Compliance with 17th edition when altering old existing installations

[whitebeetle]

Hi All,
Just wondering how you manage to comply with current regs when adding to an existing older installation.

For example if asked to wire a supply into a garage and the customer has the old type rewirable fusebox do you have to explain that they will need either RCBO Protection/ new consumer unit in order to comply ? Obviously this increases cost dramatically and could price you out of the job compared to the cowboy who'll just wire them straight in on a rewirable fuse !

What happens if the work you do complies but the rest of the installation doesn't i.e if you were to put the garage supply on RCD/RCBO but leave the rest of the property running on rewirable fuses - how much are you responsible for the total installation after you have added to or extended a circuit ?

After modifying a circuit are you totally responsible for the total installation - whats your opinions on this because i'm sure its a dilemma for many
Chris.

 

[Spudnik]

Not an easy one to answer as there are so many variables with each installation you come across.

With regards to your example, if the install is not an old TT, then if there is a spare way in the CU for a 30 fuse, the supply can be run in SWA and the RCD as part of the sub board.

Main earth and bonding should be checked and updated if required.

As for circuit mods, then if you are altering or extending it, then that circuit should be brought up to regs, although there is great debate on this, as to whether its only the modified part that needs to be to the 17th.

 

[TPES]

If your supplying a garage from the main CU in house and you come off a 32a which is RCD protected am i right in saying you wouldnt have a RCD in the sub board as main incomer, as you cant have 2 RCD's inline? So you would have the supply cable coming into a main switch and then RCD protecting all outgoing circuits from then on?

What would you do if supplying a garage from the downstairs house ring final circuit off the back of the house? how would you be wiring this to supply a garage?

Ive seen some done where theres a 20a DP isolator off the RFC then off to feed sockets.. and then fused down for lighting ect.. But surly this isnt right as this is just alot of spurs off the RFC.

 

[matt456]

could you not fit an rcd to cover the rewirable cu? im not sure if this is allowed as just getting back into the houses again!

 

[Gravid]

Your not supposed to do that anymore, although i have come across it a few times.

 

[matt456]

Not an easy one to answer as there are so many variables with each installation you come across.

With regards to your example, if the install is not an old TT, then if there is a spare way in the CU for a 30 fuse, the supply can be run in SWA and the RCD as part of the sub board.

Main earth and bonding should be checked and updated if required.

As for circuit mods, then if you are altering or extending it, then that circuit should be brought up to regs, although there is great debate on this, as to whether its only the modified part that needs to be to the 17th.

what if it was for a old tt system theres alot around where i live.

Your not supposed to do that anymore, although i have come across it a few times.

What is there reasoning behind this?
matt

 

[Gravid]

Think its to do with the consequences of a single protective device covering the whole install.

One fault and you lose the lot.

 

[matt456]

i suppose but its more cost effective! as has been said somebody will undercut and do it that way as it would be cheaper than replacing the cu

 

[Gravid]

I know what your saying and its a pain trying to convince a potential customer to have work done that he/she had no idear about. Whenever i try to explain why they need there water/gas bonding i always think thats how i must of looked when i was first taught it !! But if your going to do a job do it properly. After all your names on it.

Check out page 32 of the OSG, its all about trying to minimize the inconvenience in the event of a fault, thats why we have split load boards.

 

[jbec-john]

There are some good practice guides on the NICEIC website. They don't cover the exact problem you mentioned, but they're a good read if ever you're unsure.
Best Practice Guide - Approved contractor scheme - NICEIC Group

In the case you mention, I'd definitely recommend a consumer unit swap first, as well as a bonding upgrade if needed.

In 3 years of being self employed, I can't remember a single case where the customer hasn't agreed to have the work done when I've recommended something like that. Granted sometimes they may leave it for a few weeks to raise the money, but as long as your price is reasonable, and the work is genuinely needed you shouldn't have a problem.