Steel Building Electrical Plan

[lil_TXRanch]

Admittedly long post….thank you for taking time out of your day to read/respond, it is greatly appreciated.

So I finally got a steel building workshop put up (30x40x12), the utility to come out and drop a pole, and now it’s time to wire it up. I have spent the last year trolling electrical forums all over the net, asking questions, reading numerous articles, and while I’m no electrician I feel this is a task I can undertake. Just looking for some feedback on my plan, cost-savings ideas, etc. Please let me know if you see any issues, safety or otherwise.

From the meter/main disconnect (200 amp), 2/0-2/0-2/0-6 copper to a 200 amp load center inside building, 55-60 feet, in 2” PVC conduit.

EMT conduit run throughout, along steel purlins, and grounded. Three branch circuits (1 for each wall, excluding front) will be fed by a 20 amp GFCI breaker. Each branch circuit will have a quad box every 5 feet.

Four 240 volt receptacles will be run, one on each major support member, plus one in a corner for the compressor that will he housed outside the building in a shed. I thought for ease of installation and future stuff that I would just make all of these 50 amp receptacles and run them accordingly; i.e. 6 gauge wire and individual breakers for each.

Lighting will be T8 fluorescents overhead hung at 11’. There will be 12-18 fixtures on three different switches and breakers. This is more for convenience and sectioning off the lighting so I’m not worried about the load on the 15 amp GFCI breaker. Depending on the exact fixture, these will either be hardwired in or plugged into receptacles (my preference).

***THHN for all wire***

Overall I’m comfortable with the load calcs, placement, etc. Just looking for some last minute feedback from those who are much smarter then I. Thanks again in advance!

 

[mrb]

cant use 2/0 copper (other than on a residential service) for 200 amps -have to use 3/0

dont put your lights on a GFCI breaker

 

[Charles (in GA)]

It looks as if the power enters the building one side and the panel is on the other side. You might rethink the location of the panel and the point of entry for the power. --or-- is the PVC conduit and 50 to 60 ft of cable the run from the house to the shop? Just not clear on this.

Will this building have its own meter? Or is it fed from a house or disconnect at a meter on the house?

Might do a floorplan so you can see where your loads will be. If you plan on a workshop area in one particular corner, drill press, lathe or multi machine tool of some sort, grinder, etc, you may need more outlets in that area.

Will you be doing your own work? ie conduit install and wire pulling, etc?

If you never have bent conduit before I highly suggest this document, it is the best explanation of the calculations and process involved that I have run into.

http://www.mikeholt.com/documents/freestuff/BendingRoundRaceways.pdf

Charles

 

[Aceman]

I'd pull 3/0 3/0 1/0 #6, no reason for a fullsized neutral when you'll have plenty of 240 volt load.

Second, a 50 amp circuit only needs #8 when you're using THHN, if it were Romex you'd need #6.

 

[mrb]

I'd pull 3/0 3/0 1/0 #6, no reason for a fullsized neutral when you'll have plenty of 240 volt load.

Second, a 50 amp circuit only needs #8 when you're using THHN, if it were Romex you'd need #6.

whats the criteria for reduced size neutral? this is one of the areas where I have no knowledge.

 

[lil_TXRanch]

cant use 2/0 copper (other than on a residential service) for 200 amps -have to use 3/0

dont put your lights on a GFCI breaker

I assume this is NEC, is 2/0 safe, effective, practical? Or is it not and that's why it's code?

Would the GFCI trip often with the lights on it or is it just not practical/needed?

It looks as if the power enters the building one side and the panel is on the other side. You might rethink the location of the panel and the point of entry for the power. --or-- is the PVC conduit and 50 to 60 ft of cable the run from the house to the shop? Just not clear on this.

Will this building have its own meter? Or is it fed from a house or disconnect at a meter on the house?

Might do a floorplan so you can see where your loads will be. If you plan on a workshop area in one particular corner, drill press, lathe or multi machine tool of some sort, grinder, etc, you may need more outlets in that area.

Will you be doing your own work? ie conduit install and wire pulling, etc?

If you never have bent conduit before I highly suggest this document, it is the best explanation of the calculations and process involved that I have run into.

http://www.mikeholt.com/documents/freestuff/BendingRoundRaceways.pdf

Charles

The shop will have its own meter service. Because of the way the property is laid out with existing poles, the power will be run and the final pole set approx. 15 feet from the building (Utility requirements say that you can’t have a structure any closer to the pole so that's as close as I can get it).

From there, I already have the PVC run underground, entering the slab, it then runs through the footer and comes up from the floor right near where the walk-through door is, this is the 50-60' run. I did it this way so that the panel is easily seen and found by anyone.

As of now, I don't have all the toys that I envision in the future so I’m just doing general power layout, but I’ve drawn up many a plan LOL.

I do plan on doing my own work and have printed, read, and highlighted that article numerous times, it really is a good article.

I'd pull 3/0 3/0 1/0 #6, no reason for a fullsized neutral when you'll have plenty of 240 volt load.

Second, a 50 amp circuit only needs #8 when you're using THHN, if it were Romex you'd need #6.

So no realizable benefit to using full-sized ground, if not then 1/0 sounds good to me to?

Thank you for the clarification sir.

Thank you again for your help/comments. Please let me know if my responses make sense and what ya think?

 

[Aceman]

whats the criteria for reduced size neutral? this is one of the areas where I have no knowledge.

Outside feeders 225.3(B)-->220.61(A)-->Art. 220

Inside feeders 215.2(A)1--->Art. 220

Notice 215.2(A)1 allows us to drop the neutral to the EGC size if wanted. That could be a #8 neutral for a 100 amp feeder.

In the real world, we'll typically drop it two sizes without doing a load calc if there's some 240 volt load. The inspector won't even question it, if we tried to go even smaller(which is likely we technically could) the inspector would probably ask for a load calc. The odds he'll ever have 200 amps on his neutral is about nil.

A 1/0 neutral is still good for 150 amps, that'd be a lot of 120v load...

 

[mraredneck]

Aceman;
I do understand your reasoning for a down sized neut. However I don’t understand the reason to do it? The cost difference isn’t that much and I would have my protection for P.C, instruments if I ever use them. It is a common practice to down size with 220V loads and you would be fine doing so. I just wouldn’t in my space.


RED

 

[Charles (in GA)]

Essentially, you can ignore all 240 loads when trying to figure out neutral sizes. If you do a good job of splitting the loads of 120 circuits, you can eliminate much of the load on the neutral also.

My lighting for instance is a high draw item. A dozen MH fixtures at 4 amps each on 120V circuits. I ran a multiwire system for the lighting, double pole light switches and all, and evenly split the lights on either side of the multiwire, this places no load at all on the incoming neutral. This leaves ceiling fans (minimal) a drill press (1 hp) and a barrel fan and a few other items like trouble lights. I guess one of the highest 120v loads is the 1500 watt 2.5gal water heater under the sink.

Charles