Confirming I've got this right...

[DBGlos]

Hi people

Just confirming Ive got this right... Most of this work has been done after reading and inwardly digesting the regs but after reading a lot of your posts I'm now beginning to wonder whether I got it right... so much conflicting advice... so if I have made any glaring omissions please let me know!

Property is 4 bedroom with separate garage immediately adjacent to the house (4" between them). Overhead supply, no earth from REC. Existing earth was to steel water pipes entering the house. Existing wiring was rubber insulated 1953 effort!

So heres what I did!

New CU (Not split load) with 100A incomer.
32A RCBO's for following circuits:

Ground Floor Ring - 2.5mm T&E <68m of cable
Upstairs Ring - 2.5mm T&E <68m of cable
Kitchen Ring - 2.5mm T&E < 68m of cable

45A RCBO's for:

Oven Radial - 6.0mm T&E <10m of cable - No socket on Control unit
Hob Radial - 6.0mm T&E <10m of cable - No socket on Control Unit

6A MCB's for:

Downstairs lights I - 1.5mm T&E
Downstairs lights II - 1.5mm T&E
Upstairs lights I - 1.5mm T&E
Upstairs lights II - 1.5mm T&E

40A MCB's for:

Radial to Garage - 6mm T&E - 15m to Garage CU (see later)
Radial to Attic - 6mm T&E - 4m to Attic CU (see later)
Radial to Boiler House - 6mm T&E to Boiler House CU (seelater)

16A MCB for:

3kW Immersion Heater Radial - 2.5mm Y&E - 5m

Garage CU:

Incoming cable runs under upstairs floor in house, through house wall, across 4" gap and through Garage wall in conduit to Garage CU.
Has 40A 30mA RCD with 32A MCB connected to 2.5mm T&E ring around garage and 6A MCB for radial lighting circuit. Ring circuit has 13A FCU's for outside floodlights/bulkhead lights and has spurs to suitable exterior grade sockets in attached greenhouse.

Attic CU:

Incoming cable runs entirely in House to attic to CU. Has 40A 30mA RCD with 16A MCB for 2.5mm T&E Radial circuit for sockets - supplies Heating controls and LPG Boiler and various TV amplifiers and splitters. Also 6A MCB for Attic lighting.

Boiler House CU:

Incoming cable runs entirely in house (Boiler house is attached) to CU. Has 40A 30mA RCD with 32A MCB for 2.5mm Ring circuit for sockets - supplies water softener and Heavy duty Washing machine and Tumble Dryer and 6A MCB for lighting.

Additional items:

Some outside sockets have been taken (as spurs) from Downstairs ring main. Suitable exterior sockets were used (MK models)

Outside flood lights/PIR sensors and Bulk head lights have been fitted as spurs using 13A FCU's from upstairs ring main.

New Earthing rod fitted in Earthing rod pit using 16mm sheathed earth cable to Connector block (heavy duty type service connector type) and from there to CU. Also from Connector block - main equipotential bonding to Incoming water and Gas pipes in 16mm earth cable. All appropriate 'Safety Electrical connection' tags have been used.

Bathroom lights are of the 12 SELV type Halogen downlighters and the Shaver socket is powered by spur from one of the upstairs lighting circuits.

No electric shower - nor will there be one - ever!

Yellow and Green earth sleeving was used throughout installation as was Red 'Line' sleeving used for switch drops.

My questions, stimulated by discussions here, are these:

Although I have had no problems with nuisance tripping should I have used a type C RCBO for the F/F?

Should I have used an RCBO on the house end of the cable to the garage or perhaps a time-delayed RCD? What difference would a time delayed RCD make?

Should the cable to the garage have been 10mm T&E instead of 6mm? Perhaps I will want a Hot tub eventually!

Do you see anything wrong with what I have done?

Any advice you can give is greatly appreciated in advance.

 

[Damocles]

My advice would be to write shorter more succinct questions.

Why did you use 6mm instead of 10mm cables? 6mm is fine for up to 32A. If it is in any way enclosed then it should be de-rated and not used for 40/45A.

This appears to be a TT supply, and as such everything should be protected by some sort of RCD.

what F/F? certainly not if they are on one of the 32A rings. Using type Cs it only an issue for 6A mcb really. The nuisance trip value increases as the nominal current increases as well as by de-rating to type C.

Do you really need all those 40/45A breakers? what total load do you anticipate?

Time delayed RCD are used where you have two in series and want to stop them both going off when it is unnecessary. 100mA is used for an entire installation as it gives you more leeway against cumulative earth leakage than does 30mA. For separate circuits you should be able to use 30mA individually on each. A preferred option I would think, except for the cost.

 

[DBGlos]

Sorry the question was too long but I wanted to get all the information across instead of people having to ask for more info before they could answer... sorry if it was too much!

So I should have used 10mm cable for the radials to the garage, attic etc but do they need to be derated if they pass through a conduit through a wall? in which case a 16mm cable is needed - gonna pricey I think!

The only 40A breakers are in the main CU.. the 30ma RCD in the remote CU are just RCD's NOT RCBO's I was just stating their current rating - sorry to confuse!

So the lighting circuits need RCD protection too - so I do need a split load CU after all - would this be better:

Split load with:

100mA RCD supplying MCB's to lighting circuits

RCBO's supplying as before

More questions... sorry!

Should the immersion be on the 100mA RCD with a 16A MCB or have a 16A RCBO on the non-RCD protected side of the CU?

Thanks for your patience!

 

[HDRW]

So the lighting circuits need RCD protection too - so I do need a split load CU after all - would this be better:

Split load with:

100mA RCD supplying MCB's to lighting circuits

RCBO's supplying as before

I'm no expert, so consider my input as suggestions to think about, not solid recommendations...

It's a shame you can't get 6A RCBOs (at least I can't find any), or you could just swap them in for the lighting MCBs

To save swapping the whole CU, what about installing a small extra CU, fed from (say) a 16A RCBO in the main CU, and put the lighting MCBs in there? That satisfies the RCD requirement, and keeps the lights seperate from the rest, so reducing the chance of having to find your way to the CU in the dark... and it will be less hassle to install and may be cheaper (although this depends, RCBOs being so darned pricey!)

Should the immersion be on the 100mA RCD with a 16A MCB or have a 16A RCBO on the non-RCD protected side of the CU?

Probably best on an RCBO, so when the immersion heater tube splits open and exposes the element to the water, the lights don't go out!

Cheers,

Howard

 

[Adam_151]

If it remains as a TT system, then everything has to be on an rcd(100ma or less) and all sockets have to be on a 30ma or less rcd

I can see a couple of ways to sort this out:

1) ask your REC for TNC-S
2) swap the main incommer for 100ma time delayed RCD, (edit: and maybe an RCBO for things like the immersion for the reason in the post above this one)


and 40A protection on 6mm cable is pushing it, depending on surroundings, length etc, better to have used 10mm

have you fitted supplrmentary bonding in the bathroom?

 

[DBGlos]

With regard to PME - requested a quote for that months ago - REC wanted over £500 to fit it... not a chance!

I think 10mm would be better but think it would have to be derated cos of going through two walls both with cavity wall insulation. Therefore I think 16mm might be better or is that overkill?

Since the second response Ive been thinking about the whole RCD, RCBO thing and have come up with the following...

100A Main isolator.
6A RCBO's for lighting circuits - 1.5mm cable
32A RCBO's for the Ring circuits - 1.5mm cable
40A MCB's for radial circuits to remote CU's - 16mm cable
16A RCBO for Immersion heater - 2.5mm cable - radial circuit

Does that sound better? Otherwise, if the lighting circuits were on 6A MCB's protected by a 100mA RCD, if one lamp blew wouldnt they all go off? And living in the middle of nowhere there is no ambient light at night so you cant see a thing even with the curtains open! Not a great plan... and don't the IEE regs say something about the setup preventing the whole 'ish' going offline when something trips thus not rendering the whole house to complete darkness?

Supplementary bonding in the bathroom? What's that? JOKING! Decided after reading loads of stuff that it wasn't appropriate cos the radiators are supplied by plastic pipes as is the hot and cold water! The bath is not metal and neither is the sink. Sorted! Or did I miss something?

 

[fireman22]

if you can get a 100mA time delay rcd for your board to replace your main switch just do this. you could replace your 40A to 32A for your 6mm cables if you are unsure, if they trip in the future just cross that bridge then

 

[pdcelec]

Have you considered Part P?

 

[DBGlos]

The price of the RCBO's is getting silly so perhaps the time delayed RCD is the way to go.

Another question...

Does the time delayed RCD just replace the incomer and the busbar stay the same or does it now have to be a split load configuration?

This means the 16 module CU is now getting a bit small... damn - was hoping to have avoided future CU additions to it all by leaving some spare spaces.

Why does it all have to be so difficult... wish I hadnt asked! LOL

 

[ban-all-sheds]

Does the time delayed RCD just replace the incomer and the busbar stay the same or does it now have to be a split load configuration?

It has to be split load, as the time delayed incomer will be 100mA but your sockets need to be on 30mA...

Why does it all have to be so difficult... wish I hadnt asked! LOL

It's not difficult. Surely what you mean is you wish you'd asked before you got to this stage.....

Also, you still haven't answered the question on Part P...

 

[DBGlos]

I didnt want to get into the whole part P thing... I just wanted answers to my questions thats all...

And yes I did wish I'd asked before Id fitted it all... but it was all done between Jan 2004 when I moved in and about June 2004 by the time it was all done.

As far as part P is concerned all I need to do is get it certificated properly to make these alterations as I see it.

Getting back to the 100mA Time-delayed RCD and RCBO thing, why cant the 100ma TD RCD be used as the incomers with 30ma RCBO's used on the same busbar? Surely they would discriminate!?! Or have I got this all wrong?

 

[plugwash]

you have to be a little carefull using rcbos downstream of other rcds as many of the one module ones don't seem to isolate the neutral. So a NE fault could still take out the upstream rcd.

i think the 2 module ones generaly do disconnect the neutral but that means an even bigger CU is needed.

 

[ban-all-sheds]

As far as part P is concerned all I need to do is get it certificated properly to make these alterations as I see it.

Err - no. You should have notified them before you started work. Thinking about it, I'm not sure why we mentioned Part P, as there is now nothing you can sensibly do to get back within the law...

Getting back to the 100mA Time-delayed RCD and RCBO thing, why cant the 100ma TD RCD be used as the incomers with 30ma RCBO's used on the same busbar? Surely they would discriminate!?! Or have I got this all wrong?

No - that will work fine, as long as you use 2-pole RCBOs, but I thought you didn't want to use RCBOs. You basically have 4 options:

1) Split load board, 100mA-S incomer, 30mA downstream for sockets

2) Non-split board, 100mA-S incomer, 30mA DP RCBOs for sockets

3) A board with an incomer feeding two RCDs, one 100mA, one 30mA (or another regular incomer and RCBOs)

4) Two boards - one with a 100mA RCD incomer, one with 30mA RCD or with RCBOs

In options 3 & 4 the 100mA RCD does not need to be time delayed, and if you used RCBOs instead of the 30mA RCD they would not need to be DP.

 

[DBGlos]

I really do appreciate your help so bear with me...

I havent started this remedial work yet so I still have time to notify them... my queries and understanding that Imight have it wrong only started today!

Why do the RCBO's need to be DP? What are the indications for SP RCBO's then? Why are SP RCBO's suitable in options 3 when a 2nd Incomer is used and not on the same busbar as a 100mA TD RCD?

What would you suggest then seeing as I already have in place the 32A RCBO's so dont wanna have to throw em out useless! It sounds to me that the 3rd option might be best!

 

[mapj1]

Err - no. You should have notified them before you started work. Thinking about it, I'm not sure why we mentioned Part P, as there is now nothing you can sensibly do to get back within the law...

Rubbish.

(Ha!! bad luck B-A-S got my chance and jumped!!)


Like all un-notified building work, the rule of retrospective regularisation applies, if you really think its worth the candle.
Work may be inspected and if necessary opened up and and all deficiencies found should be corrected before a regularisation approval will be granted.
To discourage builders taking this route all the time, the fee is usually set a touch higher than the normal inspection fee, but the same pass/fail standard applies.

In fact the DSA guidlines for part P suggest a satisfactory PIR certificate should be accepted as adequate for the purposes of regularisation under part P.

In the light of that. I'd suggest that for most DIY types getting a PIR done on selling the house, if the question is actually asked at that time, is probably both easier and cheaper than notifying many dozen small jobs, each attracting the (surprisingly large) minimum building control fee.
And who knows, by then the various BCOs may actually have decided what they are doing, and have a co-ordinated policy and charge structure
for this.

Also note the much vaunted 5K fine cannot be applied solely for failure to notify once 6 months have elapsed from the date of the alleged offence -S127 of the magistrates courts act prevents non-inditable offences being considered after this limitation period. Obviously if you are guilty of a real life-endangering offence, you may be prosecuted at any time, but it was ever thus, and part P has changed nothing in that respect.

I cannot advise you to ignore the law, that would be foolish, but I can point out the almost total lack of consequence if you were to do so.

I can also point out that in a letter from the

lan Drummond Buildings Division
Office of the Deputy Prime Minister

included the give away line that suggests even they don't expect it to work perfectly either...

"There are likely to be instances of faulty work where the work is not notified but it was considered that many minor jobs, typically carried out on a DIY basis, would not be notified even if there was a requirement to do so."

I'd suggest a policy of not losing too much sleep over it.


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