I'm looking for some advice on how to improve the design of the electrical
wiring I've inherited from the previous owners of my house. The issue of
concern lies with the supply to the detached garage and pond (2 pumps and a
UV clarifier).

Last winter one of the O-rings in the UV clarifier failed whilst we were
away and let water into the electrics, this of course tripped the RCBO on
the circuit. The problem is that the garage and the pond equipment are
supplied by a fused spur from the downstairs ring-main, so it was goodbye to
the contents of the fridge-freezer and a some programmes scheduled to be
recorded on the Sky+ box.

Rather than just regularly replacing o-rings and the pond equipment and
crossing my fingers I want to find a way of stopping this happening again. I
think the obvious solution is to put all the garage and pond wiring on an
independent circuit fed from the consumer unit in the house but the consumer
unit looks to be at full capacity so presumably I would need to replace this
alltogether and start again as well as redoing much of the external wiring.
This sounds to me like an expensive and complex job probably requiring a
professional.

The only other option I can think of is replacing the fuse unit in the fused
spur to the garage with an RCD version but I'm presuming this will not
guarantee the the whole ring main won't still trip out if there is a fault.

Any advice welcome.

Martin Cook

On Sun, 21 Nov 2004 22:08:54 +0000 (UTC), "Martin Cook"
strung together this:

Any advice welcome.

I would be looking at getting a dedicated supply down to the garage
and pond.
If the existing CU is full then as you only need a 13A supply I would
remove one of the lower powered circuits from the existing consumer
unit on the non-RCD side.
Use this circuit, (with a 32A MCB fitted to it), to run a 6mm cable to
a 2 way consumer unit with main switch incomer next to the existing
one. Populate this 2 way CU with a MCB rated for the circuit you just
removed and a 16A RCBO for the outside circuit. If 16A is over-rated
for the cable that is running outside then fit a switched fused spur
between the RCBO and the supply going outside.
The other alternative is to fit an RCD onto an existing non-RCD'd
circuit to feed the outside.
The above assumes you have a split load consumer unit, if it is one
RCD supplying the whole installation then you're going to have to
change it or add another consumer unit with RCD for the outside
circuit, wired into a Henley block between the existing CU and meter
position.
--

SJW
A.C.S. Ltd
Please reply to group or use 'usenet' in email subject

Martin
Connect it to your nearest lamp post, then if it happens again you will not
be affected.


"Martin Cook" wrote in message
...
I'm looking for some advice on how to improve the design of the electrical
wiring I've inherited from the previous owners of my house. The issue of
concern lies with the supply to the detached garage and pond (2 pumps and
a UV clarifier).

Last winter one of the O-rings in the UV clarifier failed whilst we were
away and let water into the electrics, this of course tripped the RCBO on
the circuit. The problem is that the garage and the pond equipment are
supplied by a fused spur from the downstairs ring-main, so it was goodbye
to the contents of the fridge-freezer and a some programmes scheduled to
be recorded on the Sky+ box.

Rather than just regularly replacing o-rings and the pond equipment and
crossing my fingers I want to find a way of stopping this happening again.
I think the obvious solution is to put all the garage and pond wiring on
an independent circuit fed from the consumer unit in the house but the
consumer unit looks to be at full capacity so presumably I would need to
replace this alltogether and start again as well as redoing much of the
external wiring. This sounds to me like an expensive and complex job
probably requiring a professional.

The only other option I can think of is replacing the fuse unit in the
fused spur to the garage with an RCD version but I'm presuming this will
not guarantee the the whole ring main won't still trip out if there is a
fault.

Any advice welcome.

Martin Cook

"PhilÅ" wrote in message ...
Martin
Connect it to your nearest lamp post, then if it happens again you will not
be affected.


Street lighting columns are actually fused with BS88 fuses. The REC
install a fused cutout or they are private supply from a feeder
pilliar in which case they have an isolator fitted.

Jon.

Thanks. This is a great help.

I have had a look again at my Consumer Unit. Its a Crabtree
Starbreaker (1995 vintage) with a capacity of ten modules, nine are in
use.

It is laid out as follows, left to right:

1/2 Main switch (100A) - occupies 2 modules.
3 MCB B32 - Cooker
4 RCBO B32 - Downstairs Ring Main + Garage/Pond Spur
5 30mA Device (trips RCBO32 when test button pressed)
6 MCB B32 - Upstairs Ring Main
7 MCB B16 - Central Heating
8 MCB B6 - Downstairs Lighting Circuit
9 MCB B6 - Upstairs Lighting Circuit
10 Blanking Plate

Martin

I would be looking at getting a dedicated supply down to the garage
and pond.
If the existing CU is full then as you only need a 13A supply I would
remove one of the lower powered circuits from the existing consumer
unit on the non-RCD side.
Use this circuit, (with a 32A MCB fitted to it), to run a 6mm cable to
a 2 way consumer unit with main switch incomer next to the existing
one. Populate this 2 way CU with a MCB rated for the circuit you just
removed and a 16A RCBO for the outside circuit. If 16A is over-rated
for the cable that is running outside then fit a switched fused spur
between the RCBO and the supply going outside.
The other alternative is to fit an RCD onto an existing non-RCD'd
circuit to feed the outside.
The above assumes you have a split load consumer unit, if it is one
RCD supplying the whole installation then you're going to have to
change it or add another consumer unit with RCD for the outside
circuit, wired into a Henley block between the existing CU and meter
position.

Martin Cook wrote:

I have had a look again at my Consumer Unit. Its a Crabtree
Starbreaker (1995 vintage) with a capacity of ten modules, nine are in
use.

It is laid out as follows, left to right:

1/2 Main switch (100A) - occupies 2 modules.
3 MCB B32 - Cooker
4 RCBO B32 - Downstairs Ring Main + Garage/Pond Spur
5 30mA Device (trips RCBO32 when test button pressed)
6 MCB B32 - Upstairs Ring Main
7 MCB B16 - Central Heating
8 MCB B6 - Downstairs Lighting Circuit
9 MCB B6 - Upstairs Lighting Circuit
10 Blanking Plate

I shall assume that 4 and 5 are a single device - the 32A/30mA RCBO -
and that all the other circuits have no RCD protection.

That being the case you could install a suitably-rated MCB in position
10 (hopefully the busbar finger won't have been cut off) to feed your
new outdoor circuit. Then provide 30mA RCD protection somewhere
downstream - e.g. in a separate 2-module enclosure adjacent to the CU,
or by means of an 'RCD spur' unit elsewhere.

--
Andy

"Andy Wade" wrote
| Martin Cook wrote:
| I have had a look again at my Consumer Unit. Its a Crabtree
| Starbreaker (1995 vintage) with a capacity of ten modules,
| nine are in use.
| It is laid out as follows, left to right:
| 1/2 Main switch (100A) - occupies 2 modules.
| 3 MCB B32 - Cooker
| 4 RCBO B32 - Downstairs Ring Main + Garage/Pond Spur
| 5 30mA Device (trips RCBO32 when test button pressed)
| 6 MCB B32 - Upstairs Ring Main
| 7 MCB B16 - Central Heating
| 8 MCB B6 - Downstairs Lighting Circuit
| 9 MCB B6 - Upstairs Lighting Circuit
| 10 Blanking Plate
| I shall assume that 4 and 5 are a single device - the 32A/30mA RCBO -
| and that all the other circuits have no RCD protection.
| That being the case you could install a suitably-rated MCB in position
| 10 (hopefully the busbar finger won't have been cut off) to feed your
| new outdoor circuit.

If position 10 is unavailable then provided the central heating on No7 is
only a pump and controls (i.e. NOT immersion heater as well) you could wire
it through a FCU fused at 3A and and supply the FCU from one of the power
rings. Label the FCU clearly as "CH from xx ring". You could then use the
No7 16A MCB for your outdoor circuit, through an RCD somewhere external to
the CU.

Owain

Lurch wrote in message . ..
On 22 Nov 2004 10:07:53 -0800, (John
Southern) strung together this:

Street lighting columns are actually fused with BS88 fuses.

Well, that depends if they've got a BS88 fuse in them.....

Not quite sure what the anoraky bit was for, but still.

Well i can imagine some t**t breaking a door off to connect into a
column and getting a nice whack from the board cutout.
Ive know people to run xmas lighting from columns just wiried into the
lantern.

Jon.

On Tue, 23 Nov 2004 14:19:09 -0000, "Owain"
strung together this:

If position 10 is unavailable then provided the central heating on No7 is
only a pump and controls (i.e. NOT immersion heater as well) you could wire
it through a FCU fused at 3A and and supply the FCU from one of the power
rings.

Rather than any one, use the upstairs ring as this isn't covered by an
RCBO. That way the heating will still work if there is an earth fault
on the downstairs ring.
--

SJW
A.C.S. Ltd
Please reply to group or use 'usenet' in email subject

"Lurch" wrote
| If position 10 is unavailable then provided the central heating on
| No7 is only a pump and controls (i.e. NOT immersion heater as well)
| you could wire it through a FCU fused at 3A and and supply the FCU
| from one of the power rings.
| Rather than any one, use the upstairs ring as this isn't covered by
| an RCBO. That way the heating will still work if there is an earth
| fault on the downstairs ring.

I did think that, more from the opposite POV of a minor earth leak on the
heating not taking out an RCD protected ring.

Owain

Thanks to everyone for the helpful advice. It looks like I have at
least a couple of good options to go forward with and none of them are
as radical as I had feared!

Martin

On Tue, 23 Nov 2004 09:11:29 +0000, Andy Wade
strung together this:

That being the case you could install a suitably-rated MCB in position
10 (hopefully the busbar finger won't have been cut off)

No finger, the old Crabtree ones were the screw on type, the screw
fitted into a recess rather than a finger fitting under a screw.
Minor technicality I know!

to feed your
new outdoor circuit. Then provide 30mA RCD protection somewhere
downstream - e.g. in a separate 2-module enclosure adjacent to the CU,
or by means of an 'RCD spur' unit elsewhere.

I think this would be what I would do if I were called in to do the
job. Easiest solution all round, from a materials and labour point of
view, and it's effective.
--

SJW
A.C.S. Ltd
Please reply to group or use 'usenet' in email subject