Another Electrical Question

[legion]

I want to put a subpanel in my garage. Off of the subpanel, I want two circuits.

1) 15 amp circuit for some standard electrical sockets.

2) One 240v circuit to power this air compressor:

[/QUOTE]

Questions:

1) What amperage should I make the breaker in the main panel that leads to the subpanel?

2) What gauge wiring should I use from the breaker in the main panel to the subpanel?

3) What amperage should I make the main breaker in the subpanel? I assume it should be the same as #1.

4) What amperage should I make the breaker for the 240v air compressor circuit?

5) What gauge should I make the wiring from the breaker for the air compressor circuit to the socket for the air compressor?

6) What type of sockect (and pigtail) should I use for the air compressor?

[cabmandone]

Why not just pull a few wires from the main panel into the garage? Two 20A circuits for plugs and one 30A circuit for the compressor. 10/3 w ground for the compressor and 12/2 w ground for the plugs.
For pig tail I'd go hot to the compressor meaning wire from your main panel to the compressor at a J box.

Strike that! You're only 7.5 FLA to at 240V so a 15a 240v circuit should be fine. Must be a small compressor? There are wire sizing calculators for length of run. You just want to make sure your breaker is sized for the wire so you don't have a breaker size greater than the amperage the wire is rated at for the length of run.

[908/930]

Is there a reason you do not want to run this on 110v? How far is the main panel from the one you want to put in? Only one extra circuit, could also consider adding a 120v 20A circuit. Does your main panel have extra space available?

[Cajundaddy]

I like the subpanel idea better.

I'd use 4x #6 wire to the subpanel up to 50' run and a 50A breaker at the main. I'd run #12 wire for the plugs and compressor with 1x 115v 20A breaker and 1x230v 20A breaker. This way you have enough wire to run power tools on your outlets and reserve capacity on your 230v circuit and your panel for the future. Pretty standard stuff.

[look 171]

Couple question before I jump the gun.

How far is the garage from the main panel? You need to be mindful of voltage drop over vast distance between the two panels.

How big is your main panel? 200? If so, a 60 amp sub panel should be more then enough for the garage unless you have one of those monster garages and run all kinds of electrical items from it. Future HVAC plan or already in place?

Normally a #6 wire should do, depending on the distance. If its near 100' then I would suggest a 4 gauge wire

From your sub panel, run #12 for all your 120v plugs. Same wire for your 220 that goes to your compressor. Max draw is only 7.5A

[red-beard]

Questions:

1) What amperage should I make the breaker in the main panel that leads to the subpanel? Minimum 40A, but the standard would be 50A

2) What gauge wiring should I use from the breaker in the main panel to the subpanel?
6 gauge

3) What amperage should I make the main breaker in the subpanel? I assume it should be the same as #1. Yes, 40AMP minimum, but 50A would be more normal. They should match

4) What amperage should I make the breaker for the 240v air compressor circuit? 2.5* the rated amps, rounded to next highest. This will be 20 Amps

5) What gauge should I make the wiring from the breaker for the air compressor circuit to the socket for the air compressor? At 240VAC/20 Amps you will need to run 4 wires, For a motor, 10 gauge would be recommended

6) What type of socket (and pigtail) should I use for the air compressor? There are many. A NEMA L14-20P & L1420R will probably work well

[1990C4S]

Leave the compressor on 220. Put in a 40 or 50 Amp sub-panel.

Do it once, do it right.

[legion]

The spot in the garage where I want to put the subpanel is about 20 feet from the main panel, though the run will be longer.

[cabmandone]

Anyone else think it's weird that LRA isn't listed on that motor? I don't pay much attention anymore but do they not list that?

To what RB wrote, I'd probably put a star next to that 6 gauge wire from the panel to the sub panel simply because I don't think the OP listed the length of wire that will be run from the main to the sub. I'd also add that it depends on whether you're using copper or aluminum strand wire.

Strike that! Just saw OP's last post. 20' of length. 6 gauge would be sufficient. You could go to 4 gauge aluminum which probably won't cost a lot more and put a 50 amp breaker on that.

[DanielDudley]

Originally Posted by red-beard

Questions:

1) What amperage should I make the breaker in the main panel that leads to the subpanel? Minimum 40A, but the standard would be 50A

2) What gauge wiring should I use from the breaker in the main panel to the subpanel?
6 gauge

3) What amperage should I make the main breaker in the subpanel? I assume it should be the same as #1. Yes, 40AMP minimum, but 50A would be more normal. They should match

4) What amperage should I make the breaker for the 240v air compressor circuit? 2.5* the rated amps, rounded to next highest. This will be 20 Amps

5) What gauge should I make the wiring from the breaker for the air compressor circuit to the socket for the air compressor? At 240VAC/20 Amps you will need to run 4 wires, For a motor, 10 gauge would be recommended

6) What type of socket (and pigtail) should I use for the air compressor? There are many. A NEMA L14-20P & L1420R will probably work well

This is very concise. ^^^^ If you run 10 gauge wire for the 240v 20 amp circuit, you can always upgrade to 30 amps later without rewiring. 50 Amps on 6 gauge wire ran my shop for years. You can use Aluminum for the 6 gauge.

[legion]

I went to all four hardware stores in town today: Menard's, Lowe's, Home Depot, and Ace. None stock 50 amp subpanels. I see 50 amp RV panels and hot tub panels, but those aren't really the right things. I really only see 70 amp subpanels like this:

https://www.menards.com/main/electrical/circuit-protection-distribution/main-lugs/square-d-trade-homeline-trade-70-amp-2-space-4-circuit-indoor-residential-main-lugs/hom24l70s/p-1444444040087-c-6438.htm

I assume that if I were to use something like this, I'd have to have a 70-amp breaker in the main panel and it might change the wiring requirements to the subpanel.

[Cajundaddy]

Breaker size is determined by wire size, and wire size is determined by load and run distance. The 70A panel will be fine and you can then outfit it as you wish. With 2 20A circuits in the garage, #6 wire from main to sub and a 50A breaker will be fine. If you wish to have a full 70A capacity in your garage run #4 wire and a 70A breaker. This should help:
https://www.askmediy.com/subpanel-installation/

[look 171]

Originally Posted by legion

I went to all four hardware stores in town today: Menard's, Lowe's, Home Depot, and Ace. None stock 50 amp subpanels. I see 50 amp RV panels and hot tub panels, but those aren't really the right things. I really only see 70 amp subpanels like this:

https://www.menards.com/main/electrical/circuit-protection-distribution/main-lugs/square-d-trade-homeline-trade-70-amp-2-space-4-circuit-indoor-residential-main-lugs/hom24l70s/p-1444444040087-c-6438.htm

I assume that if I were to use something like this, I'd have to have a 70-amp breaker in the main panel and it might change the wiring requirements to the subpanel.

I suggest not to mess around with those and get one with more slots. You never know what you will need later. Pay a few bucks more, but the install is the same.

Look up 60 A (50 if you like) sub panel with 6-8 slots. YOur 220 will take up two slots then the 120 will take up another. That leaves you with only 3 left if there are 6 spaces for the future. Never say never

[legion]

It probably ends up being closer to 24 feet now that I've measured everything.

Something like this?

https://www.menards.com/main/electrical/circuit-protection-distribution/main-lugs/square-d-trade-homeline-trade-100-amp-6-space-12-circuit-indoor-main-lug-load-center/hom612l100s/p-1444444042902-c-6438.htm

I can use a 50 amp breaker and 6 gauge wire to supply it?

[look 171]

Originally Posted by legion

It probably ends up being closer to 24 feet now that I've measured everything.

Something like this?

https://www.menards.com/main/electrical/circuit-protection-distribution/main-lugs/square-d-trade-homeline-trade-100-amp-6-space-12-circuit-indoor-main-lug-load-center/hom612l100s/p-1444444042902-c-6438.htm

I can use a 50 amp breaker and 6 gauge wire to supply it?

I like that, but that puppy is 100 amp sub panel. You have a 200 amp main panel? If so, you must up your wire size going to the sub panel. #3 is required for 100 A

[dad911]

Originally Posted by legion

It probably ends up being closer to 24 feet now that I've measured everything.

Something like this?

https://www.menards.com/main/electrical/circuit-protection-distribution/main-lugs/square-d-trade-homeline-trade-100-amp-6-space-12-circuit-indoor-main-lug-load-center/hom612l100s/p-1444444042902-c-6438.htm

I can use a 50 amp breaker and 6 gauge wire to supply it?

Yes. 100 amp is max for panel. the 50 amp breaker goes in the main panel to feed it.

With a sub panel, you are supposed to run 4 conductors. 2 hot, a neutral, and a ground. The ground bar and neutral bar should be separate in the subpanel, with the ground bar connected to the ground wire from the main panel, and the chassis of the subpanel.



Edit: you need to buy the ground bar for that panel, description said it isn't included.

[dad911]

Originally Posted by look 171

I like that, but that puppy is 100 amp sub panel. You have a 200 amp main panel? If so, you must up your wire size going to the sub panel. #3 is required for 100 A

I don't know if CA has other requirements, but you can put a smaller breaker in the main panel as long as the wire and panel are at least rated for that current.

[look 171]

Originally Posted by dad911

I don't know if CA has other requirements, but you can put a smaller breaker in the main panel as long as the wire and panel are at least rated for that current.

I have done it and have never had issues with inspection. But then again, some of those guys are sleeping on the job.

[legion]

Would this be the correct wire to run? (I know I don't need this much.)

https://www.menards.com/main/electrical/electrical-cords-cord-management/extension-cords/cerrowire-reg-soow-portable-power-cable/283-4204c/p-1444439076381-c-6410.htm

[look 171]

Is it all interior run between the two panels? Even if it is, run it through conduit. Use flex if inside to inside, use rigid if it goes through the exterior. Don't use the ext. cord because it wouldn't past code out here.

Run wires (not Romex or extension cord) in the conduit for much needed or better protection. Like Dad911 said, make sure there is no bond or connection between the grounding and the neutral buzz bar in the sub panel.