Add Additional / secondary Fuse Panel to house

Forums › Home Workshop DIY › Add Additional / secondary Fuse Panel to house - EV Vehicle Charger

mrhaboobi

165 posts

Master Geek

#288479 2-Jul-2021 15:21

Hi All

I'm looking to install some additional items in my house, and the fuse panel we have is currently full.

Looking to run a small secondary panel for an EV Charger. ( 30A )

Will buy an 8way panel ( as I need 5 slots ).

I'm going to do the leg work of running the wires in the roof and down the walls etc..

The panel will have a 40amp RCD Type B. Will also have a 32amp breaker and the item it will power is 30amp.

( for this example assume a 32amp power point )

My question is i want to know what size wiring i need to use to extend to a second fuse box. My understanding of the worksafe rules are that a 6mm TPS 2core plus earth is suitable for 40amp load.

Is this correct when running a secondary box, or do i need to further up size the wire? My assumption is a don't.

Would love to confirm so i can do the monkey work in the roof and then engage a sparky

thanks

wellygary

8315 posts

Uber Geek

#2737982 2-Jul-2021 15:34

Talk to the Sparky first and get them to confirm what the wire specs they want are...

You are going to need to get them to sign off the board work anyway, and I suspect they will get jumpy about turning up to find a wire coming out of a hole and the customer saying "the wiring is fine, I ran it my self"...

They will likely be happy for you to do some of the grunt work, but getting them to agree to it up front is probably going to make things easier in the long run...

They might even be able to help you out by getting trade pricing on the cable and breakers/boxes for you...

elpenguino

3421 posts

Uber Geek

#2737988 2-Jul-2021 15:40

If I was planning to be charging an EV for the next X years, I'd be looking to upsize the cable where possible.

A sparky will usually derive a cable size based on a certain loss. That loss costs you in power lost as heat in the cable - so some extra money spent on a larger than minimum cable upfront will be paid back over the years.

Most of the posters in this thread are just like chimpanzees on MDMA, full of feelings of bonhomie, joy, and optimism. Fred99 8/4/21

tripper1000

1617 posts

Uber Geek

#2737990 2-Jul-2021 15:41

I'd highly recommend you sweet talk to an Electrician first and pre-arrange for them to do the final connections and certification. At this point you can also plan the job, and talk about the way things need to be for them to be happy to certify it.

It's a much better idea than calling in some Electrician cold and expect him to certify your work, and then potentially getting into a disagreement about interpretation of the rules - or a total show stopper than you'll need to rework.

As to your question it depends on what else is going on the secondary switch board (you may have to vacate some circuits from the main board in order to fit the CB's that feed the secondary board), and also how long the run is (longer runs need heavier cable even though currents may be the same), and can also depend on the routing (cabling through insulation needs to be heavier than cable in free air in order to eliminate heating risks - cables in free air can off-load more heat so can be thinner safely).

mrhaboobi

165 posts

Master Geek

#2737999 2-Jul-2021 15:57

HI,

Thanks for the various feedback , yes i think you have mis interpreted my comment, i dont plan to make ANY connections, im literally feeding a cable along the attic from the main panel, to another location, to do this i need to lift the roof, drill the framing etc. I know what im doing in terms of that work, no desire to connect, fit or terminate anything, just wanted to know if 6mm TPS is going to be the right cable to use ( seems to be correct given its use in ovens / ranges etc with similar 30a loads ) :) i wouldn't expect an electrician to certify my connections, just want to get some cable pre run to save him a good days worth of work and me some costs ) he will have full visibility of the cable as well). as for pricing, i already get trade price on all the goods. but that was a good thought.

Cheers

mrhaboobi

165 posts

Master Geek

#2738001 2-Jul-2021 16:01

tripper1000:

I'd highly recommend you sweet talk to an Electrician first and pre-arrange for them to do the final connections and certification. At this point you can also plan the job, and talk about the way things need to be for them to be happy to certify it.

It's a much better idea than calling in some Electrician cold and expect him to certify your work, and then potentially getting into a disagreement about interpretation of the rules - or a total show stopper than you'll need to rework.

As to your question it depends on what else is going on the secondary switch board (you may have to vacate some circuits from the main board in order to fit the CB's that feed the secondary board), and also how long the run is (longer runs need heavier cable even though currents may be the same), and can also depend on the routing (cabling through insulation needs to be heavier than cable in free air in order to eliminate heating risks - cables in free air can off-load more heat so can be thinner safely).

Ok the comments about the insulation is helpful, thank you. secondary switch board will literally be the one 30amp charger, the cable run is maybe 6 meters.. about 2.5 M in wall and 4M above in the ceiling space.

Cheers

Daynger

435 posts

Ultimate Geek

#2738011 2-Jul-2021 16:47

Cable size will depend on the length of the cable run.

Also an electrician will not be able to connect and certify, you will need an electrical inspector for that.

Before you start anything get familiar with ECP51, as that is the rulebook for homeowner electrical works.