IET logo
 
IET
Decrease font size
Increase font size
Topic Title: Max distance from meter to consumer unit
Topic Summary: What is the max distance from the supply to the consumer unit
Created On: 10 August 2005 09:36 AM
Status: Post and Reply
Linear : Threading : Single : Branch
Search Topic Search Topic
Topic Tools Topic Tools
View similar topics View similar topics
View topic in raw text format. Print this topic.
 10 August 2005 09:36 AM
User is offline View Users Profile Print this message



deleted_Desmo

Posts: 4
Joined: 10 August 2005

I am designing a barn conversion and would like to move the meter to an external wall. The external move has been OKd by the supply company and an access box will be installed. However, I cannot get a consistent response from the proffesional electricians regarding where I may put the consumer unit. I have been told variously "3.0m max" to "it doesn't matter so long as the cable is the correct capacity". I have very little choice where to put the external box.

My preffered room layout has a shower room on the internal wall of where the external meter will be. This is clearly an unsatisfactory location for a consumer unit. One option is to take an armoured cable externally to the kitchen - a distance of about 6m. If 3m is the max then I will need to redesign my floor plan.

Any advice would be appreciated.

Edited: 10 August 2005 at 09:41 AM by deleted_Desmo
 10 August 2005 09:53 AM
User is offline View Users Profile Print this message



peteTLM

Posts: 3152
Joined: 31 March 2005

Very similar to another one on here...
The CU could be 50m away from the meter as long as the cables are dimensioned for the job, and all factors have been taken into account. Volt drop and the effect on the Earth loop impedance are the main considerations.
Put a switchfuse next to the meter and take it away on Armoured SWA, so you are looking at either 16mm or 25mm cable depending on your load, 3 core (assuming single phase supply), using 1 core as the earth path, and earthing the armour as well.
Is the supply underground or overhead on poles?
P

-------------------------
----------------------------------------
Lack of planning on your part doesn't make it an emergency on mine....

Every man has to know his limitations- Dirty Harry
 10 August 2005 10:11 AM
User is offline View Users Profile Print this message



deleted_beenthere

Posts: 111
Joined: 24 May 2005

The rule used to be if the meter was more than 2 m away from the cut- out then you have to out a seperate switch fuse by the meter therfore the c/u could be any distance you like as long as you take into account the obvious ,VD ELI etc. although you should put the C/U as close to the intake as posible.

Cheers

Keith
 10 August 2005 10:12 AM
User is offline View Users Profile Print this message



deleted_beenthere

Posts: 111
Joined: 24 May 2005

sorry that should have read if the C/U is more than 2m away from the cut-out
 10 August 2005 10:26 AM
User is offline View Users Profile Print this message



deleted_Desmo

Posts: 4
Joined: 10 August 2005

Supply is single phase on overhead poles. Immeadiatly after the meter it splits via a Henley box to two 65A RCD switches with 16mm cable to each. One feeds the outbuildings and the other the barn. Originally there were simple old style fused boxes. I have been advised that it will be OK to leave the outbuilding supply in place (upgrading the fuse box) and that the other supply will go to the conversion.
 10 August 2005 10:53 AM
User is offline View Users Profile Print this message


Avatar for Legh.
Legh

Posts: 3488
Joined: 17 December 2004

hello Beenthere,
I think its 3m now 473-02-02 (i)
Legh

-------------------------
Why do we need Vernier Calipers when we have container ships?

http://www.leghrichardson.co.uk

"Science has overcome time and space. Well, Harvey has overcome not only time and space - but any objections."
 10 August 2005 11:03 AM
User is offline View Users Profile Print this message


Avatar for tomgunn.
tomgunn

Posts: 3236
Joined: 25 May 2005

surely it doesnt matter where....? As long as the cable is man enough!?!?! Dont tell me theres a restriction on this as well now?

Tom

-------------------------
Tom .... ( The TERMINATOR ).

handyTRADESMAN ... haha

Castle Builders

Why did Nick Clegg cross the road? Because he said he wouldn't!

I can resist anything..... except temptation! ( Karl Gunn ).
 10 August 2005 11:29 AM
User is offline View Users Profile Print this message


Avatar for Legh.
Legh

Posts: 3488
Joined: 17 December 2004

Ah Beenthere,
If, lets say, the tails are the same size as the incoming supply cables - 25mm2 - then you may consider 473-02-02 (ii) and (iii) altough I wouldn't advise it in a domestic environment, particularly for the reasons of 473-02-02 (iii)
Legh

-------------------------
Why do we need Vernier Calipers when we have container ships?

http://www.leghrichardson.co.uk

"Science has overcome time and space. Well, Harvey has overcome not only time and space - but any objections."
 10 August 2005 01:39 PM
User is offline View Users Profile Print this message



peteTLM

Posts: 3152
Joined: 31 March 2005

so,
the supply comes in via overhead, meter, and then splits into 2x RCD's to feed the outbuildings and the Barn.
Surely there should be some sort of fusing at the split of the supply- RCD's dont provide short cct protection. It is essentially split into 2 sub mains.

How big is this barn? Is a 65A RCD going to be man enough to cope with the load? What is the rating of the Suppliers fuse?
P

-------------------------
----------------------------------------
Lack of planning on your part doesn't make it an emergency on mine....

Every man has to know his limitations- Dirty Harry
 10 August 2005 09:45 PM
User is offline View Users Profile Print this message



kbro6

Posts: 38
Joined: 04 May 2005

Hi All,

If the meter tails exceed 3m, then you will need a 80 amp KMF switch (Double pole switch fuse) to protect the tails (assuming earth loop, volt drop etc. is OK). For 6m 25mm should be fine. Check on your load though. I've been working on an apartment block in Birmingham and the run is about 70 metres from the fuse room. Cables are 25mm and 35mm (35 mm for furthest away). Hope this helps.
 10 August 2005 10:06 PM
User is offline View Users Profile Print this message



Lethean

Posts: 196
Joined: 19 April 2004

Interesting to note MEM say the KMF is time served, but it does not have a BS number and correct me if I'm wrong, strictly speaking it should be listed as a departure.
 11 August 2005 01:05 PM
User is offline View Users Profile Print this message



deleted_Desmo

Posts: 4
Joined: 10 August 2005

The proposed barn conversion is single storey with two bedrooms. Heating system not yet finalised and could be either electric or gas.

The suppliers fuse is 100A. I understand that the Henley box and 16mm tails and switches are their responsibility. Clearly, if 25mm is required from the switch to the Consumer Unit then the tails will need to be changed. If, as kbro6 suggests, the switches need to be 80A KMF then they will have to be changed as well.

The situation I want to avoid is going ahead and have either the suppliers electrician or the builders electrian say that they cannot complete the work because it is not permitted under the regulations. It seems to me that there seems to be differing opinions on this forum as to what is permitted.
 11 August 2005 03:50 PM
User is offline View Users Profile Print this message



tonysung

Posts: 630
Joined: 14 September 2001

I think what you need is to ask if the supplier/contractor would agree with you putting a weather-resistance splitter terminal box (with the same Gas/electric box key arrangement for accessibility) adjacent to their meter box, from each of the building run a swa 16mm cable (preferably with a separate earthing cable or one of the core can be used as an earth cable) from each of the CCU to the splitter box; and at the supply side of the CCU, use a HRC 63A fuse to protect the RCD and the CCU in the buildings. This will leave the supplier to simply connect their 1.5m long meter tails into your own splitter terminal box.

However, you should have the arrangement agreed by the supply company and your electrical contractor before any work being carried out. The arrangement may not 100% comply with BS7671 but should comply with the fundamental safety principles. It is likely that the electrical contractor may note it as a departure from BS7671. Perhaps others can help to clarify it.

-------------------------
Tony Sung
 11 August 2005 10:59 PM
User is offline View Users Profile Print this message



kbro6

Posts: 38
Joined: 04 May 2005

Hi Desmo,

The suppliers side is only up to the meter itself. It's your responsibility after that. I've been on jobs where the REC as put a DP switch on after connecting the meter tails. Then I just come along and connect straight into it. Depends where you are though.
Kbro6
Statistics

See Also:



FuseTalk Standard Edition v3.2 - © 1999-2014 FuseTalk Inc. All rights reserved.