sub main

[mcm]

Hi all

Need to install a sub main to a holiday annex due to mains board in house at the minute. The annex and house are joined just two separate areas.

As they asked for the cu to be in the annex I was going to run a 16mm 3 core swa to new cu and connect into 63a mcb at origin with 100ma rcd as supply is tt. Does this sound about right?

Also the Plumbers are to fit a water heater just for the two sinks in the annex cold water feed from house so I take it I will need to get a 10mm bond onto the pipe work?

I would not need to fit a earth stake at the annex if I use 3 core swa using a core and swa sheath as earth?

Any thoughts would be great.

 

[Guitarist]

My first thought is that you may get the DNO to convert this supply to PME this for you for free if you ask.

 

[HandySparks]

The annex and house are joined just two separate areas.

...cold water feed from house so I take it I will need to get a 10mm bond onto the pipe work?

I would say that if the water supply runs straight through the wall from the main part of the house into the annex, then no need for any additional bonding (providing the bonding in the existing installation is OK). If the supply pipe to the annex runs underground, then bonding may be required. Of course, if the pipe is plastic, then no bonding required anyway.

 

[Richard Burns]

From what you describe the annex is just effectively another room(s) in the building. Therefore they can be considered part of the same installation, so long as you have the earthing and bonding correct at the supply end and throughout the installation then there should be no need for additional bonding.

The SWA protected by the MCB and RCD at origin sounds OK, so long as the RCD is time delayed if you have 30mA RCD(s) as additional protection at the remote CU.

"due to mains board in house at the minute" ​sounds like there are some missing words there so may have misunderstood.