planning the wiring for my new shop

[TKFireman]

I have a new shop in the works and I'm trying to plan out the electrical side of things. I'm planning on a 100 amp service to the shop from my 200amp service in the house. Its 127' from house to shop, so maybe 140' of wire total. I'm planning on using aluminum wire because of the cost - ran in electrical pvc conduit under ground. My question is what size wire? 1-1-1-3 or 1/0-1/0-1/0-3? Or other? Home Depot has the 1/0 for $2.70 a foot, also found it online here for cheaper, if its the right wire. http://www.wireandcabletogo.com/Alu...-0-3-2-ground-SER-Aluminum-Building-Wire.html

Another question I have is that I want to run a water line to the shop with a frost free hydrant outside the shop. No plumbing inside the shop. I have ran water lines around here, at least 1' under ground and no freezing problems. Can the water line and electrical lines be put in the same ditch and pass inspection?

Thanks in advance for the help.

 

[pattenp]

Your link is the wrong type wire. Go back to Lowes or Home Depot and ask for Mobile Home Feeder or wire that can be installed in wet locations such as THHN/THWN. Do not get cable that only has a USE rating because it can not be run inside. The #1 Al is the smallest you should use for 100A service to the garage.

 

[sberry]

If you go 90A you can use number 2, its designed for this and the box stores carry it.

 

[pattenp]

If you go 90A you can use number 2, its designed for this and the box stores carry it.

Very good suggestion. If you use a 90A feeding breaker you can use 2-2-2-4 Mobile Home Feeder and HD and Lowes carry it. The last time I priced it it was $1.47 a foot. It has a rating of RHH/RHW-2/USE-2 so it can enter the structure to the panels. But it does need to be in conduit inside.

Looks like this....

 

[TKFireman]

http://www.homedepot.com/p/Southwir...3104501/202316491?N=c578Z1z0zuci#.UVrizKq3PMI

Is this the wire you mentioned? I don't know that I need 100 amp, 90 would probably be enough, but I do know home depot doesn't have 90 amp breakers, only ones I saw were 60 amp, and the jumped to 100 amp. I'm sure I could find them somewhere though. Gonna go out and do some more shopping around and price checking today at Lowes and a electric supply wharehouse

 

[TKFireman]

So 2-2-2-4 would work with 90 amp breakers, even with the 140' or so distance?

 

[pattenp]

The next link is also wrong that is SER cable and can not go under ground. The 90A breaker is going to be gotten at an electrical supply because it's not a common size at the big box stores. I have the same setup but just use a 60A breaker in the main panel to power my shop with a 100A panel in the shop.

The 90A breaker is $$$ where as the 60A is cheap. The 90A breaker is the max you can use on the #2 Al.

 

[pattenp]

So 2-2-2-4 would work with 90 amp breakers, even with the 140' or so distance?

Have you figured what continuous and non-continuous loads you will have at the garage? The #2 for 90A is fine for 140' if the loads are not going to be at the max of 90A. You will have less than 3% voltage drop at a load of 80A.

 

[wyliesdiesels]

So 2-2-2-4 would work with 90 amp breakers, even with the 140' or so distance?

Actually, at that distance you're just over the recommended voltage drop of 3%, so u should go larger! What do u plan on running in your shop? Most people over estimate the amount of power they actually need! Will it be just you working in the shop?

 

[theoldwizard1]

I have the same setup but just use a 60A breaker in the main panel to power my shop with a 100A panel in the shop.

I assume this is code legal or you would not be recommending it !

But it does not seem very practical. You could trip the 60A in the main panel putting you in the dark with nothing trip in the shop. Could be a long walk !

The 90A breaker is $$$ where as the 60A is cheap. The 90A breaker is the max you can use on the #2 Al.

No kidding ! 90A "main" breakers cost way more than 90 circuit breakers.

 

[DirtRoad]

I have a 125amp panel in my shop but only feed it with 60amp breaker. Not sure how that isnt practical.

Most people i see post here about powering their shop seem to think they need 100+ amps, a one man hobby shop using more than 60amp's would be impressive. Chances are even if you turned on everything you own you wouldnt come close to using 60amps.

There are exceptions but not very many.

 

[pattenp]

I assume this is code legal or you would not be recommending it !

But it does not seem very practical. You could trip the 60A in the main panel putting you in the dark with nothing trip in the shop. Could be a long walk !

Done all the time. The 100A panel is so common and easy to get and gives you plenty of breaker space. The 100A main breaker serves no more than a main disconnect. The feed is protected by the breaker back in the main panel. And yes if I was continually overloading the feed it would be a long way back to the house but I've never had that happen.

No kidding ! 90A "main" breakers cost way more than 90 circuit breakers.

I'm talking about 90A circuit breaker compared to a 60A circuit breaker.

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[TKFireman]

Right now I only have a 60 gal 220 compressor, 110 mig and other common 110 tools like table saw, chop saw and such but I'm trying to plan for the future. I know I will not be running all these tools at once but I'm planning for a 2 post lift, larger 220 welder, refrigerator, common lights and recpticals and a little wiggle room in case I add something else in the future.

 

[DirtRoad]

Even if you had all those things you still would be hard pressed to blow a 60amp breaker.

 

[theoldwizard1]

Plasma cutter is probably the worst, because the compressor needs to be running at the same time.

 

[theoldwizard1]

The 100A panel is so common and easy to get and gives you plenty of breaker space.

I understand and concur !

Pretty much why all new homes have 200A panels. They really don't use that much, but the way the codes are written you need that many breaker slots.

 

[offroadsteve]

I agree with theoldwizard, the plasma cutter + air compressor would be your worst-case if the compressor kicks on while you are cutting... but even that is a short duration surge and probably wouldn't kick even a 60A circuit breaker. Most plasma cutters are <20A input current at 240V. I plan to do something very similar in my shop eventually, and will run the whole thing off the 60A in the panel. If it ever becomes a problem, you can pony up for the 90A breaker and you'd be totally fine.

Back to the original question... power and water in the same trench, as long as you have your depths correct you should be fine. I would be sure to verify this with your local inspector, I would suspect there could be a large variation in "professional preference" on this.

 

[TKFireman]

Can the 2-2-2- 4 mobile home feeder be used in the wall of the house without conduit? I have no way of putting it in conduit in the house

I'm not sure what amp some items pull like a large arc welder, what about the possibility of a small mill and or lathe in the future, would have to be a small single phase unit

 

[pattenp]

Can the 2-2-2- 4 mobile home feeder be used in the wall of the house without conduit? I have no way of putting it in conduit in the house

I'm not sure what amp some items pull like a large arc welder, what about the possibility of a small mill and or lathe in the future, would have to be a small single phase unit

The MHF has to be in conduit when inside the structure because the cable does not have an overall outer sheath. You would need to transition to SER cable by a splice in a large J-box either inside or outside then pull the SER to the panel.

If you use #2 you can try the 60A and if you have problems then up it to a 90A breaker.

 

[TKFireman]

That's a lot of help, SER from panel to outside then transition to the MHF. Seems simple enough. In the shop I could do the same or put the wire in MHF in conduit correct? I may contact the local electric supply store and see if they have the MHF in a #1 or 1/0. I'd rather pay a little extra now and know I have everything I may need back there than to wish I had done it later.

What is the correct way to make the connection from the SER to the MHF?

Thanks again for everyone's help

 

[pattenp]

If you transition to SER for the runs to the panels then you can use URD cable. URD is for under ground outside use only, the splice will need to be made on the outside in a J-box. I think you'll find that the MHF only comes in 2, 2/0, 4/0.

Look at this page...

Look at Aluminum 600V Secondary UD Cable (Quadruplex)

The MHF and SER are under "Aluminum Building Wire"

http://www.southwire.com/products/ProductCatalog.htm



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[TKFireman]

OK, local electric supply place has MHF in #2 and 4/0, they said that they have no other wire rated for under ground use. So, the #2 MHF and 90 amp breakers seem the way to go, with SER at the panels.

How do you connect the SER to the MHF in the j box, I assume a very large wire nut is out of the question, so maybe a clamp style connector then covered in electrical tape?

 

[pattenp]

Both URD and MHF are direct bury cable and only needs to be in conduit for the portion that's above ground but can be placed in conduit under ground for added protection. MHF can be run inside in conduit but URD can only be outside. The reason URD is outside only is because it's only USE rated which is not fire resistant rated insulation.

In the link to Southwire I posted go down to the folder for "Aluminum 600V Secondary UD Cable" and click on it and See the "Quadruplex", it's a URD cable. Oh.. and do search for UD not URD.

 

[bygasper]

Another question I have is that I want to run a water line to the shop with a frost free hydrant outside the shop. No plumbing inside the shop. I have ran water lines around here, at least 1' under ground and no freezing problems. Can the water line and electrical lines be put in the same ditch and pass inspection?

Thanks in advance for the help.

Check with your city or county on building codes. Most locations with city or county oversight (i.e., permits and inspections) require some distance between the electrical and everything else. I buried mine with at least 18" between the main electrical and anything else and 3' deep.

Before somebody says I'm wrong...yes, there are locations where no permits or inspections are needed. Common sense, experience, quality contractors, and oversight rule the day. The middle-of-nowhere is a lovely place and I'm lucky to have a piece.

 

[pattenp]

OK, local electric supply place has MHF in #2 and 4/0, they said that they have no other wire rated for under ground use. So, the #2 MHF and 90 amp breakers seem the way to go, with SER at the panels.

How do you connect the SER to the MHF in the j box, I assume a very large wire nut is out of the question, so maybe a clamp style connector then covered in electrical tape?

If using PVC you need at least an 8X8X4 box and cut your own holes with a hole saw and insert the glue in connector for attaching the PVC conduit. The splices can be done with either splice/reducers or Polaris connectors.

Splice/Reducer

Polaris Connector

 

[TKFireman]

Sounds good, I can do that, just wish I could find a wire in the #1 or 1/0 size range, seems that #2 is marginal for 90 amps at that distance, and I don't know that I want to go down to 60 amp breakers or not, would probably be fine, but I don't want to look back and wish I had gone bigger

 

[theoldwizard1]

Sounds good, I can do that, just wish I could find a wire in the #1 or 1/0 size range, ...

Run conduit and pull individual THWN.

1/0 Aluminum XWHH/THWN is about $0.90/foot.

 

[pattenp]

Run conduit and pull individual THWN.

1/0 Aluminum XWHH/THWN is about $0.90/foot.

I assume you mean XHHW.

To OP: That is an option. But the $0.90 per foot is per wire so that's around $3.60 per foot. If buying individual wires you should be able to get #1

Edit: The XHHW or THHN/THWN is not direct bury so it has to be in conduit under ground.

 

[TKFireman]

Would I need 4 wires or 3? Looks like 3 would work since I have to drive ground rods at the shop

 

[pattenp]

Would I need 4 wires or 3? Looks like 3 would work since I have to drive ground rods at the shop

You need 4 wires, got to have the equipment ground back to the main panel. Plus you need the ground rods at the shop. Also the grounds and neutrals are not bonded in the shop panel.

You can use a smaller wire for the equipment ground. A #6 Al.

Edit: The #6 Al for the equipment ground is the minimum allowed by code for no more than 100A. I would probably use a #4 Al for the equipment ground.

 

[TKFireman]

Made some phone calls
1/0 xhhw $.53/ft single strand so I would need 3 plus a ground
1/0 UD 3 wire $1.40/ft - would have to add a ground wire

So I could run 1/0 aluminum for around $2 a foot or so in 2" PVC conduit.....If I'm understanding what ya'll are telling me either way would work correct?

 

[pattenp]

You're correct. There is some funny code about the ground conductor needing to be up sized when the un-grounded conductors are increased in size. My suggestion is if you use #1/0 Al that you use a #2 Al for the equipment ground.

For the interior runs if you use SER then that should come in 1/0-1/0-1/0-2 to match up nicely for splicing.

 

[TKFireman]

Sweet, I'll see if I can check with an inspector to make sure on the wires, ground size and depth. That's much cheaper than what I had originally thought it would be. Then I need to either run conduit on the interior or transfer to the SER cable on the interior correct? 2" PVC conduit? So 100 amp service for only slightly more than the $1.47 MHF 2-2-2-4 and there will be no question that it will carry the load of anything I may add in the future.

You guys are a wealth of knowledge, thank you for straightening me out. I'm sure there will be more questions to come

 

[pattenp]

... Then I need to either run conduit on the interior or transfer to the SER cable on the interior correct? Correct

2" PVC conduit? 2" is good.

So 100 amp service for only slightly more than the $1.47 MHF 2-2-2-4 and there will be no question that it will carry the load of anything I may add in the future. Hopefully so.

Also be aware any PVC conduit that may be subject to damage (like hitting it with riding mower) needs to be Sch80 otherwise it can be Sch40.

Edit: If using 1/0 you could push it and use a 125A main breaker panel in the shop and feed it with up to a 120A breaker. The catch may be your house main panel may not take breakers larger than 100A.


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[TKFireman]

I applied for the permit this morning. The people in the inspection office were very helpful, but said that they are behind and to expect 2-3 weeks for the permit to be issued, which seems a little extreme to me.

I was able to sit down with an inspector for a while and found out some things. What he told me I'm sure will be argued some, but its what the man who is inspecting it told me. Water line has minimum depth of 12". Power 18" in conduit, 24" direct burial. Water and power can be in the same ditch without any separation. So I can dig one 20" deep trench, but the 2" conduit in the bottom, water line sitting directly on top of the conduit and pass inspection. He also told me that any wire, SER, direct burial, XHHW can be put inside the wall of the structure without conduit because the wall itself is protecting the wire, so I don't need to do any splices no mater what wire I use. He also told me to install a back flow preventer on the water line at the yard hydrant. Glad he told me that, I wouldn't have thought about it. I know some of this contradicts what some people have said, but it makes my life easier and if the inspector is happy, I'm happy.

 

[pattenp]

The only thing I disagree with is the install of the wire inside cannot be any wire. Most direct bury is not rated to be inside the structure and also any cable/wire without an overall sheathing has to be in conduit or another approved raceway. But if they allow it, so much for that.

 

[Falcon67]

I have 60' of Southwire 2-2-2-4 MHF running through the attic suspended above the insulation. Inspector had no issue with it. It's in conduit outside and underground to the shop. The line is breakered at 70A because HD had one for $40. FWIW - LHJ may vary as always.

 

[Norcal]

I have 60' of Southwire 2-2-2-4 MHF running through the attic suspended above the insulation. Inspector had no issue with it. It's in conduit outside and underground to the shop. The line is breakered at 70A because HD had one for $40. FWIW - LHJ may vary as always.

Just because a inspector passed it does not mean it meets code.

 

[TKFireman]

Still waiting for the permit but found out something new this morning. When I was told I needed a back flow preventer, I was thinking an in-line check valve. Turns out they want a full RPZ back flow preventer, the cheap ones run $100+. This thing can not be burried, it has to be above ground and completely insulated. The water line is not going to happen right now.

Started planning the interior wiring. Planning on a 125amp 24 circuit GE subpanel with separate ground and neutral bus bars. Panel comes with 6 20 amp single pole breakers. I didn't see any main breakers for the panel, but figured a 100amp 2 pole breaker will work for the main breaker correct? 2 - 5/8" ground rods, driven a minimum of 6' apart. Any height or other requirements for mounting the panel?

Planning to use MC wiring interior instead of conduit, seems much easier and appears to actually be cheaper. 12-2 for 110v receptacles and lights

3 circuits with 20 amp single pole breakers for 110 volt receptacles, each with 10 tamper resistant 15 amp receptacles, with a ground fault receptacle first inline on each circuit. I assume a GFCI is required, even though its in doors in a non-plumbed building. Metal two gang boxes with 2 sets of receptacles in each

1 circuit with 20 amp single pole breaker for lighting, consisting of 6 T8 fluorescent light fixtures - 8' length, each using 4 4' bulbs. Ran through 2 switches, for right and left side of building. 3rd switch for two exterior motion sensor flood lights. Should I add a second circuit for lighting, or will one breaker handle it?

I'll worry about wiring in air compressor and other items later. I want to build an exterior store room to house the air compressor and maybe other items so the compressor won't be so loud inside the shop. I hope to wire in the lights and receptacles and have the final inspection done. Then worry about the rest later.

Any recommendations are appreciated.

 

[pattenp]

A yard hydrant should not have to be off of a backflow preventer. Usually a hydrant only requires a hose bibb vacuum break. The backflow is usually on irrigation systems. At least that's the way it is here.

Don't mess with a main lug panel, you'll have to back feed the 100A breaker. Just buy a 200A main breaker panel.

http://www.homedepot.com/p/t/202046...0051&N=5yc1vZbm0kZlo&R=202046238#.UWh6-6KG3BY

or

http://www.homedepot.com/p/t/100149...0051&N=5yc1vZbm0kZlo&R=100149103#.UWh7paKG3BY

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