RCD splitting question

[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.

 

[High Tower]

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

sorry mate diddnt realise

 

[tuckermot]

upgrade to new board (more ways)

extend original lighting circuit ( 10a mcb instead of 6a mcb in new board ) allowing that original cable is not 1mm and using watts divided by volts to get amp usage of lights old and new )

wire smoke alarms of original / new circuit using wire less smokes

run new ring back to new board

job done !!!

 

[tonys]

tuckermo

How did you get on with the interview for that electrical/mechanical apprenticeship ?

 

[tuckermot]

hi tony

did not get there mate my normal job came 1st ( pays the bills ) still looking to go full time but just doing bits and bobs at mo !!!! .I have let part p run out as i can not compete with other sparks who just do work any way !!! and are not botherd about certs and building controle

 

[tonys]

Bad ain't it mate, from my point of view, if loads said stuff part p, there's nothing the authorities could do about it. They do not have the time or money to chase people.

Keep at it, there's a load of decent homes work up your way.

 

[tuckermot]

thanks tony

 

[Engineer54]

.....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.

I suggest you read the original OPs post, No where in that post, did it talk about granny flats, annexes, or flats, You did that!! I read the post as it was described, and i related to it, and that was as ....'A House Extension'' .

Now unless we are talking about a rather large sprawling house, there will never be a need for having 2 CUs in remote separate locations. 2 CUs Yes maybe, ...one for off peak heating tariff's, or as a means of increasing the number of circuits. But again both located at a common position.


So let me say this again, albeit a little modified to suit yourself, ''The use of 2 remotely separated CUs in a standard sized single dwelling house is a nonsense!!!'' And that is not misleading, nor is it wrong!!!

 

[tonys]

Engineer54

Your not putting with nonsense then, I reckon your part p qualified lol

 

[Engineer54]

Nope, ....i don't even live in the UK these days ...haha!!

 

[tonys]

I know, you drop the hint how many times a day lol