool circuits to have a "sure kill". I didn't have kids then. I do now.

What Rob said about GFCIs. Oh, and when you use the receptacle type...don't put them in an inaccessible area. I recently "discovered" that I stupidly buried one behind my lumber rack. D'oh! :eek: (a little used circuit, but one that I made available to my contractors...and when I tested it, it took me an hour to get to the GFCI...:o)

[Kent Fitzgerald]

Check your local code to be sure, but you're probably not required to have GFCIs for the dedicated 240V circuits.

For the 120V circuits, I think the best solution is individual GFCI protection at each receptacle. If that would be prohibitively costly, then GFCI breakers are a reasonable choice. Just don't put a lumber rack in front of your subpanel.

Regarding the kill switch, there are probably some circuits that you will want to keep live at all times (lighting, battery chargers, dehumidifier/AC, etc.). Jims idea of two subs is an elegant solution... but if there's live power anywhere in the shop, it diminishes the kid-proofing protection.

[glenn bradley]

Thanks guys. I'll be keeping the lights on the main panel for the reasons stated. The outlets will get GFCI in some form. Sounds like in SoCal, GFCI is not required on the 220 but, I await confirmation from 'those that make the rules'.

Great tip about not putting a GFCI outlet behind the "insert large, heavy or rediculously involved item here" thing. that would be a completely normal thing for me to do.

I am told (by one person so far) not to use the 100 amp main breaker as a kill switch. Apparently switching a breaker frequently causes premature wear and unreliablility(?). Sounds like a seperate DPST switch of the proper size is preferred.

[Dave MacArthur]

Glenn,
I just did this all for my garage shop. Lots of research, almost exact same setup you have.
--I used a sub-panel with a main breaker, 100A. It is fed from a 70 A breaker on the main panel. It can be used as a main switch if desired. I also placed 2 lighting circuits on the main panel, not on the sub, so that I could kill power to the whole shop when I left, for child safety etc...

--The 220 volt circuits do not need GFCI. I am attaching a link to the best synopsis of wiring a garage shop I found, it is just one of about 30 sources I used including the NEC and meeting with my local inspector for about 45 minutes. Read the "exceptions" in the article below.
--Don't use GFCI breakers for your 110! They are ridiculously expensive, and a single receptacle can be wired to protect everything downstream. I placed a GFCI receptacle as the first plug in each 110 v circuit.
--The DPST switch might in fact be advantageous for the reasons you gave. Look at the various costs however... you can get a 100A replacement main for about 35$ at HD if ever needed. The additional switch was much more.

I'm not an electrician, but about 2000 electricians posted to my thread similar to this one, or so it seemed at the time ;) I'll try to find it.

COMMON WIRING METHODS USED CONCERNING WIRING AN ATTACHED GARAGE
http://www.selfhelpandmore.com/homewiringusa/2002/maindwelling/attgarage/index.htm

Ahh, here's my similar thread:
http://www.sawmillcreek.org/showthread.php?p=601780&highlight=wiring#post601780

[Rick Christopherson]

First off, you need to understand that GFI devices are there to protect you as you plug in the tool, not as much while it is operating. Therefore, any outlet that is dedicated to a tool does not need GFCI protection, and this includes both 120 and 240 volt outlets. There are exceptions to this, but they don't apply to your workshop, unless you like to swim up to your tablesaw. You also don't need this for lighting circuits.