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Posted By Topic: 3 x joined buidings seperate tenancies

Mar 08 2018 12:11

Hi All
Have a scenario where building is 60 m long - 20 m wide with 3 x seperate tenancies, metal portal and metal clad.

There will be 3 new ICPs for the three tenancies
Can it be done with 3 x seperate supplies to 3 x MEN boards - Main Earths etc, I say this as I have seen lots done like this, or should there be a central supply say in centre of outside wall and supply 3 x tenancies as Distribution Boards with Metering in the tenancies
My thoughts is the central supply way but would appreciate any thoughts


Mar 08 2018 16:02

Tenancies have NO bearing on whether it's one installation or several. Nor does metering. Nor do ICPs - which are really just a unique ID for every place that a network delivers power to.

"electrical installation" is defined in terms of "a property". So the legal status of the land may be relevant.
From a purely electrical point of view, you can set this up as 3 x single installations, each with SEPARATE mains & main earthing system (no sharing of any cable). Or as a "multiple electrical installation"; with ONE lot of mains and one main earthing system. What you definitely must not do is try to invent some hybrid system. Downstream of the Point (or Points) of Supply, you have be one or the other. It's probable that the Point(s) of supply is where the mains cross the property boundary; but it may be elsewhere - talk to the network (and get it in writing).

I know of nothing that would prevent a single property from having several installations on it - as long as they are electrically separate. I know of nothing that says a single installation can't occupy more than one property - in fact large installations often do. Very large installations, and other (eg hospitals) that need increased security of supply, even have multiple points of supply (which will have different ICPs).
But if they are legally separate properties, you may find you need legal easements for cables that are part of or supply one installation from passing through a different property. That said, I'm not a property lawyer.
I suspect what you have is one property owned by one landlord , and all each tenant wants is to have control of their portion and to be supplied by the retailer they prefer.


Mar 08 2018 17:21

Thanks for the info
The property has one owner on one title - just three seperate tenants all doing their own thing
I was wondering if there were any implications being a total metal complex with earthing and different potentials if three seperate MEN boards and each board bonding their part of the structure etc
Seen lots of them with tilt panel buildings but havent yet come across a metal setup

Mar 08 2018 17:44

If you do it as 1 installation, with 3 separately-metered parts, you'll only need one earth connection for the structural metal.

If you go for completely separate installations, each will need it's own earth.
And if they have showers, their own bond to reo of floor.

shouldn't be any real issues with having separates, other than extra cost compared to a "multiple installation".


Mar 09 2018 11:00

Maybe Sparky59 concern is the multiple men,bond and electrode. Where a high resistance neutral could have current flow on the structure via the bond?

Mar 09 2018 12:32

earthing of structural metal, and bonding of other conductive building materials 9where double insulation isn't maintained) will take care of earth faults, and also deal with any equipotential issues arising from a bad oir open-circuit supply N.

For open-circuit supply N (assuming all one metal structure):
- a "multiple installation" will have one structure (plus bonding if required) and one MEC to electrode; and all return load current or earth fault current would try to go down the electrode. Which is likely to be a poor path, so the potential of the earthing system will rise - and bonding will ensure it all rises together so no dangerous touch voltages.
- 3 x single installations will have 3 x structure PECs (plus bonding), and 3 x MECs + electrodes; there could be some sharing of the current between the 3 systems due to each installation's earthing system being effectively connected by the structure. With 3 electrodes effectively in parallel, the impedance is likely to be lower (Ohm's law) so the rise in potential may be less; but still taken care of by fact that having everything tied together keeps touch voltages within limits.
If the electrodes were extremely effective, we might lower the impedance enough to alow serious levels of current to flow, such that there could be measurable volt drop along the path through the structure - but the VD would have to be pretty large before it led to significant touch voltage issues.

3 x single installations will have three lots, but