Electrical load calculations


Old 12-01-05, 08:33 AM
Thread Starter
Join Date: May 2005
Location: Central Florida
Posts: 206
Electrical load calculations

I'm building a shed and my City's Building Department wants the Electrical Load Calculations for the planned electric. I'm hoping that someone can help with this.

I plan on using the current service that I have running to my old shed. It is a 20Amp fused box at the outside of the house with a 50 foot run to the shed. 12 gauge wire is used in that run and I intend to use 12 gauge wire in the new shed. My plans are;

8 double GFI 20 amp receptacles.

2 florescent fixtures with 2 - 40 watt bulbs in each.

At most I may be running a 15 amp saw and the two fixtures at the same time.

Please advise.

Sponsored Links
Old 12-01-05, 09:24 AM
Forum Topic Moderator
Join Date: Feb 2005
Location: Near Lansing, Michigan
Posts: 10,533
You plan to run a 120V 20A circuit to the shed. That gives you 2400W available to use in the shed.

First, you have 160W of general lighting. Next, you should look at the motor nameplate on your saw to get the FRA. Multiply this value by 120 to get the wattage of your saw. That should be enough to tell how much of the shed electrical service you're planning to use and how much is left over for general purpose receptacles.
Old 12-01-05, 05:49 PM
Thread Starter
Join Date: May 2005
Location: Central Florida
Posts: 206
I'll have to turn calculations into the City. Is there an average number that I should allow for each receptacle, even it all will not be in use.

Thank you,

Old 12-01-05, 06:00 PM
Join Date: Sep 2003
Location: Central New York State
Posts: 13,973
You have a dilemma.

If you turn in a calculation that exceeds the 20 amp circuit, they will not approve the permit, but instead will require a multi-wire circuit or a sub panel.

However, if you turn in a calculation that fits the existing 20 amp circuit, you may not be telling them the truth.

Your job, unless you want to replace the 20 amp circuit, is to turn in a load calculation that is reasonable and that you can live with and that fits the existing 20 amp circuit.
Old 12-01-05, 06:02 PM
Speedy Petey's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Nov 2003
Posts: 2,455
They want a load calc for a 20 amp circuit to a shed???

And they wonder why folks skirt code issues and permits

No, for a residence there is no limit to the number of receptacles on a circuit. Unless you have a specific use for a receptacle, such as a fixed or large tool or applaince or motor, they do not have a bearing on the load calc.
Old 12-02-05, 06:13 AM
Thread Starter
Join Date: May 2005
Location: Central Florida
Posts: 206
For some reason my City (Palm Bay, Florida) has asked me to submit documentation that is normally required for Family residence and not for an unattached shed. Their request conflicts with what is detailed on their web site for required forms. I have a call into them to see what is going on. It took 5 weeks after my plan submittals before they told me they wanted, among other items, the following:

*Calculations showing 125 MPH wind load

*uplift calculations for trusses or submit truss engineering form truss manufacturer

*Florida product approval and installation specs for shingles, swinging doors, sectional doors and Hardi Board Plank Siding

*Electrical riser diagram showing all wire sizes, disconnects and protection for wires

*Electrical load calculations showing all load requirements

My shed plans do show 2x6 at 16" O.C. framing, Owens Corning 30 year dimensional shingles, 19/32 sheathing on the roof and sides, Tyvek, Hardie Board Plank siding, 12 gauge wire, J bolts tie down into a 4 " slab with 12" footers. It will be built like a fortress. The one I bulit and that is standing in the current location has been there for 20 years surviving numeous hurricanes. Termites finally did it in.

OK, I'm done venting.

Thanks again for the advice.
Old 12-02-05, 08:00 AM
Join Date: Apr 2003
Location: Eastern PA
Posts: 354
I'm pretty lucky in this respect and I know it. We do have strict zoning and permit requirements BUT the township does not work against you, they work for you. You tell them what you want to do and they sit down with you at YOUR convenience and tell ou wether it will fly before you apply and suggest how to pressent it so that it will fly without a hitch. For permit apps that don't require a hearing the turnaround time is seven to ten days.

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

Thread Tools
Search this Thread
Display Modes