Powering my detached garage

[UziRid3r]

Hello, built a detached 900 square foot garage recently and am just looking to power it up on a budget. I have an existing generator backfeed on the far end of the house that I would like to repurpose to run a sub panel in detached garage. This will save me the cost of getting power through my attic and to my panel which is in an interior wall and the cost to trench and conduit around to that opposite side of the house.

The wire run to that plug is 6 gauge aluminum. Can I remove the plug, replace with a junction box and run a 50 amp sub panel from it?

I have about 100 feet between the garage and that corner of the house. I won't be doing anything more than a 30 amp ev charger in garage.

 

[wyliesdiesels]

how many wires? 3 or 4?

 

[UziRid3r]

4 wires 3 insulated and one bare aluminum it's 6666 aluminum SER with a grey PVC jacket.

 

[UziRid3r]

Plan was to to run additional 6666 aluminum SER in 1 inch RMC to the garage sub panel on a 50 amp breaker.

6-6-6-6 ALUMINUM SER CABLE

6-6-6-6 Aluminum SER Cable: 60 Amps at 90°C, 600V, NEC-approved. Perfect for branch circuits and panel feeders in challenging conditions. Order today.

nassaunationalcable.com

 

[pattenp]

Assuming the run is going to be underground SER is not to be placed underground, even in conduit. You need to transition to single conductors of XHHW-2. The wires being #6 will require the correct colors, such as black, white(neutral), green (ground).

 

[UziRid3r]

So 6 ga aluminum XHHW2 4 conductors black, white, green, and bare aluminum? Or one black with red stripe?

 

[pattenp]

No bare conductors. You can use 2 blacks for the ungrounded conductors, 1 white for the neutral and 1 green for the ground. Or one of the blacks can be a red if you prefer.

 

[PCustoms]

@UziRid3r so you want to add a junction box, then trench conduit underground 100' to the new shop?

Why the mention of the sub panel, are you putting this at the house or in the shop?

 

[UziRid3r]

Yes trenching the feeder to garage for sub panel.

Just want to make sure i don't overload the existing SER cable running through the attic to that side of the house.

 

[PCustoms]

Yes trenching the feeder to garage for sub panel.

Just want to make sure i don't overload the existing SER cable running through the attic to that side of the house.

1. Approximately how long is the existing cable?
2. What size breaker is it on?
3. Can you confirm the wire gage? Should be printed on the jacket

 

[UziRid3r]

Existing cable is about 60 feet up through attic and too far side of house. Previous home owner was using this to back feed the panel during power outage with a suicide cord. I repurposed and have been using it to power a EV charger with 40 amp breaker.

I cant get a great look at the jacket as it is stripped off inside the panel. Grey jacket one black, one black with white, one black with red stripe, and a bare alum conductor. They are solid conductors and I measured the diameter of the bare conductor at 4mm.

I would like to transition to separate conductors in RMC and run to garage swapping out the 40 amp to a 50 amp breaker to feed the sub panel. Figured this will be enough to run a garage fridge, my garage lights, door openers, power tools, and charge my EV at 32 amps Max.

 

[PCustoms]

Yeah that wire looks pretty small, I don't think 50A is realistic...

EDIT: at ~4mm, that's probably #6. Could pull 40A at 3.6% drop

 

[pattenp]

To have a voltage drop of around 3% with a 50A load, the feeder extension to the garage would need to be upsized to #2 Al. This is a ballpark estimate.
Also why not use PVC conduit?

 

[UziRid3r]

To have a voltage drop of around 3% with a 50A load, the feeder extension to the garage would need to be upsized to #2 Al. This is a ballpark estimate.
Also why not use PVC conduit?

#2 for only 50amps? I was going to run metal so I only need bury 8 inches. Save alot of digging

Well if 40 amps is all I can squeeze out of it do u all think that will be enough for a 3 car garage? I'm not a welder or anything. Biggest load would be 32 amp EV charger.

 

[PCustoms]

#2 for only 50amps? I was going to run metal so I only need bury 8 inches. Save alot of digging

#4 gives me 3.05% drop at 160 total feet...

 

[UziRid3r]

Am I allowed up to 5% on a feeder to subpanel? 40 amps @ 240 175 feet is 4.1% on 6 gauge aluminum

I have to utilize the existing 6 gauge SER running across the house to save cost of trenching around entire house and getting to the panel at interior wall.

 

[pattenp]

#2 for only 50amps? I was going to run metal so I only need bury 8 inches. Save alot of digging

Well if 40 amps is all I can squeeze out of it do u all think that will be enough for a 3 car garage? I'm not a welder or anything. Biggest load would be 32 amp EV charger.

The issue is to compensate for the voltage drop of the first 60ft of #6 Al at 50A which is about 2%. An additional 100ft of #2 Al adds a little more than 1% additional VD at 50A. As said by PCustoms using #4 Al for the whole 160ft get you into the 3% VD area. With all that's been said you will be okay with a 50A breaker feeding the #6 for the 160ft.
NEC recommends 3% max VD for feeders. The 5% is the combination of the feeder and branch circuit.
The cover for RMC is 6", so you do need to dig at least 8" deep.

 

[wyliesdiesels]

I wouldnt run metal underground. it will eventually rust and disintegrate. theres a reason all new construction is PVC in slab and underground....

 

[UziRid3r]

Thank you all for the help, After considering everyone's feedback here I am going to bite the bullet now and just run a new 100 AMP service out to the garage in PVC. more work on money now but having the extra power in the future will probably be beneficial for a faster EV charger when needed.

I do have one other question that, so far, I have gotten conflicting answers on.

I am planning to run Romex around the interior of the garage for my circuits and lighting. The garage is pole construction with OSB and Vinyl siding, I have also added EPS foam board inside the wall in between the perlins for a bit of insulation and to cover all the siding nails on the inside so the kids don't get hurt.

Will it be to code to run Romex down the poles to my outlets and leave it exposed? I know I must to verticle runs but must it also be in conduit? And to what height above the floor? I don't plan on drywall, Maybe some pegboard in select areas.

Thank you!

 

[JessieAMorris]

Romex generally isn’t allowed inside of conduit. If you aren’t planning on covering with osb, Sheetrock, etc an inspector may want you to protect them somehow.

My suggestion would be something like MC. Fast and easy to run, not terribly expensive, and would cover your use case. Downsides it is more expensive that romex (1.5x), doesn’t tend to look quite as nice, and is harder to run.

EMC conduit would be another option, but they’re even harder to run, more expensive, etc. plus you’d need wire besides romex to run in it, thhn or similar.

 

[PCustoms]

Romex generally isn’t allowed inside of conduit.

Blatantly incorrect.

My suggestion would be something like MC. Fast and easy to run, not terribly expensive, and would cover your use case.

Requires same protection from damage as NM-B

 

[mike93lx]

Romex generally isn’t allowed inside of conduit

That is only found in the code book of internet myth. It's fine, unless your local AHJ has a written ammendment

 

[JessieAMorris]

Nothing better than people telling you you’re wrong but not giving OP any helpful advice.

Re-reading, it’s underground conduit (or conduit in wet locations, really. Interior conduit doesn’t count as wet typically) that Romex in conduit is not allowed. So looks like conduit it is.

Good to know about dry locations and romex in conduit.

 

[UziRid3r]

Sooooo... Is Romex down the side of the poles without conduit acceptable? I see many unfinished garages without conduit. I understand they must be run vertical to top of walls for protection. And height above floor?

 

[pattenp]

Nothing better than people telling you you’re wrong but not giving OP any helpful advice.

Re-reading, it’s underground conduit (or conduit in wet locations, really. Interior conduit doesn’t count as wet typically) that Romex in conduit is not allowed. So looks like conduit it is.

Good to know about dry locations and romex in conduit.

If you're giving wrong information, it needs to be connected. Nothing personal about it.

 

[JessieAMorris]

If you're giving wrong information, it needs to be connected. Nothing personal about it.

Agreed, and I appreciate the correction, just sayin that giving OP answers beyond just “this person is wrong” would probably be more helpful.

Cunningham’s Law (“The best way to get the right answer on the Internet is not to ask a question; it's to post the wrong answer”) strikes again. 3 hours of zero responses to OP, I post a wrong thing and within 30 minutes I’ve got two responses. I just think it’s funny is all.

 

[PCustoms]

Sooooo... Is Romex down the side of the poles without conduit acceptable? I see many unfinished garages without conduit. I understand they must be run vertical to top of walls for protection. And height above floor?

The problem here is the requirement is "protected from damage" which is ultimately open to the inspectors discretion.

If this is inspected, your best bet would be to sleeve it below 8', but even that's not a guarantee to pass.

Personally, I'm not subject to inspection, and I've got a few spots where I sleeved it and others where I didn't.

 

[wyliesdiesels]

Romex generally isn’t allowed inside of conduit. If you aren’t planning on covering with osb, Sheetrock, etc an inspector may want you to protect them somehow.

My suggestion would be something like MC. Fast and easy to run, not terribly expensive, and would cover your use case. Downsides it is more expensive that romex (1.5x), doesn’t tend to look quite as nice, and is harder to run.

EMC conduit would be another option, but they’re even harder to run, more expensive, etc. plus you’d need wire besides romex to run in it, thhn or similar.

this is misleading. NM-b (Romex is a brand of southwire), is indeed permitted in conduit INDOORS. outdoors it is not.

MC has the same protection requirements as NM-b

no such thing as EMC conduit. Did you mean EMT? Also one can run NM-b in EMT but not advisable so once again youre providing misinformation here

 

[wyliesdiesels]

Nothing better than people telling you you’re wrong but not giving OP any helpful advice.

Re-reading, it’s underground conduit (or conduit in wet locations, really. Interior conduit doesn’t count as wet typically) that Romex in conduit is not allowed. So looks like conduit it is.

Good to know about dry locations and romex in conduit.

as if your incorrect advice about NM-b being prohibited in conduit was helpful.... or that MC would be better than NM-b....

 

[JessieAMorris]

as if your incorrect advice about NM-b being prohibited in conduit was helpful....

We got to the right answers in the end and a few people (me and probably OP) learned some things along the way. I’d consider that a win!

 

[wyliesdiesels]

Sooooo... Is Romex down the side of the poles without conduit acceptable? I see many unfinished garages without conduit. I understand they must be run vertical to top of walls for protection. And height above floor?

yes unless "subject to damage" which is very subjective...

 

[dscheidt]

yes unless "subject to damage" which is very subjective...

Also lots of garages have unpermitted work done, by people of differing levels of skill, knowledge, and concern for safety.

 

[larry4406]

My detached barn with 2x6 framing has an unfinished interior with exposed Romex feeding outlets and lighting circuits. Right or wrong it passed inspection.

At the day job, we have unfinshed mechanical and storage rooms. These rooms are separated from finished spaces by a 2x4 framed wall with drywall one-sided on the finished side. Thus, we have exposed Romex in these walls that is visible from the unfinshed side. Right or wrong, these installations pass inspections and have been for my entire carrier.

 

[UziRid3r]

Thanks all, planning to run the NMB down the inside of the poles to keep them " protected" if inspector wants conduit I suppose it won't be to difficult to add it after the fact where needed.

 

[sparky 1971]

Romex generally isn’t allowed inside of conduit. If you aren’t planning on covering with osb, Sheetrock, etc an inspector may want you to protect them somehow.

You've deservedly gotten beat up on this one, but the code reference is 334.15(B)

 

[sparky 1971]

Thanks all, planning to run the NMB down the inside of the poles to keep them " protected" if inspector wants conduit I suppose it won't be to difficult to add it after the fact where needed.

Call the inspector and ask. There are a lot of places I work where Romex is ok exposed and the inspectors consider it protected if run vertically down a pole, others want it in some type of conduit. It has to be protected from physical damage, but there is no definition of what that is so it's completely up to the discretion of the inspector. I have wired a whole bunch of pole barns and only one of them saw any type of Romex and that one had 3/4 EMT sleeves down the poles to the receptacles for two sets of 12/2's. I considered using junction boxes at the top and THWN down the pipe, but that would have made a future ceiling install a ***** if it ever happened. I wouldn't run exposed NM down a pole for anyone because I have a general distrust of people and think most of them are stupid enough to find a way to destroy the wire and somehow blame me for it.