Shower fuse ratings ??
Les
for 6 sq mm cable.
Existing cable with a 7kW shower at present, I would like
to know what kW I can safely go up to.
Many thanks
Les
simon beer
probably be up rated to 10mm to comply with today's standards. Might make a
difference how long the run of cable is. Have had no problems with the
shower or fuses, but some one will tell me that this is probably by luck.
John Diamond
grouping of cables, etc etc.......Between you me and the Garden gate you'd
probably get away with an 8.5KW
JD
www.m-n-s.com
Les <super...@lineone.net> wrote in message
news:8lfghb$ak9$1...@supernews.com...
hor...@breathemail.net
as long as the cable run is less than 23 meters and that you are not
running the cable though trunking then you should use 10 mm sq.
If you want to use have 9.5 kW you MUST use 10 mm sq. cable and run a
separate earth as the earth in the cable is not adequate enough for the
load.
It is also good practice to fit a RCD between the swtich and the fuse on
the consumer unit as an extra measure of safety.
Electricity and Water the perfect couple....
Hope this helps
Alasdair
Hope this help
Dave Plowman
<hor...@breathemail.net> wrote:
> If you want to use have 9.5 kW you MUST use 10 mm sq. cable and run a
> separate earth as the earth in the cable is not adequate enough for the
> load.
Never heard this one before. Why do they provide an earth conductor then?
--
* I'm planning to be spontaneous tomorrow *
Dave Plowman dave....@argonet.co.uk London SW 12
RIP Acorn
Chris French
>
>If you want to use have 9.5 kW you MUST use 10 mm sq. cable and run a
>separate earth as the earth in the cable is not adequate enough for the
>load.
>
What would be the point of T&E with an earth conductor off to small a
size?
--
Chris French, Leeds
John Diamond
<hor...@breathemail.net> wrote in message
news:397C15E2...@breathemail.net...
>
> If you want to use have 9.5 kW you MUST use 10 mm sq. cable and run a
> separate earth as the earth in the cable is not adequate enough for the
> load.
>
Cheers JD
Ed Sirett
Chris French wrote in message <47SU0$AiPIf...@calendula.ezesurf.co.uk>...
>>separate earth as the earth in the cable is not adequate enough for the
>>load.
>>
>
>What would be the point of T&E with an earth conductor off to small a
>size?
>--
The only reason I can think that the additional earth is required is to get
the earth fault loop impedance low enough to comply with the 0.4s
disconnection time required in conjuction with the 40/45/50 A MCB.
IMHO it is better and simpler to include an RCD in the spply circuit.
Q: If the earthing is enhanced in this way are the design calculations based
only on the additonal earth wire or do you take both the aditional and the
6mm² earth conductor in the main cable together?
Ed Sirett
Property Maintainer - North London.
hor...@breathemail.net
Ed Sirett wrote:
A. The additional earth is required to achieve a low earth fault loop impedance
so that a disconnection time of 0.4s or less is attained. as for the earth in
the 10 mm sq. cable this is not used. IMHO I would use an RCD as well, maybe
this is a tad OTT and it adds extra cost to the project but I believe to always
err on the side of caution.
Electrocution, house fires & insurance investigators are not my favourite
visitors.
Q. Am I too paranoid ?
Alasdair
Jim Colyer
kinda silly me-thinks!
unless you are using 3036 fuses as your protective device, or are on a TT
supply system, the earth in 10mm is adequate!
why would it be made otherwise??
as previosly mentioned an easier way would be to use an rcd if the efli
would be too high to guarentee .4 disconnection (but this is HIGHLY unlikely
anyway)
--
Many Thanks, Jim Colyer
Andy Wade
>unless you are using 3036 fuses as your protective device,
This thread is rambling. If you don't want to do any sums, look at the
'Conventional Circuits' tables in the On-Site Guide:
Assuming 10mm^2 twin & earth cable only (CPC size is 4mm^2) and a 45A
protective device, with 0.4s disconnection time required [1]:
1. For TN-C-S earthing (PME supply), worst case external earth fault loop
impedance (Ze) 0.35 ohm:
- device BS 1361 cartridge fuse: Max. cct. length is 32m, limited by
total earth fault loop impedance (Zs),
- device BS 3036 rewireable fuse: Max. cct. length is 34m, limited ditto,
- device MCB type B: Max. cct. length is 49m, limited by voltage drop.
2. For TN-S earthing (cable sheath earthing), worst case external earth
fault loop impedance 0.8 ohm:
- device BS 1361 cartridge fuse: Compliance not possible due to excessive
Zs,
- device BS 3036 rewireable fuse: Ditto
- device MCB type B: Max. cct. length 35m, limited by Zs.
A larger CPC is only required in order to increase the permissible cct.
length up to the 49m voltage drop limit. It would not help in either of the
'not possible' cases (TN-S system and fuse protection) since either type of
fuse needs a total Zs lower than the external Ze value (a clear
demonstration of one advantage of MCB's).
> or are on a TT
>supply system, the earth in 10mm is adequate!
On a TT system you'd have to use an RCD, so this all becomes irrelevant.
[1] What is also very much to the point here is that if you can use
Amendment 3 -- the new bathroom rules -- then the problem goes away. The
compulsory requirement for 0.4s disconnection time for bath/shower rooms has
been removed in the new version, so 5s disconnection time is permitted, as
for any other fixed equipment. This relaxation is presumably on the
assumption that the local supplementary bonding will reduce touch voltages
to below a safe value. The old 0.4s requirement probably pre-dates the use
of supplementary bonding, so can, I presume, now be considered obsolete.
(Just for the avoidance of any doubt, let's be clear that the requirement
for 0.4s disconnection time for circuits feeding sockets DOES STILL APPLY.)
--
Andy
One of the Henning Family
hor...@breathemail.net wrote:
> Electrocution, house fires & insurance investigators are not my favourite
> visitors.
>
> Q. Am I too paranoid ?
>
> Alasdair
You missed "Jehovas" and "Mormons" as well as double-glazing salesmen!
Mungo ;-)
Les
Les