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Hello folks,
I've just visited the retirement flat of an elderly couple who want RCD protection added to all of their circuits. Yes,all of them. Fairplay,it's nice to see people of 95 years of age taking an interest in electrical safety!
The installation is PME,Economy 10,with two pairs of 16mm supply tails terminated in 63A isolator switches (63A AC 22 BS5419. 380/415v 50Hz) within the main Hager CU. Two separate neutral bars present. All circuit fuses BS1361. There are no RCDs or RCBOs installed in this CU. Storage heaters are present,all connected to their respective circuits by way of clearly visible lengths of flex of around 250mm in each case,terminated into flex connection boxes. While I don't believe there is a requirement for the storage heaters to have additional protection (Please correct me if I'm wrong),these lengths of flex are far from protected from mechanical damage! They could easily be snagged and I'll at least clip these up or run them in trunking.
An additional Hager CU has been installed to supply and protect three circuits entering a shower room,all on correctly rated Type B MCBS. A 63A isolator switch and 30mA RCD have been installed to isolate and provide additional protection to all three circuits. Good. The shower room CU is supplied by 16mm T&E,originating from a 50A MCB within the main CU.
Initially I considered installing two RCCBs in place of the 63A isolators,but I'd end up with the shower room RCD and the peak rate circuits' RCD being in series. Given the age of my customers,the amount of problems this could cause are numerous and it's poor practice anyway. In the event of a fault resulting in earth leakage current in the shower room,there's no guarantee of the RCD protecting the shower room tripping before the RCD protecting all of the peak rate circuits does. You could argue that either way,injury or death would have been avoided,but knocking out all lighting circuits and leaving elderly people in the dark,even temporarily, isn't an option and if nuisance tripping developed on any peak rate circuits (which the shower room supply is),well......
Installing an RCCB to protect the off peak circuits can be done,because there are four spare ways on that rail. Keeping the existing isolator and installing RCBOs for all peak rate circuits,with exception to the shower room supply circuit,would be a nice solution and would immediately eliminate the issue of RCDs in series,but would be a pretty costly one for the customer as I'd need nine RCBOs. There are a lot of circuits for a flat!
Splitting the peak rate supply via a Henley block would be nice. I could install a separate isolator and 50A MCB to supply the shower room board. The issue....the tails are short as hell,entering the main CU through the wall from behind and embedded in plaster...really chucked in there. No conduit. It's only a two metre run out to the meter cupboard on the landing,but they're not in the mood for being easily manipulated or drawn out and replaced. I'm also very anxious to avoid wall bashing,especially in a communal area of the building. At this point I will say that I've not yet referred back to the regs with regard to the question I'm about to ask,but obviously will do If it were permitted to somehow safely extend the supply tails,actually inside the main CU itself,and out by approximately 150mm to a Henley block,this would facilitate a split to the peak rate supply. If so,how would this be best achieved? I have not done this before and nor have I heard of it being done to date. Obviously space would be also an issue.
This is already way longer than I wanted it to be. Enough.
Any ideas/feedback would be really appreciated.
Cheers :wink_smile:
I've just visited the retirement flat of an elderly couple who want RCD protection added to all of their circuits. Yes,all of them. Fairplay,it's nice to see people of 95 years of age taking an interest in electrical safety!
The installation is PME,Economy 10,with two pairs of 16mm supply tails terminated in 63A isolator switches (63A AC 22 BS5419. 380/415v 50Hz) within the main Hager CU. Two separate neutral bars present. All circuit fuses BS1361. There are no RCDs or RCBOs installed in this CU. Storage heaters are present,all connected to their respective circuits by way of clearly visible lengths of flex of around 250mm in each case,terminated into flex connection boxes. While I don't believe there is a requirement for the storage heaters to have additional protection (Please correct me if I'm wrong),these lengths of flex are far from protected from mechanical damage! They could easily be snagged and I'll at least clip these up or run them in trunking.
An additional Hager CU has been installed to supply and protect three circuits entering a shower room,all on correctly rated Type B MCBS. A 63A isolator switch and 30mA RCD have been installed to isolate and provide additional protection to all three circuits. Good. The shower room CU is supplied by 16mm T&E,originating from a 50A MCB within the main CU.
Initially I considered installing two RCCBs in place of the 63A isolators,but I'd end up with the shower room RCD and the peak rate circuits' RCD being in series. Given the age of my customers,the amount of problems this could cause are numerous and it's poor practice anyway. In the event of a fault resulting in earth leakage current in the shower room,there's no guarantee of the RCD protecting the shower room tripping before the RCD protecting all of the peak rate circuits does. You could argue that either way,injury or death would have been avoided,but knocking out all lighting circuits and leaving elderly people in the dark,even temporarily, isn't an option and if nuisance tripping developed on any peak rate circuits (which the shower room supply is),well......
Installing an RCCB to protect the off peak circuits can be done,because there are four spare ways on that rail. Keeping the existing isolator and installing RCBOs for all peak rate circuits,with exception to the shower room supply circuit,would be a nice solution and would immediately eliminate the issue of RCDs in series,but would be a pretty costly one for the customer as I'd need nine RCBOs. There are a lot of circuits for a flat!
Splitting the peak rate supply via a Henley block would be nice. I could install a separate isolator and 50A MCB to supply the shower room board. The issue....the tails are short as hell,entering the main CU through the wall from behind and embedded in plaster...really chucked in there. No conduit. It's only a two metre run out to the meter cupboard on the landing,but they're not in the mood for being easily manipulated or drawn out and replaced. I'm also very anxious to avoid wall bashing,especially in a communal area of the building. At this point I will say that I've not yet referred back to the regs with regard to the question I'm about to ask,but obviously will do If it were permitted to somehow safely extend the supply tails,actually inside the main CU itself,and out by approximately 150mm to a Henley block,this would facilitate a split to the peak rate supply. If so,how would this be best achieved? I have not done this before and nor have I heard of it being done to date. Obviously space would be also an issue.
This is already way longer than I wanted it to be. Enough.
Any ideas/feedback would be really appreciated.
Cheers :wink_smile:
