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Posted By Topic: Temporary supply

Braden
May 30 2017 17:42

Hi guys,
I'm wondering what others suggest when installing temporary supplies, with regard to future installation of the mains.

For example, I'm considering running a shorter length of 16mm N/S for the temporary supply, and a 30m length at the same time for the eventual connection of the house.

Another option would be large 40-50mm duct from the pillar to the temporary supply, so that an intact length of mains could be installed at the end of the build.

Or just an underground inline join of the mains conductor, when ready to connect into the house.

What about burying a 20m live coil of mains next to the temporary supply for later excavation. 500mm down with danger tape of course...

The route from the pillar to the temp supply location is an asphalted turn around area with formed curb, so the trench can only be opened once.

Would be interested to hear how others tend to approach it.
Cheers,
- Braden

   

AlecK
May 30 2017 17:53

"For example, I'm considering running a shorter length of 16mm N/S for the temporary supply, and a 30m length at the same time for the eventual connection of the house."

wasteful - you don't need a 16 mm2 for the BTS, and whatever you use will be left behind


"Another option would be large 40-50mm duct from the pillar to the temporary supply, so that an intact length of mains could be installed at the end of the build."

perfectly valid


"Or just an underground inline join of the mains conductor, when ready to connect into the house."

also valid - but generally joins should be avoided unless necessary.


"What about burying a 20m live coil of mains next to the temporary supply for later excavation. 500mm down with danger tape of course..."

and additional mechanical protection. Perfectly valid, and probably the most common option - though perhaps not always properly implemented.

There's also having an above-ground coil for the "spare", provided you can give it adequate mechanical protection.
   

DougP
May 30 2017 19:04

Is there any reason that the temporary supply can't go all the way to the house on the permanent mains cables?

Also what is the actual route length? It's difficult to work out from your description, but it could be too long for a reasonable volt drop on 16mm2?
   

pluto
May 30 2017 21:50

many people put the permanent mains plus a bare earth wire to the house position and put the main switchboard on a temporary frame work as a builders temporary supply until the house construction gets to the point when it can be installed into the framework.
Put in the metering in the switchboard, RCD for 2 socket outlets at the initial installation.

Only one mains inspection, when doing the fit out, no need to wait for a supply it is already there including the metering.
   

AlecK
May 31 2017 08:38

The chances of avoiding a second inspection are pretty small. Remember the cables from meterbox to MSB are also "mains". So unless the final installation's main switchboard is also within the meterbox, there will be a need for another inspection.

Care is needed if wanting to use the final meterbox as the BTS enclosure, as it won't be compliant with "3012" requirements unless modified; and once modified it may be difficult to then use it later for meter enclosure.

And if there's any re-location of cable routes (mains or main earthing conductor), or of the earth electrode, at changeover time; an inspection is required.
   

Braden
May 31 2017 19:29

Hey all,
Thanks for the replies. I think I'll lean towards a buried or exposed LIVE coil of Neutral screen and situated near-ish to the final M/Box position - with adequate Mechanical protection of course!

I've often seen short lengths of Mains installed for the temp, and a separate intact section of Mains to be connected at a later date. But I take AlecK's point on the wastage of such an arrangement.

I realize 16mm N/S is overkill for a builders temp, but I would also assume that inspectors would be loath to connect a piece of 6mm TPS into a pillar even for a temp - perhaps its no biggie?

Thanks again for the feedback!






   

AlecK
Jun 01 2017 09:03

" I would also assume that inspectors would be loath to connect a piece of 6mm TPS into a pillar even for a temp - perhaps its no biggie? "

Inspectors don't connect. They only inspect. The person doing a connection may be the same person, but not acting as an "Inspector" and subject to different Regulations.

Since 6 mm2 is likely to be perfectly adequate for max demand, and also for volt drop (if 16 mm@ is OK for mains); it's compliant provided it is protected against overcurrent. Short circuit protection by (presumed) 63A HRC supply fuse; OK.
Overload protection by eg 32A mcb in BTS; all bases covered.

So issue CoC, and no competent Inspector could have a valid reason to refuse RoI. Person connecting must sight these; but CAN'T refuse connection just because they think it should be bigger.

That said, there may be a local network "rule" as part of the contract between network and consumer.

One thing a "person about to connect" can require is written test results [ESR 73A (3) - the ONLY time ESRs require recording of test results]; but I doubt that happens very often.
   

pluto
Jun 01 2017 09:07

Braden May 31 2017 19:29
Your comments (part only)

I've often seen short lengths of Mains installed for the temp, and a separate intact section of Mains to be connected at a later date.

I realize 16mm N/S is overkill for a builders temp, but I would also assume that inspectors would be loath to connect a piece of 6mm TPS into a pillar even for a temp - perhaps its no biggie?

My comments
In some areas the lines company pillar only has a limited range of service fuse sizes available to use. Usually not many in the low values say 32 A which would be OK for builders temp supply.

This factor is reason why it is necessary to use a minimum size of mains cable even though the maximum connected loading is well below the capacity of the mains cable.


   

AlecK
Jun 01 2017 09:29

Yes they may "require" (viw the supply contract)a minimum size.
But - as above - there's NO justification for such a requirement; because the overload protection can be provided at the other end.
Remember a network must provide short circuit protection and fault protection for mains. They DON'T have to provide overload protection - that's OUR job.
   

gregwires
Jun 01 2017 10:05

My dad just had a temp supply livened last week for their house, 4 x 240mm AL tailed down into the temporary box, meters, an 3 phase 32a RCD and MCB and a 532 PDL socket on the outside. The guy from Northpower also put 32A fuses in the pillar some 250m away and said he's put the correct ones once the supply is permanent and he re inspects. The Temp box is on a post that's located just outside of the future shed wall (room to dig footings) and intended location of meter box.
   

Andrew
Jun 01 2017 11:21

A minor point here, but ESR73A doesn't require recording test results, it requires the person connecting to either sight documentation of test results or do the tests themselves. If the person who prepared the CoC didn't appropriately document the tests then the person connecting can't require that they do, they are just required to test for themselves.

I'd say 73A(3) is another reason not to record results on a CoC if you're not going to be the person connecting since it means that if the person connecting is doing their job then you've had another pair of eyes checking that your work is safe (at least as far as phase rotation, supply protection, compatibility, and existence of a main earthing system are concerned).
   

AlecK
Jun 01 2017 13:37

true reg can be interpreted as giving a person-about-to-connect an option of doing the tests themselves, if you don't supply documented test results for your work. Assuming that is a valid option, it would follow that if that option is taken you should expect to be charged for the time taken.

However that is not the way ESR 73A (3) is worded. What it actually says is that if the person who connects has not done the tests themselves, they must sight signed (by the tester) documentation stating what tests were carried out, and what the results were. The Reg is written from the point of view of having reached the moment of connection - by which time the CoC must have been issued, and the "tests required by these regulation" must already have been done. At that stage it's too late to go back in time and do the tests in order to get things back on track, and a person connecting would be entitled to demand test results.They must sight the CoC and the RoI, if any). There is NO obligation on them to do testing that should already have been done before either of these can be lawfully issued.

Remember it's the person who did the work who is responsible for having work tested; and for having it certified. Asking the person connecting to do "tests required by these regulations" pretty much amounts to admitting that you didn't do them / have them done prior to certification. So not really such a clever idea.
   

Andrew
Jun 01 2017 14:01

I wrote my response on the (incorrect) assumption that the "tests required by these regulations" were the items referred to in 73A(1)(e), since 73A(4) would suggest that you can be satisfied that the testing was done based on the CoC. On second reading (3) adds extra requirements on top of (4), so I think you could only use (4) if the CoC explicitly stated that all tests required by the regulations were performed and gave a satisfactory result - and even there you're skating close to the edge of the law (i.e. probably meeting the letter but certainly not the intent).
   

AlecK
Jun 01 2017 14:25

I believe you are right as to meaning of "tests required by these regulations". It took me a while before I twigged. I believe when working out the meaning of the 'legalese"; we need to look at ESRs as a whole, not just the individual reg. Even to the extent of noting, for example, that in some places the words say "installation or part installation", while in other places it just says "installation" with no reference to "part installation". That sort of thing is (always?) done for a reason, so we can assume something slightly different is meant.

That said, there are several places where Energy Safety's "opinion" is significantly different from the natural meaning of the words. Given various legal precedents; I'll take the actual words as being right, and the opinion as not legally reliable.

One thing's for certain; the letter of the system outlined in ESRs for this stuff doesn't easily translate into practicality, so we tend to take the odd shortcut (like certifying after connection). All very well within the same company, but when third parties are involved it can be tricky.