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

[Wilko]

Bleedin more stubborn than me

Don't under rate yourself Westie

 

[Ian1981]

It is allowed that the mcb can be selected that it's higher than the ccc of the cable when overload protection isn't necessary.
As an example, A ccc of 39 amps but protected by a 40 amp mcb would be allowed if the shower had a fixed load Of say 37 amps.
There's no overload issue in this example and this arrangement is allowed by bs 7671.

 

[EddieB]

As an aside, you normally find that a "9.5kw" electric shower is built to take a 6mm T&E try and introduce a 10mm T&E and it distorts the casing the terminals are not man enough to take it but what the hell !!

 

[Simonslimline]

trying for a C3 as opposed to a C2 I believe by down rating the MCB and advising our client of the need for it to be rewired when possible we are complying

It does not comply with 433.1

 

[ebee]

An Overcurrent Protective Device (OPD) might be used for three reasons.
1/ Overload.
2/Short circuit.
3/Earth fault.
If the load is fixed such as a shower then only 2/ and 3/ apply as to the OPD clearing short circuit and earth faults.
If the load does not exceed the cable rating then all ok.
We used to quote power at 240v nominal therefore 9500/240 =39.58 amps.
If the same purely resistive load is run at 230v it would be37.92amps =8.72KW.
Now we officially declare 230v instead of 240v (although the actual voltages have never changed).
Was the power rating quoted at 230v or 240v?

 

[telectrix]

65 posts about a bleeding shower. do as I do. I have a bath every Xmas, whether I need one or not. saves a fortune on the leccy.

oh, and you can't read a book, smoke a smoke, or drink a whiskey in a shower,

a bit like the lady who demanded a refund on a packet of Tampax, as she pointed out

" Tried you product. it's useless. I still can't swim or ride a bike".

 

[sunray]

An Overcurrent Protective Device (OPD) might be used for three reasons.
1/ Overload.
2/Short circuit.
3/Earth fault.
If the load is fixed such as a shower then only 2/ and 3/ apply as to the OPD clearing short circuit and earth faults.
If the load does not exceed the cable rating then all ok.
We used to quote power at 240v nominal therefore 9500/240 =39.58 amps.
If the same purely resistive load is run at 230v it would be37.92amps =8.72KW.
Now we officially declare 230v instead of 240v (although the actual voltages have never changed).
Was the power rating quoted at 230v or 240v?

If it's quoted at 230V then at 240V it's 43A and 250V it's 45A
Even worse if it's quoted at 220V (which is often still the case with some imported kit) then at 240V it's 47A which exceeds the 1.45 factor

 

[Ian1981]

If it's quoted at 230V then at 240V it's 43A and 250V it's 45A
Even worse if it's quoted at 220V (which is often still the case with some imported kit) then at 240V it's 47A which exceeds the 1.45 factor

If it's 6mm cable and on a 40 amp mcb how is the 1.45 factor exceeded?
6mm if it's clipped direct is 47 amps.
47 x 1.45 = 68.15 amps
40 amp mcb x 1.45 = 58 amps
So what's the problem? Cable will not be overloaded.
Remember I2 needs to be equal to or less than 1.45 x Iz.

 

[telectrix]

If it's 6mm cable and on a 40 amp mcb how is the 1.45 factor exceeded?
6mm if it's clipped direct is 47 amps.
47 x 1.45 = 68.15 amps
40 amp mcb x 1.45 = 58 amps
So what's the problem? Cable will not be overloaded.
Remember I2 needs to be equal to or less than 1.45 x Iz.

if you avataar is a sample of the fuses you use, then no wonder they don't blow.

 

[Ian1981]

if you avataar is a sample of the fuses you use, then no wonder they don't blow.

Never been back to a job yet

 

[telectrix]

i also have a few customers who swore they'd never have me back .

 

[chrismoy1]

Not easy finding low powered showers these days, with that set up of 6mm and 40 mcb would anyone argue that 8.5 would be too much?

 

[Lspark]

6mm cable holds 34amps if in a wall which usually always is - therefore cable should be protected by 32amp breaker to prevent cable overheating. If a plumber decides to install a 10kw shower the cable is protected, (shower will trip out) and you are covered. Job done

 

[Andy78]

6mm cable holds 34amps if in a wall which usually always is - therefore cable should be protected by 32amp breaker to prevent cable overheating. If a plumber decides to install a 10kw shower the cable is protected, (shower will trip out) and you are covered. Job done

What sort of wall ?

 

[Dillb]

6mm cable holds 34amps if in a wall which usually always is - therefore cable should be protected by 32amp breaker to prevent cable overheating. If a plumber decides to install a 10kw shower the cable is protected, (shower will trip out) and you are covered. Job done

Nearly a year later I would like to think the problem has been resolved by now.