What Size & Type of Wire?

[Junkman]

I want to put a subpanel into my unattached garage. It is 40' from the panel to the 2" plastic conduit that I buried last fall for this project. I brought the conduit up under the floor, and it rises up the wall about 6'. From there, it goes into the garage. I was thinking that I should use 6/3 romex from the electrical box to the conduit, and make my connection there inside a 4" plastic box. Just not sure what type of wire I will need from there to the subpanel in the garage. I have read enough on these forums about this to know what I will need for ground rods.
The subpanel will power a 5 HP Quincy compressor, lights, outlets along the walls, and eventually a MaxJack. There are also 2 garage door operators, and the lighting is LED double 4' two-tube LED bulb fixtures. I think I will need no more than 60 amps of service for the garage. Am I correct that the 6/3 Romex is inside, and what type of wire should I use from inside the house to the garage? Thanks for your help.

 

[Bert_]

Either finish running the conduit so you don't have to splice or use aluminum SER. If you splice you need a bigger box. Since you ran 2" pipe I think it needs to be 10x10 or 12x12

 

[PCustoms]

Either finish running the conduit so you don't have to splice or use aluminum SER. If you splice you need a bigger box. Since you ran 2" pipe I think it needs to be 10x10 or 12x12

Since when can SER go underground?

 

[Bert_]

Since when can SER go underground?

It can't, he wants to splice it. I would rather use SER that romex

 

[PCustoms]

It can't, he wants to splice it. I would rather use SER that romex

Glad you edited this reply. The way you phrased this isn't clear (I get it, but someone asking the question probably won't).

Either finish running the conduit so you don't have to splice or use aluminum SER.

 

[theoldwizard1]

... finish running the conduit ...

Absolutely ! Then he could use THWN-2 of XHHW-2 wire.

 

[wyliesdiesels]

finish the conduit run to the panel. then run underground rate conductors from feeding panel to garage panel. will be a lot cleaner than splicing it

 

[mm08822]

Take some pics/ mark up the routes you think you want to take and what is already installed.

I would make a plan to eliminate all splices as it is less costly and more robust long term. Aluminum xhhw will be far less costly than 6-3RX.

 

[BillK]

Is the run from the conduit to the panel in a crawl space or easily accessible ? Running the conduit all the way to the main box would be nice but might not be that easy.

 

[Junkman]

I can run cable from the left outside wall to the right outside wall, which is 32', but there is no room to run conduit because of the low cellar ceiling. That was the reason for wanting to use the 6/3 Romex. The conduit is on the inside of the right outside wall, and it goes beneath the cellar floor to the outside and is buried to the garage. This was poor planning on my part, since the cellar floor was dug up to replace the sewer line, and it would have been easy to bury it then, but it didn't occur to me. The concrete has been replaced, and a wood floor has been installed on top of the concrete.

 

[wyliesdiesels]

That was the reason for wanting to use the 6/3 Romex.

AL SER would be cheaper than NM

 

[75gmck25]

Unless I've forgotten something, this was my solution.
For my detached garage I ran 2-2-2-4 AL SER across the basement to a 12x12 junction box and then spliced it with Polaris connectors to 2-2-2-4 AL MHF to go through the wall and make the run to the detached garage through 2" conduit. Conduit runs right up to the sub-panel in the garage, and MHF connects to the 100 amp sub-panel. Bonding screw removed in the sub-panel and grounded with two 10' ground rods. I used a 60 amp breaker in the main panel because it was easy to find and buy, but could have used up to a 90 amp breaker with 2-2-2-4 MHF.

 

[Junkman]

I have been studying ways to get the conduit to the electrical panel. Can the 2-2-2-4 AL SER be run in the 2" conduit if there are 4 or 5 90-degree bends to get from the electrical panel to the sub-panel? The total distance will be about 75'. Is this going to be a monumental pull requiring 2 orangutans and a baboon, or can it be done with one person pulling and another pushing the wire into the conduit? What size pulling rope would you recommend?

 

[mm08822]

5 90's would not be permitted, but making 1 or more 90's either a LB or a j-box resets the 360 max limitation. I would try to put them toward the inner locations to reduce the # of 90s to pull around.

Why run SER vs individual conductors?
SER is not permitted in wet locations in conduit.

1/4" or 3/8" pull rope will be plenty - 1 person feeding, 1 person pulling - synchronized.

 

[Junkman]

OK, I can add the LB's instead of the 90s and accomplish the same thing. Could you please tell me exactly what wire to ask for at the supply house (or I might order it online if it is less expensive)? Will I need 2 hot and a neutral, or 2 hot, 1 neutral, and one ground in the conduit going to the subpanel in the garage? When I am ready to do this, I will use my 100-foot surveyor's tape to calculate the exact footage needed, and then add a little for trimming. I assume that all wires get pulled as a bundle? thanks

 

[mm08822]

XHHW Aluminum wire:
#2 Black (2x) (or 1 could be red, blue, etc)
#4 White (1x) (or tape black with white tape)
#6 Green (1x)

Pull all together at once. Layout all conductors along each other and in serpentine manner ^^^^^^^

90a cb in main panel
2 grd rods if garage detached
neutral grd unbonded in sub panel
panel needs a main cb if detached from house (could be 100A or larger)

 

[wyliesdiesels]

you need 4-wire feeder. see the diagrams on the electrical FAQ sticky

 

[mike93lx]

OK, I can add the LB's instead of the 90s and accomplish the same thing. Could you please tell me exactly what wire to ask for at the supply house (or I might order it online if it is less expensive)? Will I need 2 hot and a neutral, or 2 hot, 1 neutral, and one ground in the conduit going to the subpanel in the garage? When I am ready to do this, I will use my 100-foot surveyor's tape to calculate the exact footage needed, and then add a little for trimming. I assume that all wires get pulled as a bundle? thanks

Don't use a tape measure. Install the conduit and use a shop vac to pull through some string, mark it, then pull it out and measure that. You can order exactly what you need.

I did this on my last pull and added something like 6 feet out of an abundance of caution, but I ended up throwing away 6 feet.

If the run is conduit the whole way, I would get aluminum xhhw individual conductors. Two black (or a black and a red), one white, one green. Pull all at once

 

[Junkman]

Spoke to the electrical inspector today, and the outside cut-off switch requirement is going into effect on July 1, so I will have to add that item to my list of requirements.

 

[Junkman]

I did a lot of checking, and I can get the 2" PVC conduit to the electrical panel. I was wondering if I could use service cable from the electrical panel to the conduit at the other side of the basement? My thought would be to mount a box like pictured below to the 2" PVC pipe and feed it with the service cable from the top. Your thoughts as to what I am thinking of?>

 

[Junkman]

Been doing a lot of reading on other websites and YouTube. I just learned about Polaris and Wengart connectors to join larger wires. I was thinking that these might be a way to join the wires. Although they are expensive, it doesn't matter as long as it is done properly and safely to code.

 

[75gmck25]

Based on your questions, I'm not sure you understand the difference between SER and MHF, and the options for the wire you pull through conduit.
- AL (aluminum) wire will be quite a bit cheaper than copper, and it should work well for your application.
- SER is service entrance wire and it cannot be buried or used in wet locations.
- Mobile Home Feeder (MHF) usually has separate wires that are in a spiral and taped together at intervals. Most products are dual-rated, and when run underground it can be direct buried or run in conduit, but in buildings it must be in conduit. The most common, and usually cheapest version for connecting to a sub-panel is 2-2-2-4 AL MHF.
- If you buy separate conductors and pull them through conduit you will have more flexibility, but you definitely need conduit, and you have to ensure you buy the right wire (i.e., XHHW).

- Polaris connectors work well, but are relatively expensive compared to split bolt or other rated connectors.
- The code for the size of the junction box (NEC 314.28) for large gauge wire is based on the conduit size, not the wire size.

- For your conduit you always want to use long sweeps or LBs to make any right angle turns.
- HD and Lowes sell pulling rope that works well for pulling large wire. Also buy the wire pulling spray foam lubricant. Make sure you are pulling in the direction that pulls the wire across the conduit joints from the larger diameter to the smaller so you are not pulling against the lip from the joint. It doesn't seem like that lip is very high, but it does make a difference.

 

[wyliesdiesels]

- SER is service entrance wire and it cannot be buried or used in wet locations.

it can be used in wet locations such as from a meter pan to an inside panel. it just cant be buried

Mobile Home Feeder (MHF) usually has separate wires that are in a spiral and taped together at intervals. Most products are dual-rated, and when run underground it can be direct buried or run in conduit, but in buildings it must be in conduit. The most common, and usually cheapest version for connecting to a sub-panel is 2-2-2-4 AL MHF.

MHF always has separate conductors and it is not taped at all.

 

[Junkman]

I did enough research to learn that MHF wire must be in a conduit, whereas SER doesn't. That is why I am contemplating using the SER wire from the house electrical panel to the other side of the house, running it across the cellar ceiling, nailing it to each joist until I reach where the conduit goes out to the garage. I will use the same gauges (2-2-2-4) wire inside the conduit going to the garage, and make sure that it is properly rated for use in buried conduit. I decided to use a 12" square plastic electrical box mounted on top of the conduit that is inside the house that goes to the garage. I will connect each wire to the Polaris connectors inside that plastic box. The wire running across the ceiling will be clamped to the top of the box with the proper electrical connector, including a plastic bushing at the end of the threaded connector that holds the wire. I will also be using the black "grease" that the electrical supply house has given me whenever I purchased aluminum wire in the past. This is the only way that I can get service to the garage.
In my attempt to learn how to do this correctly, I learned that I shouldn't use a "sub" panel because there is no disconnect in that panel; instead, I should use a smaller main panel so there is a disconnect at the top of the panel. I will also be installing 2 ground rods (10'), 8 feet apart. If you see anything wrong, please let me know so I can correct it and do this properly.
Thanks to all for their advice and help.

 

[mike93lx]

I will also be using the black "grease" that the electrical supply house has given me whenever I purchased aluminum wire in the past

It is very likely (almost certainly?) not needed. If you do use it, follow the instructions and don't just slap on a dap

 

[wyliesdiesels]

I will also be using the black "grease" that the electrical supply house has given me whenever I purchased aluminum wire in the past.

no alox isnt required unless called for by the manufacturer...

In my attempt to learn how to do this correctly, I learned that I shouldn't use a "sub" panel because there is no disconnect in that panel; instead, I should use a smaller main panel so there is a disconnect at the top of the panel.

that panel is still considered a subpanel since it isnt the main service panel. a subpanel can have a main disconnect or not. doesnt change what its called.