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Old 04-25-2019, 09:33 PM   #1
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Getting power to garage correctly


I bought a "new" house (new to me) and the previous owner seems to be a DIY-er. He brought 50A to the garage. My intention is to bring the full 200A from the house to the garage. It is pretty easy to hop online and think I know what I'm doing... I want to do this right.

If my plans are off please let me know or if there is a better way to do this.

The run from breaker to breaker is ~55-70' depending on how square I make run. I couldn't find a 200A Square-D QO breaker that wasn't a main breaker so I bought 2 100A breakers.

Basically two runs with the path: 100A breaker -> 1/0, 1/0, #2 Aluminum (direct bury cable) -> 200A main breaker in garage. This matches up the ampacity of the cable to the main breaker rating of the garage panels. (Please note the plural form.)

The cable will be buried > 2' underground with a caution tape 1' above the conductors. ...

The existing PVC conduit is 1.75" OD housing two #6 conductors.

The circuit exit/entrance (the PVC) is where my real confusion lies. I would like to run everything through one length of conduit into / out of the ground. Can I do that? (vs. 2; one for each triplex) If I remember correctly there is a percentage of the length of the cable run that can be grouped tighter than normal... would that be acceptable in that conduit? Each conduit segment is < 5% of the run. What size conduit would I need?

Looking through Appendix C of the NEC 2017 I'm not sure where this cable is in the Schedule 80 table.

The reason for the oversized cable is to match the main breaker. But as a benefit I shouldn't be creating much heat. I intend on splitting the load as evenly as possible. That currently would be ~25% of each run continuous. Since my house is 200A service the highest each run would see would be about 33%, otherwise I might have problems running the appliances for any length of time.

Thanks.
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Old 04-25-2019, 09:36 PM   #2
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Re: Getting power to garage correctly


I couldn't post a link until I had a post.... and I guess I still can post it. It's from wireandcableyourway.com. The remainder of the URL is "/1-0-1-0-2-brenau-aluminum-building-wire.html"
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Old 04-25-2019, 09:47 PM   #3
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The power company decides where you can put your service. You cannot just decide to move it on your own.

Secondly you can only have one feed to the garage.

I would say you need a.better plan and more information to properly plan this project.
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Old 04-26-2019, 05:46 AM   #4
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Re: Getting power to garage correctly


Maybe my terminology isn't correct, as I'm learning this area. But a feed already exists. I just wanted to take out the existing #6 conductors and put in something beefier.

Are there any Square-D breakers (or compatible) that are 200A that are not the main breaker? I didn't find any. If I'm stuck with one panel with 100A that's okay. Not ideal but I can make it work.

Fairly certain the previous owner did everything and everything is a hair off (electrical to garage, wiring of a vent fan in bathroom, weather stripping in doors, the garage loft floor.... it goes on... Wouldn't surprise me if the existing wire to the garage is a foot underground with no tape. I'm almost expecting it.)

What info do you need? With my current equipment I'm figuring about a 90A continuous load 24/7 @ 240V. If my numbers are wrong my usage last month was 17.6 MWH. I plan on expanding to 120A-135A continuous.... and further after I get 400A service installed. But this is temporary. My house is 100 degrees if the wind isn't blowing with the windows open while the outside is 60. I need to make this work sooner than later. Need my house at a normal temperature.

I'm sure whenever I sell it would be nice to hook up the wiring I plan on doing and have power in the garage. Fairly certain the next owner won't need a separate 400A commercial service in the garage.
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Old 04-26-2019, 07:55 AM   #5
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Re: Getting power to garage correctly


"My house is 100 degrees if the wind isn't blowing with the windows open while the outside is 60. I need to make this work sooner than later. Need my house at a normal temperature."

Where do you live where this happens (you didn't post your location in your profile thingy)?

And why do you need 400 amp service? Must be a huge home?
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Old 04-26-2019, 08:47 AM   #6
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Re: Getting power to garage correctly


Sorry but based on your first post you are over your head. Hire a pro.
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Old 04-26-2019, 09:39 AM   #7
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Re: Getting power to garage correctly


1) 2 100 amps breakers do not equal 200 amps.
2) You are only allowed to bring one circuit to the garage
3) You need 4 wire feeding the garage.
5) All that power to the garage will leave you wanting in the house.
6) Take everything back and hire a competent electrician.
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Old 04-26-2019, 10:06 AM   #8
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I think you need to get the house service increased first unless nobody is doing much in the house when you are working in the garage. A 400 amp meter socket or base ( you would probably actually get a 320 amp meter socket often used for a 400 amp service) will have dual lugs ( meter tapped twice) so the garage line can go directly from the meter to a 200 amp disconnect mounted outside to the garage.
If your current panel is inside, you will need a 2nd 200 amp disconnect to feed the inside panel because all means of disconnect for the service must be in the same area.
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Old 04-26-2019, 10:10 AM   #9
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Clarification:. The disconnect for the garage goes outside beside the meter.
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Old 04-26-2019, 12:50 PM   #10
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Re: Getting power to garage correctly


1.75" pvc -
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Old 04-27-2019, 02:26 AM   #11
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Re: Getting power to garage correctly


Hopefully this isn't too confusing but I consolidated all the replies here.

Quote:
Originally Posted by KPDMinc View Post
1.75" pvc -
THANK YOU! :D

Quote:
Originally Posted by bob22 View Post
"...house is 100 degrees ... while the outside is 60."

Where do you live where this happens ... ?

...
Load from electronics producing the heat. North Dakota. There's more detailed description of the history of this, and its future below.

Quote:
Originally Posted by rjniles View Post
Sorry but based on your first post you are over your head. Hire a pro.
My ability to navigate the NEC 2017 is poor. Your statement may also be true. This isn't a normal project. I probably know enough to get in trouble but my intention here is compliance otherwise I'd just do and not ask for help. I can get it done and be safe about it (meaning my work won't burn anything down or kill anyone), probably wouldn't be compliant though... as everyone has pointed out.

Quote:
Originally Posted by Wiredindallas View Post
I think you need to get the house service increased ... unless nobody is doing much in the house... A 400 amp meter socket or base ... will have dual lugs ...
The history of this is that the house was 100A and I increased it to 200A because I kept blowing the main. There was a 50A feeder from the house panel to the garage when I purchased the house.

The current temporary project is upgrading the feeder so the garage has access to more power so I can move these machines to the garage so my house has a normal temperature and noise level. The garage is already running at capacity: 40.5 amps continuous.

The future project is getting a second service for 400A to the detached garage and disconnecting the feeder. The dual lugs will be wired to two 200A panels in the garage. My house will have a 200A residential service, my garage 400A commercial.

Of the 18-ish megawatt hours used last month, the "residential" portion is about 200 KWH (0.2 MWH of the 18 MWH). We don't use much electricity outside these machines.

Quote:
Originally Posted by jbfan View Post
1) 2 100 amps breakers do not equal 200 amps.
2) You are only allowed to bring one circuit to the garage
3) You need 4 wire feeding the garage.
5) All that power to the garage will leave you wanting in the house.
6) Take everything back and hire a competent electrician.
#2) Okay.
#3) Thanks. Should've known better. Subpanels can't be bonded. Haven't bought the cable yet. One more reason to suspect the current feeder is 100% DIY... 6/6/8 UF-B cable.
#5) See last sentence in above reply.
#6) Have had breakers for too long but that's all I have. I'm not hiring someone for a temporary fix. I'm hiring them for the 400A service installation for the garage later this year. I've been in contact with someone for a bit. Kept in touch with the people that did my 200A upgrade... most I'll hire for is a consult regarding this project... essentially was looking to get the answers for those questions here.

#1) Please explain. 80% of 200 is 160. 2 * (80% of 100) is 160. My ability to efficiently utilize the capacity of those two circuits vs one circuit isn't there (i.e. respecting the 80% restriction I could use 24 machines with 2 circuits whereas I could use 25 with 1 circuit).... That's all I can see. Also there is a greater mass (2 circuit breakers) heated up (vs 1 breaker) and hence there is increased heat build up.

Last edited by robione; 04-27-2019 at 02:56 AM.
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Old 04-27-2019, 03:02 AM   #12
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Re: Getting power to garage correctly


Not specifically related to your question, but RE: "My house is 100 degrees if the wind isn't blowing with the windows open while the outside is 60. I need to make this work sooner than later. Need my house at a normal temperature."

We had the same problem in the summer (in Alaska where it only gets like 70*F) The house is painted dark brown on the entire back and full sun upwards of 10 hours a day so the place just baked, it'd get 80-90* upstairs constantly. Then we found out you can't buy an air conditioner up here >.< We put in low-e windows and put Tyvek wrap on the back downstairs of the house (under the sheeting) and hoped for the best. The effect was immediate and amazing. The place stays pretty constant now regardless of if the windows are open or not. I don't think the upstairs has ever gone over 70*F since then. Someday we'll get around to wrapping the rest of the house heh
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Old 04-27-2019, 09:12 AM   #13
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Re: Getting power to garage correctly


I would check with your municipality or utility to see if they will allow two separate feeds to one property. Depending on local rules, whether it is for commercial use might affect rates, Code rules, zoning, etc.



Bit coin mining? If so, haven't seen one of these threads in a while. If it is causing heat issues in the house, do you have plans for mitigation in the garage? UPS?
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Old 04-27-2019, 01:02 PM   #14
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Re: Getting power to garage correctly


What type of machines are you running?
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Old 04-27-2019, 04:11 PM   #15
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As said, I doubt you came get a 2nd service if this is residentially zoned and on one address on the city tax records. Of course, depending on the town you are in, anything is possible. I installed 3 services on one property in an unincorporated town where it is a co-op electric company. I could have never been able to do that in Dallas.
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