Discuss Shower 8.5 on a 40mcb is it dangerous in the Electrical Forum area at ElectriciansForums.net

chrismoy1

EF Member
Messages
19
Location
wales
Hi guys

My tenant just had an electrician in to connect her cooker and has told her that the shower is dangerous and not to use it because it has a 40 mcb in the consumer unit and it should be a 32.
The cable is 6mm and the shower is 8.5kw.

Can you advise me please
Thank you in anticipation
 

davesparks

Forum Mentor
Messages
12,803
Location
guildford
Ask for this to be put in writing by the electrician, explain that you need them to specify the exact regulation numbers which they are referring to and ask them to explain exactly how it is dangerous.

It 8s possible that the installation may not comply with the current regulations, but it may not necessarily be dangerous.
 

Mike177

EF Member
Messages
8
Location
IG6 2tg
Sure that 6mm can only take more than 40A if clipped direct.
So a 32A would be a sensible option surely? 8.5kw is about 35/36 amps.
So smaller shower or bigger cable.
Or is my memory and maths failing me as much as my Fantasy football team?
 

buzzlightyear

please let me back in to the prison cell.
Electrician's Arms
Messages
6,887
Location
star command
the consumer unit and it should be a 32.
The cable is 6mm and the shower is 8.5kw.
ask you tenant to ask the say sparky to work out the loading ,any way what is the shower to do with the cooker ,or is any water coming out of the cooker .;)
 
OP
C

chrismoy1

EF Member
Messages
19
Location
wales
Sure that 6mm can only take more than 40A if clipped direct.
So a 32A would be a sensible option surely? 8.5kw is about 35/36 amps.
So smaller shower or bigger cable.
Or is my memory and maths failing me as much as my Fantasy football team?
Hi Mike
I thought an 8.5 would draw a current of 35.5A so you would need an mcb higher than that and the next one up is 40.
Regards Chris
 

Dave OCD

Forum Mentor
Messages
3,163
Location
Cornwall
Chris, this is the correct sized MCB for a 8.5kW shower, a 32amp device would be running at a slight overcurrent and although it would take a long time to trip it's not permitted in the regulations. I can't stand people who find fault with work unrelated to what they're doing - especially when they're spouting BS. :)
 
OP
C

chrismoy1

EF Member
Messages
19
Location
wales
Chris, this is the correct sized MCB for a 8.5kW shower, a 32amp device would be running at a slight overcurrent and although it would take a long time to trip it's not permitted in the regulations. I can't stand people who find fault with work unrelated to what they're doing - especially when they're spouting BS. :)
Thank you very much Dave for a very clear decision on this question.

Regards Chris
 
OP
C

chrismoy1

EF Member
Messages
19
Location
wales
Dont think I agree there, if I saw a potentially dangerous situation I would point it out.

Saying that this is not a good example of that, as it's not a potentially dangerous situation.
So you are sure it is not dangerous because I think my tenant will still want it changed to a 32 because an electrician has told it is dangerous and must not use the shower.

Regards Chris
 

snowhead

Respected Member
Messages
3,610
Location
Mildlands
Rewinding to the beginning;

The tenant has just had a new cooker (delivered and ?) connected by an "Electrician".
Would this be from Currys or similar?
 

telectrix

Scouser and Proud.
Respected Member
Messages
60,292
Location
cheshire/staffordshire
apart from all the good advice given so far, as long as the 6.0mm is installed as ref. method C, i.e. it can safely carry 47A, ( Ib<Iz ) then aas the shower is a fixed load, overcurrent protection is not required so a 50A MCB could be installed. 433.3.1 (ii). (BYB 17th).
 

Paignton pete

Regular EF Member
Messages
777
Location
Over the rainbow
So you are sure it is not dangerous because I think my tenant will still want it changed to a 32 because an electrician has told it is dangerous and must not use the shower.

Regards Chris
Without actually visiting the site for an inspection I cannot commit to a definate answer as to whether your installation is dangerous, however
Having a 32A or a40A mcb on an 8.5kw shower is quite common and I would not be concerned either way.
Obviously 40A Mcb is the preferred breaker.
 

dinger809

Regular EF Member
Messages
99
Location
Essex
Doing some calculations, I don’t agree with your tenants electrician. A 6mm cable, clipped direct will be absolutely fine on a 40amp mcb. The only issue is if the shower circuit is not on an RCD. Providing the run isn't miles and miles.
Putting a 32amp mcb in the circuit will just cause annoying tripping as the 8.5 kw shower will draw around 36amps.
Sounds like the electrician needs to look at the books a bit
 

Marcus Vaughan

Regular EF Member
Messages
283
Location
Sheffield
Doing some calculations, I don’t agree with your tenants electrician. A 6mm cable, clipped direct will be absolutely fine on a 40amp mcb. The only issue is if the shower circuit is not on an RCD. Providing the run isn't miles and miles.
Putting a 32amp mcb in the circuit will just cause annoying tripping as the 8.5 kw shower will draw around 36amps.
Agree it does not need changing, and probably better not to. Not so sure 36 amps would cause the overload part of the breaker to nuisance trip though, looking at the curve for it.

That would be one seriously long shower!
 

ChrisElectrical88

Forum Mentor
Messages
1,568
Location
Norwich
apart from all the good advice given so far, as long as the 6.0mm is installed as ref. method C, i.e. it can safely carry 47A, ( Ib<Iz ) then aas the shower is a fixed load, overcurrent protection is not required so a 50A MCB could be installed. 433.3.1 (ii). (BYB 17th).
I mean, going off this even if its in trunking on its own, then it will be alright on a 40A.
 

dinger809

Regular EF Member
Messages
99
Location
Essex
Agree it does not need changing, and probably better not to. Not so sure 36 amps would cause the overload part of the breaker to nuisance trip though, looking at the curve for it.

That would be one seriously long shower!
I should have put “could” not “will” cause nuisancebtripping
 

Diver233

Fire alarms
Messages
157
Location
UK
Ask her to get her electrician to put it in writing also quoting BS as well as his or her part P approval body.
Then armed with the said information ring the help desk of the said body (they all have a help desk), quote their number etc and speak to them they will give you 100% the answer. Ensure your tennant tells sparky what you are doing. If he is fully approved and he’s correct he will not hesitate in supplying the information.
 

MG201

Regular EF Member
Messages
194
Location
Glasgow
One things for sure they should be greatful they have got a landlord that cares, the fact you are investigating there concerns rather than just saying hey it works what u complaining about shows you care not to mention new cooker
 
OP
C

chrismoy1

EF Member
Messages
19
Location
wales
Ask her to get her electrician to put it in writing also quoting BS as well as his or her part P approval body.
Then armed with the said information ring the help desk of the said body (they all have a help desk), quote their number etc and speak to them they will give you 100% the answer. Ensure your tennant tells sparky what you are doing. If he is fully approved and he’s correct he will not hesitate in supplying the information.
Thank you Tom for the advice seems like plan.

Regards Chris
 
OP
C

chrismoy1

EF Member
Messages
19
Location
wales
One things for sure they should be greatful they have got a landlord that cares, the fact you are investigating there concerns rather than just saying hey it works what u complaining about shows you care not to mention new cooker
Thank you for your comments, I just want my tenant to have a safe home they can enjoy after all the do pay the rent.

Regards Chris
 
OP
C

chrismoy1

EF Member
Messages
19
Location
wales
One things for sure they should be greatful they have got a landlord that cares, the fact you are investigating there concerns rather than just saying hey it works what u complaining about shows you care not to mention new cooker
I have since found out from the tenant that he did not even go upstairs to look at the shower so has no idea about it's power rating.
What is even more worrying he said that instead of connecting the cooker with 6mm cable he should really be using flexible multi strand cable like on her kettle or halogen cooker.
I have never heard of this can anyone please enlighten me.

Regards Chris
 
OP
C

chrismoy1

EF Member
Messages
19
Location
wales
One things for sure they should be greatful they have got a landlord that cares, the fact you are investigating there concerns rather than just saying hey it works what u complaining about shows you care not to mention new cooker
I have since found out from the tenant that he did not even go upstairs to look at the shower so has no idea about it's power rating.
What is even more worrying he said that instead of connecting the cooker with 6mm cable he should really using flexible multi strand cable like on her kettle or halogen cooker.
I have never heard of this can anyone please enlighten me.
Doing some calculations, I don’t agree with your tenants electrician. A 6mm cable, clipped direct will be absolutely fine on a 40amp mcb. The only issue is if the shower circuit is not on an RCD. Providing the run isn't miles and miles.
Putting a 32amp mcb in the circuit will just cause annoying tripping as the 8.5 kw shower will draw around 36amps.
Sounds like the electrician needs to look at the books a bit

Regards Chris
 
OP
C

chrismoy1

EF Member
Messages
19
Location
wales
Doing some calculations, I don’t agree with your tenants electrician. A 6mm cable, clipped direct will be absolutely fine on a 40amp mcb. The only issue is if the shower circuit is not on an RCD. Providing the run isn't miles and miles.
Putting a 32amp mcb in the circuit will just cause annoying tripping as the 8.5 kw shower will draw around 36amps.
Sounds like the electrician needs to look at the books a bit
The length of the run is 8 metres and there is a 30ma rcd in the consumer unit
I have since found out from the tenant that he did not even go upstairs to look at the shower so has no idea about it's power rating.
What is even more worrying he said that instead of connecting the cooker with 6mm cable he should really be using flexible multi strand cable like on her kettle or halogen cooker.
I have never heard of this can anyone please enlighten me.

Regards Chris
 

Wilko

Electrician's Arms
Messages
5,385
Location
Berkshire
Hi Chris - site unseen that doesn't sound like something an Electrician would say as an 8.5kW shower is not normally connected by flex. Certainly not a kettle flex as they will be rated about 3kW max.
 

dmxtothemax

Regular EF Member
Messages
763
Location
Australia
Your electrician is absolutly wrong
8500w @ 240v = 35.4A
or even
8500w @ 230v = 36.9A
so 32A is not sufficent.
40A would be minimum.
What electrician in his right mind would hook up a water heater
without knowing for sure it's ratings ?
Scheer madness.
 

Electrician Talk

Electrical Forum

Welcome to the Electrical Forum at ElectriciansForums.net. The friendliest electrical forum online. General electrical questions and answers can be found in the electrical forum.
Top