Shed power electricians who size the cable before you dig

The single biggest cost on a shed job is the trench, and the single biggest mistake is undersizing the cable in it. If your shed sits 60 or 80 metres from the house, the cable that would have been fine at 10 metres will drop enough voltage over that run to make a welder struggle, a compressor stall and LED battens flicker every time the pump kicks in. Once the trench is backfilled, fixing that means digging it again. So we size the submain for what the shed will be used for in five years, not what it is used for on handover day.

What we actually do on a shed job

We have done 805 shed and outbuilding jobs. The work usually breaks into four parts. We work out the load, which means asking real questions about welders, hoists, compressors, a second fridge, a caravan point, a granny flat kitchen or a future air conditioner. We calculate cable size against the distance and the voltage drop allowed under AS/NZS 3000, the Wiring Rules, and size to the AS/NZS 3008 tables. We run the submain, almost always underground in conduit at the correct depth with marker tape, because overhead spans across a paddock in cyclone country are asking for trouble. Then we install the shed board. Anything past a couple of lights and a power point needs a dedicated board with its own main switch and safety switches, so you can isolate the shed without walking back to the house in the dark.

Acreage out here has its own problems

Most of this work is on blocks at Shannonvale, Mowbray, Killaloe and up towards Cape Tribulation, and a few things come up over and over. Ants and geckos get into outdoor enclosures and shed boards, nest across the terminals and cause nuisance tripping that looks like a wiring fault until you open the lid. Proper gasketed enclosures and sealed conduit entries fix it. Salt air chews through cheap fittings and unprotected gland plates faster than people expect, even a few kilometres back from the coast. Wet season groundwater finds any conduit that was not sealed and glued properly, and water in a submain conduit is a slow-motion disaster. And on acreage the shed is usually where the bore or tank pump lives, which is why pumps show up 1,051 times in our job history. If the pump is on the shed board, the shed submain needs to carry the starting current without dropping the lights.

Boards, safety switches and paperwork

A shed board is not just a smaller version of the house board. It needs correct earthing back to the main earth, correct labelling, and safety switch protection on the socket-outlet circuits. If the outbuilding is a granny flat or anything someone sleeps in, the smoke alarm rules apply too. Interconnected photoelectric smoke alarms are required in all existing Queensland homes, townhouses and units by 1 January 2027. Worth sorting while the walls are open rather than after the gyprock goes on.

When the job is finished you get a Certificate of Testing and Compliance from us, as the licensed electrical contractor. Keep it. Your insurer, a future buyer and a building certifier will all ask for it eventually, and uncertified shed power is the sort of thing that surfaces at the worst possible moment during a sale.

Who does the work

Brad, Leanne and the team have been running BH Electrics since 2017, and Blake Henning had it for ten years before that. Four electricians and two apprentices, QLD Electrical Contractor Licence 82270, fully insured. We fit Clipsal, NHP and Olex gear on this work because it holds up in the heat and the humidity. If you are planning a shed, ring us before the slab goes down. A conduit stub through the slab costs almost nothing at that stage and saves a core drill later.

Source: Queensland Fire Department, smoke alarms.