Underground Wiring from House to Garage

[mwilson]

Ok, need input here. Bought a new property and it has two garages, now I can store twice as much crap.....

Ist garage was wired at one time, once for 110 volt and then once for 220 volt as there are two old panels out there. No wire left inside the garage, looks to me like it was taken out and sold during the copper wire frenzy a few years back...

There is an existing 10/2 cable coming from the house that looks like it was cut off by a weed whacker where it enters the garage judging by the 6" of blackened casing and the hot and ground fused together. Must of been quite a show there for a second or two...

The 10/2 is NOT underground wire........bad juju...but I removed the damaged portion and kicked the breaker back on in the main panel and it held...so no damage to it....yet.....

My question is this.....my heart and soul tell me to run plastic conduit with indvidual wires inside, proper thru wall connecters at each end and to make it 220 right off of the bat. I'm torn between doing that and if I do that should I run 10 gauge or 8 gauge??? Basic lighting, power tools and a 220 volt air compressor. At some point in the future possibly a small gas welder. I think 10 gauge will be adequate...

Or just hook the 10/2 back up for new and hope to hell that the frost doesn't push a rock through the cable and make a short???

The ground will be freezing shortly so I have to decide pretty quick, can't waffle too long....

 

[NIsaacs]

How far are you going? I run 6 gauge to mine, about 60 feet. I used just the plain underground wire, no conduit.

 

[TFucili]

I have nothing against direct burial UF wire, but conduit is the better way to go IMHO.

Are you planning to put a fresh sub-panel in the garage? If so, Amps and distance will lead to wire gauge pretty quickly.

 

[mwilson]

Yes, a small sub panel with several breakers. I like to balance and reduce the load when feasible.
Haven’t put a tape measure to it yet, but looks to be about 50’ from house to garage. Then probably 25’ feet more from where it enters the house to the main panel.

 

[seafish]

IMO digging and refilling a properly deep trench is the most expensive and time consuming part of outdoor wiring...running conduit and properly sized THN wiring is NOT that more expensive then properly sized UF wire and is simply the safest way to go.

 

[Jim W]

Mike, I have found in the past that the friendly little rodents like the wire coating on electrical wiring. So, in my humble opinion I would use the plastic conduit buried in the ground to the garage. It is better to be over cautious where electricity and water/snow come together.
Where I live it is a building code requirement that any power that is provided to an out building under ground must be in plastic conduit.
Just my $0.02

 

[TFucili]

I can't find the handy dandy chart, but I would guess at that long of a run you'll need at least 8 ga, maybe 6 ga to feed a 50 A panel.

 

[DavidC]

Personally and being an electrician for over 49 years. I would run 1 1/2" or 2" PVC code wise is 30" deep encased or not. #6 wire minimum (50 amps) maybe # 4 (90 amps) with a 125 or 200 amp with the most breaker spaces available. The more spaces the better as there always seems to be things added.

Dave

 

[mwilson]

Thanks a million guys, keep the info coming. I just don’t have time to properly research this and you are all saving me a pile of work.
David, there seem to be split opinions during the little time I have had to search the inter web regarding grounding the sub panel. Some say yes, some say no.

 

[DavidC]

I would consider your main panel to be the ground point (already grounded) so I would pull 2 hots, 1 neutral and 1 Bond wire (no smaller than a #6). On residential the grounding conductors (rod, water,gas) usually wind up on the neutral bus). I would get an uninsulated ground bar for the sub panel and attach the bond and any other grounds to that bar securely fastened to the sub panel can.

Dave

 

[jgillott]

Mike, last winter I had to replace the underground service from the pole transformer to one of my houses approximately 300'. It was buried without conduit. Of course, it did last 40 years, but by the looks of it when it came out of the ground, I don't know how.

Go with what the others are telling you. Put it in plastic and be done with it.

 

[TJJEEPER]

Mike, Do it once and do it right...

Conduit and wire IMHO... is it possible that the RV might be parked next to it and need power? Size accordingly... (and you ALWAYS add stuff after your initial estimate!)

 

[DavidC]

A passing thought. I "assumed" you have space in your house panel for the appropriate breaker. If that is true I would locate the breaker you are going to use and make sure it fits (some take up 4 spaces, as in 2 on the right and 2 on the left). I mention this as the last house I had was a 42 space panel completely full. I wound up removing the 50 amp stove/oven breaker ( the stove was gas) and installing my sub panel CB in it's spot.

Dave

 

[mwilson]

I would consider your main panel to be the ground point (already grounded) so I would pull 2 hots, 1 neutral and 1 Bond wire (no smaller than a #6). On residential the grounding conductors (rod, water,gas) usually wind up on the neutral bus). I would get an uninsulated ground bar for the sub panel and attach the bond and any other grounds to that bar securely fastened to the sub panel can.

Dave

So that's four #6 wires, black, red, white and green?? Just looked quickly on Lowes site and looks like that will run me about $4.00 per foot. Not as bad as I thought it might be.

 

[mwilson]

A passing thought. I "assumed" you have space in your house panel for the appropriate breaker. If that is true I would locate the breaker you are going to use and make sure it fits (some take up 4 spaces, as in 2 on the right and 2 on the left). I mention this as the last house I had was a 42 space panel completely full. I wound up removing the 50 amp stove/oven breaker ( the stove was gas) and installing my sub panel CB in it's spot.

Dave

There is a non functional 220V wall heater in the kitchen, figured I would use that breaker. Or at least the slot that it occupies, can't remember what amp the existing breaker is.
Can't get too carried away, this new to me house only has a 100 amp entrance.....my house on the lake has a 200 amp panel so have been able to add just about anything over the last 20 years.....

 

[mwilson]

Another electrian type question...

When you enter the house using the plastic conduit and THHN wire does one install a juction box and switch to some other type of wire OR do you continue the conduit to the breaker panel???

Bear in mind I'm in the land of pretty much no code as far as working on your own house....I could string spliced 14 gauge extension cords through the trees with black taped twist connections and not a word would be said....I've seen it done.....

In Maine a homeowner has the right to do his own electrical / plumbing / etc. work on his property.....sometimes it is a bit scary.....

The Propane delivery companies come and do inspections on propane lines and appliances from time to time which is not a bad thing......but that is a fairly recent trend...

 

[DavidC]

So that's four #6 wires, black, red, white and green?? Just looked quickly on Lowes site and looks like that will run me about $4.00 per foot. Not as bad as I thought it might be.

That is correct. Check your breaker existing/replacement and make sure you have/or can get one. Some times finding one can be a challenge on old services. That wiring would give you 50 amps on each leg of a 220v service.

Dave

 

[DavidC]

PVC conduit end to end with male connectors and locknuts. If the PVC is going to be exposed it is best to paint it otherwise it will turn brown and become brittle.

Dave

 

[DavidC]

If the PVC to the panel is a headache waiting to happen you could switch to flex either metal or sealtite with a jbox (flex determined if exposed to weather. That would be done with either a jbox or female adapter on the PVC. They do make a 6/3 SE (service entrance wire but the last I checked it was 2 insulated and 1 bare conductor which leaves 1 conductor short without some improvising with either the bond or neutral. That part can get messy. The PVC only needs paint where exposed to the elements.

Dave

 

[mwilson]

If the PVC to the panel is a headache waiting to happen you could switch to flex either metal or sealtite with a jbox (flex determined if exposed to weather. That would be done with either a jbox or female adapter on the PVC. They do make a 6/3 SE (service entrance wire but the last I checked it was 2 insulated and 1 bare conductor which leaves 1 conductor short without some improvising with either the bond or neutral. That part can get messy. The PVC only needs paint where exposed to the elements.

Dave

I don't think it's be too bad, but it will add about 25' in additional conduit and materials. There may be a carrying joist that would have to be worked around, don't think it could easily be drilled but I really need to study it some more over the weekend.....may be another route I could take looking at it with the conduit in mind instead of sheathed cable....

Plus the fuse panel has a six breaker generator panel wired in right beside it and that makes things pretty busy wire wise in the panel......