# Forum Home Renovation Electrical  Running power underground

## djlenny

Hi Forum, 
Can anyone point me in the direction on NSW requirements for running power underground (distance of approx. 30 metres) to a 'granny flat' ..? 
Thanks

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## Bros

NSW is no different from other states as it relies on AS 3000 which is nation wide

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## djlenny

Thanks, found the details

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## Random Username

If it's in heavy duty conduit, 500mm is the depth; if it's covered by no  less than 75mm of concrete this can be reduced to 300mm.   
There should be marker tape half way above the conduit.  Conduit should  be bedded in 50mm of sand all around.  Keep it at least 100mm away from  gas/phone/stormwater/sewer/water pipes. 
Cable entry points to buildings should be permanently marked if they are not obvious. 
See also: http://www.renovateforum.com/f195/po...44/#post749460

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## r3nov8or

A while back, 500mm was great news to me (I was expecting 600mm) as the trencher at my Kennards only goes to 500mm  :Smilie:

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## Bloss

> Hi Forum, 
> Can anyone point me in the direction on NSW requirements for running power underground (distance of approx. 30 metres) to a 'granny flat' ..? 
> Thanks

  Fair chance your electrician would know . . .  :Wink:

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## Smurf

> A while back, 500mm was great news to me (I was expecting 600mm) as the trencher at my Kennards only goes to 500mm

  Note that it's 500mm COVER, so the actual trench depth needs to be a minimum of 500mm + the diameter of the conduit.

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## r3nov8or

> Note that it's 500mm COVER, so the actual trench depth needs to be a minimum of 500mm + the diameter of the conduit.

   Well, maybe it was 500 and something...  :Smilie:

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## Brian7886

> Note that it's 500mm COVER, so the actual trench depth needs to be a minimum of 500mm + the diameter of the conduit.

  exactly. say you run 50mm conduit you would need it to be 600mm deep or more to allow for bedding in sand etc.  
as a sparky, i cringe at trenches. i dont do mains to houses, so the only trenches i do a crap jobs where theres no point hiring a trencher, but effort to dig the trench manually. My apprentice is getting pretty good at it

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## r3nov8or

What exactly is the sand for, as opposed to using the soil?

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## OBBob

Probably drainage, avoidance of sharp rocks near cable, heat rise etc.

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## r3nov8or

My research, including AS3000:2007, has not found any requirement to bed and cover cables in 50mm of sand when the cable is enclosed in heavy duty conduit. Unenclosed cables, yes, bedding in sand is required. 
Happy to be pointed to info to the contrary.

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## Cuppa

I have recently had underground power run from house to a shed site - length of underground trench approx 60 metres. Electrician specified minimum of 500mm above conduit & suggested I should go at least 600mm to allow for thickness of conduit plus any soil which might fall back into trench before & whilst conduit was being laid. Orange warning tape to be laid about 300mm above conduit. Ground is about 50mm top soil & then dry hard clay with quartz chips. Hiring a hydraulic ‘walk behind’ chain trencher for half a day was just sufficient. Depth varied a bit, but was all between 600mm & 700mm. I spent more time clearing out loose soil from the spots where I had needed to change trench direction, not easy in a 700mm deep 100mm wide trench! I’d advise anyone needing a trench which is not a straight line to consider a machine with a bucket & dig the trench wider. It’d be less work in the end, especially if like me you get a hire trencher on which the chain is a little worn (most hire trenchers?) & cuts a trench that is just a tad too narrow for a trenching shovel to fit into!  Heavy duty orange conduit (housing 2 x 16mm cable + earth) & no sand.

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