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Old 11-10-2019, 07:32 AM   #1
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EE Help needed for Shop Project.


Hello, my name is Matt and Iím new here.

I hope to get some advice from a pro regarding a shop project Iím working on.

Overall, we live in SE Texas, out in the country on 1.5 acres. Our underground utilities are provided to the street side of the residence. The Service is provided by a ground mounted transformer supplying a 200A Meter. The service wire enters a Sch 80 PVC into the ground and runs approximately 160 feet to an external 200A Disco, then enters the house to feed a 200A Main Service.

I want to build a shop behind the house, and the run is approximately 240 feet behind the house. Based on current and future demands, I wish to provide 200A to the shop.

Ideally, I would also like to provide for the addition of a Whole Home Generator at some point in the future. I would prefer to have the generator at the shop, but may have to pass on that for now.

Iíve had a few Electrical Contractors take a look at the job, and only one seemed confident of their ability to perform the work. The downside is their quote was very expensive, and far more complex than I feel it needs to be.

So here is the ask, can anyone provide a rough concept of how to simply supply the shop, and another concept of how to both supply the shop and provide for a future generator upgrade?

For the first option, could I go with a 400A Fusible Disco in a rack next to the Meter, then go to a splitter, then one feed to the house and another to the shop? I like this concept as the existing feed to the house could be reused, not abandoned in place as some Contractors have suggested.

The second option Iíve cooked up, is a single feed to the shop where I then have that split with 200A returning to the house and 200A to the shop. This would be ideal for a generator setup, and even better if I could use 480V and a Step down transformer at the shop.

At this point, Iím totally open to ideas and welcome constructive advice.

Thanks,

-Matt
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Old 11-10-2019, 08:31 AM   #2
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First, you cannot just change the disconnect from 200 to 400 amps without increasing the wire size from the transformer to disconnect. You must contact the power company for verification.
What is the actual demand needed for both house and shop at any one given time?
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Old 11-10-2019, 08:46 AM   #3
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Re: EE Help needed for Shop Project.


Sorry, I failed I’d to mention the POCO is in the process of upgrading our residential service to 400A. Their engineer comes out tomorrow and I wanted to know what to ask for.

I haven’t done a load calc, but the house is currently supplied by a 200A main, fairly heavy use of 3 A/Cs, 2 refers, etc.

The Shop needs to support a 5 ton A/C and 3 mini splits, plus a 50A RV outlet, and welders, saws, etc. I also want enough capacity to support a future pool, so I need capacity for pumps, etc. Add a bunch of lights, and outlets and we are probably just under what the house uses.

Thanks,

-Matt
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Old 11-10-2019, 09:05 AM   #4
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Re: EE Help needed for Shop Project.


You why would you enlist help from a DIY site when you have already dismissed the opinions of professional contractors that have on-site knowledge of the project? The only viable option is a separate service to the shop.
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Old 11-10-2019, 10:15 AM   #5
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Re: EE Help needed for Shop Project.


Brric, I havenít dismissed anyone thus far. Between disregarding a bid, and blindly writing a check, there seems to be a LOT of room for me to perform my due diligence. No 2 Contractors have suggested the same way to solve this puzzle.

The reason Iím asking for advice is that I feel $11,000 to bring 400A to the house, and another $16,000 to run a 200A service to the shop is a bit on the steep side. Iím trying to flesh out the optimum design and then evaluate for myself what appropriate and reasonable costs are. If, as Contractor #1 says, $27,000 to power the shop seems reasonable, Iíll cross that bridge.

Iíve done a residential upgrade to 400A in the past and while it was as easy as they come, it was under $2000 all done. That house had the pole behind the garage, there was about 30í of trench. The entire Setup for the Service was on the exterior of the garage.

This setup is different in a few significant ways, none the least of which are the losses over such a long run.

While Iím not an Electrician, I do recognize there are a few different ways to solve this puzzle.

A separate service to the Shop is one.

I feel like Iím at the place in a Chiltonís Manual where it says ďTake it to an Authorized Service Center.Ē All Iím trying to do is define why the costs are so high. So far, nobody has mentioned anything exotic.

Thanks for the input.

-Matt
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Old 11-10-2019, 12:57 PM   #6
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Re: EE Help needed for Shop Project.


If I may comment on this. Your asking these electrician pros to do something that is out of the ordinary. Even though, you yourself have a couple of ideas on how it should be done. These electricians are working in the blind & if the detect any vague ideas, questions on your part, that would scare them off from the job...or giving you an excessive high cost to cover themselves.

I've run into this type of situation before. Best advice I ever paid for in these situations was to hire a suit & tie professional....in your case talk to a an electrical engineer & pay him for the service. Well worth it as part of the project cost. Some power companies may offer that to you. Some will not.

One time I had the need to bring 3 phase power into a garage being outfitted with some really large motors. It took me four month of arguing with the Power co. because they said it was in a residential zone & they had no way odf delivering 3 phase. I had to go out & hire an E.E., who drew it up for them from the pole to the panel & everything needed right down to the hardware & screws to hang the panel. Then they did it.
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Old 11-10-2019, 02:13 PM   #7
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Re: EE Help needed for Shop Project.


Thanks for that suggestion.

Iím actually going to do that.

I havenít really aimed anyone at any particular solution. Iíve been simply asking for a way to get 200A power to the shop with and without provisions for a generator.

So far, Iíve gotten 3 different ideas, and only one price tag.

I like the idea of using an engineer to design the system, then everyone can bid the job from a common stand point.

-Matt
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Old 11-11-2019, 10:06 AM   #8
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Re: EE Help needed for Shop Project.


I suppose you could use a pair of 480/240 (50kVA) transformers at either end of the run to lessen the wire gauge in the trench. That said its $2500 or more just for the transformers. Then add the switch gear for disconnects at 480 volt side and this might get pretty expensive. So you'll need to do the math if 240' of lesser gauge wire offsets the cost of $2500 of transformers (assuming 480/240 50KVA sizing) plus misc other hardware.



I think you'll find running a separate service to the outbuilding putting the cost burden on the Poco will be far cheaper in the end.
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