Shower Electrics Advice

[ICanDoItWell]

My old 7.2 Kw Gainsborough Shower has failed and it's not worth fixing due to it's age which could be very old as I have owned this property for 9 years and it was fitted a long time before that.

Based on the 6mm2 cable I decided to have an electrician fit some 10mm2 cable to the consumer unit and into the loft without connecting it as I intended moving the shower to the opposite wall when I changed the bathroom.

The shower failure, a bad leak from a broken solenoid valve, which couldn't of been worse timing due to the recent hot weather has meant I had to decide to change the shower now before the bathroom was replaced. To make matters worse, my CH boiler is not working either so it's a right time consuming nightmare filling a bath with a kettle. Hence the need for a new shower ASAP.

I received the shower today after further delays, no stock and now need to get a couple of quotes for connecting the electrics up and provide the necessary documentation. I intend fitting the shower and doing the pipework, leaving the electrical work to an electrician.

That is where I need some advice. I need to know what I must make sure the electrician provides in the way of documentation and to what level he is certified to carry out the work.

Also the 10mm cable with a 9 Kw Mira Advance shower and the cable ATM is just sitting on top of the insulation in the loft. I do intend adding some more insulation fairly soon so is it adequate to just put any new insulation under the cable or would supporting the cable above the insulation be better to prevent any insulation of the cable where it lies on the insulation? I was thinking of using some wood to raise it above the insulation. Is this worth doing and would it provide any benefit to the cable?

It's been very hot recently and I am wondering whether such temperatures of probably well over 30C affect high current carrying cabling and whether it would benefit from being held above the insulation. Is it worth spending a few quid for me to do this? I was thinking of a T bar of wood or an X support.

 

[securespark]

There's no harm when installing the cable in clipping it up to the rafters and away from the floor and insulation.

The regs allow you to run it through 500mm of insulation without de-rating, so where the cable enters the loft to go up to the rafters, goes down to the switch, back up into the loft and back down to the shower, you should be OK.

This should keep the cable out of contact with the insulation as much as possible.

The only thing is, it'll make the cable run a little longer. The alternative is to run the cable along a beam or purlin where it's unlikely to get covered in insulation or damaged by stored items or by being walked on.

 

[riveralt]

Based on the 6mm2 cable I decided to have an electrician fit some 10mm2 cable to the consumer unit and into the loft without connecting it as I intended moving the shower to the opposite wall when I changed the bathroom.

Does your Consumer Unit have this circuit protected by an RCD and does the MCB have a rating of 40A since these are the requirements in the manufacturers instructions?

That is where I need some advice. I need to know what I must make sure the electrician provides in the way of documentation and to what level he is certified to carry out the work.

This depends on the interpretation of the new Building Regulations regarding what constitutes a new circuit - you can search for it on the website - but you would be best guided by what the electrician who connects the shower up for you determines.

Also the 10mm cable with a 9 Kw Mira Advance shower and the cable ATM is just sitting on top of the insulation in the loft. I do intend adding some more insulation fairly soon so is it adequate to just put any new insulation under the cable or would supporting the cable above the insulation be better to prevent any insulation of the cable where it lies on the insulation? I was thinking of using some wood to raise it above the insulation. Is this worth doing and would it provide any benefit to the cable?

10mm ² T&E cable will give you a lot of headroom in terms of current carrying capacity (ccc) - I think it is a round 63w when clipped direct. However wrapping it in insulation is not recommended since that will seriously impair the ccc. The proposal to clip it to some raise timber seems the best way to avoid this.

 

[riveralt]

The regs allow you to run it through 500mm of insulation without de-rating,

I only have my red OSG to hand but it seems to say at 50mm the derating factor is 0.88
and at ≥500mm it 0.5.

 

[securespark]

Thanks, riveralt.

That'll teach me to quote something off the top of me head without looking it up first...

 

[ICanDoItWell]

There's no harm when installing the cable in clipping it up to the rafters and away from the floor and insulation.

The regs allow you to run it through 500mm of insulation without de-rating, so where the cable enters the loft to go up to the rafters, goes down to the switch, back up into the loft and back down to the shower, you should be OK.

This should keep the cable out of contact with the insulation as much as possible.

The only thing is, it'll make the cable run a little longer. The alternative is to run the cable along a beam or purlin where it's unlikely to get covered in insulation or damaged by stored items or by being walked on.

Thank you for the advice. The cable is already loosely fitted and it's a question of whether there is sufficient cable to go up to the roof beams and back down. The roof pitch/inclination is fairly low and it is fairly close to the roof edge so it probably wouldn't use up that much cable. Doing it that way would save a bit of money, however the roof felt does need changing and having the cable so close would make it more difficult unless it was released.

I will have to take a look when I go up into the loft.

Does having cable laying on top of insulation mean it is effectively 50% covered? 10mm2 cable is fairly heavy so would tend to sink into insulation.

Based on the 6mm2 cable I decided to have an electrician fit some 10mm2 cable to the consumer unit and into the loft without connecting it as I intended moving the shower to the opposite wall when I changed the bathroom.

Does your Consumer Unit have this circuit protected by an RCD and does the MCB have a rating of 40A since these are the requirements in the manufacturers instructions?
The current shower is on an RCD circuit and that has Wylex B32 on top and NSB32 on the bottom. I guess that that might require replacing?

That is where I need some advice. I need to know what I must make sure the electrician provides in the way of documentation and to what level he is certified to carry out the work.

This depends on the interpretation of the new Building Regulations regarding what constitutes a new circuit - you can search for it on the website - but you would be best guided by what the electrician who connects the shower up for you determines.

Is there anything I should look for and ask about in regard to qualifications when I talk to electricians? Is being NICEIC registered sufficient? Are there any qualifications needed to do this type of work above any other types of electrical installation? I have the business card that I believe is from the man that fitted the 10mm2 shower cable in front of me and it only says Showers to IEE Regs on it and no mention of NICEIC.

It's such a minefield of rules and regulations now that if you don't get it right it could come back and bite my ass at a later date.

What paperwork should be provided by an electrician when the job is completed to say that the job was done correctly and passes any scrutiny such as when the house is sold? Is it just a case that if I don't get any then don't pay him?

I don't like the idea of just accepting that it is done correctly because experience suggests that many are prepared to bypass rules and regulations to get work. I had someone quote me to fit a boiler a few years ago and he told me that he was not corgi, now gas safe, registered but what if he hadn't?. He said that Corgi charge so much for registration and they are supposedly a none profit organisation that he objected to paying them so much in order to work. He claimed that he was once registered but stopped paying them. Needless to say, I did not have him fit a boiler.

Also the 10mm cable with a 9 Kw Mira Advance shower and the cable ATM is just sitting on top of the insulation in the loft. I do intend adding some more insulation fairly soon so is it adequate to just put any new insulation under the cable or would supporting the cable above the insulation be better to prevent any insulation of the cable where it lies on the insulation? I was thinking of using some wood to raise it above the insulation. Is this worth doing and would it provide any benefit to the cable?

10mm ² T&E cable will give you a lot of headroom in terms of current carrying capacity (ccc) - I think it is a round 63w when clipped direct. However wrapping it in insulation is not recommended since that will seriously impair the ccc. The proposal to clip it to some raise timber seems the best way to avoid this.

I might now go with my first idea, using some support timbers fixed to joists. It's more complicated and costly but will get around any problems when replacing roof felt. I think that having large cables dangling from the roof joists seems like tempting fate and like painting a large red cross on my home when lightning is close by. I have enough already with a TV aerial and a satellite dish above the roofline although I do intend earthing them but it's finding something big enough to do the job without costing a fortune. 35mm² cable with fine threads meant for welding doesn't seem good enough when it comes to lightning strikes. I think that it should be as solid as possible. Anyway getting off topic.

 

[securespark]

Ask the chap what he intends to do to comply with the IEE (now IET) regs.

The following is not necessarily an exhaustive list.

He should check the existing supply unit and tails are rated to the job. If not, new ones may need installing. Ditto the main fuse. Some houses have only a 60A (or less) main fuse. Run a 40A shower and that's most of your 60A gone straight away!

But he should be asking the electrical company to upgrade the supply if necessary, not doing it himself.

Is there RCD protection? PEB's to Gas and Water services.

Paperwork? New circuit plus it's in a zoned area of the bathroom - double whammy!

So need EIC plus he will have to notify the LABC.