Lights and electrical outlets can significantly enhance a shed, especially if you’re using it as an area for a workbench and tools. Extending the wiring to an isolated or detached shed might look daunting, but it can be done.
First, plan the cable routing to provide electricity to a shed (or any other detached outdoor building). Excavate a trench between the home and shed and run a suitably-sized cable through a conduit. Install a new GFCI circuit breaker in the main panel or extend an existing circuit and install a GFCI outlet.
The lighting circuit can easily be shared and extended up to the point where you’re going to place the bulb holder. Complete the wiring from the breaker to all lights and outlets in the shed. Backfill the trench after testing all the new lights and outlets.
I go into more detail below, and I’ve included a diagram showing one option for you that you can adapt to your situation.
Electrical outlets and wires can only handle so much load.
One thing you’ll need to consider is how many amps you need for the circuit to be capable of handling. The wire gauge and type of outlet must then be chosen accordingly. The lighting circuit doesn’t usually require a thick wire, but you might need to install a power outlet for the tools and machines. You might even require a 220-volt outlet and/or a dedicated circuit.
Additionally, if the shed is separate from the rest of the house, i.e., there’s a gap of some distance between the two, you’ll need to decide on a suitable path for the electrical cable.
So, four important considerations are:
- What (tools and machines) will you be using the shed for (what’s the total load)?
- What type of outlet is required, and will you need a dedicated circuit?
- Can the main panel handle the extra load?
- What path will the cable take from the house to reach the shed?
You might keep power tools or machinery in the shed, but if they include an air compressor or welder, you’ll also need to ensure the outlet can support the heavy load.
If, for example, the total power load is 2,000 watts, you’ll need a 25- or 30-amp breaker and 10-gauge wire if you use a 110-volt outlet. However, I recommend installing a 220-volt outlet to allow for future expansion. In that case, you can get by with a 15- or 20-amp breaker instead.
Type of Outlet
If there’s a risk of moisture in the shed, use a GFCI outlet, or if there’s a risk of electrical arcing, use an AFCI outlet. Otherwise, an ordinary outlet can do.
Modern American homes are equipped with a 200-amp service.
This should have enough space for an extra connection running to your shed. If in doubt, do the necessary calculations to work out the total load or capacity or consult with an electrician. A sub-panel can also be installed if necessary.
Choosing the underground path is an important part of the planning process. You want to minimize the digging and avoid re-digging.
Here’s a list of what you’ll need: Conduit; electrical cable; switches, light bulb holders, and electrical outlets.
Conduit – The length should cover the walls where you will run the cable. I recommend using a plastic pipe instead to ensure it is liquid-tight for the underground portion. It can be PVC, uPVC, CPVC, or other. As for depth, it should lie between 18” and 24” below the surface.
Electrical cable – 12/2 cable should suffice.
It’s sufficient for a 110-volt outlet and up to 16 amps of current. If you need to go higher, you’ll probably need a 220-volt outlet with a 30- or 40-amp breaker and size 10- or 8-gauge wire, respectively.
Note that sheathed cable is not permitted inside a conduit. So, only pull three unsheathed wires (black, white, and green) through the conduit. You can use UF underground cable for the underground portion; otherwise, protect the rest of the exposed wire with a conduit.
Also, ensure the wire is inside the conduit before starting the insulation.
As required, you will need suitable switches, light bulb holders, and electrical outlets.
The switch box should be fixed inside the house so it would be easy to switch the electricity on or off. This arrangement is more convenient than having the switch inside the shed.
It is also for safety reasons. By having it inside the house, the underground wire will not be energized while not being used.
For the circuit breaker – The capacity must bear the load easily and have a rating of 125% of the load.
You will need a shovel to dig the trench, a power drill, a screwdriver, a wire stripper, and an electrical tester.
Wiring to a Shed for Lights and Outlets
Step 1: Mark the Exact Locations
Mark the locations where you want to install each light, outlet, conduit, switch, and circuit breaker.
Remember that I recommended you place the main switch for the shed inside the house, not in the shed. Otherwise, you can keep other fixtures inside the shed (outlets, light switches, and junction box) if that’s convenient for you.
Step 2: Dig the Trench
The planning includes where you will connect the house to the shed along the ground with the electrical cable.
I suggest you get all the dirty work out of the way after the planning and before you lay the pipe and work on the project’s electrical side with clean hands.
Step 3: Set the Cable Under the Ground
Either lay plastic pipe along the trench or use UF underground cable instead.
Then pass the cable through it if you use a plastic pipe.
Don’t cover the trench just yet. Wait until the circuit is complete, you’ve tested everything, and it works fine.
Step 4: Attach all Fixtures
Attach all the fixtures to the chosen spots.
This includes the electrical boxes, switchboard, light holder, and outlet(s).
Step 5: Attach the Conduits
Attach the conduits in place.
The conduit ends should be flush against the fixture, such as the switchboard and outlet. Use weather-tight connectors in outdoor areas. Secure the conduit using brackets and hangars when appropriate.
Step 6: Run the Wire
With all the fixtures and conduits in place, you can run the wire through the entire conduit.
Step 7: Wire the Fixtures
Now, wire all the individual fixtures.
Use wire strippers to strip the wire ends to connect them to each switch, holder, and outlet.
Step 8: Connect Circuit
After all the fixtures are in place and the wiring is done, you can connect the circuit to the switch and main panel.
(A) Circular Holder and a Cross Block
Use circular ceiling light holders because they are easier to work with.
Also, if the shed has a gable roof with open rafters, I suggest you add a cross block between two opposite ones. This will give you a flat area for mounting the ceiling box.
(B) Conduit and Wire Binding
Extend the conduit along the entire run (from the service point to each fixture, including the outlet). Bind the wire ends with electrical tape. It will be easier to fish the wires through the conduits.
(C) Tucking and Testing
Tuck the capped wires inside the boxes after attaching the wires to the switches, light fixtures, and outlets.
Only turn on the power in the main service panel when all the wiring is complete. Then test the whole circuit before using it.
Mark Johanson. Black & Decker The Hardworking Home, A DIY Guide to Working, Learning, and Living at Home. Cool Springs Press. 2022
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