Electrical wiring to tractor shop

Dave Sherburne NY · Nov 29, 2013

Just saw John T's post about old barns and made me think of an electrical question I have.
There are 2 UF cables, 3 #10 wire plus ground wire in each cable running from my house to the shop underground. Red Black, White and 1 bare. Right now one cable powers the Circuit breaker panel in the shop and 2 wires in the other go to the phone out there. Works fine. Don't know what size breaker is powering the shop now. QUESTION, if I hook the 2 reds the 2 whites, the 2 blacks, and the 2 bare grounds together to make one 3 plus ground wire cable what size DP breaker can I put in the house to power the garage? Hope you can understand my goal here, I can hardly understand it myself. The house is in the process of getting a new square D service entrance installed right now.

Sparktrician · Nov 29, 2013

If I understand, you are wanting to "parallel" the two cables? By code, you cannot parallel any cable smaller than 1/0......so.....legally....no you can not do that.

With that said.....a #10UF cable is good for 30amps....

Samuels68 · Nov 29, 2013

If I understand correctly, you want to combine the two feeds into one parallell feed, right?
By code, you cannot parallel #10 wires, so if you did it would not likely pass an inspection. #10 is good for 30 amps, so in theory, you would have 60 amps of load capacity, however, the code doesn't say what it would be, because the code doesnt allow it.
Another option may be to put in two small subpanels, each with a 240V 30A feed. Around here you can buy 6 circuit subpanels for less than $20, or a slightly larger 12 or 20 circuit for around $50. In the end, you would wind up with the same current carrying capcity, and it would be a code compliant install. Don't forget to separate neutrals and grounds in subpanels, and do not bond the neutral and ground together!

Bob Bancroft · Nov 29, 2013

I would go with Samuels plan. The good news is you have four wires, giving you enough to meet code with separate neutral and ground.

John T · Nov 29, 2013

You didn't mention the length of wiring run from house to shop, depending on the current draw and distance, that 10 Gauge wire may or may not cause excess voltage drop to be a concern???

I don't think the NEC has changed since then, but we weren't allow to use such small wire in parallel runs IN THE EVENT THE NEC OR ANY OTHER LOCAL AUTHORITY MATTERS TO YOU?? That's between you and them. YES BILLY BOB it could "work" to carry 60 amps of current since 30 amps plus 30 amps equals 60 amps, in theory at least.

So if you were to use parallel runs (NOT my advice) you need to protect the feeder(s) so you "could" therefore use a 60 amp 240 volt 2 pole breaker in your main panel (with proper splicing and feeds to breaker). The other option listed below I believe is to just use 2 panels and 30 amp breakers?

Sounds like youre already well aware for that 120/240 volt single phase SUB Panel you run out 2 UnGrounDED Conductors, 1 Grounded Conductor (Neutral), 1 Equipment GroundING Conductor, DO NOT bond Neutral and Ground at the sub (keep separated and isolated from each other) and dont forget the GroundING Electrode out at the shop.

John T

TractormanNC · Nov 29, 2013

Not to rain on this party but, in the back of my mind I think there is a provision in the code of not more than ONE service to building unless they are different voltages,or maybe one single phase and another 3 phase. Am I losing my mind or not?????????

Bob Bancroft · Nov 29, 2013

I have heard that too. Someone explained to me that emergency workers should be able to quickly locate and shut off power to a building. Multiple feeds would complicate that. But then I've seen commercial buildings which have been added on to several times, with separate feeds to each one!

dr sportster · Nov 29, 2013

It has to have a sign on the outside of notice to more than one service feeders.

Samuels68 · Nov 29, 2013

Yeah, I was thinking of that as I made my reply. My interpretation (Not saying its right) was that you do not have two separate services, but two separate circuits, since both originate from one panel, presumably with a single service feeding the upstream panel. Many commercial buildings have dozens of panels, subfed through main distribution panels, but a single incoming service.
I do agree with sportster, a sign noting seperate feeds would not be a bad idea, at least on the panels themselves.

paul · Nov 29, 2013

You can't do that by code.

If one of the parallel wires fails somehow, the other one would burn up but the breaker wouldn't know it, so you would be unprotected in case of failure. So you can't twist the wires together.

You also can't run them both as seperate feeds to the same building, safety issue for being able to cut the power off to the building with one switch.

To know the amount of current the wire can carry, you would need to tell us how long the wire is. Just as water pressure decreases in a longer garden hose, so too there is voltage drop in a wire.

Paul

Ted in NE-OH · Nov 29, 2013

I would not do it. One wire will have slightly lower resistance than the other and hog all of the current. Same with paralleling fuses.

Pete in MD · Nov 29, 2013

If there's no need for more than 30 amp service in the shop now and you don't plan on adding anything that will need more than 30 amps, just hook up 1 UF cable to your new house service panel and move the phone power circuit in the shop to the subpanel that feeds the shop now. The other UF cable can then be a spare if the cable in use develops a problem.

dr sportster · Nov 29, 2013

It is not an idea it is a code article 230-2 states that a building must be supplied by only one service then exceptions A-D list cases where it can be supplied by more than one service [fire pumps etc] exception E states that a plaque [as I called a sign ] must be at each feeder entrance to notify anyone who needs to know -- fire deptment. Most of the code has to do with fire more than electrocution. Read 200 - 220 -2 220 -3. That is if you are into the NEC otherwise work on a tractor and forget electrical code. Disclaimer - I also make up stupid electrical answers at times for my own sick amusment.

Samuels68 · Nov 29, 2013

OK. I agree that if the building was in fact fed by 2 or more SERVICES the signs would be a requirement. I am using the definition of "service" from article 100 "The conductors and equipment for delivering electric energy from the serving utility to the wiring system of the premesis served"
By that definition, I would not classify a SUBFED PANEL as a service but as premisis wiring, thus no requirement for signage, but still a good idea.
As far as a single disconnecting means, if you throw off the main breaker or disconnect at the SERVICE ENTRANCE, you will still disconnect the entire premisis wiring system.
The fact that two supposedly educated and trained individuals (You and I) can have a difference of interpretation is exactly why 90.4 states that the AHJ has the responsibility for making interpretations of the rules.
I am not saying my suggestion is perfect, take it at what it is, a suggested solution to a problem, posed by a faceless individual on a discussion forum.

dr sportster · Nov 29, 2013

I don't think we are having any difference of opinion. Two service enterance feeds -plaque on building. Art 100 should be gone over before reading the 220 section stuff. Just to be clear on definition terminology. I am agreeing with you [I think}

Samuels68 · Nov 29, 2013

Awesome. Now we are all on the same page, what should we tackle next, religion...politics...climate change...oil additives?
John T has spent many a time trying to educate many on here about electrical issues, and often references the value of free advice. He is right. The best advice for any code related issue brought up here should be a standard "Contact your local Authority Having Jurisdiction" but that would seem to go against the whole purpose of asking a question on a public forum.

Bob Bancroft · Nov 29, 2013

I'll take climate change. That's the easy one. The climate has ALWAYS changed. Sometimes dramatically so.

John T · Nov 29, 2013

Seems Gun Control,,,,,,,Electrical Questions,,,,,,,,,Whats the best oil or best spark plugs,,,,,,,,,,,,Legal Questions, AND THEY ALL CRAWL OUT OF THE WOODWORK LOL

Back to "lectricity" we didn't like multiple services either for the safety reasons stated below, it would be safer if one service was shut down the other would automatically. In some applications I used a shunt trip breaker if I wanted to shut off power to something. I take it this is his home shop service and were unsure what, if any, local authority may or may not be there to approve or disapprove what he does, but REGARDLESS I wouldn't parallel two of those small conductors and if he went against any code and installed 2 services Id have an auto shut down procedure so in case one was turned off the other would be also.

Yep I usually end such topics with that ask local authority for advice, a body cant go to wrong with that yet that dont stop Billy Bob n Bubba now does it lol

John T

dr sportster · Nov 29, 2013

All you really needed was the first posted answer by Sparktrician. It stated exactly what you needed to know without everyone else who did crawl out of the woodwork. Crawling back in now.

David G · Nov 29, 2013

I will crawl out and agree with sparktrician.

John T · Nov 29, 2013

Don't........Stop,,,,,,,,,,,,Crawl back out lol

G night yall

John T

Electrical wiring to tractor shop

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