New power to subpanel for detached garage

Orionrising · Oct 7, 2014

the garage on the property I bough this spring does not currently have power. It previously had its own meter that was pulled and the drop removed at some point.

To avoid the minimum and having another line drop, I am planning on running a 90 amp line to the old panel ( I know I have to detach the neutral bar etc)

~100-150 feet of total wire
http://www.homedepot.com/p/Southwire-2-2-2-4-Aluminum-Quad-****-Wire-By-the-Foot-55417399/205001803#specifications

Probably gonna use this cable as about 20 feet will be buried.

rest will be in conduit under overhang

to here

and either direct through wall to new panel or in conduit to attic floor truss.

I assume I can run it un protected in the truss correct?

any problems with this wire choice?

brewchief · Oct 7, 2014

That URD wire isn't rated to be run indoors, you want what is commonly called MHF, it will be rated USE,RHH, RHW-2.

It will need to be in conduit the whole way, if you can't do conduit you may have to transition to a different type of wire like SER.

Orionrising · Oct 7, 2014

I would prefer not to have to do conduit the whole way and this appears to be the least cost option by far for wire.

It would be an option to move the garage panel to the other wall of the garage and have the wire run panel to panel with only the wall/ panel penetration indoors.

(the panel is not currently connect to anything, previous owners lost the roof at some point to snow load, and it was replaced, but the wiring never redone)

Charles (in GA) · Oct 8, 2014

You need THIS cable which is Mobile Home Feeder. It is multi rated as USE-2/RHH/RHW-2. Don't believe the specs on the HD page I linked to, it is OK as a direct bury cable, but must be in conduit anywhere it is exposed, inside or out, that includes running thru trusses, etc. Direct bury it and bring it up in a long sweep ELL and then in a straight riser on out of the ground.

URD is not referenced anywhere in the NEC and thus cannot be used.

Charles

Orionrising · Oct 8, 2014

is this the equivalent (the previous poster one is not available locally)

Lowes

2-2-2-4 Aluminum SER Service Entrance Cable (By-the-Foot)

(cannot direct link it for some reason with lowes site)

I definitely want direct bury as there are an annoying number of corners to pull if in conduit the entire way.

(cannot go direct out of panel in house which is directly inside under porch to ground as there is a pool pump and plumbing in the way in the ground outside)

with direct bury, two 90s and a sweep on on end, sweep and 90 on other vs continuos

90-90-sweep-sweep-sweep-90

pattenp · Oct 8, 2014

2-2-2-4 Aluminum SER Service Entrance Cable is an above ground wire only, is not to be placed under ground, even in conduit. Lowe's should have 2-2-2-4 MHF.

theoldwizard1 · Oct 8, 2014

pattenp said:
2-2-2-4 Aluminum SER Service Entrance Cable is an above ground wire only, is not to be placed under ground, even in conduit. Lowe's should have 2-2-2-4 MHF.

Orionrising said:
I would prefer not to have to do conduit the whole way and this appears to be the least cost option by far for wire.

So could he

Run 2-2-2-4 Aluminum SER under the overhang of the house with no conduit
At the end of the house, install a weatherproof J-box and splice to MHF
Down a Schedule 80 conduit sweep to under ground
Over to the garage without conduit
Up the outside with another Schedule 80 sweep
LB into the garage
Conduit from the LB to the panel.

Sounds more complicated than it really is.

Orionrising · Oct 8, 2014

Hmm I will have to call some places to see who has MHF by the foot around here.

Does anyone see any code issues with the following?

My main is a old overfull 100 amp square D box that at some point needs a service upgrade and replacement.

Install a new 200 amp 30 slot panel next to the main box, fed off the main on a 90 AMP breaker. Then MHF out of the new panel off a 90 amp breaker in 2" schedule 80 to burial depth, back out of ground in schedule 80 to relocated panel in garage with 2 8' ground rods.

Minimum installed in garage for inspection to code is switched light over man door and one GFCI circuit I believe?

Is there a code requirement for minimum panel seperation for an exteriod door?

any better ideas or things I am missing?

(I want the 90amp to garage as I focus on woodworking, and will probably eventually end up with multiple large electric motors on at once. IE planer, dust collection, heat etc.)

theoldwizard1 · Oct 8, 2014

If you are going to install a new a new load center in the house, why not just move all of the circuits ? If you put it in the same location, you might have enough wire to just connect the wires to the new breakers.

Besides, running a 90A branch circuit off of a 100A main is not very logical.

Orionrising · Oct 8, 2014

the eventual intent would be to change the second panel to be the main and upgrade to 200 amps. All the wires are too short and will need to be extended (20 circuit box with neutral/ ground bar over the bus at the top of the box), none of the nuetrals/ grounds are more then about 6 inches long, its a crowded mess, that is gonna take a lot of work to redo at some point. A good winter project, priority right now is get garage powered, ceiling insulated and some heat.

Plan on moving the circuits over and splitting them up more over time as I can properly identify them, and when done, have the service upgraded/bond the neutral and trash the old panel.

I could certainly run the sub off a 60 amp breaker I guess, I need the circuit slots in the house mostly as that panel is only twenty slots with no tandems for it, and has doubled and mixed circuits that need to be separated and fixed etc.

Not much electric load in the house, small electric water heater, dryer, small stove that will be change over to gas. Eventual load in garage will likely be higher then the house with a dust collector planer/lights and maybe heat running at the same time.

Orionrising · Oct 8, 2014

hmmm now that I check 60 amp breakers are only about 10 bucks vs 90 amps are about $30 which is probably don't need.

Orionrising · Oct 9, 2014

yep definitely gonna have to replace the garage panel... its a challenger, hadn't looked closely at it before.

So no reason not to move it over by the man door.

scoob8000 · Oct 9, 2014

I sort of skimmed most of the posts in this thread but I've been weighing similar options for putting power to my new detached garage.

I need to bury about 120' of wire to get to my house. By far the cheapest option has been 2-2-2-4 mobile home feeder. It can be direct buried and here runs $1.00 - $1.25 per foot from the local electric supply shops (Vs $1.68 from lowes).

2-2-2-4 mhf is rated for 100amps.

To run the mobile home feeder inside however, it will need to be in a conduit.

Then I picked up a 100amp Murray (Siemens) value pack panel from Amazon for $55. It includes the 100 amp main breaker, ground and isolated neutral bars and 6 20 amp breakers. (Remember you'll need to drive a ground rod at the garage and bond it to your panel and the feed from the house.

pattenp · Oct 9, 2014

scoob8000 said:
I sort of skimmed most of the posts in this thread but I've been weighing similar options for putting power to my new detached garage.

I need to bury about 120' of wire to get to my house. By far the cheapest option has been 2-2-2-4 mobile home feeder. It can be direct buried and here runs $1.00 - $1.25 per foot from the local electric supply shops (Vs $1.68 from lowes).

2-2-2-4 mhf is rated for 100amps.

To run the mobile home feeder inside however, it will need to be in a conduit.

Then I picked up a 100amp Murray (Siemens) value pack panel from Amazon for $55. It includes the 100 amp main breaker, ground and isolated neutral bars and 6 20 amp breakers. (Remember you'll need to drive a ground rod at the garage and bond it to your panel and the feed from the house.

As a branch feeder the 2-2-2-4 MHF is to be overcurrent protected at no more than 90 amps.

Orionrising · Oct 10, 2014

hmm after analzing my existing house panel, I think I can pull at least two circuits and skip the side panel for now and just upgrade the whole service later this winter.

or Maybe throw a cheap 6 slot sub next to it in case that doesnt happen as soon lol

Orionrising · Oct 12, 2014

alright got the conduit in, and cable pulled, and panel in the garage in, ground rods and hookup tomorrow.
Will be running it off a 60 amp breaker for now, didn't find any 90s will see how it works and upgrade breaker if I ever have any issues.

The more I think about it the more I don't get the 4 conductor thing. The nuetrals and grounds are of course bonded together in the main panel... so the neutral and ground leg of the outbuilding panel will run back to the main and then be right next to each other on the same bar, how is that any different then having the outbuilding bond screw in?

rdsk8ter · Oct 12, 2014

You don't want to form a ground loop. Basically yes they are the same thing but if you loose your neutral at the out building they don't want that undersized ground to carry the load. I have seen this in person and boy does that undersized wire run hot under full load. I know it seems to be a pain to mount that ground bar but its just the right thing to do.

Orionrising · Oct 13, 2014

Oh I certainly will finish the install correctly just doesn't make sense in my head.

Now I am trying to figure out derating calculations for romex if I use conduit to the ceiling vs building a chase.

I am thinking it is going to be frame in a chase

rdsk8ter · Oct 13, 2014

Ill tell you a secret that most pros know it is that your small conductors 14-12-10 are already de-rated and you don't have to worry about them unless its a long run. if you still feel the need to hurt your brain then make sure you start your de-rating factors off the 90 degree column not the 60 you'll end up dropping the final number to 14awg =15 amp 12awg =20 amp etc

Orionrising · Oct 15, 2014

ahh, well I already pulled some drywall and ran plywood up the wall for a chase rather then a riser conduit

CNGsaves · Oct 15, 2014

OP . . . . update your GJ Profile with City / State / Country.

New power to subpanel for detached garage

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