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Topic # 123212 28-Jun-2013 16:54
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I'm looking to help my grandparents underground their overhead power & phone lines as they currently run through the middle of a tree which is increasingly threatening the lines. They also need to replace the underground water pipe as it has developed a leak and volumetric water charges are coming in soon. Luckily they are on sand, so trenching shouldn't be too hard (Grandad dug all the service trenches himself 50 odd years ago).

We will be engaging an electrician at some point, but would appreciate a bit of GZ wisdom just to scope the project.

1) I'm familiar with the Chorus lead-in guide, I'm confident to run green conduit & 2pair gel-filled cable, but I get the feeling I should leave the actual connecting to Chorus? It's a bit difficult as the phone pedestal is across the road, so the overhead line goes from the house to the nearest pole, then across the road and down another pole to the pedestal. In this case would they just install a demarc style box on the nearest pole, so that the underground lead-in connects to the overhead leadin that runs across the road?

2) What scope is there to put power/phone/water in the same trench? I gather that power needs to be >600mm deep, phone >450mm deep, and the two separated >300mm. How far should water be from these two? I'm wondering if it's worth doing separate trenches rather than one big wide trench, given we will be digging by hand rather than with a digger.

3) With power I think the options are conduit + warning tape, or direct burial + magslab mechanical protection. What is typical for a leadin to standalone house? What size conductor would I typically use for this? There is a separate incoming line for ripple control, but I believe it is redundant as they use RF over power signalling.

TIA
Nick

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  Reply # 846852 28-Jun-2013 18:16
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1) Lay the conduit right up to the pole and then Chorus will take it up the pole and joint it to the OH line that takes it to the DP.

2) Drain layers will normally dig a 600mm trench that is around 400ish wide and lay the phone conduit on one side and power on the other. So they are the same depth but separated horizontally. They then normally back fill 200mm or so and lay warning tape and the water at that level.

3)My understanding is if the cable is neutral screened it can be direct buried with just standard warning tape. But don't know for sure on that one.



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  Reply # 846855 28-Jun-2013 18:49
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Great, thanks for that!

A single 400 wide trench would make things very simple

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  Reply # 846951 28-Jun-2013 22:14
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Our new house was built 2 years ago, replacing on old house and reusing existing service connections. We were required to take the power underground and pay for a connection pit at about $2500 which the neighbour now can use for free (there is one per 2 houses, first person to need one pays the full cost).

The phone line was done as described above, green conduit to the pole and then also grey conduit some height up the pole to a connection point and then across the road.

Water was also a new connection as we moved it to the other side of the driveway, just blue line somehow connected to the main pipe.

Everything came down one trench. I would have to go through photos, but I think the power came down corrugated pipe or transitioned from corrugated to rigid (from just outside house to pit), can't remember now.




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  Reply # 847017 29-Jun-2013 06:48
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Cable size depends on loading and distance from the service pole, you'll need to talk to your electrician  to work that out, typically 16mm2 1c neutral screen.

Just need to be careful, if you have a combined inside meterboard fuse board you will be required to move the meter point outside and upgrade the old fuse board to something more modern.

The reason behind this is that in the process of installing a new service line that meets the current regulations you also vastly increase the prospective short circuit current, which means that old style  re-wireable fuse can't handle.

It's kind of a sliperly slope, one small thing leads to another and so on, snow balling the costs along the way.

Talk to your electrician about other things that may be required as a result of the service main upgrade

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  Reply # 847049 29-Jun-2013 09:57
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chevrolux: 3)My understanding is if the cable is neutral screened it can be direct buried with just standard warning tape. But don't know for sure on that one.


Correct.




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  Reply # 847064 29-Jun-2013 10:13
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gregmcc: if you have a combined inside meterboard fuse board you will be required to move the meter point outside and upgrade the old fuse board to something more modern.

The reason behind this is that in the process of installing a new service line that meets the current regulations you also vastly increase the prospective short circuit current, which means that old style  re-wireable fuse can't handle.

It's kind of a sliperly slope, one small thing leads to another and so on, snow balling the costs along the way.


Interesting! Our place had the meters moved outside when our street was changed to underground power (unknown how many years ago, before we bought the place). The fuseboard wasn't upgraded or changed at all though. Obviously the regs have become stricter in the meantime.




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  Reply # 847067 29-Jun-2013 10:25
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gregmcc: Cable size depends on loading and distance from the service pole, you'll need to talk to your electrician  to work that out, typically 16mm2 1c neutral screen.

Just need to be careful, if you have a combined inside meterboard fuse board you will be required to move the meter point outside and upgrade the old fuse board to something more modern.

The reason behind this is that in the process of installing a new service line that meets the current regulations you also vastly increase the prospective short circuit current, which means that old style  re-wireable fuse can't handle.

It's kind of a sliperly slope, one small thing leads to another and so on, snow balling the costs along the way.

Talk to your electrician about other things that may be required as a result of the service main upgrade


Thanks, really appreciate the advice. Hadn't thought about that - the meter is already combined with the switchboard outside, but probably has old-style fuses

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  Reply # 847176 29-Jun-2013 16:41
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DarthKermit:
Interesting! Our place had the meters moved outside when our street was changed to underground power (unknown how many years ago, before we bought the place). The fuseboard wasn't upgraded or changed at all though. Obviously the regs have become stricter in the meantime.


They will typically put a big cartridge fuse in the outside board for the inside board, which based on a friends experiance will blow well before any inside fuse when you have a short from cutting thru an extension cord with a hedge trimmer, and then will be a prick to find a replacement for.

IIRC it was a 40A cartridge fuse for the inside board, and a normal 16A breaker for the hot water which they re-wired to go from the new outside board.

Then about a year after that all went in, they got a smart meter so no need for the meter to be outside at all wasting all their time moving it when undergrounding things.




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  Reply # 847178 29-Jun-2013 16:43
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Oh, and swapping fuses out for plug in breakers isnt allowed anymore according to the sparky that does work. They have to put a din housing on the board and a proper din rail breaker which isnt fun when the board is full.




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  Reply # 847180 29-Jun-2013 16:48
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We have two HRC fuses in the "pod" by the roadside connection. There are no fuses (nor a mains switch) on the outside meter board.

Our power company installed one of those smart meters on our meter board in 2012.




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  Reply # 847181 29-Jun-2013 16:50
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I'd love to get the whole crappy old fuseboard replaced with a nice modern DIN rail job (and the old crappy TRS wiring!!) when $$$ allows.




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  Reply # 847639 1-Jul-2013 10:58
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richms: Oh, and swapping fuses out for plug in breakers isnt allowed anymore according to the sparky that does work. They have to put a din housing on the board and a proper din rail breaker which isnt fun when the board is full.


Hmm. I did exactly that in the weekend after wifey accidently shorted a light bulb. Old wire fuse replaced with breaker bought from bunnings.



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  Reply # 847666 1-Jul-2013 12:18
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Checked out their circuit board today - it's relatively empty with only 7 breakers (including main), two of which have been upgraded already. So worse case they have to upgrade 5 breakers, and there's plenty of room for the sparky to do his thing.

Thanks all for the input, I've passed it on to them so now they know what they're up for. I think a 400x600mm trench will be my xmas gift to them!

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  Reply # 847682 1-Jul-2013 13:16
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Sorry to burst your bubble a bit but from what I understand regulations state power needs to be buried at no less than 500mm. The power and phone can run at the same depth BUT need to be separated. Then like others have said plenty of warning tape.

Also If I was you I would get 25mm conduit so when UFB comes to their home you have enough space in the duct to run the fibre. Also don't forget a draw wire!


Good luck and happy digging.



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  Reply # 847699 1-Jul-2013 13:36
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I meant 600 deep 400 wide, as per Chevrolux's post. I'm pretty sure I have to use a conduit for phone, as it is an urban connection

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