I have a garden shed to which I would like to run electrical power. I have a source of power in my workshop that has a few open breakers in a 125AMP panel. Any running from the current panel to the garden shed would be roughly 60 feet long. I was thinking of running a 10-3 wire with two hots, a common and the ground to split into two circuits once I got to the shed. One would be for a few outlets (internal and outside) and another circuit for the lighting. I would be exiting the workshop for about 20 feet to get to the garden shed where I would put the cable 18 underground in a 1 1/2 inch conduit. If this is OK, what sort of breakers would I need at the workshop panel? I was thinking 2 20-amp single pole for each wire (hots-redblack), the common to the neutral bar and of course the ground. Is this enough information to help me ensure I would be NEC compliant? Any safety issues? Is there a better way to do this?
Connect your 10-3 to a double pole 30 amp breaker in the work shop. Use type UF wire underground. 18 deep with PVC conduit will work well. Or just bury the wire without conduit at 24. Buried conduit is considered a wet location so UF must be used either way. At the shed install a lug panel with 2 or more breakers. No more than 6. If you use a 15 amp in one space you can wire the lights with #14 wire. 20 amp in the other for the receptacle outlets wired with #12. Keep the ground and the neutral separated at the shed box with the neutral bus isolated from the box. You are required to install a single ground rod at the shed. This is for lightning and power surges only. BCNU is wrong about not installing a grounding conductor with the circuit conductors. It is not allowed to use an electrode for equipment grounding. Install GFCI protected receptacle outlets. Lights are not required to be GFCI protected. Any other questions, send a reply.
1 inch pipe plenty big . add a spare for anything in future while it is open. use gfi in outlets in garage/shed. split the ground from the white in new baby panel and you got the idea pretty good.
The wiring may be fine but it is illegal for a uk landlord to rent a property withou having an annual electrical and gas safety certificate that is copied to the tenant. Ask your landlord for them. If he does not give you any go to local citizens advice for the way to deal with the issue where you live. This is not optional and I'd suspect your wiring is fine. If the gas is not up to standard you're in danger.
You are running two single-pole 20-A hots out there. That is considered more than one branch. NEC 250.32 requires that the outbuilding subpanel have its own grounding electrode (e.g., buried rod) connected to the grounding bar in the panel. If there are no other metallic paths to the shed (water or gas pipes, TV cable, etc), then you can even skip the grounding wire in the PVC conduit completely (running two hots and a neutral) and just ground the new panel to the new electrode. Look at the cost of running two 10 AWG conductors and one 8 AWG rather than 10/3 w/g. Probably not far enough to make a difference. Agree that 1-inch pipe is plenty big. Run two in at the same time, in case you ever want a phone line, CCTV, alarm/bell wire, or any other low-voltage wiring to the shed. If you do use 10-3 w/g for the feeder, do not bond the neutral bar to the panel ground (i.e., leave out the tap screw that they may give you for that purpose). But you still need to connect the new grounding rod to the grounding bar in the panel. The 250.32 Exception would apply if you were just running 10-2 w/g for a single branch, relieving you of the need for the new grounding electrode. If anybody has a newer code that gives some other grounding rod exceptions, please chime in. I'm looking at my old NEC 2002 Handbook, Exhibit 250-18, showing two hots, neutral and EGC running through u/g feeder conduit, isolated neutral bar in subpanel and grounding conductor from first building bonded to grounding bar at subpanel and separate electrode rod.
Generally what you are proposing would work except you need to use a 2-pole breaker to feed it. If you are going to use 10-3 uf you don't need and shouldn't use conduit at all, and you can't use NM-B in a wet location, which buried is considered wet. If you do use conduit you can use thhn conductors and just a 1/2 conduit. Conduit needs to have 18 cover, and UF cable needs 24. #10 wire may actually be larger than necessary, single phase 120v with #12 loaded to 20 amps would produce a 4% voltage drop, 5 percent is considered acceptable, any load on the opposite leg or less than full load would reduce the voltage drop. And then garden shed, you would have to treat this like a separate building, a service rated disconnect (or panel) and ground rods would be required. Skipping the ground wire is no longer legal.
