3 Phase Dist Board change in flats

sparky200 · Sep 17, 2011

I have been asked by one of my clients to change his 12 way 3 phase cartridge fuse dist board which covers the communal circuits throughout 4 storey block of flats. The majority of the wiring is pvc/pvc twe buried in wall less than 50mm deep. Protection is by rubber type capping. There is normally a warden in charge of the complex most of the time. I propose to fit rcbos on the ground floor socket circuits but can I get away not fitting on the rest of the installation as I did not allow for this when i originally quoted? My only get to this I believe would be that the warden would police the communal areas and is a type of competent person - flimsy I know but any other suggestions?

John

isitnow · Sep 17, 2011

could you not just get a 4 pole rccb main switch at 30ma, considering its the communal db im assuming theres only a couple of ring mains for cleaners sockets and lighting and maybe a door entry supply etc, also by changing the main switch you could do away with the individual rcbos for cost issue although seperate rcbos are ideal, i wouldnt put trust in other people if the jobs done properly atleast you could sleep easy as you being the last spark there youre liable for the work and its you that would have to go to court if something happened?

pennywise · Sep 17, 2011

How many ways have you used?

alli · Sep 17, 2011

Could you discuss with your client the benefits of RCBO's and the extra cost, pointing out that if there is a fault on any part of the electrical installation only that part/flat will be effected, and the rest of the installation would function normally, This would cause the least disruption to the other occupiers/tenants, and well worth the extra cost

Knobhead · Sep 17, 2011

Why are you changing the board in the first place?
The landlords (communal) supply, why can’t that be supplied from a 17[SUP]th[/SUP] RCD protected board purely for the communal areas.
Each flat needs it’s own RCD in the flat. Not down a flight of stairs. A cartridge fuse is all that’s required to protect each individual feed.

As to fitting a 30mA RCD to protect the whole lot, I’ll treat that with the derision it deserves. Not aimed at the OP.

adslev · Sep 17, 2011

Well he mentions communal circuits so we must assume he is talking about the corridors and stairwells etc not supplies to flats, theirs not a vast difference in price between 60898's and 61009's, so for the extra few pound notes it would be worth it in the long run, that's also assuming its 4 way 3 phase board (12 circuits)and not a 12 way 3 phase(36 circuits)

isitnow · Sep 17, 2011

Tony said:
Why are you changing the board in the first place?
The landlords (communal) supply, why can’t that be supplied from a 17[SUP]th[/SUP] RCD protected board purely for the communal areas.
Each flat needs it’s own RCD in the flat. Not down a flight of stairs. A cartridge fuse is all that’s required to protect each individual feed.

As to fitting a 30mA RCD to protect the whole lot, I’ll treat that with the derision it deserves. Not aimed at the OP.

tony the issue was the cost of the original quote as he mentioned as did he mention it was a communal db and didnt mention the flats or their protection what so ever, you basically slated what i said then said the same thing the main switch i mentioned was for the landlords db not a mains rcd at 30ma that would be stupid, but i agree a 17th standard db protecting the communal db sorts out the problem

sparky200 · Sep 18, 2011

Many thanks to all of you for taking the time to reply. Just to clarify a couple of items. Firstly the board is 36 way ie 12way TP&N. This feeds communal lights inside and out (inc non maintained emer) and sockets on 4 floors, a small communal kitchen, small laundry and rec area + fire alarm and boiler circuits. The flats are supplied individually from separate feeder panel. The existing board is being changed due to asbestos arc shields and practicability of resetting mcbs. Proposing to replace with merlin board but rcbos are north of £55 cost ( such a rip off)ion to . Did initially give consideration to 4 pole rccb and moving the critical circuits off to another board but as op said in practice if this operates just relying totally on emerg lights until reset.

Thanks again for comments, thinking that rcbos are only option and if re-quote not acceptable move on.

John

malcolmsanford · Sep 18, 2011

Sparky just to throw my tuppence worth I would certainly not be thinknig of putting a 100 amp 30mA RCCB main switch as this will cause more problems that it is worth.

I assume your worry is the buried cables and sockets that require additional RCD protection.

Well if it were me I would be going down the line of the installation is under the supervision of a skilled or instructed person, and I would emphasize the instructed.

The chances are of anyone drilling into a wall of a communal area of a block of flats without either the landlord given permission, or the instructed person knowing is very slim, and so I would take that not much chance of a situation happening.

The sockets and the laundry are slightly different. You could put the sockets on RCBO,s how many circuits are there?

You could in fact fit RCD sockets which are a lot cheaper than the 55 pounds you quoted per RCBO, how many sockets are there?.

But for the bottom line again the installation is under supervision of an instructed person in that warden, and you may feel you can rely on the MCB devices especially if you are getting good Zs values and the MCB will be tripping under fault conditions in 0.1secs

Who uses this small kitchen again I assume the Warden and perhaps sometimes cleaners and staff, again the sockets the same scenario as the hall sockets

Finally the laundry I assume this is used by the tenants, so how are the appliances connected??

sparky200 · Sep 18, 2011

Malcolm thanks for your detailed reply. Having considered the definition of the 'instructed person' this could be an option to consider especially if I follow up with a written instruction to the client.

Skilled person. A person with technical knowledge or sufficient experience to enable him/her to avoid dangers that electricity may create.

Instructed person. A person adequately advised or supervised by skilled persons to enable him/her to avoid dangers which electricity may create. The workplace (Health & Safety at Work Regulations)

I did allow for 4 rcbo's to cover the ground floor circuits + laundry ( which in affect is just 2 x 3kw tumble dryers on own circuit) but if I consider the lighting circuits as well as the upstairs sockets that would add another 10 RCBOs which has the potential for an additional £550 cost. Did check the price of MEM Eaton but without serious pressure on discount not that much different. Purely out of interest would like to know what the group might consider as a labour material price for this type of job bearing in mind also need to maintain essential supplies whilst switch over takes place and disposal of asbestos arc shields.

John

malcolmsanford · Sep 18, 2011

http://www.asbestosremovalcompany.co.uk/downloads/a30.pdf This H&S document is for the asbestos John.

Well again the 3kw tumbles you could put on double pole switches if they are now going through a BS 1363 socket, and so not having to worry about regulation 411.3.3 if that is the case.

To be honest I would try and put all the sockets on an RCBO as you never know.

Engineer54 · Sep 18, 2011

sparky200 said:
Many thanks to all of you for taking the time to reply. Just to clarify a couple of items. Firstly the board is 36 way ie 12way TP&N. This feeds communal lights inside and out (inc non maintained emer) and sockets on 4 floors, a small communal kitchen, small laundry and rec area + fire alarm and boiler circuits. The flats are supplied individually from separate feeder panel. The existing board is being changed due to asbestos arc shields and practicability of resetting mcbs. Proposing to replace with merlin board but rcbos are north of £55 cost ( such a rip off)ion to . Did initially give consideration to 4 pole rccb and moving the critical circuits off to another board but as op said in practice if this operates just relying totally on emerg lights until reset.

Thanks again for comments, thinking that rcbos are only option and if re-quote not acceptable move on.

John

Merlin Gerin DB's are multi configurable with the multi 9 system, so i'm sure you can figure a way to get RCD protection to those circuits you consider necessary, while leaving those that don't on MCBs. Going with RCBOs for every socket circuit is an expensive alternative, to splitting the circuits between say 3 RCDs or combination of RCDs and RCBOs. If you don't already have a multi 9 catalogue then get hold of one, and see if you can't come up with a suitable solution. I'll be surprised if you can't!! ....

glasgowbiker42 · Sep 18, 2011

Try wylex they are much cheaper though obviously not the same quality as MEM.
Also always clarify on any price you issue exactly what you have allowed for.