UK Shower pump wired off shower

[User101]

Work for a company who sub contracts to the local council and looking for some advice.
In the domestic properties the council have wired a shower pump off the load side of the showers in 2.5mm (40A RCBO) which then serves a 13A switched fused spur to feed the shower pump. I am unsure this is ok as a shower is a fixed load and worried about overload on the 2.5mm?
the council say it’s covered under section 434.2 but this relates to fault current. Can anyone provide some help on the matter,
Thanks

 

[Julie.]

Work for a company who sub contracts to the local council and looking for some advice.
In the domestic properties the council have wired a shower pump off the load side of the showers in 2.5mm (40A RCBO) which then serves a 13A switched fused spur to feed the shower pump. I am unsure this is ok as a shower is a fixed load and worried about overload on the 2.5mm?
the council say it’s covered under section 434.2 but this relates to fault current. Can anyone provide some help on the matter,
Thanks

Providing there is a fcu to provide overload protection for the pump.

(A pump is NOT a fixed load)

And a fault on the 2.5mm (far end) cable before the fcu has a low enough Zs to provide ADS by the 40A MCB/RCBO ( or the use of the RCBO/RCD for fault protection instead of additional protection)

Then there isn't a problem.

I know many would feel uncomfortable, especially if the fcu is some distance away, but it is absolutely fine.

But it isn't a blanket OK - if there is no fuse or other overload protection for the smaller load (pump or ufh etc) then it would be unacceptable.

(some may say ufh is a fixed load so doesn't need overload protection - fair enough for the actual heating cable - but not so for the controller!)

The testing of the Zs at the smaller cable is critically important - a good Zs at the shower doesn't prove the whole of the circuit - so in your example if it was an MCB the Zs must be low enough for the 40A MCB at ALL points up to the fcu. (After the fcu the Zs has to meet the value for the 13A fuse).

Since you have a RCBO the Zs value merely determines if the RCD aspect is additional, or fault protection)

 

[User101]

Providing there is a fcu to provide overload protection for the pump.

(A pump is NOT a fixed load)

And a fault on the 2.5mm (far end) cable before the fcu has a low enough Zs to provide ADS by the 40A MCB/RCBO ( or the use of the RCBO/RCD for fault protection instead of additional protection)

Then there isn't a problem.

I know many would feel uncomfortable, especially if the fcu is some distance away, but it is absolutely fine.

But it isn't a blanket OK - if there is no fuse or other overload protection for the smaller load (pump or ufh etc) then it would be unacceptable.

(some may say ufh is a fixed load so doesn't need overload protection - fair enough for the actual heating cable - but not so for the controller!)

The testing of the Zs at the smaller cable is critically important - a good Zs at the shower doesn't prove the whole of the circuit - so in your example if it was an MCB the Zs must be low enough for the 40A MCB at ALL points up to the fcu. (After the fcu the Zs has to meet the value for the 13A fuse).

Since you have a RCBO the Zs value merely determines if the RCD aspect is additional, or fault protection)

Thanks for the reply. Very helpful. My only concern from that was because showers run at a constant rate i.e 38amps, wouldn’t the 2.5mm where it is connected at switch end up having to deal with that current to some extent?

 

[Julie.]

Thanks for the reply. Very helpful. My only concern from that was because showers run at a constant rate i.e 38amps, wouldn’t the 2.5mm where it is connected at switch end up having to deal with that current to some extent?

Depends how it is connected, which is of course a practical issue, the terminals are usually designed for 6/10mm cable so if you can ensure the larger cable makes direct contact with the termination, then the smaller cable isn't in the path.

If the smaller cable is squeezed between the main connections then yes, current would pass through this and could cause a hot spot

That comes down to plain good workwomanship - not really a direct aspect of the regs in general.

The bigger issue, is actually ensuring that the smaller cable makes proper contact, and isn't squeezed to the side ending up loose even though the termination is tight.

Again though, it's just good workwomanship