PDA

View Full Version : For the RJ Electrical-mos... Garage wiring issues



cmcolfax
09-02-2008, 10:29 PM
The background:

My garage has power to it, but it all seems to be home-brewed and sketchy.

So this afternoon, during a bout of home improvement project ADD, I started pulling covers trying to figure out how everything was wired. (I was supposed to be putting up pegboard.)

What I found scared me.

Like a very old, small two-fuse box with a disconnect switch running to a standard single pole switch, to another box, to a switch, with multiple colors of single lead (not romex-type) wire wire nutted and taped together, etc etc etc. Even a 14GA orange extension cord with the male plug cut off attached to the load points inside the box.

So I decided that the best course of action would be to simply run new wire and then pull all the sketchy stuff out.

The main feed for the garage is tapped off the house.

The "fuse box" inside the garage had two screw in type fuses; a 30A and a 20A so I took that to mean there was 50A or 60A service to the building.

On further investigation, I found the breaker panel inside the house has a double-pole 20A labelled "Garage". Now, I am wondering if there is only 40A feeding to the garage.

Either way, according to my basic understanding of construction wiring, there should be enough power being fed to the building to accomodate my needs.

The proposed solution:

I bought a 70A max, 2-space/4-circuit indoor breaker box. Two 30A and two 20A breakers (I'll return whichever two I don't use.) and 250' of 14/2 + ground romex-type wire.

I plan to run one switched circuit for 3 or 4 flourescent light fixtures hung from the ceiling joists.

One circuit for 2 or 4 duplex outlets along one wall.

Another switched circuit for 2 floodlights on the outside of the building.

I did not plan to run anything on the fourth circuit since I am concerned about the actual amount of power available.

I am not planning on big power draws. The most I can think of at any one time would be a cordless tool battery charger, a scanner, some iPod speakers, maybe a drill or a grinder or a sawzall and a drop light.

If I am going to run my table saw, mitre saw or compressor I can run them via an extension cord from the house.

The questions:

Does all of that seem "do-able"? Because I now have NO power out there thanks to my curiosity. I used to have one working flourescent light and two working outlets. Heh.

And I don't have the time/money/inclination to deal with running a new feed, etc...

Thanks guys!

-cmc-

cmcolfax
09-02-2008, 11:50 PM
Reply from another board:


If that 250' of 14/2 you bought was to wire everything then you bought the wrong breakers. You need 15 amp for that wire rating. I would suggest you return the 14/2 and buy 12/2 and continue as planned. Your double pole 20amp feed is (2) 120 volt lines. You should have a "main breaker" installed in your new sub panel so you can disconnect the garage power if needed. Verify the size of wire feeding your garage and wire accordingly unless you want to replace that feed which you said you didn't. You can always "over wire" meaning run 12/2 and only use a 15 amp breaker, but you cannot run a 30 amp breaker on 14/2 wire etc.

And my next questions:


Thanks Tim.

Yes, the 14/2 was to wire everything.

And of course I should have bought 12/2. Because the 14/2 was on sale ($48 for 250'!). Heh.

If I understand you correctly, the double-pole 20A is two 120V lines each with a 20A rating so I only have 40A of service available in the garage.

And I should add a separate "Main Disconnect Breaker" inline between where the feed enters the building and the new sub-panel.

As for the size of the wire... heh... it's old... so I will have to guestimate... and there is not a lot of it to work with so I will have to patch in new wire between the new garage main and the new garage sub-panel.

OK.

I understand "over wiring", so the question becomes:

If I use the 14/2 wire and 15A breakers will I still have power enough for my estimated usage while still leaving a "margin for error" since there is 40A being deliverd to the building?

Or am I simply better off getting the 12/2 wire with 20A breakers and using all of the available power?

Thanks again!

-cmc-

Ace4wd
09-03-2008, 07:01 AM
http://www.garagejournal.com/forum/index.php