Detached Garage Power with MHF

Yarz · Mar 18, 2014

I just moved into my first house in November, and since then I've been doing a lot of reading on this site, getting ideas for my garage. Thanks to all of you! :beer:

One of the main things I NEED to fix this summer, is the power feeding it. Right now, there is a single, 15 amp circuit running to it through a switch in the house, and then via overhead cable. I've already blown the breaker a few times, just trying to run a little 3 gallon air compressor.

My plan, based on reading here, is to run SER in the house (because it doesn't need conduit, correct?), transitioning to 2-2-2-4 MHF in Junction box using splitbolts, run underground in pvc conduit (there is approx. 30 or so feet between the house and garage), then back to SER in garage junction box with splitbolts, to the subpanel.

Also, I want to run a 3way switch in the house for the outside light circuit (powered by garage power – the switch will be on the end of the run), so I planned to run UF in the conduit as well.

So my main questions are:
Is there any issue running the MHF and UF in the same conduit?
I planned on looking at 2" conduit next time I'm at the store. Should this be big enough?
And one final question about the conduit laying itself: Is there a certain direction the flared end should face (ie. toward the house or toward the garage), or should I pull the wire a certain direction? :dunno:

Thanks in advance! :thumbup:

Aceman · Mar 18, 2014

Yarz said:
So my main questions are:
Is there any issue running the MHF and UF in the same conduit?

For what you are doing, no problem.

Yarz said:
I planned on looking at 2" conduit next time I'm at the store. Should this be big enough?

2" should work just fine.

Yarz said:
And one final question about the conduit laying itself: Is there a certain direction the flared end should face (ie. toward the house or toward the garage), or should I pull the wire a certain direction?

It doesn't matter.

I have one question though. Why isn't the 2" running right into the garage panel? It sounds like you want to install a j-box on the exterior wall instead of the subpanel?

Yarz · Mar 18, 2014

Thanks!
As for the extra junction box, I was trying to avoid having to run conduit inside the garage, because as I understood it, the MHF needs to be in conduit inside of the structures.
Perhaps I should just run the conduit straight in and eliminate that extra connection..

Hmm...

pattenp · Mar 18, 2014

If the sub panel is on an outside wall where the feed comes out of the ground you can use a LB conduit body to bring the feed in through the back of the panel. If you don't want a long run of pipe coming up on the outside to the panel's height you can use 2 LB's back to back and bring the feed up through the bottom of the panel.

Yarz · Mar 19, 2014

I had to google what the LB conduit body was because I never knew the proper name. I think 2 back to back will work, and then it'll be a couple feet straight up to the panel.

Yarz · Jun 4, 2014

Finally got the subpanel wired into the existing light circuit and one plug, for now. I'll add more once I decide how I want to arrange the garage.

It took me so long because I had to do it as time/funds allowed, and I wanted to take my time and make sure it was done safely and correctly.

Started with 2-2-2-4 SER and used split-bolts to transition to 2-2-2-4 Mobile home feeder, in a junction box in the basement, right next to the exterior wall:
https://scontent-a-lga.**.fbcdn.net/hphotos-xpf1/t1.0-9/1503999_668444016280_4270730259588045344_n.jpg

Then ran 2" conduit to the subpanel (these pictures are from before I got the LB's and did the vertical conduit to them:

https://scontent-a-lga.**.fbcdn.net/hphotos-xaf1/t1.0-9/10376277_668443966380_2552759572077522190_n.jpg

https://scontent-b-lga.**.fbcdn.net/hphotos-xpf1/t1.0-9/10004076_668443981350_7493759623463210012_n.jpg

https://scontent-a-lga.**.fbcdn.net/hphotos-xfa1/t1.0-9/10403495_668443956400_8163717578162433718_n.jpg

https://scontent-a-lga.**.fbcdn.net/hphotos-xfp1/t1.0-9/10360246_668443961390_6414860446930594938_n.jpg

I haven't completely figured out where I want the switch for the outdoor lights in the house yet, so the UF is coiled up at both ends of the conduit. I just need to anchor the SER to the wall in the basement, anchor the NM to the wall above the panel, and finish removing the old overhead wiring, and it should be done for a while!

MoFoJoe · Jun 5, 2014

Pic #1 The split bolt doesn't look to be dual rated (CU/AL) based on the color and lack of a separation saddle. I can't tell, but did your apply any alum. inhibitor compound (Noalox) to the alum conductors in the Jbox as well as at all connections (load centers)? If your ditch is still open you may want to lay electrical caution tape about 6" below the topsoil finish.

ETA. Also, strip back more insulation on the splicing conductors so the split bolts' nut makes good metal to metal surface contact without insulation interference. I was "googling" 2-2-2-4 MHF cable for an undergound job and your thread popped up

pattenp · Jun 6, 2014

Good catch. Looks like Cu split bolt only. Should use Al split bolt since it's Al to Al.

MoFoJoe said:
Pic #1 The split bolt doesn't look to be dual rated (CU/AL) based on the color and lack of a separation saddle. I can't tell, but did your apply any alum. inhibitor compound (Noalox) to the alum conductors in the Jbox as well as at all connections (load centers)? If your ditch is still open you may want to lay electrical caution tape about 6" below the topsoil finish.

ETA. Also, strip back more insulation on the splicing conductors so the split bolts' nut makes good metal to metal surface contact without insulation interference. I was "googling" 2-2-2-4 MHF cable for an undergound job and your thread popped up

Yarz · Jun 6, 2014

MoFoJoe said:
Pic #1 The split bolt doesn't look to be dual rated (CU/AL) based on the color and lack of a separation saddle. I can't tell, but did your apply any alum. inhibitor compound (Noalox) to the alum conductors in the Jbox as well as at all connections (load centers)? If your ditch is still open you may want to lay electrical caution tape about 6" below the topsoil finish.

ETA. Also, strip back more insulation on the splicing conductors so the split bolts' nut makes good metal to metal surface contact without insulation interference. I was "googling" 2-2-2-4 MHF cable for an undergound job and your thread popped up

****! I'll have to confirm on the packaging if it was dual rated or not. Thanks for catching that. What happens if it isn't, corrosion from the dissimilar metals? I assume my house isn't going to burn down tomorrow, if I need to and can't replace it for a week or so.

Yes, every connection got the oxidation prevention.

The ditch is filled, but I did put some caution tape in, about a foot above the conduit (so about a foot down from the surface). I forgot to mention that.

Pooch897 · Jun 7, 2014

where did u buy the wire from? Im going to be buying 100' and I live near you. Just seeing what I should expect to pay

PRH44 · Jun 8, 2014

The split bolt will be marked CU/AL for copper/Aluminum . It will be marked AL for aluminum only and CU for copper only.
Dissimilar metals will have a galvanic reaction. Less Noble metals (anodic) Like Aluminum and more noble (cathodic) Like copper have different electrode properties. Add some moister (an electrolytic) such has humidity and the process begins. Galvanic reaction create an attack on the anodic metal. The ions will travel from the anodic metal and collect on the cathodic metal. Leaving the Aluminum to corrode quicker than normal.

Yarz · Jun 8, 2014

The MHF? It came from Lowes, was $1.47/ft

Yarz · Jun 8, 2014

PRH44 said:
The split bolt will be marked CU/AL for copper/Aluminum . It will be marked AL for aluminum only and CU for copper only.
Dissimilar metals will have a galvanic reaction. Less Noble metals (anodic) Like Aluminum and more noble (cathodic) Like copper have different electrode properties. Add some moister (an electrolytic) such has humidity and the process begins. Galvanic reaction create an attack on the anodic metal. The ions will travel from the anodic metal and collect on the cathodic metal. Leaving the Aluminum to corrode quicker than normal.

I assumed it was corrosion from dissimilar metals. I just found the packaging, and it is actually not marked as to what it is for. But when I look the part number up online, it does say for copper to copper connections. I will get those changed out ASAP

Thanks Guys!

Pooch897 · Jun 8, 2014

Winlectric in Brackenridge has pretty much everything you'll need at good prices.

Yarz · Jun 8, 2014

Made some time to take care of the split bolts today. These are dual rated:

https://scontent-a-lga.**.fbcdn.net/hphotos-xpa1/t1.0-9/10462496_669051344190_5444549416349368703_n.jpg

JohnX14 · Jun 9, 2014

MoFoJoe said:
Pic #1 The split bolt doesn't look to be dual rated (CU/AL) based on the color and lack of a separation saddle. I can't tell, but did your apply any alum. inhibitor compound (Noalox) to the alum conductors in the Jbox as well as at all connections (load centers)? If your ditch is still open you may want to lay electrical caution tape about 6" below the topsoil finish.

Oxide inhibiting compound isn't required and isn't recommended for aluminum wires manufactured after 1981. (IIRC on the date.) Somewhere I have a memo from a manufacturer.

MA took that requirement out of their code in 1993. I'm not sure if it was ever in the NEC.

Aceman · Jun 9, 2014

JohnX14 said:
Oxide inhibiting compound isn't required and isn't recommended for aluminum wires manufactured after 1981. (IIRC on the date.) Somewhere I have a memo from a manufacturer.

MA took that requirement out of their code in 1993. I'm not sure if it was ever in the NEC.

I think you're mistaken. There is a big difference between "not required" and "not recommended."

Here's Southwire's take on it:

When terminating aluminum conductors, there are several practices one should be aware of to ensure a
quality connection that will remain trouble free.
1) Always use a connector that is listed for use with aluminum wire.
2) The following is recommended but not required. Always follow the connector manufacturer’s
instructions
a. The surface of the conductor should be wire-brushed to break any aluminum oxide
barrier leaving a clean surface for the connection.
b. The use of anti-oxidant compound, joint compound, is not required unless the
connector’s manufacturer requires it. However, the use of a listed joint compound is
always a good practice.

http://www.simpullsolutions.com/documents/SIMpullTHHNInstallationandApplicationGuide8-15-07.pdf

alfredeneuman · Jun 9, 2014

It was never in the NEC. It was left up to the manufacturers.

It was enforceable because of NEC110.3(B) which says "Listed or labeled equipment
shall be installed and used in accordance with any instructions
included in the listing or labeling."

They just failed to include it in the instructions.

Detached Garage Power with MHF

Yarz

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Aceman

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Yarz

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pattenp

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Yarz

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