Shower EICR Code- 9.5kW- 40amp mcb!. De rate MCB to 32 or rewire cable to 10mm

[CM 1]

I'm surprised the local authority are not being more causious with this as its a potential fire hazard

They believe it should be a C3

 

[CM 1]

The problem here is the short time the shower operates for,
Years ago our company added lots of heaters to a ring main in a school, despite me protesting as the QS that it was non compliant, and should be on a dedicated ring or radial circuits, every winter the circuit would trip after about 6 hours , I calculated there was a load of 4 x 12 Amps = 48 amps plus other stuff on the ring yet took 6 hours to trip on a 32amp ring !

 

[Ian1981]

I2 must be equal to or less than 1.45 x Iz so what are you actually basing Iz as?

 

[Leesparkykent]

The 32amp mcb will likely trip on overload as 9.5kw is 39amps at 240v or 41amps at 230v. Advise a down rate size of shower to suit cable or they need to upgrade it to 10mm2 for the 9.5kw
Is there any signs of over heating at all the terminals?

If the shower is rated 9.5KW at 240V then at 230V it's 38A.

 

[CM 1]

If the shower is rated 9.5KW at 240V then at 230V it's 38A.

Yes but a 32 amp mcb will take that for an hour plus

 

[Leesparkykent]

Yes but a 32 amp mcb will take that for an hour plus

So what? It's still wrong isn't it....IMO it's simple, no code if the CCC based on design current is adequate taking installation method in to account. Code 2 if the CCC based on design current isn't adequate taking installation method in to account.

 

[buzzlightyear]

My own shower is a 9.5 kw on a 32 and 6.0mm , never trips no signs of damage , cable might be stressed but aren’t we all?

If the shower is rated 9.5KW at 240V then at 230V it's 38A.

I total agree with you leesparky
why post a question on here if you know the answer. not!

 

[buzzlightyear]

well .you may has well put the shower on bell wire .and see what you get!

 

[Wilko]

Just looking at some ABB reference info on BS 60898 - it says the mcb must not trip before 1.13 times it's rating and must trip at 1.45 within an hour (if I'm reading it right).
So the OCPD may not be protecting the cable from sustained overloads less than 1.45, which is probably why Ib < In < Iz is drummed into us
https://library.e.abb.com/public/114371fcc8e0456096db42d614bead67/2CDC400002D0201_view.pdf

 

[CM 1]

well .you may has well put the shower on bell wire .and see what you get!

 

[telectrix]

if installed ref. method C, 6.0mm is pessimistically rated @ 47A. what's the problem? shower is only 39.5A @ 240V, and that's probably over rated. bet a clamp meter would show no more than 35A. no code.move on.

 

[CM 1]

if installed ref. method C, 6.0mm is pessimistically rated @ 47A. what's the problem? shower is only 39.5A @ 240V, and that's probably over rated. bet a clamp meter would show no more than 35A. no code.move on.

That only applies if clipped direct , none are always underfloor and through roof!
I still think 32 amp MCB is safe until shower circuit is rewired which was the point I was trying to make ?

 

[Ian1981]

Well that's another debate as some people may say cables installed underfloor boards should be reference method B
Others may not agree so the cable could be under the boards and chased and buried in the wall which may make it reference method C.

 

[KEV 1 N]

If the shower is rated 9.5KW at 240V then at 230V it's 38A.

9500 / 240 = 39.58
9500 / 230 = 41.3

 

[Leesparkykent]

9500 / 240 = 39.58
9500 / 230 = 41.3

(240x240)/9500= 6.06 Ohms

230V/6.06 Ohms=37.9 Amps

The resistance of the shower is fixed. If it states 9.5KW at 240V then it's not 9.5KW at 230V....More like 8.729KW.