I’m doing all the prep work for my new boiler – ie I am drilling holes, running pipes and cables etc but not connecting/soldering etc anything as I want to make sure it is done properly and to all the regs.

So just after some advice as wanted to see if an idea is viable before I call an electrician and get some funny looks.

Long story cut short(ish) – I have a switched fuses supply from the old boiler that terminates in the cupboard where all the pipes are. I am already cutting trenches for the new pipe work so can I cut a separate trench and run an SWA cable in the floor? Floor is concrete/screed.

Floor covering is going to be hardboard stuff and then laminate (unfortunately but it is a decent one and I’m renting it out) so no fixings will be going into the floor. I wasnt planning on re-screeding around the pipes or cable and just capping off the trenches with wood so new pipe/cable can be routed easily if required.

Is SWA going to be okay for this and is there a minimum depth baring in mind it’s not going to be re-screeded and just capped and labelled for anyone who takes the floor up?

Also the boiler states 3A fuse and 0.75mm flex. The current cable is 3+earth and smaller than normal socket flex so I am assuming its 1.5mm. Is this okay to connect 1.5mm SWA to this and what do I do with the 3rd yellow insulated cable that was used for switching the back boiler on? Can this just be earthed at both ends?

correction – will the electrician just earth this both ends or do I need to prepare to run a new cable?

A few questions
why are you using swa ?
Are you using swa glands if so what are you glanding onto.
3a sounds like a controls supply only, can I assume your switched fuse supply is a spur ?
1.5mm should be ok
If you have a redundant core this can be cut back and insulated with tape no need to earth, if you are just laying the cable for the spark to finish off then I would think he would look after all of the above,

cheers

Just put a conduit in the floor with a draw wire in it, let the electrician decide on the cable type and size.

There are a number of factors needed before deciding how to do this.
Have you got RCD protection for this circuit?
Why dont you use the existing spur?
Are there going to be any remote, wired controls, like a room stat?
If so, then these cables will have to be put in too.

Why would you use SWA?
Yes, 1.5mm T+E will be fine for the majority of boiler installs (1mm would too), so long as the circuit protection allows for this size of cable. A 6A breaker would be fine, or, if spurred off another circuit, a 3A fuse.

If there is no RCD protection, then cables must be 50mm below the surface. SWA can be less than that as it has in-built shock protection if the armoured sheaf is earthed correctly. It is an expensive way of doing it.

Far more info needed to give a correct view of what you want.

alan.

Cheers for the replies.

I’ll try and answer all the above:

I am using the existing spur but it is no where near the new boiler location. Re-using the existing one is the whole point as I have no where else to take a spur from.

Only way to get to the new boiler without ugly external conduit is in the floor which I am already cutting channels in for the water pipes.

If I use conduit and normal wire in the floor I assume I need to use galvanised steel conduit which has to be properly earthed.

SWA would be of course be used with glands which would be secured to the boxes at each end and appropriately earthed – by the electrician.

The 3A supply is all the boiler needs.

Controls are wireless so no need to worry about those.

RCD – no. Fuse box is all MCBs with one master switch but no RCD. Wondering if I need to have an RCD anyway or does that mean a whole new consumer unit?

50mm into the concrete is no problem but reason for thinking SWA is that I won’t need an earthed conduit. Distance is about 6m under floor so cable and glands will be <£20 – much less than faffing with conduit.

This is nice and clear: http://www.ultimatehandyman.co.uk/consumer_unit_split_load.htm

Will whip the front off my consumer unit tomorrow and see if it’s split so an RCD can be added. I suspect not though. Might get a whole new unit put in when I get the electrics done as it will be cheaper to get the whole lot done in one go.

Take a pic of your CU, and I’ll tell you if you can fit an RCBO – these are small RCDs that protect one circuit only. They fit in the same size slot as a MCB, but are slightly taller.
One of these would be perfect if you are fitting it, as it solves any problem with buried cables – you will be safe with normal cable just under the surface.
RCBOs are around £18, so far better than trying to fit either conduit or SWA.
I presume you are not bothering with a Part P notification? For DIYing, I woudlnt bother too.
Whereabouts are you?

HTH
Alan.

I am renting the place out so needs to be all certified hence getting an electrician in to do what they need to do.

I am basically just extending the current fused spur so according to the Part P I think I am safe to do it but as I am getting an electrician in to wire up an electric element into the towel rail and do a general safety check and landlord check then I will get them to connect up and check the fused spur is all above board. I’ve got no problem doing electrical work but I don’t know the exact regulations regarding wire depths and types and protection required.

Priced up the SWA and glands from here: http://quickbit.co.uk

Came to £10+vat and postage for 10m. Floor run is 6m.

There is a very low risk of anyone ever putting a nail etc through the cable as when you take up the flooring it will be obvious it’s there but it’s nice to know for sure it’s got a bit of extra mechanical protection.

PS in Bristol. Am still yet to find an electrician. Not asking the one the builders used as he didn’t even wire the lights up correct so you have to get the 3 switches in the hall in the right combination to get the lights on. An amusing game at first but quickly loses it’s appeal.

If he fits a new Radiator element, then it will need RCD protection to comply with both the 17th Edition wirings regs, and Part P legislation, so it would be daft to run SWA to the boiler, if you can get the circuit rcd’d.
He will have to give you/the landlord an Electrical Installation Certificate, as well as informing the Council, via his Governing body.
If this is not done, then the owner of the house can be prosecuted (though unlikely)

There is no such thing as a Landlords check or safety check, he can do a quick look at the install, charge you for that, and it will tell you nothing.
The only correct option is a Periodic Inspection Report, which has just, as of Jan 1st, been renamed as an Electrical Install Condition Report. This can be done on one, or all of the circuits,or parts of circuits as required. If done properly,it will find a lot of faults with your existing installation, not all of which will need rectifying, as if it doesnt meet the current regulations, there is no onus on getting it upgraded to the latest regs.
If anything is deemed as ‘dangerous’ then it MUST be rectified, or that circuit isolated.

Basically, if a competent electrician does work for you, the new work has to meet the current regulations, and that means ANY electrical work in a bathroom needs to be RCD protected, and he also has to make sure that the earth bonding, to the main earth terminal, the gas pipe and the water pipe all meet the current regulations, that is, generally, a 10mm cable to gas and water, and a 16mm to the main earth.

So, the main advice would be to wait until a sparkie sees it, and ask how he wants it done. If he says there is no need for a rcd for the radiator element, then he is wrong.

HTH
Alan.

By landlord check I mean certificates I need to make sure I am legal to rent it out.

Not looking hopeful for my CU. Looks like it could have an extra neutral bar on the left but there is not much room in there. I guess the bus bar under the cover can just be split into RCD side and normal side. The shower breaker will be going and the lights and cooker (freezer runs off the cooker circuit) will be left on the right. Looking at the price of RCDs and RCBOs it’s not much more to buy a whole new box!

If I need a whole new CU then I’ll just forget the towel rail element.

Going back to the original question…

SWA is not a problem cost wise. If it saves me having to make a large trench for plastic trunking/conduit or have metal earthed conduit the few £ more over normal wire is worth it. I just wanted to check this was okay. I am doing all the floor cutting now as it makes a hell of a mess and once the new rads and boiler are in I’m not making any major dust!

edit forgot CU pics:

If you are not replacing the gas pipe all the way to the meter, then consider checking before doing any making good in case your boiler installer decides it is under-sized/under-pressure.

You will be able to fit an RCBO in that CU, so that is by far the easiest, and cheapest option. Niglon RCBOs are a straight fit into it.Using SWA is complicating an easy job. Why bother with 2 termination boxes,and the hassle of fitting them, and their visual appearance, when all you need to do is buy one or two RCBOs, and you just use normal T+E cable, with no extra boxes on the wall.

No, you cannot (easily) fit a RCD into that CU, but the future is RCBOs, and these are perfect for it, so you can fit 1 or 2 when you do this work, and then upgrade the rest of the circuits with RCBOs when you feel it is necessary.

You do not need any electrical certification for a rented house. The wording of the Act says the install must be ‘safe’.

Paying for anything less than a Periodic Inspection Report (or EICR) is a waste of money, the PIR/EICR is the only one that fully meets the requirement of checking the installation. Some electricians (dodgy ones in my opinion) will offer a ‘safety check’, which basically comprises of half an hour looking at the sockets/switches/CU etc, and giving you a quick report. This will cost you £50+, when you can get a proper PIR/EICR for around £100. Only one of these has any legal meaning – guess which one?

Gas pipe should be okay – already been checked as much as they can. It’s 22mm from the meter and the flat 2 floors up has just had a similar boiler put in with the same pipe but twice as far. Have the provision to fit 28mm in any exposed parts where the bends are anyway which will reduce the losses.

RCBOs – unfortunately the boiler power is on one ring main, the towel rail will be on another so it will mean 2 RCBOs which don’t seem to be cheap. I was hoping that you could just buy spars neutral bars, split the bus bar and fit an RCD powering a couple of the circuits (not the lights or cooker due to fridge freezer). Hagar 63A 30mA RCD is pretty reasonable unlike some of them which seem to be cheaper to buy a whole new CU.

If I run any cable in the floor – be it SWA or normal T&E on an RCD circuit then how deep does it need to be burried in the slab? My angle grinder can only go down about 1.5″ so going down past 50mm needs more work but I want to get it all done before.

Another option I do have is can you run a fixed appliance (at 3A) and a twin socket as a spur off an existing socket? I have a socket right next to the new boiler but its running a twin socket spur so I had thought it was not possible to use that.

Yes, you can, generally, have a fused spur off existing circuits, with a few limitations.

RCBOs are £18 from my electrical wholesalers, cheaper online, dead expensive at Screwfix.
http://www.eleconline.co.uk/zdriverel/form/category/NIGLON-RCBOS
http://www.electricalcomponentsdirect.co.uk/acatalog/RCBO.html

It is worth it to give you extra fault protection, and saves lots of hassle with getting cables more than 50mm deep.
Modifying an existing CU to fit a RCD is a mugs game, and far more trouble that it is worth, just fit a RCBO in place of the MCB, and you are covered in 10 minutes, with no disturbance to any other circuit.

Really, you want to forget about using SWA and adding a RCD to your existing set up, no-one with any sense would even suggest doing that in domestic premises.

Alan.

Interesting update – took all the sockets off to take a good look and the external wiring in trunking is actually part of the ring main (I had a hunch after looking at another socket in an adjacent room).

Well ‘ring’ was more like a horseshoe as one of the live wires was not connected! Also what I thought was a switched spur turns out to be in the ring main so after all that it turns out I can just run a spur to the boiler off the socket next to it and then use the switched connection to the cupboard to power the towel rail which is screwed to the other side of the wall.

Just need to get one RCBO installed to cover that whole circuit which will do all the sockets, boiler and towel rail.

Thanks for your help Alan! I’m now a lot clearer on all this RCD, RCBO stuff.

Is there any current regulations to state that all sockets need to be RCD protected? I have one socket which runs off an old immersion heater breaker by itself (single 2.5mm t&e direct from CU) but if it needs to be RCD’d then I might just blank it off.

Also does it need to be a Hagar RCBO or should any fit? I understand that some manufacturers say you should stick with theirs.

All new installs should have RCD protection for socket outlets, apart from a few minor exceptions.
As yours is an older install, it doesnt need to be brought up to the current standards, unless you do some work on that circuit.

Yes, you can fit other makers MCBs/RCBOs into different CUs, the Makers always say fit the same make, yet there are some makes that are no longer made, so how do you fit the same make then?

Niglon are a straight fit into Hager boards, I know as I’ve fitted a few of them recently.

Just looked at those prices for RCBOs and now I see why you were saying go that route! They are 1/2 or less of the price in other places.

So for the main ring main I will need a 32A 30mA RCBO and I am gussing that removing the immersion heater and fitting a socket in it’s place on a single feed of 2.5mm will need a 16A 30mA RCBO or will a 32A be okay there too? Nice to see the latter link has RCBOs up to 50A that are not extortionate too so I guess electric showers and cookers can be fitted much cheaper with those.

Just off to see what this B and C curve thing is about.

Will get an electrician in before I go any further though, at leas tnow I know there is no more drilling needed. Had enough of cutting channels in my concrete for gas and water pipes. Had to dig down and locate the gas pipe in the living room floor last night and carefully cut around it so it can be cut and diverted.

Thanks again.

B type or curve will be fine.

I would also point out that consumer unit manufacturers such as hager will state that the their CU’s meet the relevant standards as they have only been tested using their own circuit breakers/RCBO’s, any circuit breakers from other manufacturers (such as the MK circuit breaker in your Hager consumer unit) used in their CU’s may negate this.