Project Pemberton: House Electrical

Electrical work must be performed by electricians. But this will be a story about how to wire your holiday house anyway.

Electricians "house bash" ie run all the cables, switches and fittings through the house, put in the meterbox and switchboard and any underground cabling. Once they fill out the paperwork the electricity supplier does the final hook up for you. Okay?

Meterbox, out near the road.

For my place the local sparky firstly put in the meterbox on a pole out near the transformer. You are allowed to have the meterbox connection up to 18m from the transformer, the sparky made it 18m exactly :) He then trenched down to the house, 25mm2 cable used on the 120m run, and installed a temporary box for me - ie, an RCD trip, a circuit breaker and a GPO. The temporary box stayed there through the construction, powering all the tools via extension cables.

The sparky is also a telecommunications installer. Telstra pay for the home connection up to the first point in the house; very kind. Unfortunately the Telstra connection was about 100m away from the transformer connection so I had to pay for the extra 100m of trenching, by at $1.50 per metre I thought it was well worth doing.

My electrical plan.

Obviously, for the electricals in your house, you need a plan, this was mine. At first I went overboard with 2 GPOs in every room and cat5 cabling throughout the house but later came to my senses and just drew in what I really needed. With electrical plans, I do a mental walk through the house and check how easy it would be to find switches. When you arrive at night time is it easy to turn the lights on? Where are the logical places to have the kitchen and bedroom switches? Where about is the fridge going to be?

I had other tricky things like a run down to the shed, a spa, a hot water system - these all ran back to the switchboard on separate 4mm cables and run off individual breakers. The AS2000 regulations changed a few years ago, "Up to 4 GPOs allowed off one RCD; 5-20 GPOs must run off two RCDs." So basically every house must have at least 2 RCDs. The GPOs are thus split across the RCDs; the light and shed CBs are on one RCD, the spa CB on the other. The electric hot water system is not on an RCD, it would trip it too much just in normal operation.

Cables get run around the house before the plasterboard is installed. Little cable clips are nailed on to hold the cables in place.

AS2000 calls for 2.5mm TPS for all GPO runs and 1.0mm light circuit runs. 1.0mm is speaker wire if you ask me, 1.5mm was used throughout instead. GPOs just daisy chain; ie, from the switchboard CB a cable runs to the first GPO where it is connected; the cable then leaves that GPO and on to the next GPO, and so on until the last GPO. Lighting is a bit different - a cable is run to each light in the ceiling, but from there the active is broken out and a two core "twin active" cable runs to the switch on the wall. Thus, the active isn't connected directly to the light, it connects down to the switch and then back again to be connected to the light. Make sense?

There ended up being a double-switch arrangement for the main area lights. The way it works is an active is run to the first switch, the normally open and normally closed both run to the NO/NC on the second switch which in runs to the lights. The neutral is picked up from the main lighting run. Changing the position of either switch will change the current state of the light - on or off. I'll save it for you to draw on a piece of paper to verify for yourself :)

Inside the first (rather full) switchboard.

Once the house is wired, the temporary box is removed and the connection made directly to the switchboard. I had a 11 unit Clipsal switchboard laying around I installed for the sparky to put the breakers in, I figured it would be plenty big enough, not realising the new requirement for 2 RCDs per switchboard. Sadly, it is already full! There is still an oven circuit to go in so at some stage in the future, when Wifey wants to bake a cake, it will have to be upgraded to a 2 row switchboard. Oh well.