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Shop sub-panel install (and more)

48K views 356 replies 24 participants last post by  Mikauai 
#1 ·
This thread will document the installation of an electrical sub-panel for my 15 year old pole barn/garage/shop. After having a concrete floor installed and building a pair of insulated sliding barn doors, I feel the need for "more power" as a 200 foot 12/3 extension cord is just not cutting it anymore. I've popped the breaker at the house three times and have to crank up the generator for some tools as the voltage drop is just too large for them to start up.

The setup:

Meter/Combo on house, this has a 200A breaker for the real main panel in the center of the house. And a 40A breaker for in-feeding an 8KW solar array. No main breaker on the meter/combo. The shop (as we call it now) is located 200 feet away. Actually about 25 feet away from the power transformer that feeds the house.

Normally, one would pop in a 100-125A breaker in the meter/combo, trench a feed to shop sub-panel, wire out and done. But I have to be complicated. :)

The plan:

The eventual plan is to move the meter to the shop, then feed the house from there. As we (wife and I) get older, man-handling the generator will get harder and I'd like to place a generator/auto-transfer switch at shop, maybe some Tesla Powerwalls for power storage. There just is not enough room around house for this. Well, there is room but it would look ugly as sin and my wife would kill me...

Contemplated doing the job less permit but eventually concluded this would ultimately bite me in the rear down the road. Also contemplated doing everything myself but decided against that because while I'm electrically savey, have little experience in dealing with inspectors and electrical codes and such. Time is money as they say and I'd rather pay experienced persons to deal with that part, and not spend tens of hours fiddling and getting pissed off at silly rules. So I'll be contracting the sub-panel install with minimal "extras" that will satisfy passing inspection. After passing inspection, then I'll finish wiring out the shop over time.

200 feet is a pain in the rear regarding power drop at large amperage. The cable costs are the dominating factor in this whole project. For 200A, it's a 4/0 or 250kcmil Al, the later better choice. Cable will run in a 2-1/2 schedule 80 conduit, trench dug by me of course as I recently added a 485 backhoe to my 20 year old JD4500/460.

Signing and returning the contract today, they say maybe around Feb, 22. So about two weeks to get 811 to do their job, find the propane line (not 811's job), and dig the trench. Going to freeze my rear off :) Nothing like spending time on cold days outside, sitting and just moving your arms around. lol.

Picts when the sun comes up to get a better idea of the tasks.
 
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#2 ·
How large is your generator? If it is larger, in amperage, than the sub-panel you're adding, I'd just increase the size of the sub-panel and backfeed it down the feeders. I can't hink of anything in the code that would prohibit that, but I could be wrong. Re-locating that meter is a lot of work/expense.
 
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#10 ·
Sorry, you are correct. I was typing in a fury and with that, got ahead of myself.

Now that I'm back from my appointment and taking my time, I was thinking of the generator part being out in the pole building and the transfer switch at the house or near the meter. The generator cables could be in the same trench as the feeder conductors, along with any control cabling.

An 8kw generator is not going to power your whole house and a 200 amp transfer switch is probably pricey. You are buying a whole lot more switch than you 'll be able to utilize. I don't know how much room you have adjacent to your home panel, but perhaps you could put the transfer switch there, between the main panel and another feeder panel that would serve only the branch circuits you seek have powered from the generator.
 
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#7 ·
Sounds like a good opportunity to put in a 200 amp manual transfer switch. Then you can break line service and run solar, batter, generator, or whatever else you want.
 
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#8 ·
Here's pictures of the mess. :)

Meter/Combo. This area is a bit of a mess that I'd like to clean up. Cable came in after Solar Array which they put above the phone. The power out outlet was where the cable box is but I moved it and still have to shorten the flex-conduit. I'd like to also move the phone box to left of cable box, then drop the solar box down to a more pleasing height. :)

As you can see, meter/combo has 8 slots, two are for 200A to populated panel in house. Below that is 40A solar feed.
A junction box (12x12) is needed to join the large cable feed to/from shop to 125A breaker in the meter/combo. You can't do the joint in the meter/combo box and no 125A breaker will take above 2/0.

This panel would get replaced in future with standard exterior panel with main cutoff and 6 or 8 slots.

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1st leg, to bend in drive. Follow the yellow extension cord. :)

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Looking from shop to house.

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Shop entry point, in the center.

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And inside. 200A main cutoff with feed-though. For now, ignore feed-though. In future, flip the panel and use the feed-though to feed the house. Add meter/etc to feed this panel.

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For kicks, the power transformer, the green thing between the trees.

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#9 ·
When I bought my property the horse barn which I have converted to my shop had a 60 amp sub panel off the main breaker box in the house. I had an electrician test the worst case scenario for my usage, my jointer, dust collector, all the lights and AC turned on and the compressor running. The actual draw was nowhere near the 60 amp capacity so no need for me to increase the wire size for the larger sub panel I installed.

I also installed a plug to connect my generator to the house in the event of a power outage. It does require what you are trying to avoid, rolling the generator over to the house to a location where I can plug it in. However, if you have to pull wire in the first place I believe 4 gauge will be sufficient for your shop needs (it is for mine, your needs may be different). The same wire will be more than large enough to send line voltage back to the house if necessary. It would be necessary to put a switch at the main panel to prevent power from going back down the line when the generator is running.
 
#11 ·
Sdavilla,
Hey I want to say thank you. As a retired linemen we worry about back feed all the time in power outages. Thanks for caring for us.

That green thing is called a pad mount.🙄
 
#12 ·
Sdavilla,
Hey I want to say thank you. As a retired linemen we worry about back feed all the time in power outages. Thanks for caring for us.
My wife's father (deceased, not electric related) was a lineman, I have a deep appreciation for them and the pure guts it takes to so the things they do. I have his climbing gear and the green '86 Ford F-150 that you might see in my pictures was his.
 
#13 ·
Yea, an 8kw generator is tiny for what I would need to power the house. Need more like 20-30kw generator but that's a future project. With 8kw, I'd toss the breakers on most everything except downstairs HVAC (propane), well pump and some lights and specific outlets. Upstairs HVAC is heat pump and it sucks power in the winter.
 
#14 ·
Not sure where you are located, but my local power cooperative does not allow storage of solar power on a line tied solar system. They require the inverter to be line tied with a 5 minute restart delay. They did agree that they MIGHT consider a properly designed back up storage and inverter with an automatic transfer switch when i asked how a solar storage system was any different than a backup generator. Both need a proper transfer switch for grid safety. In my case the transfer switch would have to be 400A, since that is our service (2ea 200A panels side by side in the office). We have 12kw (60A) of solar panels on the South facing roof slope of a 108x48 horse barn. Barn has 100A service run from one of the 200A panels at the house.


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#15 ·
No friends with a metal detector... Make a note, need more friends with manly toys. :) Looked into renting one, $20-35 a day. Mumm, always wanted a metal detector, who knows what's buried on my 11.3 acres. Might find some hidden cache of gold bars from the civil war.

Amazon is so deadly, one click and a Garrett CSI 250 will be here tomorrow. The CSI 250 is similar to the ACE 250 model, different display but about $40 cheaper and comes with headphones and carrying bag. Talked to a metal detect guy that does not rent them anymore. He said, no problem, that model will find a copper propane line easy.
 
#16 ·
I have a 6500 watt generator and a 200 amp panel in my house. For my purposes the 6500 watt generator is sufficient. The goal of my backup generator is not to replace the power system long term, only protect the house during an emergency.

I have used my generator to run my furnace, well pump, frig, sump pump and a few lights. It does so without any complaint. No need to run the oven, AC, shop equipment, and any of the other electrical components. A generator large enough to replace the power supply to my house would be crazy expensive and not portable.
 
#17 ·
Job scheduled for Feb 22nd. Now I have two weeks to grow a pair and dig the trench. :)

Called 811, that was interesting. No, not near a railroad track. No, not doing any blasting or horizontal boring. They had Piedmont Electric and Spectrum/Charter listed. Reminded them about CenturyLink. Ticket expires Feb 25th, extend on 22nd but trench will be long dug by then.

They did ask me a silly question, when was I going to start. Well, that depends on when the locate process is done... :)

Got email from CenturyLink. "The described dig area of your locate request has been checked and is clear for CenturyLink local Network." Hahah, they never come out so they don't have a clue where I'll be digging. I guess since we don't use CenturyLink for phone anymore, and are not a current customer, they don't care. Ok, your problem if I cut it...

Metal detector arrives tomorrow, can't wait to try it out and see what it underground lines/pipes it can find.
 
#18 ·
Step one, frame out for sub-panel. As this is a pole barn type construction, the girts that are on the outside of the 6x6 posts create a 1-1/2 recess. The plan is to fill these with 1-1/2 insulated foam board that gives an R7.5 on about 90 percent of the walls. Studs will be 2 x 6 x 10 feet, 16 inch spacing here (for sub-panel), 24 inch spacing to match the roof trusses elsewhere. These studs will tuck inside the two 2x12 headers at top. Then 6 inch of insulation (R19) goes between studs, either fiberglass or rockwool, have not decided yet. Giving about an R26.5 ish. Maybe overkill for NC put I'm thinking more summer heat than winter cold. Roof insulation is a future task too.

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Thought about using 2x4's and playing the "the insulation tucks behind the 2x4, blah, blah". Nice theory but a 10 foot 2x4 stud will have some flex so concerned about the eventual walls flexing too.

As the 2x6's will cross the 2x6 purlins, the wood cross section is going to be very small compared to rest. Rough calculations say less than one percent... I'd rather have stiff, sturdy walls thank you please.
 
#19 ·
Garrett CSI 250 metal detector feedback. The "locate" mode works best, gives a ramping tone as you cross the signal source. It works when detector is stationary. Note to self, move extension cord and flags with metal rods away from area you are probing. lol.

No issues finding power line, it's a direct burial cable, about 36 inches down if done by code. They used a cable trencher. Makes the metal detector scream in pain.

Spectrum/Charter cable line is also easy to find, was not around when they "trenched" it in but smells like about 4-6 inches down. They used a slit trencher.

Same for CenturyLink phone line, little more difficult than the cable line but detector can find it. Smells like 6-8 inches. They also used a slit trencher.

Propane line. Grrrr, can find it near house where it's not very deep. Maybe 4-6 inches down. Mr. goldfish can't remember what they used. Near tank, it's 12+ inches down and the metal detector just does not see it at all.

So the plan is to dig the trench in depth stages of 6 inches by however far I can reach out. Dig down 6 inches, buzz around with metal detector. If I get no indication, do another six inches until the trench is down 24 inches or so. Sounds like a plan... :)

No sign of Piedmont Electric and Spectrum/Charter location services yet. If I can catch them, I'll see if I can 'motivate' one of them to probe for propane line. Toss a $20 bill on the ground and say, "I think you dropped this". HAHAHA.
 
#22 ·
Propane line. Grrrr, can find it near house where it's not very deep. Maybe 4-6 inches down. Mr. goldfish can't remember what they used. Near tank, it's 12+ inches down and the metal detector just does not see it at all.
Plastic natural gas lines usually have a small wire buried with them that can be activated for toning. 'Any chance that was done for your propane line?
 
#21 ·
Figured I'd pull out my Paslode framing nailer. Not used it since the pole barn was built 15 years ago. NiCd battery was finicky and took a few cycles to get any charge. Found two gas cylinders for it, 2004 expiration date but they still had propellant in them. Shot a few 3-1/2 nails, then refused to cycle and striker rod was jammed. Take apart time... Humm, why is the piston not sitting flat to cylinder. More disassembly. The end of the cylinder has some type of plastic (nylon ?) bushing that has completely disintegrated and the piston rod is bent.

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I'd bet a few hundred to fix (if I could even get parts) which puts a new DeWalt framing nailer into range. Only issue that keeps me from pulling the trigger is the reviews say it has a hard time with 3-1/2 nails, leaving them 1/4 inch proud. The Paslode would sink them without problem, even ring shank. Can't decide so I'll just use 3 inch #10 torx deck screws with impact driver for now.
 
#23 ·
We have 400A service but a 6500W works for us. Like mentioned before it is only to keep the fridges and freezers going. Can also run the furnace and well not to mention the septic lift pump.

When we upgraded the service I looked into a 400A auto transfer switch. Yeah that got cut from the project because $$$$$. Sure it would have been nice but wow they don't give those things away.
 
#28 ·
Locate showed up. After he was done with electric, cable and phone, told him I make it worth it if he could do propane. No problem, tried to hand him a $20 and he said "I can't accept it but if you happen to drop it on the ground..." HAHAHAHA. Google is telling the truth for once. Location was done by clipping a tone generator to the ground line, then sweeping a probe/sensor over ground, for all and for propane, right on the copper pipe.

House side, the 1 inch PVC is so I can figure out the 45 degree sweeps better.

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House to driveway.

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2nd 45 sweep,

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Past propane tank

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Heading to shop

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Red flags mark the tentative location of the trench. Orange is power, orange dots are phone. Red is cable. Planning to shoot between propane and electric/cable lines. Phone is far away. I'll have to tweak it a little but there's really only one place where I have to be careful and that's near the 2nd 45 sweep where the trench will cross the propane line.

Oh yea, anyone know how much bend slop I can get with 2-1/2 inch schedule 80 PVC ? This is maybe 3-4 feet over 125 feet. Worst case if the answer is "not much", will need another 45 degree sweep and straighten the trench run.
 
#29 ·
Oh yea, anyone know how much bend slop I can get with 2-1/2 inch schedule 80 PVC ?
You may be able to get it around the gradual bend if I'm understanding correctly.

I've "bent" 1-1/2" PVC using an el-cheapo heat gun. 2-1/2" would require more patience. If it wasn't -15°F out I'd get a photo.

When I used to work around industrial facilities, the ECs (electrical contractors) had ovens made for heating and bending PVC conduit.
 
#32 · (Edited)
I vacuum pulled the strings after laying 225" of 1 1/4" conduit for a 100A service to the barn. No problem.

I assume that your code requires sch 80 pvc. I used sch 40 pvc in the trench for both the barn run and the 200' run of 3 1/2" for the house service (400A). Power company spec was required for the 400A service since it was their side of the meter, but conduit was not required for anything on my side of the meter.

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#33 ·
Electrical contractor said it would be sch 80. As he's dealing with permit, I assume he knows what he's doing. lol. Around here, risers have to be sch 80, I think the in-ground can be sch 40. But I'd have to go digging through local code. They will be laying pipe and pulling wire, how they get the pull line through is their problem. :) I'd vacuum pull a smaller line followed with the actual pull line.

All I'm concerned with is if 2-1/2 inch sch 80 will have enough flex to follow the slight curve. If not, then it will need another 45 and the curve straighten out. Another 45 makes it 270 degrees of bends so less than the 360 limit by code. And they specifically mentioned, "must be less than 360 or they will need to add an in-ground junction box. I'm just the newbie trench contractor for this job. :)

Planning on starting the difficult areas this weekend. I know there are quartz fingers that point up around the pole barn, ran into them auguring the holes. About 18 inches down. When the house foundation was dug 20+ years ago, no issues with quartz or rocks/boulders/etc.
 
#34 · (Edited)
Sorry if these have been answered in earlier posts.....

Are you supplying and installing the conduit in the trench? If so, lay it out on the ground first and see what kind of bend radius you can achieve.

Or are you just digging the trench? If so, could you get an opinion from the EC as to the curve or intentional 45's? They may have the oven to make the required bends if the gradual curve is too much for the Sched 80.

Just some thoughts. Good luck with your project.
 
#35 ·
Grrrr, it's raining now and forecasted to last at least a week. Looks like I need to build up a poor mans tractor canopy because I'll be digging in the rain. I'll reposition the rake/shovel ROPS clamps to the top, extend out with some rails and cover with plastic. Oh joy...
 
#36 ·
The pipe will bend enough for what you need I would think. We don't have to use schedule 80 here so obviously that is a bit harder to flex but there should still be no problem doing it.
 
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