Help with installing consumer unit

[newdomestic]

Ok here goes..
I am about to install a new c/u in my home for inspection as my first job to be inspected by napit or elecsa(havent decided which yet, any thoughts?)

Looking at the tails they say 35mm and appear to have 10mm earth to board.

The new c/u came with 25mm tails , 16mm cpc and 10 mm cpc.

1st question, do I need to replace the tails, they look in good condition? I live in an ex council house so is that why the over spec on the tails?

The tails and earth are sheathed in grey plastic where they go into the walls (looks similar to cooker cable) the house is timber framed and has stud walls throughout.. the cable runs behind the brick skin up to ist floor level, then under the floor boards and drops down into the c/u through the gap in the internal wall. (so is thi buried???)

2nd question do I need to upgrade the cpc to the board to 16mm. It is TN-C-S.

3rd question the equ bonding is separate and runs from the tails box (as does the other cpc), it is 10mm also,
it is one contiuous and goes from gas to c/heating to water,.. problem is the water one is not within 600mm of stop tap. As i cannot extend due to 17th ed do I replace with 3 seperate cables from a an earthing block in the meter board which is located outside?

I think I know the answers that are forthcoming, but thought it best to check.

I will be grateful for all your input

Regards Paul

 

[SirKit Breaker]

The size of your tails is determined by the rating of the cutout fuse. I like most use 25mm tails, you dont need to replace them as long as they test out OK electrically and visually and are at least 16mm with 80a fuse or 25mm with 100a fuse. The CPC must be a minimum of 50% cross sectional area of the supply tails so 16mm for 25 and 10mm for 16.
The main bonding cables should be a minimum of 50% of the main CPC so 10mm for 16 and 6mm for 10, its is acceptable to retain the 6mm bonding cables if it is not practical to upgrade due to whatever reason.This must be noted as a departure on the certs.

It is also acceptable to link gas to water to whatever if it isnt practical to do them individually, but make sure you verify connection back to the earth rail in the board.

If you cant bond within 600mm then do it where you can, as you cant not bond.

The regs are sometimes seen as the be all and end all of electric, but sometimes common sense has to prevail and we must always leave the job safe.

Cheers............Howard

 

[Mac]

Ok here goes..
I am about to install a new c/u in my home for inspection as my first job to be inspected by napit or elecsa(havent decided which yet, any thoughts?)

Looking at the tails they say 35mm and appear to have 10mm earth to board.

The new c/u came with 25mm tails , 16mm cpc and 10 mm cpc.

1st question, do I need to replace the tails, they look in good condition? I live in an ex council house so is that why the over spec on the tails?

The tails and earth are sheathed in grey plastic where they go into the walls (looks similar to cooker cable) the house is timber framed and has stud walls throughout.. the cable runs behind the brick skin up to ist floor level, then under the floor boards and drops down into the c/u through the gap in the internal wall. (so is thi buried???)

2nd question do I need to upgrade the cpc to the board to 16mm. It is TN-C-S.

3rd question the equ bonding is separate and runs from the tails box (as does the other cpc), it is 10mm also,
it is one contiuous and goes from gas to c/heating to water,.. problem is the water one is not within 600mm of stop tap. As i cannot extend due to 17th ed do I replace with 3 seperate cables from a an earthing block in the meter board which is located outside?

I think I know the answers that are forthcoming, but thought it best to check.

I will be grateful for all your input

Regards Paul

The council are the biggest bodgers in the world mate.What do you mean the CU came with new tailsHow far do the tails run from the meter to the CU?You should have a 16mm earth from the cut out to the CU and 10mm for the equipotential bonding to gas and water.It sounds like they may have run 1 continuous earth for the equipotential bonding,which is ok, if all they have done is strip the sheath and not cut the cable.

 

[newdomestic]

The main fuse is 100ma and is using 35mm tails 10mm cpc, the run from the meter is close on 3m as it goes to the first floor and drops down.

I guessed i need to use 16mm cpc to board and replace the equ bonding as the water one isnt within 600mm of the stopcock

ps. i got the CU off ebay!! new, with full 12 way 17th compliant with 4 RCBO's and tails and cpc's all wylex, and also included crimps and extra wire for extending

 

[Mac]

You could take a 16mm from the meter box to an MET near the CU.16 mm from there to the CU and take the 10mm from the MET to your utilities.It only has to be within 600mm of where it enters the premises or where practical

 

[newdomestic]

ps. Sirkit says that the main board bonding should be at least half the supply, i presume i will have to change the 35mm to 25mm so i can comply with 16 main earth??
I thought i had read that 16mm was ok with 35mm??

I thought equ had to be connected to the first run of water pipe b4 branching??

 

[Mac]

True.I have always used 25mm tails in house rewires,have never come across 35mm in domestic.Are you sure they are 35mm,the sheathing was pretty thick years ago

 

[newdomestic]

one final thing, can i take the equ bonding from the earth bar on the board there is space , and it is possible to screw the MET thru plastic casing into wood mounting or is this outlawed..

I ask this as the pre drilled holes in wood frame of house will be tightish if i more CPC's or can i have the MET loose in the void between the floor boards and ceilig or mount on joist??

pps. is there a length limit on tails??

 

[Mac]

ps. Sirkit says that the main board bonding should be at least half the supply, i presume i will have to change the 35mm to 25mm so i can comply with 16 main earth??
I thought i had read that 16mm was ok with 35mm??

I thought equ had to be connected to the first run of water pipe b4 branching??

It does or where practical

 

[newdomestic]

ok sorry for bein pain in the ---, just wanna get this right!! the twin with earth that runs to the board looks cooker size stuff, cant see any markings, but there is some sheathing in the metercupboard over the taiis on the two supplies from the meterl to where the grey shaething has been cut back to, that says BICC 35mm

 

[Mac]

ok sorry for bein pain in the ---, just wanna get this right!! the twin with earth that runs to the board looks cooker size stuff, cant see any markings, but there is some sheathing in the metercupboard over the taiis on the two supplies from the meterl to where the grey shaething has been cut back to, that says BICC 35mm

No worries then mate,but regarding the earthing,have you got your BRB to hand.BS7671 2008 17th Edition says;
Reg 544.1.2 The main equipotential bonding connection to any gas, water or other service shall be made as near as practicable to the point of entry of that service into the premises

 

[Amp David]

Hello newdomestic,

Don't mean to put you down or take the pee, but are you sure you're ready yet for an assessment.
Seem to be asking some quite basic questions, as all the answers are in the BRB anyway.

 

[newdomestic]

Thanks for your input Amp.. but if you read through carefully the posts, the first one states i knew what answers where coming back... and alludes to solutions.
I was confused by the current set up as the tails are labeled up as 35mm, I dont profess to have the most practical experience but have passed all the 17th, part p, initial verification..
I know what the books say and was after some practical knowledge from very kind people who replied. This is my first major installation and want to get it right, i dont want to start a job then ask questions . I want to be safe foremost and get full accreditation, otherwise I would be hard pushed to earn a living, which is everyones aim

 

[SirKit Breaker]

I had my annual assessment last month, in discussion with the assessor about other things we got on about the regs and how we interpret and appy them, we agreed that some of them are bollox, whatever you do must be safe be it to the regs or not and as i said earlier common sense must prevail, your assessor is not looking for a job that is to the letter of the regs, he is looking to convince himself that you are capable of working to a safe standard and that you know what you are doing, convince him of these two things and the rest is a walk in the park, i think you are getting too worked up and hung up on this assessment thing, your assessor like mine has been there and done it they are or were all sparkys just like us.

If i were you i`d go for a beer and stop sweating.

 

[Amp David]

I had my annual assessment last month, in discussion with the assessor about other things we got on about the regs and how we interpret and appy them, we agreed that some of them are bollox, whatever you do must be safe be it to the regs or not and as i said earlier common sense must prevail, your assessor is not looking for a job that is to the letter of the regs, he is looking to convince himself that you are capable of working to a safe standard and that you know what you are doing, convince him of these two things and the rest is a walk in the park, i think you are getting too worked up and hung up on this assessment thing, your assessor like mine has been there and done it they are or were all sparkys just like us.

If i were you i`d go for a beer and stop sweating.[/QUOTE]


Sounds like a plan, but not before your assessment