AJB Temple
DIY
Long time lurker so this may be my first question. I am a qualified electrical engineer, but in aeronautics not domestic installations, and I may therefore ask silly questions. We have purchased a property that is unfinished, and where the electrician went bust before the installation was completed. 90% of the building is certified with BC, but there is a new kitchen in an attached outbuilding, that is substantially wired but not yet connected. My question relates to circuit protection.
There is a conventional Hager late 2018 twin RCD CU in the main house, along with a Henley block that splits to the meter tails to another Hager board containing a twin pole switch and 5 RCBOs. Each of these feeds a different out building via SWA in each of which there is a metal small CU with a handful of MCBs and usually a rotary isolator switch as well.
The new kitchen is fed from one of these Hager RCBOs via 16mm 3 core Doncaster SWA, which reaches a Hager CU in a cupboard in the new kitchen. It is presently not connected.
The new kitchen has a bunch of radial circuits. In essence some feed an Island with oven, hob etc - all radials. Others feed a steam oven, coffee machine, conventional oven, quooker tap with 7l cylinder, and a dozen sockets on a separate area in the same kitchen (basically wall side and island side).
Whoever specified the CU has bought and fitted a Hager which has two RCDs and numerous MCBs. My understanding, which may be wrong, is that if the CU is fitted with RCDs and fed by the RCBO, then nuisance tripping is inevitable? I think the developer may have made a wrong assumption or the ex electrician made a mistake.
I think the CU will need to have the RCDs removed? However, that would leave all of the appliances in the new kitchen prone to simultaneous failure in the event of a fault tripping the RCBO. Very inconvenient, especially as the user has to trek through five other rooms to get to the RCBO box near the meter.
I have yet to find a local electrician who is clued up (had a couple of false starts with people not capable of certifying). So, my questions:
1) If I wish to replace the dual RCD and MCB set up in the new kitchen with RCBOs (ie circuit dedicated), can the RCBO at the source box near the meter be retained, or would having an RCBO feeding a board containing RCBOs cause nuisance tripping? I am assuming it would.
2) Therefore, should the feed RCBO (ie the box near the meter) be replaced with a suitable switch in the CU box? There is only enough space for a single unit in the CU box at the meter end, if the RCBO is removed - ie there are no spare slots, although there are two RCBOs not presently in use so if necessary both could be replaced.
Many thanks. Adrian
(PS, I am looking for a good, friendly electrician near Paddock Wood / Tunbridge Wells in Kent, who can work with me on this, so if you know anyone, please PM me. It's a bit fiddly as I am finishing off the kitchen cabinets etc myself as time and limited budget permits.)
There is a conventional Hager late 2018 twin RCD CU in the main house, along with a Henley block that splits to the meter tails to another Hager board containing a twin pole switch and 5 RCBOs. Each of these feeds a different out building via SWA in each of which there is a metal small CU with a handful of MCBs and usually a rotary isolator switch as well.
The new kitchen is fed from one of these Hager RCBOs via 16mm 3 core Doncaster SWA, which reaches a Hager CU in a cupboard in the new kitchen. It is presently not connected.
The new kitchen has a bunch of radial circuits. In essence some feed an Island with oven, hob etc - all radials. Others feed a steam oven, coffee machine, conventional oven, quooker tap with 7l cylinder, and a dozen sockets on a separate area in the same kitchen (basically wall side and island side).
Whoever specified the CU has bought and fitted a Hager which has two RCDs and numerous MCBs. My understanding, which may be wrong, is that if the CU is fitted with RCDs and fed by the RCBO, then nuisance tripping is inevitable? I think the developer may have made a wrong assumption or the ex electrician made a mistake.
I think the CU will need to have the RCDs removed? However, that would leave all of the appliances in the new kitchen prone to simultaneous failure in the event of a fault tripping the RCBO. Very inconvenient, especially as the user has to trek through five other rooms to get to the RCBO box near the meter.
I have yet to find a local electrician who is clued up (had a couple of false starts with people not capable of certifying). So, my questions:
1) If I wish to replace the dual RCD and MCB set up in the new kitchen with RCBOs (ie circuit dedicated), can the RCBO at the source box near the meter be retained, or would having an RCBO feeding a board containing RCBOs cause nuisance tripping? I am assuming it would.
2) Therefore, should the feed RCBO (ie the box near the meter) be replaced with a suitable switch in the CU box? There is only enough space for a single unit in the CU box at the meter end, if the RCBO is removed - ie there are no spare slots, although there are two RCBOs not presently in use so if necessary both could be replaced.
Many thanks. Adrian
(PS, I am looking for a good, friendly electrician near Paddock Wood / Tunbridge Wells in Kent, who can work with me on this, so if you know anyone, please PM me. It's a bit fiddly as I am finishing off the kitchen cabinets etc myself as time and limited budget permits.)
