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Posted By Topic: Splice mains to add metered supply

Nov 25 2019 17:05


I have a 3 phase installation and have been given permission to piggy back off the red phase for a new single phase install.

Is it ok to have 2 red phase cables on the live side of the existing main switch (if they fit) so long as that main switch is sealable?

Appreciate any advice.


Nov 25 2019 17:14

does this pic work better


Nov 25 2019 18:00

don't waste your time posting pictures here as the resolution is too poor to see, use another web site and link to them.

You can do what you have asked, but the network company may require separate fusing so a fault in one building won't take out power to the other. You will need to check the mains is big enough to support power usage for both buildings.

Nov 25 2019 19:47

You could try the site below for loading images.

Who did you "get permission" from? The network?

Without knowing the details about the type of installation, or where the point of supply is, it's difficult to give an answer.

But possibly you might have to arrange it so that the current "main switch" becomes a "main isolating switch", then there is a "main switch" for each installation downstream of that. But it's going to depend on your local network rule, and where the meters are positioned in the setup.

Nov 29 2019 07:37

Thanks Doug.

I have talked to our inspector and he suggests as you do. Turn the current main switch into a main isolating switch that isolates both sites. From there both sites can be supplied, i have to add a downsized fuse to protect my 10mm mains which is all good so long as the fuse is sealable (as it will be before the meter) Its really hard to explain without being able to supply a drawing. THanks again

Nov 29 2019 09:59

The key issue is whether what you end up with is going to be 2 installations, or a "multiple installation". That determines how a whole raft of other rules apply.
In order to get clarity on this, you need to know where the "point of supply is" - which the network should be able to tell you (preferably in writing).
Neither metering set-ups, nor 'ICP' numbers, have any bearing whatsoever on this; what matters is the POS; which by default, under Section 2 of the Act, is at the property boundary.

Based on the limited info provided so far, this would appear to be a case of converting a single installation into a multiple installation.

It can't be 2 separate installations unless the PoS is at the splitting point. Separate installations are NOT allowed to share mains [], so if it is intended to be separate installations the PoS must be at the split, with "mains" for each installation commencing at that point (and the supply cables upstream of that point are consequently NOT "mains", but rather privately-owned "works").

Unless the network owns these cables they can't dictate how you go about it - and they can't give "permission" for any particular configuration. Permission has to come from the owner of the assets. That said , networks can legitimately impose requirements to avoid interference with / disruption to their other customers, and that may include the addition of significant load

If the PoS is some distance upstream, then one way you can do this is as a normal MSB with submain to DB. I suspect the reason you're not doing that is so they can be separate tenancies, each responsible for their own portion.

In which case you need to set up a "multiple installation".