i am about to have my basement fully rewired,i have a fairly new consumer unit with an rcd in my basement all ready, my question is, to comply with the 17th regs do i need a brand new consumer unit which include rcbos on every circuit? or can i just reuse my existing board and use ordinary circuit breakers and an rcd?
installing a consumer unit in acordance with 17th regs
- Thread starter chronik2000
- Start date
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sparkyspike
No, you don't need individual RCD protection on circuits in the same room. The RCD will cover it. Ideally, you could fit a normal isolator and use RCBOs, but it's not necessary in this case.
thanks for your reply sparkeyspike, 1 more question if i was planning on rewiring my whole house would it be ok to use a split load board with just the 1 main rcd, or would i have to us rcbos on seporate circuits because iv been told you have to use rcbos in every installation now to comply with the 17th regs. im just a bit confused!
chronik,
Have a look here: Hager Guide to 17th Ed Consumer Units
It should clear some things up for you.
Have a look here: Hager Guide to 17th Ed Consumer Units
It should clear some things up for you.
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You would need a dual RCD split load board or as you say RCBOs on all circuits.
Depending on how many circuits you have a RCBO setup might not be too expensive in comparison and is I believe preferred to two RCD's but the cost of RCBOs can sometimes prohibit this.
If you are doing the rewire yourself make sure you contact your LABC before you start any work. All work must comply with Part P of the building regulations and this work would be notifiable to your local authority.
See here for more info.
Depending on how many circuits you have a RCBO setup might not be too expensive in comparison and is I believe preferred to two RCD's but the cost of RCBOs can sometimes prohibit this.
If you are doing the rewire yourself make sure you contact your LABC before you start any work. All work must comply with Part P of the building regulations and this work would be notifiable to your local authority.
See here for more info.
How come that Hagar doc doesn't list as an option a 'conventional' split load CU with RCD and unprotected sides, with some circuits on the RCD side, and a bunch of RCBOs on the unprotected side? I was under the impression that is also acceptable (it is listed as an option in an alternative '17th edition consumer unit guide' that I have read on the net - will try and dig it out).
Liam
Liam
There's nothing at all wrong with that configuration - in fact it's a better, although more expensive split than the now standard dual RCD units.
Ah good - thought so - cos that's what I'm proposing to do on my rewire! Seems like a reasonable compromise between cost and dividing up the installation to minimise inconvenience. Just wonder why it's not on that Hagar doc? Perhaps they are discontinuing single RCD split load CUs and only want that doc to relate to current products?
Liam
Liam
and so begings another debate on the intentions of the regs vs the wording of the regs...
many electricians believe that split load, dual RCD boards don't comply with the regs ( specifically section 314 ), since a fault on one circuit and the subsequent operation of one of the rcd's interupts the supply to multiple circuits
many electricians believe that split load, dual RCD boards don't comply with the regs ( specifically section 314 ), since a fault on one circuit and the subsequent operation of one of the rcd's interupts the supply to multiple circuits
The way I look at it is from the minimising hazards point of view before minimising inconvenience.
You are always going to come up against cost vs best methods, the best way imo is to use a fully loaded CU with RCBOs. However if someone is going to quote twice the price for half of that by using a dual RCD split board then they are going to win the contract.
You could argue if you split it so that upstairs sockets and lights are on opposite RCDs, similar for downstairs you have taken steps to minimise the risk associated with someone using an appliance such as a drill and the electricity tripping.
As a play off between the two above methods, I quite like the idea of using an old split load board with sockets etc on the RCD and lights etc on the other side of the board fed from RCBOs.
You are always going to come up against cost vs best methods, the best way imo is to use a fully loaded CU with RCBOs. However if someone is going to quote twice the price for half of that by using a dual RCD split board then they are going to win the contract.
You could argue if you split it so that upstairs sockets and lights are on opposite RCDs, similar for downstairs you have taken steps to minimise the risk associated with someone using an appliance such as a drill and the electricity tripping.
As a play off between the two above methods, I quite like the idea of using an old split load board with sockets etc on the RCD and lights etc on the other side of the board fed from RCBOs.
For what it's worth, this is the guide I'd read before which lists 'my' method as compliant...
http://www.alertelectrical.com/17th-Edition-Fuse-Boards.asp
Oh OK - should have known it'd be an oft-debated can of worms
Anyone care to give me a one sentence summary ? At a guess, does it stem from the reg's use of the word 'minimise', relating to the inconvenience caused by multiple circuits tripping? One camp insisting it must mean to the minimum possible (in which case surely they should be advocating individual RCBO protected radials for each socket/appliance and not just RCBOs for each ring etc ); and the other camp (seemingly including most manufacturers, practising sparks, competent person schemes and the BSI/IEE themselves) suggesting the requirement is merely to reduce inconvenience within reasonable bounds of practicality? Something like that?
Liam
http://www.alertelectrical.com/17th-Edition-Fuse-Boards.asp
Oh OK - should have known it'd be an oft-debated can of worms
Anyone care to give me a one sentence summary ? At a guess, does it stem from the reg's use of the word 'minimise', relating to the inconvenience caused by multiple circuits tripping? One camp insisting it must mean to the minimum possible (in which case surely they should be advocating individual RCBO protected radials for each socket/appliance and not just RCBOs for each ring etc ); and the other camp (seemingly including most manufacturers, practising sparks, competent person schemes and the BSI/IEE themselves) suggesting the requirement is merely to reduce inconvenience within reasonable bounds of practicality? Something like that?Liam
for what it's worth, those hagar board can be obtained with 1 or 2 non rcd protected ways, and are constructed such that you can re-configure the busbars to give you more unprotected at the expense of less protected ( you just swap the 3 way busbar for the 5 way or whatever.. )
I never said I was one of the many...
I generally take the regs for their intent, not word for word exact..
I agree that in it's intent, reg 314.1 ( i ) is about minimizing the inconvenience within reasonable or practical extents, but many ( including our 17th reg teacher ) say if it meant within reasonable or practical extents then it should say so..
I never said I was one of the many...
I generally take the regs for their intent, not word for word exact..
I agree that in it's intent, reg 314.1 ( i ) is about minimizing the inconvenience within reasonable or practical extents, but many ( including our 17th reg teacher ) say if it meant within reasonable or practical extents then it should say so..
MCBs often trip when a lamp pops, RCDs sometimes might trip but in my experience not as often.
The idea of having the lighting and sockets spread across 2 RCDs anyway is so if you lose the lighting in one area, the sockets will still work and vice versa.
The idea of having the lighting and sockets spread across 2 RCDs anyway is so if you lose the lighting in one area, the sockets will still work and vice versa.
what's the odds that you have table lamps and such though?
also, what about bungalows or flats where there is only one lighting circuit?
would you put wall lights and central lights on different circuits? that would minimise inconvenience...
also, lamps tend to cause massive short term overloads as they blow as a result of the decreasing resistivity of the filament..
OAP's should really have emergency lighting for such occurences.. My Nan has... ( she's also usually in bed before it gets dark though.. )
with filament lamps becoming obsolete ( or I read somewhere maybe even illegal ), then what do CFL's do to breakers and RCD's when they go?
also, what about bungalows or flats where there is only one lighting circuit?
would you put wall lights and central lights on different circuits? that would minimise inconvenience...
also, lamps tend to cause massive short term overloads as they blow as a result of the decreasing resistivity of the filament..
OAP's should really have emergency lighting for such occurences.. My Nan has...
( she's also usually in bed before it gets dark though.. )with filament lamps becoming obsolete ( or I read somewhere maybe even illegal ), then what do CFL's do to breakers and RCD's when they go?
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