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Discussion Starter · #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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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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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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Discussion Starter · #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.

773283
 

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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.
 

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Current generator is 5500/8500 Watt, not that large but the real problem with back-feeding through the sub-panel is there is no main cut off on the meter/combo. Very bad to be back-feeding the neighborhood :)
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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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.🙄
 

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Discussion Starter · #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.
 

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Discussion Starter · #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.
 

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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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Discussion Starter · #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.
 

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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.
 

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Discussion Starter · #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.
 

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Discussion Starter · #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.
 

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Discussion Starter · #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.
 
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