Shower change

[PC Electrics]

Option 2 is what I would do......use existing CU for overload protection, split the tails and put in a 30mA RCD to feed the original CU which would cover all the circuits for shock protection. Complies to regs and cost effective.

DOES NOT comply to BS7671:2008

(I don't think it complied with 16th either for that matter - but that's a moot point now)

 

[Foxmeister]

Why not have a small four circuit board, a main switch and an RCBO? take the tails from a Henley block?AndyGuinness

Firstly, cost.(Board+RCBO+Shower etc) Imagine it would end up expensive.

Secondly, space, dont think i could fit in a small DB.

Third, adaption, dont have Henley block etc to connect to or means of isolation of the mains internal to the house by the look of it.

So at the moment the option 2 sounds ideal really, thanks for the idea thou mate.

 

[Zeespark]

You install the Henley block as part of the works if needed, do you not? and the costs are marginally different.

AndyGuinness

 

[Foxmeister]

You install the Henley block as part of the works if needed, do you not? and the costs are marginally different.AndyGuinness

Of course, when possible and required, but as i have stated i have no means of isolation to mains, so then would have to deal with energy supplier and likely pay for a double pole switch to be installed by them!

Cost of single RCBO(

 

[S60TEM]

I would think having one RCD for whole installation is a serious no no who trained you?

Page 113, Reg: 531.4 RCD's in a TT System

Reg: 531.4.1 If an installation which is part of a TT system is protected by a single RCD, this shall be placed at the ORIGIN of the installation unless the part of the installation between the origin and the device complies with the requirements for protection by the use of Class II equipment or equivalent insulation. Where there is more than one origin, this requirement applies to each origin.

Now correct me if i'm wrong but does that not just confirm what I said?

If a customer has a BS3036 board which has had the rewirable fuses replaced with MCB's as an upgrade and the whole wiring has been tested and proved safe and satisfactory but wants a shower fitted or a new circuit ie: sockets etc but cant afford a new 17th ed board. This option complies with the Regs. Where I live and work there are a LOT of TT installations.

Granted, its not the best solution as we advise but it works out the most viable and cost effective for the "cheapskate" customers.

Please someone correct me if i'm wrong and explain why?

 

[Zeespark]

The OP hasnt stated, as far as I am aware, the type of earthing system in the premises. Until that is accertained, then everything else is purely acedemical.

AndyGuinness

 

[Apache]

Page 113, Reg: 531.4 RCD's in a TT SystemReg: 531.4.1 If an installation which is part of a TT system is protected by a single RCD, this shall be placed at the ORIGIN of the installation unless the part of the installation between the origin and the device complies with the requirements for protection by the use of Class II equipment or equivalent insulation. Where there is more than one origin, this requirement applies to each origin.

Now correct me if i'm wrong but does that not just confirm what I said?

If a customer has a BS3036 board which has had the rewirable fuses replaced with MCB's as an upgrade and the whole wiring has been tested and proved safe and satisfactory but wants a shower fitted or a new circuit ie: sockets etc but cant afford a new 17th ed board. This option complies with the Regs. Where I live and work there are a LOT of TT installations.

Granted, its not the best solution as we advise but it works out the most viable and cost effective for the "cheapskate" customers.

Please someone correct me if i'm wrong and explain why?

The regs you quote refer to a TT installation and there is no mention of that as far as I can see? Therefore they are meaningless in this context.

The reason [as I see it] that putting a single RCD in before the board is nuisance tripping. A N-E fault anywhere and the RCD won't reset and you are in the dark until you can find a friendly spark.

Now assume that we put the shower in it's own little board with RCD&MCB (or RCBO) then a fault would only affect that. This is why there is a move towards boards full of RCBO's.

It would be very bad practice to engineer such a scenario intentionally.

 

[S60TEM]

The regs you quote refer to a TT installation and there is no mention of that as far as I can see? Therefore they are meaningless in this context. The reason [as I see it] that putting a single RCD in before the board is nuisance tripping. A N-E fault anywhere and the RCD won't reset and you are in the dark until you can find a friendly spark.

Now assume that we put the shower in it's own little board with RCD&MCB (or RCBO) then a fault would only affect that. This is why there is a move towards boards full of RCBO's.

It would be very bad practice to engineer such a scenario intentionally.

I totally agree with what your saying BUT if your customer wants a shower circuit installed and isnt aware of the Regulation implications to fitting it within their existing installation then they are VERY reluctant to part with extra cash even the difference between a single RCD and a RCD/MCB shower CU! We advise that the single RCD is not the best option but all they see is

 

[Apache]

You can get a cheap shower unit for

 

[S60TEM]

You can get a cheap shower unit for

 

[Apache]

I get and RCD and enclosure for around

 

[sellers]

2 ways with me on this,

1. Ideal world, change full CU

2. Cheapest option, Add RCD in small enclosure on outgoing cable

No inbetween really.

 

[batty]

Page 113, Reg: 531.4 RCD's in a TT SystemReg: 531.4.1 If an installation which is part of a TT system is protected by a single RCD, this shall be placed at the ORIGIN of the installation unless the part of the installation between the origin and the device complies with the requirements for protection by the use of Class II equipment or equivalent insulation. Where there is more than one origin, this requirement applies to each origin.

Now correct me if i'm wrong but does that not just confirm what I said?

If a customer has a BS3036 board which has had the rewirable fuses replaced with MCB's as an upgrade and the whole wiring has been tested and proved safe and satisfactory but wants a shower fitted or a new circuit ie: sockets etc but cant afford a new 17th ed board. This option complies with the Regs. Where I live and work there are a LOT of TT installations.

Granted, its not the best solution as we advise but it works out the most viable and cost effective for the "cheapskate" customers.

Please someone correct me if i'm wrong and explain why?

Sorry I should not have said who trained you but it really does bug me when I find new installations that have been done since the 17th edition that have only one RCD. If you put one RCD in it does not comply with 17th edition. I am not a great quoter of reg numbers but try 314.1 which says every installation shall be divided into circuits as necessary to (i) avoid hazards and minimize inconvenience in the event of a fault.

(iv) Reduce the posibiility of unwanted tripping of RCD's due to excessive protective currents produced by equipment in normal use.

Now i know you said if the installation test out ok but if you put one RCD in surely you can see you are looking for trouble.