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New garage sub panel or just another circuit

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Dec 23, 2013, 04:16 AM
New garage sub panel or just another circuit
Here is my situation and the two options I am weighing.

Current garage has all of 1 outlet, yes 1. House built in 2000 and in my younger days I didn't think I'd need a garage for anything but parking cars.

Years later I "DIY" because I'm too cheap to pay other people to do stuff I can learn on youtube, ha ha.

Current set up means extension cords and power strips to run multiple tools, not a great set up.

Was thinking about just tapping into the current outlet and running more BUT that outlet and the garage lights are tied into the 1/2 bath on the first floor (not sure why but it is, the garage door openers are tied into the laundry room and the microwave is tied into the dining room, I think they were drunk when they ran the wire).

So I'm thinking two options:

Option 1) Run a new 240V 50AMP breaker out of the main panel to feed a mini subpanel in the garage, running circuits off that panel. Also assuming I could expand in the future, like if I got a big compressor or something (only have 6 gal now so it's not a big deal), I guess can I run a larger compressor or similar and outlets off that 240V sub panel?)

Option 2) just run nomex with 20A breaker to the garage for a separate circuit.

either way was going to run THHN wire with PVC conduit once it's in the garage.
Dec 23, 2013, 07:50 AM
All things considered Option #1 would be my route. By chance is the garage attached? {If not stranded cable rated for wet locations is required when cable pulled in PVC is run underground}.

This message has been edited. Last edited by: CommonwealthSparky,

Popeye only reached for the Spinach can as a last resort...
Dec 23, 2013, 07:51 AM
You can only have one feed.
That's a big pet peeve of mine when I see someone run under sized wiring to a garage like that.
Is this an attached garage? If not your going to need to add two ground rods no closer then 6' apart.
Are the walls still open?
What are you using for heating and cooling out there now or in the future?
There will be very little cost difference between a 50 amp and a 60 amp. or better yet a 100amp. panel.
The way I run mine right or wrong but have never regretted it or had a breaker trip is:
I run the wiring for the garage openers on one circuit.
I run a 15 amp. circuit for lighting using at least 3 outlet boxes per bay in the ceiling and another one over the work bench, that way I can use 4' fluorescent fixtures attached to the ceiling and just plug them in so if one needs to be worked on all the rest still work.
I run 20amp. GFI protected outlets every 6' along the outside walls. Over the work bench area I used doubled up outlets.
I like to add outside outlet on all the outside walls, that way no matter what I'm doing outside there easy to get to.
I run a dedicated line to outlets near the windows to later add a window A/C unit if I need one and another one to where the compressor plugs in.

This message has been edited. Last edited by: joecaption,

Dec 23, 2013, 11:45 AM
I have learned a lot about grounding from ham radio forums. -ALL- grounds must be referenced back to the main panel ground bus with at least a #6 copper wire suitable for the purpose. the common grounding point must be the main panel ground bus.

after an encounter with some computer guys who had vexing issues with equipment burning up, and their electrician who almost got fried like a holiday turkey touching two adjacent metal buildings at the same time, I believe that this ground should be capable of carrying all aggregate current supplied to the buildings. failure to do so led me out in the cold back in my newsman days to film a fire in a paint store back in the 70s when an undersized ground from the annex to the main building ended up carrying just that when wind took down the second power mast.

your local inspector's determination may vary. his is the only opinion that counts in your neck of the woods. can't hurt to ask.

since you're wiring it out, wire out double the size subpanel feed you think you're ever going to need. a 60 amp would suit most home shops. if you're really getting the itch and might have a dust collector and two stand tools going, with lights and heat on, a 100 might be better. you don't have to use it all, you know, but going inside to reset the breaker with wood half-cut or shaped really Hoovers.

sig: if this is a new economy, how come they still want my old-fashioned money?
Dec 23, 2013, 01:19 PM
The garage is attached to the house so no worries there.

The openers and the current outlet are on other circuits, connected to strange combinations within the house, all new circuits will be for the garage only.

Walls are closed up and insulated, no current plans for more heating/cooling, do have a space heater if I'm in there but it's never gotten below 40 even on the coldest nights. But running the 240V panel would give options in the future should I decide to put something in.

Looks like option #1 is the best idea for future planning just in case.

when I run the 240V wire into the garage, should I cover it with pvc as well once it comes into the garage? It will be inside the basement until it comes into the garage, which is on a slab but attached to the house. It will be a short distance to the breaker panel, less than 6 feet. I've read somewhere about heat issues?

The THHN wire is a must for the PVC install? Again, read that running nomex inside conduit is not a good idea.
Dec 23, 2013, 04:21 PM
Good to hear about the cable path.
So the stranded cable you have chosen {THHN dry locations only} is correct for your work. Cable must be protected at all times. So the entire run of THHN must be protected by say PVC.
Properly sized PVC will allow for the conductors to cool if that is a concern, and it should be to some degree. But not as critical as believed. Say you are install 1" PVC you can tug 5 cables of #6 copper which is allowed 50 amps {actually 55, methinks}. PS,Grounding cable generally is one size smaller that current carrying cables, but we can work on that later.
1 1/4" PVC allows an awesome 9 {#6 copper} cables, by the way...Post exactly what your pull will be and we can work up the numbers. {Think about it as the different sized PVC is the least costly material needed}.

The other posters mentioned about 100 amp sub, but that would be based on your current needs and any possible future upgrades. Hard to make that call, but remember that all types of up grades are needed for a 100 amp sub. The 100 amp breaker, PVC & PVC connector sizing, straps, the THHN cable, the sub panel box itself. Weighting the price of the difference of the two set ups and your needs can be vexing in itself.

As long as you pull a separate neutral and ground cable then ground rods are NOT needed. Equipment grounding bar must be bonded to the subpanel enclosure, but the bonding jumper to neutral bar must NOT be installed. This is the allowable NEC setup to safely protect your circuits. Got all that? If not ask exact what is cloudy, no biggie.

Romex can legally be tugged in PVC as long as all sizing rules are observed, but rarely ever is. But it can be done.
Throw all the questions to the board and all will help. Big Grin
One addendum: What I have posted works fine for inspectors where I live, but it is paramount to run your plans by your local inspector, as Jaybee posted. Telling him that CommonwealthSparky told you all is well via the net may not fly very far.

This message has been edited. Last edited by: CommonwealthSparky,

Popeye only reached for the Spinach can as a last resort...
Dec 27, 2013, 09:31 PM
Got some measurements finally.

Sub panel: From the main panel to where the sub panel will be located is about 50' on the nose. I was going to use 6-3 romex (same stuff I used to do my oven gas to electric conversion). It will be run through joists until it gets to the garage from there it will go in about 4 feet of conduit to new sub panel. so I believe I'll have a 50 amp breaker in the main box?

In the garage, from the sub panel, my longest run will be no more than 30 feet (adding in extra run around doors etc...). I plan on initially 4 runs. One on each side for lights and outlets (i.e. single run for lights on each side, single run for outlets on each side). I plan on running 12 gauge THHN through PVC conduit.

Question 1 - should I run 3 wire (black/white/bare) or 4 wires? I guess three since that is what every other outlet is in the house.

Question 2 - I was planning on 1/2 or 3/4 inch, from what I've researched, 1/2 at 12 gauge can run 10 wires, I doubt if I'll need that many as I think the 3/4 I run should be sufficient for life so to speak, so 1/2"?
Dec 28, 2013, 06:35 AM
The breaker in the main shall be a 50 amp size, correct.

Question #1 Tug a black, a white and a green {ground} THHN cable along all paths in the PVC for the various garage devices and fixtures. Correct.

Question #2 Half inch PVC will meet your needs in the garage. The main advantage of three quarter is less friction {in PVC elbows} while pulling the THHN cable, but products are available in the electrical isle if friction is an issue. One example is Ideal Aqua-Gel pulling lubricant. Ideal products are about everywhere. But runs of 30' should present little friction issues.
Good lock on your project.

This message has been edited. Last edited by: CommonwealthSparky,

Popeye only reached for the Spinach can as a last resort...
Dec 28, 2013, 11:51 AM
Cool, thanks.

the panel I'm looking at has a "main breaker" in the sub panel, that should be the same 50 amp as in the main box?
Dec 29, 2013, 07:35 AM
Correct on that size. Note: Could be but a sub panel can be purchased without a main breaker installed. This set up is NEC allowable as long as the feed is protected by that 50 amp breaker that supplies the sup panel.
One drawback without a sub panel main breaker is you will have less protection while landing circuits on the sub. Unless you hike back to the main and de energize the sub by switching the 50 amp breaker supplying the sub panel off.
The advantage of a sub minus the main breaker is a less expensive purchase.

This message has been edited. Last edited by: CommonwealthSparky,

Popeye only reached for the Spinach can as a last resort...
Jan 22, 2014, 12:16 PM
The sub panel will have a breaker.

Trying to piece together funds after some automobile state inspection repairs, PA sucks.

New question is running conduit with romex? I know it can be done but should it?

I had planned on 12 guauge THHN and conduit for the new garage receptacles and lighting.

I found a guy who has a couple hundred feet of 12/3 romex for about 1/3 of what it is at retail (I think a contractor going out of business).

So would the romex be OK with that application?

This message has been edited. Last edited by: NuclearSeal,
Jan 22, 2014, 12:59 PM
harder to pull, but legal. provided the internal wire insulation is of the minimum type required for the conditions the conduit is run in.

sig: if this is a new economy, how come they still want my old-fashioned money?
Jan 22, 2014, 08:34 PM
You can strip the sheathing off the Romex and tug like it were say THHN cable. Will be an easier pull for sure. Making sure you have double the white wire to tug. That way the second white you change to the ground, with the help of a green Sharpie that is. Recycle the bare ground present if stripping the sheathing off the Romex, by the way. I would never tug a bare ground in conduit, not even PVC.
As Swschrad posted it is NEC legal. But tugging more than one 12/3 Romex in say 3/4" PVC is a pain for sure. Would have to check its NEC legality as well. Off the top of my head not quite sure of what that amount would be. Not even sure what NEC table to search that type of tug, truth be told.

This message has been edited. Last edited by: CommonwealthSparky,

Popeye only reached for the Spinach can as a last resort...