Electrical Service To New Shed - Electrical - DIY Chatroom Home Improvement Forum

Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Electrical


Thread Tools Display Modes
Old 02-20-2011, 07:30 PM   #1
Join Date: Feb 2011
Posts: 1
Rewards Points: 10

electrical service to new shed

want to run a subpanel to new machine shed from shop. Shop has 100 amp service. New shed is 140' from shop. How big of underground line do I need. Will only need some lights and plug-ins. Also small 220 v air compressor.


form one is offline   Reply With Quote
Old 02-20-2011, 09:20 PM   #2
Join Date: Jan 2011
Posts: 247
Rewards Points: 212

how much power do you use in your shop? 40 amps?
how many amps do you need for your compressor?
what other tools do you plan on running?
the problem is that you have a subpanel feeding a subpanel and what you have running to the first subpanel is as large aas you can go on to the second
You also need four wires a 2 hots,ground,neutral, and the ground an neutral have to be isloated in a subpanel they cannot be on the same bar like a reg service panel


Last edited by bluebird5; 02-20-2011 at 09:27 PM.
bluebird5 is offline   Reply With Quote
Old 02-20-2011, 09:31 PM   #3
Join Date: Jan 2011
Posts: 247
Rewards Points: 212

use a voltage drop calculator. You are allowed 3 percent drop to reg circuit and 5 percent to a to a circuit through a feeder panel
bluebird5 is offline   Reply With Quote
Old 02-20-2011, 09:46 PM   #4
Electrical Supplier
Join Date: Jun 2010
Location: Dayton, OH
Posts: 205
Rewards Points: 150

IIRC minimum sub panel size is 30a on a 4w 120/240 service.

@OP the "size" is the final calculation you make when designing a service.

You start with your Load requirements at the sub panel. Compressor, lights, outlets etc. Also figure for possible expansion, you dont want to redo this do you? What ever you figure your load is or will be, I STRONGLY suggest either rounding up to the nearest 10 amps OR adding 10 amps and rounding to the 10s place.

Example: 32 amp load, I would do 40 amp service. 38 amp load, I would do 50.....

Then figure your circuits and spaces required. (At this point you can shop for your service panel and equipment)

Next you get your distance. 140 is what you said; this is a feasible system that leaves you do reasonably put in whatever amperage you want to up to 100. (as you posted your origin panel main is)

So now you calculate voltage drop with your Main and standard wire size for that amperage. If it is greater than 5% upsize your wire ONE size and recalc. Repeat till you are under 5%

make sure you calculate using the CORRECT wire temperature/jacket.

Table for COPPER UF, direct bury or in conduit are as follows:

30A: #10
40A: #8
50A: #6

You wont get UF much larger than that. If you need more than that go with Aluminum USE/URD OR run THHN inside conduit.

IMO UF is your easiest route, but it wont be the cheapest necessarily. You are looking about $1 a foot or so on #10.........and up from there.....

Just remember, If you want it done RIGHT, size your WIRE to the SERVICE, unless it is not feasible, at which point you size your SERVICE to the WIRE......
"Do it right the first time and avoid duplication of effort"

Your AHJ/Inspectors ALWAYS have the final say on ANY electrical code issue.
If in doubt, contact a licensed, experienced, reputable electrician to perform the work.
LyonsElecSupply is offline   Reply With Quote

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Do I have any more electrical service capacity? (Power for Shed) Magnus357 Electrical 7 10-13-2012 08:52 AM
underground electrical service rsec Electrical 5 07-30-2010 06:05 AM
electrical service line bmancanfly Electrical 4 07-21-2009 07:07 PM
Help with electrical service hookup near meter! jayp Electrical 12 03-25-2009 11:05 PM
electrical service to barn bsteven Electrical 1 04-18-2005 08:43 PM

Top of Page | View New Posts


Search Engine Friendly URLs by vBSEO 3.6.1