New shop feeder and wiring

[Razorback0162]

Hello Everyone, I have finally built my new shop 30x62 (30x50 enclosed) and now I'm ready to run power to it. I plan on running from my house panel (200 amp) to a 100amp sub-panel in the shop (150' away). Since Copper is high, I am considering using AL MHF - use2 rh / rhw-2 to run between the panels and then 12/2 - 14/2 for the internal shop wiring to lights, etc. I have the normal power tools and will have a couple of receptacles for welders (one at a time). The only continuous motor running will be a fridge. I will have heat but no A/C....figure on fans for that. I figure on a 90amp breaker at the house and another at the shop as a main/disconnect...square D box with 20 spaces.
Anyone see where I may be off the rails?

 

[pattenp]

You most likely will be fine with 90A. What wattage of heater are you thinking of using? Use a 100A or 125A main breaker panel for the sub. The 100A or 125A main breaker in the sub-panel will be the disconnect. The 90A breaker in the main panel is what protects the feeder.

I assume you are thinking 2-2-2-4 MHF? The MHF needs to be in conduit where above ground and inside the structure.



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[Razorback0162]

Yes i was looking at using 2-2-2-4 MHf from Lowes..$1.47 ft. 2" conduit the whole way above and below ground. Yes...I think I typed wrong earlier....100amp at sub for disconnect. The heater is a gas furnace given to me...just need to change the orifice and spring as it was running on propane and I will be putting natural gas to it. Need electric just for the blower. I am a little unclear on grounding though....my understanding is new detached structures must have their own ground rods and ground back to main panel?

 

[fastbike02]

This may help you

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yes depending on your local code you will need 1 or 2 grounding rods spaced 6' apart, you will also remove the bonding screw inside your sub panel

 

[theoldwizard1]

Another picture

View media item 33304

 

[Razorback0162]

That is pretty much what I had in my head.....thanks....I just didn't/don't understand the need for the ground rods at the building when the box is grounded back to the house ground. Assuming NEC is allowing for newer structures these days to have more electronics in them ( I will have a flat screen and Satellite receiver)
So I'll have to figure on running back out of the box with a ground wire in a small conduit to go through the wall to ground rods. What do you think? 6ga copper?

 

[pattenp]

Yes use a #6 bare copper to the ground rods. The ground from sub-panel back to main is the equipment ground for clearing fault current. The ground rods are for lighting strikes. Totally two different purposes of the grounds. The ground rod conductor does not need to be in conduit as long as it's not in a place where it may be damaged. There should be a very small knockout in the bottom of the panel that the ground wire can pass through and you can bore a small hole in the wall to get the wire to the outside. Be sure to space the rods 6 feet from each other along the grounding conductor.



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[wyliesdiesels]

That is pretty much what I had in my head.....thanks....I just didn't/don't understand the need for the ground rods at the building when the box is grounded back to the house ground. Assuming NEC is allowing for newer structures these days to have more electronics in them ( I will have a flat screen and Satellite receiver)
So I'll have to figure on running back out of the box with a ground wire in a small conduit to go through the wall to ground rods. What do you think? 6ga copper?

As pattenp said, grounding electrodes and EGC/equipment grounding conductors are 2 different animals. Both are required for NEW detached structures.

Here's a good read for u:

http://www.electriciantalk.com/articles/the-confusion-of-the-term-grounding/

 

[bullnerd]

Razor, my utility company has all the info on their website, including how many/where to put the rods. Might check yours.

 

[Razorback0162]

Thank You all...makes sense now ....I will run the ground out of the box and through the wall in conduit as it is a post frame metal building.

 

[vision8]

This is my exact layout 200A main in the house (1984 build ) and have a 100S in my workshop 150 feet from the house. I put everything in conduit or pipe for protection in the trenches that I dug ( John Deere backhoe on my CUT ). Dug two trenches so that the lines we isolated and shortest distance from feeders).
Trench 1 has 2" PVC Conduit with 3 - # 2 Copper feeds and a # 6 Copper neutral if I recall ?!? )
Two 1" abs runs for water inside a 3"ABS pipe.
Trench No. 2 has two 2" abs pipes for cat 5 and cat 6 and a couple of runs of alarm/security feeds. One 1" black pipe connected to 1" poly gas line for the heat.
When doing the investigation the use of aluminum feeders kept coming up with my electrical engineer and electrician as 'Not a good Choice' !!! Yes it is approved but has been showing up as problematic after five years or so in sub-divisions around here ; if the protective coating on the cable is damaged even small cuts will produce corrosion from water and aluminum in our clay soils. Decided it was not worth the risk and the copper was a better solution for me.
My use will be for auto/motorcycle repairs and inside out of the COLD ( it's -24 F + 24 mph wind today ) out there ! Shop has been at 42 F with only a 30,000 BTU direct vent temporary furnace installed so far , radiant floor heat for next year ?!?
Good Luck on your Shop.

 

[Razorback0162]

Been listening to some friends...I think I'm letting them get in my head, but they are making me a little afraid not to use copper wire as the feeder instead of MHF al wire. If I was to go with copper, any suggestions, tips, tricks?

 

[Norcal]

Improperly installed copper is just as bad as improperly installed aluminum I would not listen to folks who do not know what they are talking about. If you have lots of money to spend then buy copper.

 

[pattenp]

Improperly installed copper is just as bad as improperly installed aluminum I would not listen to folks who do not know what they are talking about. If you have lots of money to spend then buy copper.

+1 to that.

 

[wyliesdiesels]

Been listening to some friends...I think I'm letting them get in my head, but they are making me a little afraid not to use copper wire as the feeder instead of MHF al wire. If I was to go with copper, any suggestions, tips, tricks?

People who are afraid of todays aluminum alloy wires are stuck in the 60s...

http://www.southwire.com/commercial/ALBuildingWire30YrsOfReliability.htm

 

[bullnerd]

( John Deere backhoe on my CUT ).

No way! Not heavy enough!

 

[Pwrgeek]

Al wire of today is fine. Just make sure you don't tear up the insulation putting it in the pipe and dope the connections with noalox and it'll outlast you.


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[rburke65]

PVC conduit is inexpensive. Run it BIG and run an extra run...or 2!