upgrade partial 2 wire to 3 wire

[kmehr]

I'm planning an upgrade of my garage wiring and have a few questions- currently my garage is all two wire with some GCFI outlets and some ancient old school two wire ungrounded outlets. My electric panel is on the outside of my house which makes it really convenient. The garage wiring travels through a conduit to a mast on my roof, travels across my yard in the air, and then another mast on the roof of my detached garage. My main box for my house was just upraded in 2017 and has an earth ground rod right below the box. Running from the box to the mast is 12 gauge 2 wire which is tied to 6 gauge 2 wire between the masts. Wiring in the garage is a real hodge podge and will be replaced.

Plan: I want to add a subpanel in the garage, with (2) 30 amp 220v outlets for a compressor and welder, then (2) 20 amp 115v circuits for lighting and outlets.

main question- DO I need to run 3 wire between the main panel and the sub panel in the garage, or can I use the existing 2 wire 6 gauge and use an earth ground from the subpanel?


Thanks

 

[pattenp]

The feed to garage needs to be upgraded to 4 wires. 2 hots, 1 neutral and 1 ground.

 

[Terry D]

You will need (4) conductors. 2 hots, 1 neutral and a eguipment ground. If you are still planning on going overhead with it, A quadplex cable is good for this. The garage would need a main disconnect of some sort, Using a 100 amp main breaker panel would work, but it would be a sub panel. You will have to install 2 ground rods also, even though you are carrying a equipment ground from the house, you still need the rods. Make sure you keep the neutrals and grounds separated from each other. The neutral buss cant be bonded to the panel enclosure, but the ground bar does. Is it possible to go underground with the feeders? It would eliminate all the need for masts and switching from different types of conductors.

 

[kmehr]

I could definitely go underground. To follow the current wire path using the masts, it would take about 60 feet. If I buried it and put the subpanel on the closest corner of the garage, it would cut that distance by more than half.

 

[Terry D]

I could definitely go underground. To follow the current wire path using the masts, it would take about 60 feet. If I buried it and put the subpanel on the closest corner of the garage, it would cut that distance by more than half.

I would really consider going underground then.

 

[pattenp]

If you are not sure about what type of wire to use underground whether it be direct bury or in conduit please ask. Too many times people will comment about what wire they used to find out it was the wrong type and not NEC approved for underground use or for use inside of the structure.

 

[kmehr]

I was looking at 6/3 romex buried in pvc conduit- "Southwire Romex SIMpull Type NM-B Cable". Then a bare cooper ground wire in there as well?

Looks like local building code requires 18in bury depth.

 

[bob15]

I was looking at 6/3 romex buried in pvc conduit- "Southwire Romex SIMpull Type NM-B Cable". Then a bare cooper ground wire in there as well?

Looks like local building code requires 18in bury depth.

I don't believe you can use that cable underground because underground conduit is considered a wet location and that cable is rated for dry locations only.

If you are running the conduit from one box to another, run individual THWN-2 cables. They are rated for wet, dry, conduit and are rated at 90****C°

 

[kmehr]

https://www.homedepot.com/p/Southwire-50-ft-6-3-Gray-Stranded-CU-UF-B-W-G-Wire-14782722/300916640

this stuff doesn't look like it even needs conduit

 

[Terry D]

Correct, no romex underground in conduit. Use #6 THWN for your hots and neutral. #10 for your equipment ground. Feed in from a 2-pole 60 amp breaker in you main panel and install a 100 amp main breaker panel in the garage. You could use a 100 amp main lug panel and back feed it with a 60 amp 2-pole with a hold down kit, but the first way is easier.

 

[Terry D]

https://www.homedepot.com/p/Southwire-50-ft-6-3-Gray-Stranded-CU-UF-B-W-G-Wire-14782722/300916640

this stuff doesn't look like it even needs conduit

That is UF cable, it is direct burial. I personally prefer conduit. you can use it.

 

[wyliesdiesels]

I was looking at 6/3 romex buried in pvc conduit- "Southwire Romex SIMpull Type NM-B Cable". Then a bare cooper ground wire in there as well?

Looks like local building code requires 18in bury depth.

You CANNOT use that wire underground

https://www.homedepot.com/p/Southwire-50-ft-6-3-Gray-Stranded-CU-UF-B-W-G-Wire-14782722/300916640

this stuff doesn't look like it even needs conduit

This wire is permitted underground however individual conductors would be far cheaper. And i would definitely use conduit. Its cheap insurance. UF-b is a pain to pull in conduit.

Go with individual conductors- 8-8-8-10 THWN

The #8 neutral will need to be white jacketed and the #10 EGC will need to be green jacketed.

 

[kmehr]

Could you put that stuff in conduit?

 

[kmehr]

Go with individual conductors- 8-8-8-10 THWN

could you send me an example of this?

 

[Terry D]

Could you put that stuff in conduit?

You are defeating the purpose of buying direct burial wire and putting it in conduit. You would be spending more money than needed, plus as already said , it would be a pain in the *** to get it in there.

 

[Terry D]

Go with individual conductors- 8-8-8-10 THWN

could you send me an example of this?

I would go with #6 to give you 60 amps

 

[kmehr]

So something like

https://www.amazon.com/dp/B07KQP6SR7/?tag=atomicindus08-20

plus a ground in conduit, vs the direct burial stuff?

 

[wyliesdiesels]

Could you put that stuff in conduit?

What “stuff”?

You need to be a little more specific

 

[wyliesdiesels]

So something like

https://www.amazon.com/dp/B07KQP6SR7/?tag=atomicindus08-20

plus a ground in conduit, vs the direct burial stuff?

Thats a ripoff

You can buy 50’ spools of #6 THWN at home depot for about $32+ tx

 

[Terry D]

So something like

https://www.amazon.com/dp/B07KQP6SR7/?tag=atomicindus08-20

plus a ground in conduit, vs the direct burial stuff?

Yes, that is the wire for going in the conduit, but it has to be in conduit all the way. Cant run it exposed. You can probably get from your local supply house or Home depot a lot cheaper

 

[Terry D]

Thats a ripoff

You can buy 50’ spools of #6 THWN at home depot for about $32+ tx

Now that I look at it, that is 50 ft of each color, its for 150 ft

That's about .75 per ft. probably can still get it cheaper

 

[kmehr]

Thanks for all the responses. I'm amazed at how fast and knowledgeable everyone is.

So the consensus is individual wires in conduit is preferable to the all-in-one "buriable" wire?

 

[Terry D]

Thanks for all the responses. I'm amazed at how fast and knowledgeable everyone is.

So the consensus is individual wires in conduit is preferable to the all-in-one "buriable" wire?

You have my vote for conduit with individual conductors

 

[wyliesdiesels]

Now that I look at it, that is 50 ft of each color, its for 150 ft

That's about .75 per ft. probably can still get it cheaper

yes home depot has it for about .60 per ft if buying 50' rolls. one could save a little more buying 100' of black.

the amazon price is a premium for hand picked color coded wire

 

[sberry]

This is a high equity upgrade. Well worth your time to put in a new underground service, digger up, its not that big a deal, even rent a little trencher to get started. I have got the shovel out and simply spent the morning digging till its done on modest short runs. You are eliminating hazardous old junk and putting in a service could work decades, insurance co loves it. Big chance to redesign and upgrade. Underground is upscale.

 

[sberry]

If I was piping copper and went to the effort it would be number 6. You can be welding away and the air comp comes on and not leave you in the dark. 60 is the largest cheap breaker. Ground would cost the same. Goes thru inch pipe. In a small garage its not hard to not weld if the comp is running but 60 is a lot of poop. 6 is super easy to install. I use 2 alum most of the time, cheaper and can help a little with motor starts at some distance. At 60A the wire is at 2/3 capacity. In a garage feed situation a standard is 5 hp comp and a 50A welder circuit. With number 2,,, applied loadcalc the breaker be but a switch here and really applying it to a 90A circuit Both loads may approach the threshold of a 60 breaker but no where near the thermal capacity of the wire.
If I was a plumber would consider this th difference between 3/4 and inch with it terminating in 50 ft of garden hose. Even heavily loaded the appliance wouldn't know it wasn't right at the panel.

 

[sberry]

While the capacity of copper may be reduced it might not be an issue, the cost may be similar with size smaller pipe and even easier to route? Can buy alum direct burial even about 1.50 a foot or so. Even adding some extra is not much an issue. Route it to a location it makes most sense.

 

[kmehr]

my compressor is 4hp and the welder im looking at upgrading to is the Hobart 210MVP, which is a max 30 amp draw machine. Kicking around the Hobart Ironman which would need a 50 amp service, but i really don't have the need to justify a machine that big.

THe underground section would only be about 17 feet, so pretty easy to do by hand.

 

[pattenp]

If you go with conduit and the four #6 copper conductors I suggest using no smaller than 1" conduit.

 

[kmehr]

What are thoughts on copper vs aluminum wiring?

https://www.homedepot.com/p/Southwi...Gray-Stranded-AL-SER-Cable-13102999/205001908

this aluminum is approved for wet locations and is about 1/3 price of the individual copper wires.


I do have a sprinkler system, though I'm not sure it's path. Would it be ok to bury the wire even if I had to run it under or over a sprinkler line?

 

[mike93lx]

UF ***** to work with already. Putting it in conduit would be terrible.

Also consider Aluminum XHHW. #2 (good for 90a) is 0.35/foot

 

[pattenp]

The SER cable you linked to has the same install rules as NM-b other than it can be used in wet locations above ground. It cannot be installed underground.

 

[kmehr]

https://www.homedepot.com/p/Southwi...ded-AL-Quad-****-URD-Cable-55417399/205001803

here we go. buriable and even cheaper

 

[jchetty]

Use conduit if you decide to go underground. I personally think it should be a requirement

 

[mike93lx]

https://www.homedepot.com/p/Southwi...ded-AL-Quad-****-URD-Cable-55417399/205001803

here we go. buriable and even cheaper

URD can't go inside at all, even in conduit.

You have to transition to something else while still outside, in a junction box. Like SER

 

[wyliesdiesels]

URD can't go inside at all, even in conduit.

You have to transition to something else while still outside, in a junction box. Like SER

Some URD is triple rated RHH/RHW but that one is NOT! NEXT!

 

[mike93lx]

https://www.homedepot.com/p/Southwi...ded-AL-Quad-****-URD-Cable-55417399/205001803

here we go. buriable and even cheaper

If you want to do this right, stop. Going off on your own for magical solutions. This thread has already provided you with the right answer, from electricians, no less

 

[pattenp]

My suggestion is to use #4 Al XHHW-2 and put it in no less than 1" PVC conduit panel-to-panel. Buy enough feet of the XHHW in black to cut it up into 4 conductors and reidentify the ends with tape to the correct colors. This is most likely the cheapest option you have short of doing direct bury which would be to use #4 Aluminum XLP/USE-2/RHH/RHW-2 and having conduit only above ground and inside. The conduit for the #4 USE-2/RHH/RHW-2 will need to be 1.25".
See here: https://www.wireandcableyourway.com/aluminum-building-wire/
Edit: The #4 Al is good for up to 65A.

 

[mike93lx]

My suggestion is to use #4 Al XHHW-2 and put it in no less than 1" PVC conduit panel-to-panel. Buy enough feet of the XHHW in black to cut it up into 4 conductors and reidentify the ends with tape to the correct colors. This is most likely the cheapest option you have short of doing direct bury which would be to use #4 Aluminum XLP/USE-2/RHH/RHW-2 and having conduit only above ground and inside. The conduit for the #4 USE-2/RHH/RHW-2 will need to be 1.25".
See here: https://www.wireandcableyourway.com/aluminum-building-wire/
Edit: The #4 Al is good for up to 65A.

The extra capacity may never be needed, but I can't imagine doing all that work and not throwing #2 in instead of #4. Maybe a hundred bucks more including up sizing conduit to 1.25" or 1.5"?

 

[pattenp]

The extra capacity may never be needed, but I can't imagine doing all that work and not throwing #2 in instead of #4. Maybe a hundred bucks more including up sizing conduit to 1.25" or 1.5"?

If it's not needed, it's not needed. Why waste a $100. Everyone has an opinion.