17th Edition RCD Protection

[Clitheroe]

HI Everyone

Just wanted to know a few things with all this talk regarding extra RCD protection etc,

Are the regulations saying that all circuits etc ACTUALLY HAVE TO BE protected?

Are standard split load boards still going to be permitted?

What about TT systems with Time Delay RCDs of 100mA trip?

I have seen Consumer Units available with two 30mA RCDs installed so how would one arrange which circuits on which side?

I know shower circuits and all socket circuits will require RCD protection of 30mA trip but also things like batroom lighting and certain wiring not buried at a certain depth-will this therefore include lighting circuits?

What would an Electrician most likely install when doing a Consumer Unit replacement in a domestic property?

Personally I think what I have said about shower and socket circuits will be a good idea but regarding lighting circuits and depths etc I think is going a bit too far myself.

Regards

 

[Spark123]

Are the regulations saying that all circuits etc ACTUALLY HAVE TO BE protected?

Nope, only certain circuits will need to be RCD protected.

Are standard split load boards still going to be permitted?

I don't see why not

What about TT systems with Time Delay RCDs of 100mA trip?

The disconnection times for TT systems have been changed, hence type S RCDs which cannot meet these disconnection times cannot be used.

I have seen Consumer Units available with two 30mA RCDs installed so how would one arrange which circuits on which side?

50/50?

I know shower circuits and all socket circuits will require RCD protection of 30mA trip but also things like batroom lighting and certain wiring not buried at a certain depth-will this therefore include lighting circuits?

yup.

What would an Electrician most likely install when doing a Consumer Unit replacement in a domestic property?

I'm leaning towards using a normal split load unit using the RCD side for the likes of sockets, shower etc and RCBOs on the non - RCD side for the likes of lighting. Not sure how everyone else is considering going about it.

 

[DESL]

I think what will determine the CU configuration will be the bottom line cost to comply with 17th.

In an ideal world each cct on RCBO would be the best solution IMO but at £25 per cct it makes it an expensive exercise.

In most domestic CU upgrades all ccts will require RCD protection as in my experience I've never seen cables installed deeper than 50mm.

 

[SeanT]

The new "17th edition" boards have two banks of RCD protected MCBs, the idea being that for every socket / ancillary circuit the lighting circuit for the same area will be protected by the opposite one - good for big properties with the now commonplace everything split across floors, however in small older properties (like mine) these are thoroughly useless as provided the existing wiring is ok it's more expensive to start splitting the whole house lighting and ring main (except kitchen) circuits than it is to buy a couple or three RCBOs and a split load board - one for the lights, one for the separate fridge freezer socket, one for the outbuilding - leaving everything else on the same RCD.

 

[davelx]

In most domestic CU upgrades all ccts will require RCD protection as in my experience I've never seen cables installed deeper than 50mm.

It's impossible on the internal walls of many 1930's terraces/semis (including mine) The internal walls are only 80mm thick - one block plus plaster.

 

[Chri5]

In an ideal world each cct on RCBO would be the best solution IMO but at £25 per cct it makes it an expensive exercise.

Funny, but I think all RCBo's have jumped in price, with VAt most make are up at £40+ each.

If you consider SPF- single point of failure, that explains why double RCD CU's are being designed and sold.

Having a mix of circuits across the 2 x RCD rails prevents the total lost of all circuits due to the only RCD in the board tripping.

There's a strong debate that suggests that not only should a CU have 2 x RCD rails, but a 3rd dorect rail for RCBO's for smoke detection and leaky 'other' circuits such as cooker, fridge and shower.

 

[Cremeegg]

Hager have been doing double RCD boards for years - with a little work you can have two non RCD ways and then two lots of six ways. Other combinations are possible by cutting the bus bars. Other manufacturers boards can also be altered to do the same thing.

 

[DESL]

Funny, but I think all RCBo's have jumped in price, with VAt most make are up at £40+ each.

I'm paying £21 + VAT for MK RCBOs

There's a strong debate that suggests that not only should a CU have 2 x RCD rails, but a 3rd dorect rail for RCBO's for smoke detection and leaky 'other' circuits such as cooker, fridge and shower.

The 17th ed configured MK CUs are set up this way.

 

[Clitheroe]

Thank You everybody,

OK then.

Will Time Delay RCDs still be available? I hope so since I fitted a Wylex split load board in my home in 2004 (seriously, before the following January ..... ) with a 30mA for sockets etc and a 100mA TD for everything else (TT system) so what I was thinking about is what happens should the TD RCD ever fail and require replacement? I don't want to have to go and change half of the MCBs to RCBOs or whatever.

Also with the new 17th Edition boards like Spark123 mentioning a 50/50 setup how would the following circuits for instance be setup in a board with two 30mA RCDs?

Cooker (no socket outlet on CCU)
Immersion Heater
Workshop/Garage
Shower
Downstairs Sockets
Upstairs Sockets
Kitchen Sockets
Upstairs Lights
Downstairs Lights
Outdoor Lights

I have omitted smoke alarms asuming this is an existing installation without them.

I have to say though as well as going too far with things the regulations in this case I think are not been clear enough explaining things

Many Thanks for any help with the above

 

[Chri5]

Read this, it covers pretty well every 17th CU requirement.

It also gives very clear, fool proof suggestions on design, why's and methods

http://download.hager.com/hagergrou...rmation/ConsumerUnitGuideToThe17thEdition.pdf

 

[mdbalson]

With the 17th Edition are Split load Dual Tariff CU's still aloud to be used (The CU's with a mains switch & RCD for the Peak Circuits, & a mains switch for the Off Peak Circuits)

Say if it was a upstairs maisonette with the following circuits:

All circuits are in PVC T+E cables

Peak Circuits

Non-RCD Circuits

1st Circuit Smoke alarm x 2 (1 in hall by front door & 1 in upstairs hall) (On a 6A MCB, as Cabling in PVC surface Trunking up the wall, & then running in the loft to the 2nd smoke alarm)

2nd Circuit Lights (On a 6A RCBO as cabling less<50mm in the walls)

3rd Circuit Shower (On a 50A RCBO for safety, the cabling is in trunking from the cu cupboard by the front door up to the loft, it then runs along the loft, & then it goes down in to the 45A DP in the bathroom)


RCD Circuits

1st Circuit Cooker (cooker ccu with 13A outlet on) (On RCD side as cabling less<50mm in the walls & as ccu has a 13A outlet)

2nd Circuit Socket Ring (On RCD side as socket circuit & as the cabling is less<50mm in the walls)

3rd Circuit Socket by front door & FCU for Door Entry Phone (On RCD side as circuit has socket outlet on it)

4th Circuit Spare

5th Circuit Spare

6th Circuit Spare


Off Peak Circuits

1st Circuit Upstairs hall E7 Storage Heater (Does not need RCD Protection, as Cabling in PVC Trunking, then run in the loft, & then in PVC Trunking down to the DP SW in the upstairs hall)

2nd Circuit Spare

3rd Circuit Spare

4th Circuit Spare

(The 3 spare off peak circuits would be used for E7 extra heaters, if ever needed)

 

[nozspark]

Smoke alarm circuits will still need to have RCD protection (with certain exceptions - same as other circuits), they must also be protected by a RCD which does not protect a socket circuit (fire alarm reg's)!!

EDIT - just saw that you have surface trunking (lovely!! ) so no RCD protection for those cables is needed

 

[Spark123]

Say if it was a upstairs maisonette with the following circuits:

All circuits are in PVC T+E cables

Peak Circuits

Non-RCD Circuits

1st Circuit Smoke alarm x 2 (1 in hall by front door & 1 in upstairs hall) (On a 6A MCB, as Cabling in PVC surface Trunking up the wall, & then running in the loft to the DP SW in the bathroom)

2nd Circuit Lights (On a 6A RCBO as cabling less<50mm in the walls)

3rd Circuit Shower (On a 50A RCBO)

I think you have mixed something up here? Why would the smokes be to a DP switch in a bathroom? All circuits in a bathroom to be on RCD.
Any bog standard PVC cables concealled directly in a walll less than 50mm need to be RCD protected.

RCD Circuits

1st Circuit Cooker (cooker ccu with 13A outlet on) (On RCD side as cabling less<50mm in the walls)

Ckt 1 will need RCD protection regardless of cables being concealed as it incorporates a socket.

 

[mdbalson]

EDIT - just saw that you have surface trunking (lovely!! ) so no RCD protection for those cables is needed

Well needs must (I know that surface trunking is not the nicest thing, as at home there is some which I had to use for SW drops & Extra sockets in my bedroom)

The cable for the smoke alarms comes from the cu cupboard & goes into the boxing in where the gas, water pipes & shower cable are. From there a piece of trunking goes to the 1st smoke alarm (on the ceiling above the front door), then from the alarm the cable goes up into the front bedroom, in trunking into the loft. The cable then runs along the loft & down into the upstairs hall to the 2nd alarm.

 

[mdbalson]

Say if it was a upstairs maisonette with the following circuits:

All circuits are in PVC T+E cables

Peak Circuits

Non-RCD Circuits

1st Circuit Smoke alarm x 2 (1 in hall by front door & 1 in upstairs hall) (On a 6A MCB, as Cabling in PVC surface Trunking up the wall, & then running in the loft to the DP SW in the bathroom)

2nd Circuit Lights (On a 6A RCBO as cabling less<50mm in the walls)

3rd Circuit Shower (On a 50A RCBO)

I think you have mixed something up here? Why would the smokes be to a DP switch in a bathroom?

Sorry the 'DP SW' part was meant to be about the shower circuit.

All circuits in a bathroom to be on RCD.

All of the bathroom circuits would be on a RCD.

As the lighting circuit will be on a RCBO.

The shower circuit will be on a RCBO.

The underfloor heating, Mirror lights & shaver outlet are connected to a FCU, which is on the socket ring, which will be on the RCD protected side of the CU.

Any bog standard PVC cables concealled directly in a walll less than 50mm need to be RCD protected.

All of the circuits who's cables are in the wall will be RCDed.

The lights will be a RCBO

The Sockets Ring & the cooker will be on the RCD side of the CU.

RCD Circuits

1st Circuit Cooker (cooker ccu with 13A outlet on) (On RCD side as cabling less<50mm in the walls)

Ckt 1 will need RCD protection regardless of cables being concealed as it incorporates a socket.

I was going to put the cooker on the RCD side of the CU, as it as the 13A outlet on the ccu & as the cabling is less<50mm in the wall.


So is it still OK to use the split dual tariff CU in this setup