Unsatisfactory EICR is an absolute shower?

Unsatisfactory EICR is an absolute shower?

11:28 AM, 13th April 2021, About 3 years ago 23

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The electrician who recently did an EICR for my property found the installation “Unsatisfactory”, one of the reasons being that the shower circuit (6mm twin and earth) is overrated with a 40A overcurrent device.

In 2017 I had a new 18th edition consumer unit installed and that electrician provided a complete Domestic Electrical Installation Certificate valid for 5 years to the next inspection. This work was done about a month after installing a new 8.5kW electric shower, and there have not been any electrical issues since – until this EICR. I believe that the 8.5kW shower draws 37amps while a 6mm cable’s capacity depends on how it’s installed and the length of the run, in this case, less than 9m.

Obviously, I don’t want to have to change the cable or the shower, which have been fine for the 4 years since the shower was installed, but if he changes it from a 40A MCB to a 32A MCB I’m concerned the shower will keep tripping that. Advice from our Landlord electricians would be much appreciated.

Silver Flier


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Comments

Silver Flier

10:27 AM, 15th April 2021, About 3 years ago

Reply to the comment left by Ron H-W at 14/04/2021 - 10:47
Thank you for your very interesting reply. We tend to think of these things as instantaneous, I wasn't aware that there were different MCBs with different response times, nor that these could be so long.

Silver Flier

10:52 AM, 15th April 2021, About 3 years ago

Reply to the comment left by Paul landlord at 14/04/2021 - 16:03
Thanks Paul for your detailed and sensible reply. I'm sure you're right, as it has been in operation for 4 years without any issues, and yes the Insulation Resistance on the shower circuit was recorded as >99.9 Mohms. Unfortunately I wasn't able to attend when the electrician did the inspection, or we could have discussed and resolved the issues he found, and avoided the issuance of an Unsatisfactory EICR. I would strongly recommend any landlord to be present when an EICR is done.
I e-mailed the electrician to ask whether the 8.5kW shower wouldn't keep tripping a 32amp MCB and he has said it will work fine - so we shall see.

michaelwgroves

10:10 AM, 17th April 2021, About 3 years ago

I am an electrician, I agree with everything Paul has said. But I wanted to draw your attention specifically to the reference method Paul mentions.
You need to dig out the Electrical Installation Certificate (EIC) you received when the shower was installed.
Please can you advise what reference method it advises for shower. From this information, Paul or I can advise if it is safe.
I think it highly likely you don’t need to do anything.

Paul landlord

10:41 AM, 17th April 2021, About 3 years ago

Reply to the comment left by Silver Flier at 15/04/2021 - 10:16
Actually i think if you read the 18th edition wiring regulations and expanded specialist book on inspection and testing from the BSI and IET 'guidance note3' you will find it is also upon change of tenant.

However nobody did (even us that did EICRs as responsible landlords before it became mandatory did) and nobody will.

Your gas cert should also be redone on turnover- in 30 years of landlording neither anyone I know or myself ecer has- just for interest purposes

SJKDevon

11:22 AM, 17th April 2021, About 3 years ago

Paul, I'm glad you have enlightened people a little bit - I am also a fully qualified electrician, I have my own business although now avoiding electrical due to doing it for nearly 30 years !
I've had rental properties since the mid 90's too.
Landlords - if you are not an electrician do not try and GUESS !

The reason we go to college and spend several years learning this stuff is because we need to, if you could learn it in a day everyone would do it - same as Gas engineers, Solicitors, Doctors - stick to what you know. That said, if you are not happy with what an electrician tells you then ask him to clarify it and maybe get a second opinion.

Cable calculations have many variables, you need the circuit design current & select the correct rating of protective device then you can start - type of cable, length of run, installation method, ambient temperature, insulation, grouping factors, it is not black & white.

If you have a doubt then simply ask the sparks to show you the calculation for the fail, if the electrician cannot justify it then call another one !

Most importantly - the reason cables have a rated current carrying capacity and we have protective devices (MCB's) is to prevent FIRE. having rewired several properties due to electrical fire I simply say do not take a chance for the sake of a couple of quid !

___ baldelectrician

14:51 PM, 17th April 2021, About 3 years ago

Reducing the MCB on a 37A load to 32A would fail the EICR
Calculation for sizing electrical cable/wire, see below
Ib ≤ In ≤ Iz
Ib = Amperage load
In = Circuit Breaker size
Iz = Current rating for cable/wire

The load of the item (the shower in this case) at 37A should be less than or equal to the MCB size (32A after alteration) and the MCB size should be less than or equal to the current capacity of the cable.

In other words a 37A load on a 32A MCB is a no-no.

Silver Flier

17:24 PM, 17th April 2021, About 3 years ago

Reply to the comment left by michaelwgroves at 17/04/2021 - 10:10
The shower was installed by a plumber as a straight replacement for the old one. Shortly afterwards I commissioned the electrician to upgrade the consumer unit to an 18th edition metal one, as the old one had no RCDs.
The 2017 Domestic Installation Certificate shows Reference Method C for all circuits. The new Unsatisfactory EICR shows Reference Method B for all circuits, except the lights which are 100.

michaelwgroves

17:54 PM, 17th April 2021, About 3 years ago

Reply to the comment left by Silver Flier at 17/04/2021 - 17:24
I think it is highly unlikely the shower cable is a multicore cable (reference method B). It is much more likely to be thermoplastic, so reference method C. Therefore I have much more confidence in the original electrician.
But in either case, a 6mm cable for reference method B is 38A, and reference Method C is: 47A.
Therefore there is nothing wrong with your shower cable, tell the electrician to adjust his report, or you will report him to his competent person scheme (CPS).
Show him the original EIC which shows Reference method C, that being correct, and ask him to review BS 7671:2018 table 4D5.

michaelwgroves

8:17 AM, 19th April 2021, About 3 years ago

Reply to the comment left by michaelwgroves at 17/04/2021 - 17:54
I've just noticed an error in my last post, if it were reference method B, technically it's a fail. But I would argue it's not that straight forward.
But as mentioned previously, it's very likely reference method C, so in my eyes it's a pass.

Silver Flier

11:32 AM, 19th April 2021, About 3 years ago

Reply to the comment left by michaelwgroves at 19/04/2021 - 08:17
Thanks Michael for taking the trouble over this. I found a photo of the old shower before removal which showed the incoming cable was standard cable - twin and earth (unsleeved), with the earth in between, sheathed with grey plastic.
Unfortunately I am unable to meet the electrician and the remedial work has to be completed by the end of this week, so I shall accept what he says as I need that satisfactory EICR. I have it in writing from him that the new 32A MCB will not affect the performance of the shower, which was my main concern. Thanks again for your advice.

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