Adding subpanel for new welder

[Chris611]

Hey guys. I just picked up a Miller Maxtron 450 w/ S22A wire feeder. I am going to run on single phase 240 which means that I will need an 89 A circuit for full power. Don't know how often I will run at full power, but would like the option. Currently I have 200 A service to the house. I would like to add a 100 A sub to the garage to run the welder, etc. I understand that I will not be able to have all the electric appliances in the house and garage on at one time. Currently there is a utility pole 10' from the corner of the garage. It has a box with a meter and a 200 A breaker with slots for more breakers below. I have attached a pic of this box. From the box the wires go underground to around the back of the house into the service panel for the house which has a 200 A main breaker also. The service panel in the basement is bonded. It also appears that the panel on the pole is bonded. The bare ground wire seen in the pic goes to a metal rod in the ground. I was hoping to put a 100A breaker in the box on the utility pole, then run power to a 100 A subpanel in the garage. Hopefully all this is correct. One thing I don't know is if the subpanel in the garage should be bonded or not bonded. If I understand properly, if the sub was coming off the main service panel that was bonded, then the sub should not be bonded, but in this case, I'm not sure. Sorry for the long post, hope it's not too confusing. If so I can attach a diagram.

Thanks
Chris

[N20Silverado]

Chris,

The subpanel in the garage should not be bonded. You will need to run a total of 4 wires to your shop: 2-Hot, 1-Neautral and 1-ground. The neutral will run to an isolated neutral bar and the ground will run to a bar screwed to the metal enclosure. The panel in your house is bonded beacuse they didn't run a seperate neutral and ground.

Did that answer all of your questions?

Tim

[Chris611]

Thanks for the reply. From what you said, I take it that maybe the panel inside the house should not have been bonded, but for whatever reason they didn't run a ground wire so they bonded it? Is the idea to have only one ground per "system" or structure? Sorry, didn't mean to turn this into an electrical forum. I may look for some books on it. I just like learning about these things.

Thanks
Chris

[Sberry]

It needs a fault return path, 3 wire feed needs bond. You have a main lug feed thru panel. Good setup. Some you can put 125A breaker in. If your house isnt intense you will have no problem

[Chris611]

Want to make sure I understand. I will need to run 4 wires (2hot, 1 neutral, 1 ground from the thru feed panel on the utility pole (shown in the picture) to the sub panel in the garage and leave the ground and neutral in the sub seperated. When I connect these 4 wires at the feed thru panel on the utility pole, the neutral and ground will be connected to the same bar since the panel on the pole is bonded? Is it correct to say that I do not need to drive a ground rod in since I am hooking to the ground at the thru feed panel which has a ground rod. Also what are the opinions on metal vs plastic conduit? I will be buring 24" deep and the run is approximately 12' plus down the pole and up the side of the house into the subpanel.

Thanks
Chris

[dcsound]

Want to make sure I understand. I will need to run 4 wires (2hot, 1 neutral, 1 ground from the thru feed panel on the utility pole (shown in the picture) to the sub panel in the garage and leave the ground and neutral in the sub seperated. Is it correct to say that I do not need to drive a ground rod in since I am hooking to the ground at the thru feed panel which has a ground rod. Also what are the opinions on metal vs plastic conduit? I will be buring 24" deep and the run is approximately 12' plus down the pole and up the side of the house into the subpanel.

Thanks
Chris

You are correct on the wiring. For burying conduit I would use PVC (plastic) because it is will not corrode and is easy to work with. It is assembled by solvent welding together the pipes and fittings. The fittings for EMT metal conduit do not seal out moisture and therefore preclude it's use outside and underground. You could use ridgid, threaded metal conduit but this is more expensive than PVC and must be cut and threaded. Use #2 copper wire for the two hots and the neutral and at lease #6 for the ground. You can also use aluminum wire for the hots and neutral as long as the breakers and panel are rated for it. The wires feeding the wire in your picture appear to be aluminum. If you use aluminum wire, apply anti oxidizing compound to the ends of the aluminum wires before tightening the terminals. This step is not necessary with copper wire. This compound should be available wherever you are purchasing the electrical supplies. There is type UF cable that is approved for direct burial without conduit but personally I prefer the protection of conduit and this cable may be more expensive than conduit and wire. According to the electric code, plastic tape marked "buried electric line" is supposed to be placed on top of the buried conduit prior to backfilling the trench, but I have no idea if most people working on backyard projects actually do this.

[MAC702]

...According to the electric code, plastic tape marked "buried electric line" is supposed to be placed on top of the buried conduit prior to backfilling the trench,...

Do you have a Code reference for this?

[Sberry]

You need a ground rod also.

[Sberry]

If it was my place and intended on hanging around I would be digging up the line to the house and adding a wire. I have done it, not as hard as it seems sometimes but the 3 wire sub setup is not ideal these days, probably never was. We have so much interconnected equipment in a modern residential setting. A lot of places over the years I dug up and fixxed.

[Sberry]

Do you have a Code reference for this?

Man, a guy dont get much slack here does he??? ha

[flukecej]

The Reference number is NEC 300.5 (D)(3) for warning ribbon above conduit or buried cable.

Also, as a rule, even a private property owner should call his states one call center before digging more than 16" deep in the yard. Better to be safe than sorry.

[Chris611]

I called Iowa OneCall on Monday morning, which is Iowa's locating service. Everything is to be marked by today. Good point though. I have also called a professional electrician to give me an estimate on the work. I went and priced out the supplies last night. That way I can get an idea of what he is charging for supplies vs. labor. I wonder if the electrician would be up for me doing the work paying him a fee to check it over? In other words if I do all the digging, wiring, mounting boxes, except the final hookup and pay him to inspect it and let me know its installed correctly. Do you guys think anyone would go for this. I would like to do my own work, but I know this circuit will be pulling a lot of amperage and don't want to have any problems.

Thanks
Chris

[unib63]

What does it hurt to ask? You will already have the guy at your house. I would probably ask him right away before he puts time into putting together an estimate. I know that my electrician was more than willing to let me do what ever I felt comfortable doing. I would explain to him that you would have done it your self but were concerned with what may happen if something was wrong. My guy loved the idea, as he got paid a little to inspect what I did and was able to also work on other projects. He told me exactly what needed to be done to make code requirements and also had some suggestions of stuff that could be done during install that would be a benefit later on. Most of his ideas I never would have thought about until I was finished.

Hope this helps!
Brennen

[Sberry]

It isnt that hard of job, digging is part of it. I had a bud whining about the cost of an install, I said, well you pay 2 electricians to dig a trench. You woulda thunk college boy would have thought there might need a hole for the wire but I guess that didnt occur to him, http://www.selfhelpandmore.com/homew...rage/index.htm This link shows the general layout.

[MAC702]

...According to the electric code, plastic tape marked "buried electric line" is supposed to be placed on top of the buried conduit prior to backfilling the trench,...

The Reference number is NEC 300.5 (D)(3) for warning ribbon above conduit or buried cable.

Also, as a rule, even a private property owner should call his states one call center before digging more than 16" deep in the yard. Better to be safe than sorry.

The reason I asked is because it was an improper reference and NOT the requirement that a reader would be lead to believe.

This Code applies only to DIRECT-BURIED SERVICE CONDUCTORS. That's a far cry from a branch circuit in conduit. And it should be noted that the ribbon is pretty much useless unless, as the Code specifies, it is placed a foot above the cable.

I wholeheartedly agree that Call-Before-You-Dig is a necessary step. And each person should also clearly map anything he puts in his own yard. You'd be amazed how handy that information will be many years down the road.