Shower MCB question after electrician installed new Consumer Unit

[Plantman2000]

Hello all. A few years ago we had a new kitchen installed and as part of those works we had an electrician in to install a new feed to this kitchen and a full new consumer unit as well.

This is a metal CED branded unit with CED MCB's.

We have two showers, one upstairs and one downstairs.
The upstairs shower is a Triton Cara 8.5 KW (I know, cheap, they came with the house) and downstairs is an Aquatronic 2 Plus 9.5 KW.

They are both on separate MCB's but these are CED CUB32SP B32 units which I take to be 32A?

My question is, are these rated high enough?

I recently browsed an install guide on a relatives new shower and noticed this table:

CIRCUIT PROTECTION
Unit Rating MCB
7.0 KW 30/32A
7.5 KW 32A
8.0 KW 40A
8.5 KW 40A
9.0 KW 40A
9.5 KW 40/45A
10.5 KW 45A

This seems to indicate we should have 40A MCB's installed and not the 32's that the electrician installed.
The showers were both installed already at the time of the new consumer unit and the electrician did go around the house to test all sockets etc.

Sorry I do not know the thickness of the wires feeding these showers. I think the upstairs looks to be 2 cm in width and the one to downstairs might only be 1.5 cm.

Many thanks.

Chris

 

[telectrix]

would need a site visit. first to determine the exact size of the shower cables, the installation method of same ( in insulation or not), and then would be able to say if MCBs could be upgraded to 40A. it's the cross sectional area of the conductors that matters, not what you have measured. did the sparks leave a certificate for the work? if so, there should be a schedule of test results, showing what size cable is for each circuit.

 

[Pete999]

Hello all. A few years ago we had a new kitchen installed and as part of those works we had an electrician in to install a new feed to this kitchen and a full new consumer unit as well.

This is a metal CED branded unit with CED MCB's.

We have two showers, one upstairs and one downstairs.
The upstairs shower is a Triton Cara 8.5 KW (I know, cheap, they came with the house) and downstairs is an Aquatronic 2 Plus 9.5 KW.

They are both on separate MCB's but these are CED CUB32SP B32 units which I take to be 32A?

My question is, are these rated high enough?

I recently browsed an install guide on a relatives new shower and noticed this table:

CIRCUIT PROTECTION
Unit Rating MCB
7.0 KW 30/32A
7.5 KW 32A
8.0 KW 40A
8.5 KW 40A
9.0 KW 40A
9.5 KW 40/45A
10.5 KW 45A

This seems to indicate we should have 40A MCB's installed and not the 32's that the electrician installed.
The showers were both installed already at the time of the new consumer unit and the electrician did go around the house to test all sockets etc.

Sorry I do not know the thickness of the wires feeding these showers. I think the upstairs looks to be 2 cm in width and the one to downstairs might only be 1.5 cm.

Many thanks.

Chris

You need to get an Electrician in to ascertain if the cable already installed are adequate for the size of the showers you have, having the wrong size cables could prove problematic, safety wise, to small and the will overheat, possibly catching fire, not trying to alarm you, just get the cable size verified, and upgraded if required, along with the OCPDs (fuses), and I agree with Tel's observations as well.

 

[DPG]

You are right to be concerned and you have done the right thing in asking. As above. Can you show us the installation certificate for the consumer unit change. Blank out any names/addresses though.

 

[Plantman2000]

Thanks for the replies all.

Please find attached the board characteristics test. This is just one page of 9 within the document so I can always look for something specific if required.

I was well out on the wires, only 6mm for the upstairs shower and 10mm for downstairs.
[automerge]1595326433[/automerge]
For any aficionados here is the board itself too.

 

[telectrix]

that looks good to me. both those showers should be on 40A for the upstairs shower, as long as the cable is nowhere covered in insulation, and a 40A or even a 50A for the downstairs shower. simple job to get him back to swap out the MCBs.

as a side note, though, 32A MCBs will withstand the 4A t0 8A overcurrent for far loger than it takes to have a shower, so even as it is, it's safe. might get the occasional trip on the 9.5kW shower, but unlikely. the lifespan of the 32A MCBs may be shortened somewhat as they are running at their rated limits.

 

[Plantman2000]

Thank you telectrix, good to know we are ok as it is. I presume there is a balance on whether to put a lower rated MCB in to protect the cable rather than a higher MCB and risk overheating the cable?

Sadly this installation was done back in 2016 (!) and being just a homeowner I never questioned the install work or decisions on the ratings installed by the electrician. Doubt they would return now and I wouldn't blame them

The house is pretty old and the wiring has been a bit poor in many places since I've had to tighten many socket terminals (limp wrist?) when we moved in due to them not working at all and the previous home owner even wired a socket at the porch into the lighting circuit (doh!) - bet they wondered why it kept tripping! That was the other reason to get the new consumer board in and have a full test as part of the kitchen install.

I only really delved in to ratings due to the new shower being installed at a relatives and wanted to check what we had....which brings me on to my next question (you know what it will be)....

What is the max rated shower we could install at both the upstairs and downstairs locations please?

 

[DPG]

It's not OK to leave it as-is with the 32A MCBs.

 

[telectrix]

9.5kW is on the limit of 6mm cable. 10mm cable can happily supply 10.5kW. another thing to bear in mind is that the MCB only needs to protect the cable against short circuit faults. it does nort have to provide overload protection, as a shower is what is known as "a fixed load". so you may see installs where you'd think the MCB was over rated for the circit.

 

[Plantman2000]

Ah, lovely, thank you. That does make sense.

I appreciate your help to clear my questions up!

Cheers,
Chris

 

[Markyd]

Shouldnt one of these be fitted to stop both showers being run at once and causing a big bang

https://www.garo.co.uk/docs/2020/info/shower%20boards%20info%20sheet.pdf

 

[hasel5]

Do the shower MCBs ever Trip?

 

[Plantman2000]

Do the shower MCBs ever Trip?

Hi, no they never trip and we have had nearly 4 years with this setup and not a single problem.
The consumer unit was installed back in Aug 2016. The shower units remain the same.
The shower duration is reasonable, especially since we do have 2 children so the showers do get well used.
[automerge]1595494173[/automerge]

It's not OK to leave it as-is with the 32A MCBs.

Sounds like the electrician should not have installed this with 32A MCB's then?
[automerge]1595494253[/automerge]

Shouldnt one of these be fitted to stop both showers being run at once and causing a big bang

https://www.garo.co.uk/docs/2020/info/shower%20boards%20info%20sheet.pdf

To be fair I don't think we have ever run both showers at the same time.
Presume the electrician would have catered for this when he tested the house back in 2016.

 

[Julie.]

......
Presume the electrician would have catered for this when he tested the house back in 2016.

Given he has fitted undersized MCBs, Probably not!

Your two showers would take around 37A and 41A respectively, as you can see both are above the 32A of the MCB so the MCBs should be changed.

If you run both showers together it's around 78A, most houses are fitted with a 60A fuse (sometimes 80A) and even the electric meter itself is only rated to 80A usually.

So you really don't want to use both together - especially as you are likely to have other loads such as lighting, hairdryers, cooker/oven, central heating etc. This all could take you well over the fuse rating and potentially result in having to get the DNO (Electric board) out to change the fuse.

 

[Plantman2000]

Given he has fitted undersized MCBs, Probably not!

Your two showers would take around 37A and 41A respectively, as you can see both are above the 32A of the MCB so the MCBs should be changed.

If you run both showers together it's around 78A, most houses are fitted with a 60A fuse (sometimes 80A) and even the electric meter itself is only rated to 80A usually.

So you really don't want to use both together - especially as you are likely to have other loads such as lighting, hairdryers, cooker/oven, central heating etc. This all could take you well over the fuse rating and potentially result in having to get the DNO (Electric board) out to change the fuse.

So a poor job from that electrician then! Disappointing from someone in the trade
The report shows it being signed off by a supervisor too!

Seems like there is a bit of a conflict from answers too so my confusion remains.

 

[Julie.]

So a poor job from that electrician then! Disappointing from someone in the trade
The report shows it being signed off by a supervisor too!

Seems like there is a bit of a conflict from answers too so my confusion remains.

I must be missing something, where is the conflict in answers?

All the posts I see are indicating that the MCBs should be changed, although it isn't dangerous as is.

 

[Pete999]

Do the shower MCBs ever Trip?

How many MCBs does the shower have then?

I must be missing something, where is the conflict in answers?

All the posts I see are indicating that the MCBs should be changed, although it isn't dangerous as is.

HV Approved person, what is that Julie? is that the same as a HV Authorised Person?

 

[Plantman2000]

I must be missing something, where is the conflict in answers?

All the posts I see are indicating that the MCBs should be changed, although it isn't dangerous as is.

I've read above and some are saying it's not ok to leave as is, and another answer was it was safe as is.
The MCB's will protect for short circuit faults.

Remember, I am just an end user here and the installation in 2016 was completed by an electrical contractor (with, from what I can see, has a good reputation), so in all honesty I am no further on now than I was before I started this thread

 

[DPG]

How many MCBs does the shower have then?

HV Approved person, what is that Julie? is that the same as a HV Authorised Person?

There are 2 showers, so 2 MCBs.

 

[Plantman2000]

How many MCBs does the shower have then?

Just the one (per shower) in the main consumer unit as per my picture.