selv bathroom

[user 30718]

A new wetroom bathroom is added to a large bedroom.

The only electrics in the bathroom are a 12v extractor fan and a 12v light.

The power supplies are both marked SELV and will be housed in the partition wall with an access hatch to the bedroom. The power supplies will be switched using a remote RF switch (powered by the action of moving the switch).

This means there will only be 12v from SELV supplies in the wetroom.

Water to the wetroom will be supplied through plastic pipes.

The shower is fed from a combi boiler. The shower mixer tap, shower head and pipes are metal. There is also a wash basin.

Will the electrician need to connect an earth bonding cable to the wetroom shower or sink?

I’m asking because I plan to pull the cables whilst the bedroom floor is up. There will be a 1.5 T&E for the electrician to use when adding a fused spur to power my transformers. The electrician will add a new mcb to the fuse board when connecting the 1.5mm T&E.

Many thanks for your thoughts...

 

[Sharpend]

What did your electrician ask for? 

Is the wetroom separate to the bedroom in that it is enclosed and has its own door? 

Will any if the existing bedroom outlets be within the wetroom? 

 

[user 30718]

Hi Sharpie,

The wetroom has its own door.

The only electrics in the bathroom are 12v.

There are no mains cables anywhere in the bathrroom but I would like to pass one inside the partition wall (but I can avoid doing this if required).

I will need an electrician to connect, test, verify, certificate the whole house wiring. There are a few 'upgrades' and modifications that I know will be required elsewhere. Building work is in progress and I'm currently only in the house to sleep. Sadly I've already waited in for electricians to visit and advise but they simply dont show (I don't blame them - how much can you charge to answer a question about a room that hasn't been built!)

It looks like I need to wait and not get the electrician in until I am ready for them to do some work - not just talk about it. Therefore I need to organise the cabling in advance. If this is too difficult to answer then I just run a 16mm earth (matching the 'tails) alongside the 1.5 T&E - if the electrician does not need it - then its a waste but still better than getting the floor up a second time.

Thanks

 

[Sharpend]

Woah! Krusty, what’s the 16mm earth and tails for? 

Where are you in this green land of ours? 

 

[user 30718]

Calm down Sharps!

The main board is fed with a 16mm earth.

To avoid any question of the bathroom earth being too small - if I cant get advice in advance, I will blow £65 on earth cable of that size.

16mm tails feeding a bunch of 12v transformers? that would allow me > 1200A @12v. Bit of an overkill for a 20w fan and 15w led light. Would make the certifier laugh!

 

[Evans Electric]

Forget all this 16mm  earth stuff  Krusty  , that won't be required and would be a total waste of money . 

Most of your questions will be covered when your electrician  ( if he ever turns up)   fits an RCD  to the circuit , so forget bonding the pipes .

I note that you are using terms that an electrician would use  , as opposed to a layman .  (  16mm earth ,,tails , SELV,  20W att fan ,  LED    etc  ) 

 

[Murdoch]

Best you identify a spark that is happy to sign off your work before you do it ................ very few do this ................ and if you are in England or Wales this work falls under Part P of the builfing regs too.

 

[user 30718]

Many thanks Deke,

I have a little knowledge (enough to be dangerous) but absolutely no electricians qualifications. Over my time (I think) I’ve seen bathroom regs vary to include bonding to all pipes and even a period when an additional link from the pipe bonding to an existing bathroom earth (ie lighting ring) was required.

I appreciate this is really a matter of what the electrician inspecting it is prepared to accept. that’s why its just loose guidance I’m looking for. Now I know this approach can/may be acceptable, I’ll just pull the T&E. It's a split load board with twin 30ma rcd.

In 2012, I had a meter installer who would not replace a prepayment meter in a cupboard 5’ off the ground. His initial argument was its too high for the user to reach. I explained the user was 6’6”. He then said he was not happy to fit it at that height but he could fit a credit meter there. He then donned his full face mask in case any wire trimmings should hit him in the cheek. I imagine an inspector was in the area and my meter installer was expecting a visit on one of his jobs that morning.  

Again – many thanks all for a great forum.

Best you identify a spark that is happy to sign off your work before you do it ................ very few do this ................ and if you are in England or Wales this work falls under Part P of the builfing regs too.

Thanks Murdoch.

Yes, this is under part p.

The spark will be doing ALL the work, I'm just cable pulling and dont want the floor up twice.

 

[Sharpend]

Calm down Sharps!

The main board is fed with a 16mm earth.

To avoid any question of the bathroom earth being too small - if I cant get advice in advance, I will blow £65 on earth cable of that size.

16mm tails feeding a bunch of 12v transformers? that would allow me > 1200A @12v. Bit of an overkill for a 20w fan and 15w led light. Would make the certifier laugh!

I was just wondering if perhaps you were not telling us how many 12v lights you were putting in msl:

 

[user 30718]

I was just wondering if perhaps you were not telling us how many 12v lights you were putting in msl:

12v tanning salon perhaps?

Many thanks

 

[Doc Hudson]

A couple of observations re your earlier statements;  "The spark will be doing ALL the work, I'm just cable pulling and dont want the floor up twice."  This surely is a contradiction in terms, anyone not doing the cable installation is not actually doing all of the work?  "I will need an electrician to connect, test, verify, certificate the whole house wiring."  You actually need an electrician to design it as well, if you are expecting them to sign an electrical certificate for you. The signed declaration on an electrical certificate is for "Design, Construction, Inspection and Testing" not just connect and testing as some people think. This is one of the reasons why a lot of electricians will be reluctant to do half a job where they are not involved from the initial design process. Cable selection, routes, installation methods etc, are all just as important as the connection & testing.

Doc H.

 

[user 30718]

A couple of observations re your earlier statements;  "The spark will be doing ALL the work, I'm just cable pulling and dont want the floor up twice."  This surely is a contradiction in terms, anyone not doing the cable installation is not actually doing all of the work?  "I will need an electrician to connect, test, verify, certificate the whole house wiring."  You actually need an electrician to design it as well, if you are expecting them to sign an electrical certificate for you. The signed declaration on an electrical certificate is for "Design, Construction, Inspection and Testing" not just connect and testing as some people think. This is one of the reasons why a lot of electricians will be reluctant to do half a job where they are not involved from the initial design process. Cable selection, routes, installation methods etc, are all just as important as the connection & testing.

Doc H.

Hi Doc,

The 'design' is a single 3A fused spur at the end of the cable I've pulled. The spark will be connecting the T&E to the input of the fused spur and the transformers (via the remote switch) to out put of the fused spur. The spark will perform the insulation test then the earth resistance and calculate (look up on his sheet) the correct mcb curve. Then add it to the CU.

The SELV power supplies have over current (in/out) and overheat protection. The 12v cable will be of a diameter correct for at least twice the protected value of the power supplies (accounting for the length of the cable).

The T&E will be correct size for the length and load.

Providing the spark does not feel the need to check my 12v wiring, what could they disagree with?

I appreciate they could go looking for problems but unless they want to expose the full T&E run - we should be OK.

I beleive I'm capable of calculating and selecting the correct cable. If I'm wrong then its my fault and a new one will need to be pulled.

There is only one route currently open to me - following all the other cables installed before I owned the property. If the route is not acceptable to the spark, I'll need to find another spark or rewire the entire upstairs. The same goes for installation method.

I appreciate people prefer to only certify their own work but unless you are suggesting a full house rewire (way beyond my budget) then that's simply not possible.

The jobs that need doing to bring the house up to spec are things like relocating cooker isolator switch (move it from under the sink at the back of the cupboard and place it next to the cooker), installing a shower isolator switch and removing dodgy spured sockets from a bygone era.

I'm sorry if my previous message suggested sparks just test it and plug in. As well as knowing the regs, a good spark has a great understanding of how and why (this includes the mechanical and electrical properties of the materials being used). If I dont get one of those first time, I'll have to try again.

Many thanks for a great forum and good information.

 

[SLIPSHOD & SLAPDASH]

To add what Doc said above, the Part P 'cert' is not electrical. Its to state the electrician followed all building regs when doing the electrical work. If he/she did not do the work in any part or fully see the full cable run etc they should not be submitting the  paperwork. Also in your case a 3 signature installation cert could be used where you sign the design & installation and the electrician signs only the testing outside the bathroom-to the spur. If a keen eyed building inspector notes the electrician is not signing for the work in the bathroom he may not accept it. 

 

[Tony S]

I’m just curious as to how the OP intends to get 14.4kVA’s worth of transformers installed in a partition wall.

 

[kerching]

I’m just curious as to how the OP intends to get 14.4kVA’s worth of transformers installed in a partition wall.

It's a very thick wall

 

[Doc Hudson]

Hi Doc,

The 'design' is a single 3A fused spur at the end of the cable I've pulled. The spark will be connecting the T&E to the input of the fused spur and the transformers (via the remote switch) to out put of the fused spur. The spark will perform the insulation test then the earth resistance and calculate (look up on his sheet) the correct mcb curve. Then add it to the CU.

The SELV power supplies have over current (in/out) and overheat protection. The 12v cable will be of a diameter correct for at least twice the protected value of the power supplies (accounting for the length of the cable).

The T&E will be correct size for the length and load.

Providing the spark does not feel the need to check my 12v wiring, what could they disagree with?

I appreciate they could go looking for problems but unless they want to expose the full T&E run - we should be OK.

I beleive I'm capable of calculating and selecting the correct cable. If I'm wrong then its my fault and a new one will need to be pulled.

There is only one route currently open to me - following all the other cables installed before I owned the property. If the route is not acceptable to the spark, I'll need to find another spark or rewire the entire upstairs. The same goes for installation method.

I appreciate people prefer to only certify their own work but unless you are suggesting a full house rewire (way beyond my budget) then that's simply not possible.

The jobs that need doing to bring the house up to spec are things like relocating cooker isolator switch (move it from under the sink at the back of the cupboard and place it next to the cooker), installing a shower isolator switch and removing dodgy spured sockets from a bygone era.

I'm sorry if my previous message suggested sparks just test it and plug in. As well as knowing the regs, a good spark has a great understanding of how and why (this includes the mechanical and electrical properties of the materials being used). If I dont get one of those first time, I'll have to try again.

Many thanks for a great forum and good information.

You have no need to try and prove any of your perceived skill or competence to the forum by quoting numerous irrelevant facts. The bottom line is; either you are able so certify, (& notify if applicable), your work in accordance with BS7671 & part P building regulations or not?  If not then it is all down to the electrician who will be signing documents and accepting liability for the alteration/addition/modification to the installation. There is always more than one way to achieve a safe and functional solution to any problem, what you describe may well be perfectly acceptable. But without seeing the actual installation it is hard to say if you haven't missed something bleeding obvious that you have overlooked.  I have seen too many "simply jobs" that actually turn out to be a bit more complex than was first perceived by a customer. And as you need very small amounts of electricity to kill a healthy adult, I would be very wary of suggesting another unknown electrician who is not a member on this forum would be happy to test & sign off your work. You really do need to discuss your proposals with the person who will be doing the testing & certification,  they may want to pop in and visually check a few points before you bury any cables out of sight? If the job doesn't need and formal paperwork to complete it, then just carry on as you think best. DIY electrical work is still legally permitted in the UK.

Doc H.

 

[binky]

OK, apart form the good advice above it would seem you have no need for bonding anything - no mains voltages in the bathroom, and twin RCD protection in board already, so everything has RCD protection which generally precludes bonding.

My ony concern is mounting transfomers in a wall, due to possible lack of air circulation to allow self cooling, but then many attic spaces get really hot anyway. 

As for not being able to get an electrician - it would appear to be a small job, so it is alway harder to attract a busy person to do the work, but I would try now, not later. I'm usually booked up for weeks in advance. Most good sparkies will be also. It does also put people off when you have done bits and bobs yourself.