spur units


Postby ajax » Sat Feb 16, 2008 1:17 pm

I am just having a new bathroom put in, and the elctronic shower mixer, and bath whirl pump, combi boiler need to be wired in. I will be having a certified electrician in to check and certify when finished. My question is, as my units all require a 3am spur unit, how would i wire in all 3 units ? Would I create a seperate ring for the bathroom, and, as there will be no sockets on that ring, just have 3am spured units of it (x3), or a direct supply from the consumer unit to all 3 items, with a 3am spur unit, or a 3am plugged unit... etc.. etc.. hopefully you can see where i am going from here. At the moment, I do have access to put cables anywhere, and straight to the consumer unit.

Can anyone help ?
many thanks
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Postby ericmark » Sat Feb 16, 2008 10:24 pm

An electrician can't sign a completion certificate unless he has been in control of the work. He can inspect and test but this is not the whole of the form only the person responsible for the installation can sign for it being done correctly so you need an electrician to at least act as Clark of works and he will tell you how he wants it wired. If we suggest how to wire and he does not agree you may have to rip it all out and start again. If you go to projects and look for Part P you will find a link to PDF down load which has a sample picture on how a house is wired and also samples of the forms that need filling in. It explains how the electrician must be in a position to know the routes and how the cable is clipped etc. For the current you are talking about I would expect a radial would be enough and but so much would depend on your actual setup not really something that can be done without seeing the job.
ericmark

Postby 333rocky333 » Sat Feb 16, 2008 11:19 pm

I would not think you would find someone prepared to sign off work
INSTALLED by someone else, even more so in a bathroom .

Part p !!!
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Postby 333rocky333 » Sat Feb 16, 2008 11:32 pm

POSSIBLY
For the two pumps, two switched fcu's, a 20 a radial circuit direct from the cu wired in 2.5mm, from a 30ma rcbo would suffice.
Or a 20a mcb if the cu already has a 30ma rcd fitted

Same again for the boiler with one switched fcu, this MAY not require rcd protection
Your PART P ELECTRICIAN WILL ADVISE. before you START the work.
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Postby ajax » Sun Feb 17, 2008 9:06 am

hi,

i can see the good points mentioned in the above replies, so thought I would add a couple of extra items.

ALL the actual wiring, spurs are in the loft, well away from the bathroom, the house currently has no floors down, as it is a complete renovation/decorate, the electrician, said he would be happy to certify it, providing all floors were still up, and everything was accessible, and able for vieing. I do also have actual scaled drawings on the OC of wiring routes, whats where, type etc...
Its merely a case of (as it appears with all home trades at the moment), they are sooo busy to do the actual work, so rather that wait a year, as i work away out of the country for 8 months of the time, is to get as much done, safely and legally, in order to help and speed things up. I understand the implications of Part P, and do have a downloaded copy, but it is easier to talk with someone rather than leave to "translations" which could go a miss somewhere, especially as the electrician is not available every week for a small conference. Dont get me wrong, i'm not a cowboy electrician, i am a certified electrician myself, but not for domestics under Part P, but more marine and 690V 11kv systems, so unsure of domestics, so just trying to close a few question marks.
many thanks everyone.
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Postby ericmark » Sun Feb 17, 2008 5:24 pm

As you are an electrician, you can sign parts of the installation document your self but looking at the time scale you will be under 17th Edition wiring regulations.
1. Output from combi boiler can’t be pumped and is not enough output for side jets. The electronic shower mixer is not something I have seen. The units I have used have been purely mechanical.
2. 2.5mm² will run all you list and a radial would seem to be adequate for your requirements. It is normal that any fusing required is contained within the units. Some method of isolating is required although not always necessary to fuse so if a fuse is required then it is normally fitted in the unit. If the appliances do need remote fusing then you will need spur units. The norm would be ceiling pull switches or wall switches near the bathroom door outside the bathroom itself.
3. You will need earth leakage protection there are three ways you can do this. Put spur units with built in RCD in on wall not recommended as you would need three, Using a large RCD in consumer unit that in turn feeds the MCB’s cheap method, Using a RCBO on non protected side of consumer unit more expensive but best method as it will not affect other items in the house should it trip. Some makes of consumer units need 2 module width others only one so check first.
In any house in the main the more circuits the better so if it can be feed from the consumer unit then that’s the best way.
I am not sure if you intend to mount boiler in bathroom. If so I think it would need to be 3 meters from bath as it is not essential to be in a bathroom. Otherwise you may need to fit it in a cupboard?
ericmark

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