# Forum Home Renovation Electrical  Switchboard location - new residence

## dutchroll

Important background:
- This property has an *off-grid* single phase 240V electrical supply via solar & battery storage with gen backup. So yes everything currently installed is signed off AS3000 compliant but there are no consids about meter locations, meter reader access, etc (in fact Ausgrid has never been here in 8 years and seems totally disinterested).
- Existing supply comes from the machinery shed. Provision for residence was included in the original installation via MCB on the busbar in the main 240V distribution board.
- Distances are longish. 35mm XLPE already runs underground 90-ish metres in 63mm conduit to the next main shed (horse stable facility) and from there via 6mm to a couple of small submains. 35mm was for voltage drop. Distance to planned house will be similar. 
The basic DA plans (by a licensed builder) are about to go to Council, so I'll probably be retired before they're approved  :Roll Eyes (Sarcastic):  and before a sparky contractor is engaged. In the meantime I have an excellent relationship with a local wholesaler who will give me a better-than-trade price on stuff which is rapidly increasing in price so I'd planned to pre-purchase conduit and XLPE for the submain and store it in the big shed. The builder is fine with this. The million dollar question is: where is a likely or acceptable location for the residential dist board, which could be up to 100m away from the supply? 
See diagram. The garage would be the shortest run (and the garage has plenty of space available), but the entrance area to the residence might make more sense. Any thoughts? Either way I'll add enough to get it out of the ground and behind the board with plenty for the sparky to work with.... but avoiding being left with a whole swag of unused 35mm XLPE destined for sale as scrap metal would be good.

----------


## doovalacky

Garage looks to be a detached building? If so it should have its own board.
Personally the "Or here" looks best to me. Slightly away from entrance so out of sight but still easy access. 
However contact your sparky and get them to sign off on whatever size cable you are buying first. They need to do a load calc for the house and you may need 50mm2.

----------


## dutchroll

Yes you're right the garage is detached and I didn't think of that. It certainly should have its own little sub-board. 
Yeah I was wondering about 50mm2 for the load & voltage drop given that it's a pretty big house. Crikey at the current copper price.....  :Cry:  However the one thing about being off-grid that might alleviate that is that we're designing to keep loads down because it will start complicating the system (in terms of inverter and DC voltage demands) a lot if we to load up the electrical demand like a conventionally powered residence. So for example we'll be using gas cooktops, rooftop solar hot water with gas boosting, etc. One of the bugbears of experienced off-grid system designers is the person who says "I want to be off-grid...... but I want 24kW reverse cycle ducted air, an electrically heated pool and spa, electric underfloor heating throughout the home, 6 fridges and 3 ovens!" and the solar guy just rolls his eyes and mumbles "ffs!"

----------


## Bart1080

"or here" looks good.  One thing you want to consider in the location of the sub board is how easy it would be to add additional circuits in the house if ever it were needed.  
...as Doovalacky said, check the 35mm will be large enough dependant on loads.  Mine was simular and 35mm was borderline so could have got away with it from a compliance point but spent the extra on putting in 50mm.  That was 8 years ago so may have been a bit more affordable!!  :Smilie:  
Also at the time, I seem to recall running 3 X double insulated 50mm was more economical than XLPE and the sparky prefered this method from a fault viewpoint. 
While the trench is open, you may want to consider running some 32mm comms conduit with the large sweeping bends rather then the short ones ...its cheap as Sh&t, yes over sized but real easy to vacuum suck a builders string line through over those long distances and super easy to pull in CAT5e/6 if you ever need to extend your WiFi, internet connection, camera's etc.

----------


## dutchroll

Yep plan is for 3 x conduits in the same trench. Large HD orange at the bottom on one side for the main supply, then 40mm HD orange on the other side to pull through a low voltage signal wire (overkill on size but this is a long distance with at least 3 bends) which is needed to activate relays at the switchboard which are controlled by the solar inverter for loads which need to be locked out from running at night. Warning tape halfway, and somewhere near there will be comms conduit for a fibre link. Cat 5/6 is cheap yes but I've had historical problems with that conducting lightning strikes through the ironstone here and repeatedly frying network gear at both ends! So that 100m run was replaced with fibre - no problems since. 
Trenching isn't an issue..... we own an excavator!

----------


## dmac

I'd also chuck in some blueline water pipe, maybe 50mm, you never know. 
Dave

----------


## dutchroll

> I'd also chuck in some blueline water pipe, maybe 50mm, you never know. 
> Dave

   Yep that's a good idea. We don't have town water and will be on rainwater, but we also have a good quality bore which can pump to top up rainwater tanks when needed. That'll just go in towards the top of the trench. 
I was worried about the conduit size for 50mm2 cable but there's only a tiny OD difference to 35mm2 by the looks (which I have plenty of experience in pulling through between our existing big sheds), so 63mm conduit seems like it will still be fine for anything if the sparky calculates 50mm2 needed for the house. 
Also checked the voltage drop for our workers cottage, which is a 1&1/2 bedroom plan 70 metres away about the size of a granny flat. 35mm2 seems like it would be perfectly fine for that (slightly closer than the house, and much less demand with just lights, <20 GPOs, single door fridge, gas cooktop, solar hot water, and probably 5kW reverse cycle a/c).

----------

