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

[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.

 

[cprfenom]

I have to say the EICR is only to determine the current state of the installation unless there is a C1. Surely you as the tester have to define the condition of the installation and code appropriately. Remedial works and costs should not dictate the code you give it?

For me it's a C3 if the cable is clipped direct.

 

[cprfenom]

I have to say the EICR is only to determine the current state of the installation unless there is a C1. Surely you as the tester have to define to condition of the installation and code appropriately. Remedial works and costs should not dictate the code you give it?

For me it's a C3 if the cable is clipped direct.

 

[KEV 1 N]

(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.

It's been a while since I did these sort of calculations at college, can you please explain why you have 240 X 240 then devide by 9500?

 

[KEV 1 N]

(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.

It's been a while since I did these sort of calculations at college, can you please explain why you have 240 X 240 then devide by 9500?

 

[CM 1]

I have to say the EICR is only to determine the current state of the installation unless there is a C1. Surely you as the tester have to define the condition of the installation and code appropriately. Remedial works and costs should not dictate the code you give it?

For me it's a C3 if the cable is clipped direct.

If the cable is clipped direct then it’s fine on a 40amp mcb
It’s when it’s run through floor and roof voids it gets complicated! A 40 amp mcb does not protect the cable , a 32 will, but the load of the shower will cause a thermal effect on the cable and the MCB, HOWEVER both MCB and cable are designed to withstand higher currents for a certain amount of time, although my question was if we downrate the MCB as part of test I believe the code would be C3, no one can agree or offer a definitive solution
Brian Scaddens calls appear to make it ok with no code required?
A C3 Indicates “ improvement required”

 

[happysteve]

It's been a while since I did these sort of calculations at college, can you please explain why you have 240 X 240 then devide by 9500?

(1) R = V / I
(2) I = P / V

Substitute (2) into (1):
R = V / (P / V)
R = (V x V) / P
R = V squared / P

 

[Andy78]

It's been a while since I did these sort of calculations at college, can you please explain why you have 240 X 240 then devide by 9500?

 

[Leesparkykent]

As the two posts above

 

[Andy78]

If the cable is clipped direct then it’s fine on a 40amp mcb
It’s when it’s run through floor and roof voids it gets complicated! A 40 amp mcb does not protect the cable , a 32 will, but the load of the shower will cause a thermal effect on the cable and the MCB, HOWEVER both MCB and cable are designed to withstand higher currents for a certain amount of time, although my question was if we downrate the MCB as part of test I believe the code would be C3, no one can agree or offer a definitive solution
Brian Scaddens calls appear to make it ok with no code required?
A C3 Indicates “ improvement required”

I don't see why it gets complicated when the cable routes through floors and roof voids. If you can inspect these areas then all good. If not then assume worst case or most likely scenario and make a judgement.

What do you mean downrate the MCB as part of the test ? A change in protective device should generate a certificate. That cert should certify the alteration conforms to the regs. Which it won't do.

 

[KEV 1 N]

As the two posts above

Thanks guys, now I understand where I've gone wrong

 

[KEV 1 N]

Well after all this debate about showers.....think I'll have a bath instead!

 

[cprfenom]

If the cable is clipped direct then it’s fine on a 40amp mcb
It’s when it’s run through floor and roof voids it gets complicated! A 40 amp mcb does not protect the cable , a 32 will, but the load of the shower will cause a thermal effect on the cable and the MCB, HOWEVER both MCB and cable are designed to withstand higher currents for a certain amount of time, although my question was if we downrate the MCB as part of test I believe the code would be C3, no one can agree or offer a definitive solution
Brian Scaddens calls appear to make it ok with no code required?
A C3 Indicates “ improvement required”

It honestly feels like you are trying to get out of putting in an unsatisfactory report.

A c3 to me is something that doesn't meet the regs, but is neither immediately dangerous or may become dangerous. If the cable could degrade as a result of the installation then it has to be a C2 and as Andy said any changes would require a cert.

 

[Leesparkykent]

The OP says "argument at work". I gather from your posts the other electricians at work, just like every other electrician who's participated in this thread do not agree with your argument of down rating the MCB to 32A?... So you can C3 it and give a satisfactory report?

The mind boggles that you want to down rate the MCB to a current rating of less than the design current for this purpose....This is the sort of workmanship that drags our trade down.

 

[westward10]

58 posts and no one was ever going to change his mind.

 

[westward10]

Bleedin more stubborn than me