RCD splitting question

[High Tower]

The more I read, the more i find out the more I think with 15th edition equipment then possibly the whole house could do with attention to bring it up to the same standard as the new addition and incorporate it into one installation

 

[piggyitm]

So i have to install a new board to create a new way rather than tap off the tails and put in an extra 17th CU that can feed the extension board because there is no supplied main isolator and because the house is only 4 bedrooms?Isn't this just like tapping off a busbar chamber with a new board and labeling it DB2 then making the extension DB2/1 at both ends?

 

[pushrod]

So i have to install a new board to create a new way rather than tap off the tails and put in an extra 17th CU that can feed the extension board because there is no supplied main isolator and because the house is only 4 bedrooms?Isn't this just like tapping off a busbar chamber with a new board and labeling it DB2 then making the extension DB2/1 at both ends?

Just replace present CU with a larger one. Arrange for supplier to fit an isolator.

 

[piggyitm]

Hey Hightower while your on...same extension....do i have to install mains interlink smokes in the existing house to connect in with my extension smoke install?
And do i need to change 25% of the lights in the existing to conform with L1A?Also there are some existing spots that aren't fire rated in the kitchen will these have to have hoods AND all the sockets are below 450mm

 

[High Tower]

As far as I know fire hoods and socket Heights arnt retrospective, so no for them but you will have to update smokes mate, and as for lighting do a quick search on here as there was a thread debating the lighting issue, not sure what the outcome was

 

[Deleted member 9648]

First off .... It wouldn't then be a ''Single Dwelling'' house if the extension was to be an annexe or separate flat, would it?? Then you would be correct...That info wasnt available in the OP,therefore your general statement about having 2 DB's in one propety was misleading

If this was a large house to start with, it would be very doubtful the owner would be adding a two storey extension, ....not impossible, but doubtful!! I would suggest that the now present size of house is in all probability a 4 bed-roomed house converted from a 2 or maybe even a 3 bed-roomed house. ....So how many 4 bed-roomed houses have you seen with 2 completly separate CUs supplying it's electrical needs??? That info was not in the OP either....you appear to have an uncanny ability to decipher imformation that is not provided

I stand firmly behind my statement, ...it's certainly not misleading and it's not incorrect either. If we were talking about a very substantial 3 or 4 storey house, or of the like you could possibly have a valid point.

.....If the property is as you describe I absolutely agree with you,final circuits should be run to a single DB...but as this info was not provided your all encompassing statement concerning additional DB's in a single property is misleading and incorrect.......you dont have to agree,but you are wrong.

 

[malcolmsanford]

Well no mate....if it's a TT an RCD with be necessary at the origin to provide fault protection to the distribution circuit...ideally a 100ma time delayed with a split rcd board in the extension.....if it's a TT and thats how the OP is going to do it

Though we now know it's a TN-S system the sole use of RCD protection for a SWA distribution cable is not totally correct. Reg 411.5.2 does state the prefered method of fault protection should be an RCD, but providing that the Zs allows disconnection time then another type of protection device can be utilised such as a BS 88-3 ( 1361) fuse.

I know that in design you may not be able to achieve the required Zs by calculation, but in reality with earth paths and bonding it may be achievable.

 

[Amp David]

Absolutely loath submains run in twin nad earth. Its the skin flint way IMO!

 

[High Tower]

Absolutely loath submains run in twin nad earth. Its the skin flint way IMO!

I did try and make that point, I diddnt say it was against regs just said it's a bad idea,

I still say that if it's not possible to amalgamate the new circuits with the existing then the best way in
My mind would be split the tails, switch fuse then swa to the remote board.

 

[Amp David]

DIdn't see your post High Yower, will teach me to read the full thread in future lol

 

[High Tower]

No your post was spot on, just this topic has caused quite the debate

 

[Deleted member 9648]

Though we now know it's a TN-S system the sole use of RCD protection for a SWA distribution cable is not totally correct. Reg 411.5.2 does state the prefered method of fault protection should be an RCD, but providing that the Zs allows disconnection time then another type of protection device can be utilised such as a BS 88-3 ( 1361) fuse.

I know that in design you may not be able to achieve the required Zs by calculation, but in reality with earth paths and bonding it may be achievable.

Technically correct.yes...but in practice the chances of getting a low enough Zs for a 60a bs 88 fuse with a rod are around zilch.

 

[Deleted member 9648]

Absolutely loath submains run in twin nad earth. Its the skin flint way IMO!

I'd do it in SWA as well.......

 

[High Tower]

Technically correct.yes...but in practice the chances of getting a low enough Zs for a 60a bs 88 fuse with a rod are around zilch.

theres no rod, its TN-S

 

[Deleted member 9648]

yeah I know...but those posts originated before the earthing system came to light.