Re-wiring and Part P etc

[Andrew Gabriel]

Does anyone ever go for all RCBOs, or a significant proportion of RCBOs?

[Brett Jackson]

Thanks all for your help and advice - very useful.

I had a chat today to my local BCO who does the Part P stuff. Very helpful chap and the process seems straighforward and sensible. Basically I pay my money and he pops round to have a look at what I'm doing and discuss my requirements and how I'm going to meet them. Another visit in my case after I've installed the CU, then a final safety inspection when it's all done in a few years time.

The only mention of a PIR or sign-off other than standard BCO stuff was a recommendation that I get a spark in to do a PIR when it's all done.

Finally (I think), are there any recommendations on CU/MCB brands? I like the MK sockets and switches etc due to the quality, so I'm inclined toward an MK CU, however they're more expensive than the others...

[Tim W]

Brett Jackson wibbled on Monday 04 January 2010 21:27

I like Hager CUs - a very decent choice of devices and lots of enclosure options.

I've been using GET accessories - they seem reliable and look nice and are inexpensive. They do some nice grid based, but domestic appearance (ie not pug ugly) light switches (and dimmers of various types, which is why grid is cool - one dimmer + one switch in the same single plate - no problem... etc)

[ARWadsworth]

I do a lot of "landlords specials" for 2 bed terraced houses. They use the

17th edition CU.

On larger properties I use a mixture of RCBOs and RCDs.

Only one customer has chosen all RCBOs

And I am not happy with the setup.

Adam

[Owain]

Not if every circuit is protected either by a RCD or a RCBO

I'm not convinced they actually comply with the 16th Edition regarding unnecessary disconnection of circuits.

For a small installation MCBOs not excessively expensive, for 20+ circuits cost would be more.

No extra work to wire up though, and easy to rearrange the order of circuits as new ones are added without having to juggle the neutral and earth bars separately (for those people who like wires on the busbars to be in the same order as the breakers).

DP isolation of individual circuits also useful when working on an installation in stages.

Owain

[Owain]

Standard circuit is 20A.

You could always put uncompleted rings on 20A while the work is being done (treat them as radials) and then change the MCB to 32A when the ring is complete. Reuse the 20A for the immersion heater or similar; even if you end up with a couple of redundant 20A MCBs it would still be cheaper than a 20+ way CU.

Owain

[Andrew Gabriel]

Although I've used lots of RCBOs in many CU's, I've never used DP RCBOs.

[Tim W]

Owain wibbled on Monday 04 January 2010 22:19

The Hager single module RCBOs don't break the neutral - even though you have to present the load's neutral to it for RCD purposes. The DP RCBOs are 2 module width - so best to be careful...

[Andrew Gabriel]

I like MK sockets and switches, and MK MCBs/RCBOs, but not their current plastic CU's. I liked the previous generation with clear perspex covers. Last few I've done have all been commercial CU's (MEM Memshield2, or whatever Eaton call them now), but they are a good deal more expensive than residential grade CU's.

[Steve Walker]

Just out of interest. I have a garage with a shed right next to it (so close that they share the same guttering - that took some careful arrangement!). The garage is supplied with SWA to a consumer unit inside. Is it notifiable to extend the circuits across the gap (due to the short length, two T&Es in a plastic conduit just under the guttering should be sufficient)?

SteveW

[Steve Walker]

I've been perfectly happy with my Crabtree Starbreaker CU, but then again my father used to work for an electrical accessory manufacturer and sat on (and chaired) a number of BS committees - when my house needed re-wiring 16 years ago, he asked his contacts at other companies for free samples (he did tell them what for) and my entire house re-wire, including the CU, cost me thirty quid! Some of it was slightly overdone though, such as the 16mm^2 T&E for the cooker point - hey it was free, but it was an absolute bastard to get in the box! Typically, we now have a gas cooker!

SteveW

[Brett Jackson]

This is the conclusion I'm coming to as well. In fact the NICEIC state in their FAQ that dual RCD is one of several solutions. I'm seeing it as the lowest cost option to meet the req's, rather than a minimum standard.

There doesn't seem to be an electrical safety aspect to there being more than one RCD as providing a circuit is RCD protected then it's protected. The regulation seems to state reduction of inconvenience, which read literally probably means lighting & fire, but with the caveat that you don't want both lighting circuits on one RCD.

So, what I'm pondering is...

- a single RCD to cover all the sockets outside the kitchen, and maybe CH, immersion heater etc. - an unprotected circuit going out to the garage via SWA where there'll be a sepearte CU with RCD. - RCBO's for everything else - lighting, fire alarms, kitchen ring & appliances

I was thinking 20 just to give plenty of empty slots for future expansion. I'll probably only use half to begin with.

[js.b1]

That sounds like a few inches...

Heh-heh.

- You are allowed to fit an external light with cable entering at the rear.

- You are allowed to maintain an existing external light where the cable enters say from the bottom running along a wall.

- You are not allowed to fit an external socket because it can be used to supply across a garden, however kits exist to do exactly that from just about every DIY store in the country re B&Q, Wickes and I think Homebase. Indeed I think some now exist with pre-fitted SWA in various lengths to reach a distance socket which can be fitted into a shed or on a wall.

Legally you could construct a wooden frame (tube) which spanned the two entities and run cables through that - ensuring that the cable is

Practically do the job correctly to BS7671.

- I would not use conduit just under the guttering as an aluminium ladder could be placed against it and crush it

- I would prefer to run SWA from the garage to the shed, more suitable for outside use & earthed armour

- Alternatively ensure the conduit is visible and substantially supported between two nearly touching buildings

Note if you are exporting PME from house to garage or shed...

- To do so requires 1) no incoming services (gas/water) 2) no metalwork introducing a potential into the garage 3) floor is dry (not likely with some garages) 4) no class-1 tools used outside or within a damp garage - or you would need to TT supply the garage

- The same 4 criteria apply to exporting PME from garage to shed

- The only way to export PME where any of the 4 are broken is to use an SWA back to the house of a sufficient conductor or armour cross- sectional area to meet the MEB requirements and bond it back to the MET accordingly (so the external garage/shed are at the same potential as the house).

Note PME can not be exported to a caravan, some DNO are liberal in their interpretation (such as steel containers to statics).

[ARWadsworth]

I would consider putting the CH on it's own RCBO. The last thing you want is a fault on another circuit taking out your heating.

I quite often use a dual RCD CU that has some non RCD slots eg

would then mix the lighting and sockets up between the two RCD and use RCCBOs on the non RCD slots for smokes and mayby a kitchen ring or the CH

Adam

[Tim..]

I've often used some DP RCBO's for plant switchgear, and temporary installs. Only prob is you end up with a CU that is 1 metric yard wide !!

Tim.

[Steve Walker]

The gap is around eight inches, shed wall to garage wall.

Just about impossible - the conduit would be six inches to a foot in from the end of the shed, an inch or less below the gutter crossing a gap of 8 inches. The gutter itself is overlapped by the roofs of both the garage and shed, from opposite sides, with a gap of only two inches between them. The chances of anything contacting it are vanishingly small.

The armour is probably not necessary, due to the above, unless for earthing.

I would use steel conduit, but then we get into ensuring that that is reliably earthed. White plastic conduit will certainly be visible against the brown guttering.

Not a problem.

Again no problem.

Was a problem until recently, but re-covering the roof, properly sealing the sectional concrete panels to the base slab and re-aligning the gutter have solved that.

Pretty sure that the only portable earthed tool I've got at the moment is an old welder and that's not even mine and is only used inside anyway.

Garage is already supplied via SWA and does indeed export the earth. All done correctly already, RCDd, etc..

As TT is not really necessary for the shed as none of the four rules are broken, I'll stick with exporting the earth and I'll probably just export from the garage, as I really don't fancy digging a deep enough trench up the garden from the house.

And as I started my post with "Just out of interest," I'll probably save myself any hassles, use old colours and insist that it's been there for years! Just in case anyone asks.

SteveW

[Dave Osborne]

This is what I would do and not worry about it. ;-)

[Owain]

Oh.

Suppose one uses the SP RCBOs and gets the tails the wrong way round ... could be nasty.

Owain

[ARWadsworth]

But a tripped single pole RCBO still cuts the live or am I missing something?

Adam

>

[Owain]

"tails the wrong way round"

Owain