I have an economy seven supply. Two 25mm wires go from the main fuse
block to the meter (presumably live and neutral) and then to a switch
and then to two Henley blocks. From one of these a 25mm wire goes to a
radio controlled switch, and out of this time switch another 25mm wire
goes to a third Henley block. The house supply runs from the first two
blocks, and a separate wire from the third block presumably supplies
live to the night time only supply.


However, there are two 10mm wires from the main fuse block to the radio
switch, and one 6mm wire joins the radio switch to the meter.

Can I assume that none of the Henley blocks is live when the main fuse
is open? In theory any one of the last three wires by-passes the main
switch and could internally connect the night time supply to the live
via the radio switch box. And theoretically could back feed the main
house CUs via the live in connection to the radio switch. Is it safe
to assume with a high degree of reliablity that the internal
construction of the radio switch is such as to make this impossible?

(Obviously I wouldn't work on anything without checking it is not live,
but the radio switch is, after all, a switch and if it could connect
live to the wrong wiring could presumably do it suddenly and
unexpectedly.)



--

Roger Hayter

On 06/02/2019 12:58, Roger Hayter wrote:
I have an economy seven supply. Two 25mm wires go from the main fuse
block to the meter (presumably live and neutral) and then to a switch
and then to two Henley blocks. From one of these a 25mm wire goes to a
radio controlled switch, and out of this time switch another 25mm wire
goes to a third Henley block. The house supply runs from the first two
blocks, and a separate wire from the third block presumably supplies
live to the night time only supply.


However, there are two 10mm wires from the main fuse block to the radio
switch, and one 6mm wire joins the radio switch to the meter.

Can I assume that none of the Henley blocks is live when the main fuse
is open? In theory any one of the last three wires by-passes the main
switch and could internally connect the night time supply to the live
via the radio switch box. And theoretically could back feed the main
house CUs via the live in connection to the radio switch. Is it safe
to assume with a high degree of reliablity that the internal
construction of the radio switch is such as to make this impossible?

(Obviously I wouldn't work on anything without checking it is not live,
but the radio switch is, after all, a switch and if it could connect
live to the wrong wiring could presumably do it suddenly and
unexpectedly.)




With the main fuse out everything should be dead.

--
Adam

When they were working on mine they switched the house supply off.
ahem. Careful prudent, safe?
Brian

--
----- --
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
"Roger Hayter" wrote in message
...
I have an economy seven supply. Two 25mm wires go from the main fuse
block to the meter (presumably live and neutral) and then to a switch
and then to two Henley blocks. From one of these a 25mm wire goes to a
radio controlled switch, and out of this time switch another 25mm wire
goes to a third Henley block. The house supply runs from the first two
blocks, and a separate wire from the third block presumably supplies
live to the night time only supply.


However, there are two 10mm wires from the main fuse block to the radio
switch, and one 6mm wire joins the radio switch to the meter.

Can I assume that none of the Henley blocks is live when the main fuse
is open? In theory any one of the last three wires by-passes the main
switch and could internally connect the night time supply to the live
via the radio switch box. And theoretically could back feed the main
house CUs via the live in connection to the radio switch. Is it safe
to assume with a high degree of reliablity that the internal
construction of the radio switch is such as to make this impossible?

(Obviously I wouldn't work on anything without checking it is not live,
but the radio switch is, after all, a switch and if it could connect
live to the wrong wiring could presumably do it suddenly and
unexpectedly.)



--

Roger Hayter

ARW wrote:

On 06/02/2019 12:58, Roger Hayter wrote:
I have an economy seven supply. Two 25mm wires go from the main fuse
block to the meter (presumably live and neutral) and then to a switch
and then to two Henley blocks. From one of these a 25mm wire goes to a
radio controlled switch, and out of this time switch another 25mm wire
goes to a third Henley block. The house supply runs from the first two
blocks, and a separate wire from the third block presumably supplies
live to the night time only supply.


However, there are two 10mm wires from the main fuse block to the radio
switch, and one 6mm wire joins the radio switch to the meter.

Can I assume that none of the Henley blocks is live when the main fuse
is open? In theory any one of the last three wires by-passes the main
switch and could internally connect the night time supply to the live
via the radio switch box. And theoretically could back feed the main
house CUs via the live in connection to the radio switch. Is it safe
to assume with a high degree of reliablity that the internal
construction of the radio switch is such as to make this impossible?

(Obviously I wouldn't work on anything without checking it is not live,
but the radio switch is, after all, a switch and if it could connect
live to the wrong wiring could presumably do it suddenly and
unexpectedly.)




With the main fuse out everything should be dead.

True, but I only want to change an MCB for an RCBO in the economy 7 CU
and would prefer to rely on the main switch if it isafe to do so.
Removing the main fuse is potentially hazardous, isn't it?

--

Roger Hayter

Brian Gaff wrote:

When they were working on mine they switched the house supply off.
ahem. Careful prudent, safe?
Brian
Where was the switch they used? Or did they take out the main fuse?

--

Roger Hayter

Roger Hayter wrote:

ARW wrote:

On 06/02/2019 12:58, Roger Hayter wrote:
I have an economy seven supply. Two 25mm wires go from the main fuse
block to the meter (presumably live and neutral) and then to a switch
and then to two Henley blocks. From one of these a 25mm wire goes to a
radio controlled switch, and out of this time switch another 25mm wire
goes to a third Henley block. The house supply runs from the first two
blocks, and a separate wire from the third block presumably supplies
live to the night time only supply.


However, there are two 10mm wires from the main fuse block to the radio
switch, and one 6mm wire joins the radio switch to the meter.

Can I assume that none of the Henley blocks is live when the main fuse
is open? In theory any one of the last three wires by-passes the main
switch and could internally connect the night time supply to the live
via the radio switch box. And theoretically could back feed the main
house CUs via the live in connection to the radio switch. Is it safe
to assume with a high degree of reliablity that the internal
construction of the radio switch is such as to make this impossible?

(Obviously I wouldn't work on anything without checking it is not live,
but the radio switch is, after all, a switch and if it could connect
live to the wrong wiring could presumably do it suddenly and
unexpectedly.)




With the main fuse out everything should be dead.

True, but I only want to change an MCB for an RCBO in the economy 7 CU
and would prefer to rely on the main switch if it isafe to do so.
Removing the main fuse is potentially hazardous, isn't it?

In response to a very sensible email suggestion, here are some photos.
As an added bonus, does anyone think a Wylex RCBO will fit in the one
unit CU photoed?

Thanks all for advice.

http://www.photobox.co.uk/album/5568689698

--

Roger Hayter

On 07/02/2019 13:30, Roger Hayter wrote:
Roger Hayter wrote:

ARW wrote:

On 06/02/2019 12:58, Roger Hayter wrote:
I have an economy seven supply. Two 25mm wires go from the main fuse
block to the meter (presumably live and neutral) and then to a switch
and then to two Henley blocks. From one of these a 25mm wire goes to a
radio controlled switch, and out of this time switch another 25mm wire
goes to a third Henley block. The house supply runs from the first two
blocks, and a separate wire from the third block presumably supplies
live to the night time only supply.


However, there are two 10mm wires from the main fuse block to the radio
switch, and one 6mm wire joins the radio switch to the meter.

Can I assume that none of the Henley blocks is live when the main fuse
is open? In theory any one of the last three wires by-passes the main
switch and could internally connect the night time supply to the live
via the radio switch box. And theoretically could back feed the main
house CUs via the live in connection to the radio switch. Is it safe
to assume with a high degree of reliablity that the internal
construction of the radio switch is such as to make this impossible?

(Obviously I wouldn't work on anything without checking it is not live,
but the radio switch is, after all, a switch and if it could connect
live to the wrong wiring could presumably do it suddenly and
unexpectedly.)




With the main fuse out everything should be dead.

True, but I only want to change an MCB for an RCBO in the economy 7 CU
and would prefer to rely on the main switch if it isafe to do so.
Removing the main fuse is potentially hazardous, isn't it?

In response to a very sensible email suggestion, here are some photos.
As an added bonus, does anyone think a Wylex RCBO will fit in the one
unit CU photoed?

Thanks all for advice.

http://www.photobox.co.uk/album/5568689698


You cannot fit a RCBO into that CU. That looks like an old plug in fuse
that has been swapped for a MCB.

Thanks for the pictures.

--
Adam

Roger Hayter wrote:
I have an economy seven supply. Two 25mm wires go from the main fuse
block to the meter (presumably live and neutral) and then to a switch
and then to two Henley blocks. From one of these a 25mm wire goes to a
radio controlled switch, and out of this time switch another 25mm wire
goes to a third Henley block. The house supply runs from the first two
blocks, and a separate wire from the third block presumably supplies
live to the night time only supply.

However, there are two 10mm wires from the main fuse block to the radio
switch, and one 6mm wire joins the radio switch to the meter.

OK, so it sounds to me like the 25mm wires carry the power. The 10mm
ones power the timeswitch, and the 6mm one signals the meter to change
rate. If you can find a model number of the timeswitch you may be able
to Google somthing that will confirm it.

The supply that powers the timeswitch should be isolated from the
switched terminals. If power flowed between them it would be dangerous
for a number of reasons - as you say, the switch would not reliably cut
power, but also with the switch open the electric heaters would run
through a 10mm tail protected only by a 100A fuse. So I think you can be
fairly confident that the switch does in fact cut all output power -
only the timeswitch and meter stay live.

The consumer units should also have shrouds on the incoming terminals,
so as long as the main switch in the CU is also off the CU won't become
live even if power was supplied unexpectedly. If I was working on the
input side of the CU, I'd be tempted to remove the main fuse anyway
(though strictly this is illegal).

It's something to be careful of in multi-rate installations that there's
often not a single switch to cut all power to the building. My house
used to have THTC, which meant there were *four* main switches
(general supply, 24 hour heating, water heating, timed heating). Unless
all four were off, something was still powered or could become powered
under timeswitch control.

Mike

ARW wrote:

On 07/02/2019 13:30, Roger Hayter wrote:
Roger Hayter wrote:

ARW wrote:

On 06/02/2019 12:58, Roger Hayter wrote:
I have an economy seven supply. Two 25mm wires go from the main fuse
block to the meter (presumably live and neutral) and then to a switch
and then to two Henley blocks. From one of these a 25mm wire goes to a
radio controlled switch, and out of this time switch another 25mm wire
goes to a third Henley block. The house supply runs from the first two
blocks, and a separate wire from the third block presumably supplies
live to the night time only supply.


However, there are two 10mm wires from the main fuse block to the radio
switch, and one 6mm wire joins the radio switch to the meter.

Can I assume that none of the Henley blocks is live when the main fuse
is open? In theory any one of the last three wires by-passes the main
switch and could internally connect the night time supply to the live
via the radio switch box. And theoretically could back feed the main
house CUs via the live in connection to the radio switch. Is it safe
to assume with a high degree of reliablity that the internal
construction of the radio switch is such as to make this impossible?

(Obviously I wouldn't work on anything without checking it is not live,
but the radio switch is, after all, a switch and if it could connect
live to the wrong wiring could presumably do it suddenly and
unexpectedly.)




With the main fuse out everything should be dead.

True, but I only want to change an MCB for an RCBO in the economy 7 CU
and would prefer to rely on the main switch if it isafe to do so.
Removing the main fuse is potentially hazardous, isn't it?

In response to a very sensible email suggestion, here are some photos.
As an added bonus, does anyone think a Wylex RCBO will fit in the one
unit CU photoed?

Thanks all for advice.

http://www.photobox.co.uk/album/5568689698


You cannot fit a RCBO into that CU. That looks like an old plug in fuse
that has been swapped for a MCB.

Thanks for the pictures.

OK so its a new CU or delete the economy 7 cirtuit. Thanks, that's
useful to know. It is mainly borderline OCD that makes me want to
change it just because it is the only circuit in the house not protected
by an RCD.

PS I suppose I can't use an RCBO on its own without a mains switch a) to
make servicing the RCBO safer and b) because I won't find an RCBO with
16mm terminals. Is there a more fundamental reason?

(I realise me doing it is all theoretical because of part P, of course,
but I can influence the specs! Another practical electrician question
is whether someone who replaced this CU would have to test the whole
house installation?)

I've carefully avoided checking that the economy 7 circuit is wired as a
ring so far, but I suppose I could always use a smaller MCB.


--

Roger Hayter

Mike Humphrey wrote:

Roger Hayter wrote:
I have an economy seven supply. Two 25mm wires go from the main fuse
block to the meter (presumably live and neutral) and then to a switch
and then to two Henley blocks. From one of these a 25mm wire goes to a
radio controlled switch, and out of this time switch another 25mm wire
goes to a third Henley block. The house supply runs from the first two
blocks, and a separate wire from the third block presumably supplies
live to the night time only supply.

However, there are two 10mm wires from the main fuse block to the radio
switch, and one 6mm wire joins the radio switch to the meter.

OK, so it sounds to me like the 25mm wires carry the power. The 10mm
ones power the timeswitch, and the 6mm one signals the meter to change
rate. If you can find a model number of the timeswitch you may be able
to Google somthing that will confirm it.

The supply that powers the timeswitch should be isolated from the
switched terminals. If power flowed between them it would be dangerous
for a number of reasons - as you say, the switch would not reliably cut
power, but also with the switch open the electric heaters would run
through a 10mm tail protected only by a 100A fuse. So I think you can be
fairly confident that the switch does in fact cut all output power -
only the timeswitch and meter stay live.

Thanks for confirming my thinking, I am much happier for a second
opinion.




The consumer units should also have shrouds on the incoming terminals,
so as long as the main switch in the CU is also off the CU won't become
live even if power was supplied unexpectedly. If I was working on the
input side of the CU, I'd be tempted to remove the main fuse anyway
(though strictly this is illegal).

It looks as though the whole CU will need replacing, the one with the
single, uncovered, MCB in the picture



It's something to be careful of in multi-rate installations that there's
often not a single switch to cut all power to the building. My house
used to have THTC, which meant there were *four* main switches
(general supply, 24 hour heating, water heating, timed heating). Unless
all four were off, something was still powered or could become powered
under timeswitch control.

Mike
That's complicated, did you have four separate incoming cables and main
fuses, or was it all done after the meter?

--

Roger Hayter

On 07/02/2019 23:27, Roger Hayter wrote:

I've carefully avoided checking that the economy 7 circuit is wired as a
ring so far, but I suppose I could always use a smaller MCB.

Aren't E7 storage heater circuits radials?

Mike Clarke wrote:

On 07/02/2019 23:27, Roger Hayter wrote:

I've carefully avoided checking that the economy 7 circuit is wired as a
ring so far, but I suppose I could always use a smaller MCB.

Aren't E7 storage heater circuits radials?

The circuit only supplies two sockets, AFAICS, one for a tumble dryer
(unused) and one for a single small storage heater. It is wired with
2.5mm T&E, so if it isn't a ring it probably wants a smaller MCB than
the 32A one fitted. But I will get round to it, I've only been here 15
years.

--

Roger Hayter

On 08/02/2019 10:55, Mike Clarke wrote:
On 07/02/2019 23:27, Roger Hayter wrote:

I've carefully avoided checking that the economy 7 circuit is wired as a
ring so far, but I suppose I could always use a smaller MCB.

Aren't E7 storage heater circuits radials?

Normally, although it's not a requirement.

--
Adam

On 07/02/2019 23:27, Roger Hayter wrote:
ARW wrote:

On 07/02/2019 13:30, Roger Hayter wrote:
Roger Hayter wrote:

ARW wrote:

On 06/02/2019 12:58, Roger Hayter wrote:
I have an economy seven supply. Two 25mm wires go from the main fuse
block to the meter (presumably live and neutral) and then to a switch
and then to two Henley blocks. From one of these a 25mm wire goes to a
radio controlled switch, and out of this time switch another 25mm wire
goes to a third Henley block. The house supply runs from the first two
blocks, and a separate wire from the third block presumably supplies
live to the night time only supply.


However, there are two 10mm wires from the main fuse block to the radio
switch, and one 6mm wire joins the radio switch to the meter.

Can I assume that none of the Henley blocks is live when the main fuse
is open? In theory any one of the last three wires by-passes the main
switch and could internally connect the night time supply to the live
via the radio switch box. And theoretically could back feed the main
house CUs via the live in connection to the radio switch. Is it safe
to assume with a high degree of reliablity that the internal
construction of the radio switch is such as to make this impossible?

(Obviously I wouldn't work on anything without checking it is not live,
but the radio switch is, after all, a switch and if it could connect
live to the wrong wiring could presumably do it suddenly and
unexpectedly.)




With the main fuse out everything should be dead.

True, but I only want to change an MCB for an RCBO in the economy 7 CU
and would prefer to rely on the main switch if it isafe to do so.
Removing the main fuse is potentially hazardous, isn't it?

In response to a very sensible email suggestion, here are some photos.
As an added bonus, does anyone think a Wylex RCBO will fit in the one
unit CU photoed?

Thanks all for advice.

http://www.photobox.co.uk/album/5568689698


You cannot fit a RCBO into that CU. That looks like an old plug in fuse
that has been swapped for a MCB.

Thanks for the pictures.

OK so its a new CU or delete the economy 7 cirtuit. Thanks, that's
useful to know. It is mainly borderline OCD that makes me want to
change it just because it is the only circuit in the house not protected
by an RCD.

PS I suppose I can't use an RCBO on its own without a mains switch a) to
make servicing the RCBO safer and b) because I won't find an RCBO with
16mm terminals. Is there a more fundamental reason?

(I realise me doing it is all theoretical because of part P, of course,
but I can influence the specs! Another practical electrician question
is whether someone who replaced this CU would have to test the whole
house installation?)

I've carefully avoided checking that the economy 7 circuit is wired as a
ring so far, but I suppose I could always use a smaller MCB.




A couple of options.

First of all find out if is a ring or not. Now is the time to find out!

If not a ring then swap the Wylex box for a new CU with 2 x 20A radial
circuits with RCBOs or a RCD main switch. Don't consider a 2 way garage
CU as you have 25mmm tails. You might just squeeze a 4way with main
switch CU in there.

If it is a ring then

a) swap the sockets for sockets with RCD built into them. Job done in
minutes.


b) swap the Wylex unit for a 32A double width RCBO in a suitable
enclosure (going to be tricky with 25mm tails)

or

c) follow the advice for the radial circuit and have 3 spare ways and
one 32A RCBO.
--
Adam

ARW wrote:

On 07/02/2019 23:27, Roger Hayter wrote:
snip

I've carefully avoided checking that the economy 7 circuit is wired as a
ring so far, but I suppose I could always use a smaller MCB.




A couple of options.

First of all find out if is a ring or not. Now is the time to find out!

If not a ring then swap the Wylex box for a new CU with 2 x 20A radial
circuits with RCBOs or a RCD main switch. Don't consider a 2 way garage
CU as you have 25mmm tails. You might just squeeze a 4way with main
switch CU in there.

If it is a ring then

a) swap the sockets for sockets with RCD built into them. Job done in
minutes.


b) swap the Wylex unit for a 32A double width RCBO in a suitable
enclosure (going to be tricky with 25mm tails)

or

c) follow the advice for the radial circuit and have 3 spare ways and
one 32A RCBO.

Thanks for the advice!

I've looked, and now wish I hadn't! The MCB is connected to a 10mm
cable (could just be 6mm, but I think it is 10). However, by the time
it gets to the sockets they are each wired with single 2.5mm cable.
There is presumably some sort of junction box somewhere, but what he
used that takes one 10mm and two 2.5mm wire I don't know. You'd think
it would be big enough to spot! I presume branched radials are frowned
upon, even with a suitable MCB. Fortunately I can scrap one of the
sockets, as it is unused, being intended for running a washing
machine/tumble dryer on Economy 7.

Actually, I don't benefit significantly from Economy 7[1] so I may just
scrap the timeswitch[2] and connect the single storage heater to a spare
way on the main CU, with a timeswitch at the socket. I expect they will
charge me to change the meter.


[1] with my current supplier who I was allocated to when Iresa went
bust I think I am paying significantly more on Economy 7. More round
tuits needed.

[2] very few supplers will charge one on a flat rate tariff if one has
an Economy 7 meter, despite the simplicity of the arithmetic needed it
hasn't been programmed into most of their billing systems.



--

Roger Hayter

On 10/02/2019 21:54, Roger Hayter wrote:
ARW wrote:

On 07/02/2019 23:27, Roger Hayter wrote:
snip

I've carefully avoided checking that the economy 7 circuit is wired as a
ring so far, but I suppose I could always use a smaller MCB.




A couple of options.

First of all find out if is a ring or not. Now is the time to find out!

If not a ring then swap the Wylex box for a new CU with 2 x 20A radial
circuits with RCBOs or a RCD main switch. Don't consider a 2 way garage
CU as you have 25mmm tails. You might just squeeze a 4way with main
switch CU in there.

If it is a ring then

a) swap the sockets for sockets with RCD built into them. Job done in
minutes.


b) swap the Wylex unit for a 32A double width RCBO in a suitable
enclosure (going to be tricky with 25mm tails)

or

c) follow the advice for the radial circuit and have 3 spare ways and
one 32A RCBO.

Thanks for the advice!

I've looked, and now wish I hadn't! The MCB is connected to a 10mm
cable (could just be 6mm, but I think it is 10). However, by the time
it gets to the sockets they are each wired with single 2.5mm cable.
There is presumably some sort of junction box somewhere, but what he
used that takes one 10mm and two 2.5mm wire I don't know. You'd think
it would be big enough to spot! I presume branched radials are frowned
upon, even with a suitable MCB. Fortunately I can scrap one of the
sockets, as it is unused, being intended for running a washing
machine/tumble dryer on Economy 7.

Actually, I don't benefit significantly from Economy 7[1] so I may just
scrap the timeswitch[2] and connect the single storage heater to a spare
way on the main CU, with a timeswitch at the socket. I expect they will
charge me to change the meter.


[1] with my current supplier who I was allocated to when Iresa went
bust I think I am paying significantly more on Economy 7. More round
tuits needed.

[2] very few supplers will charge one on a flat rate tariff if one has
an Economy 7 meter, despite the simplicity of the arithmetic needed it
hasn't been programmed into most of their billing systems.




I thought that suppliers were falling all over each other in a rush to
fit meters for free?

It reminds me of a rewire I did some years ago when the customer had gas
CH fitted at the same time as the rewire. Some months later she called
back to say she was having problems with the electricity company and
could I tell her the date on which we disconnected the economy 7 meter.

I could give her the exact date. September the 11th 2001.


--
Adam

ARW wrote:

On 10/02/2019 21:54, Roger Hayter wrote:
ARW wrote:

On 07/02/2019 23:27, Roger Hayter wrote:
snip

I've carefully avoided checking that the economy 7 circuit is wired as a
ring so far, but I suppose I could always use a smaller MCB.




A couple of options.

First of all find out if is a ring or not. Now is the time to find out!

If not a ring then swap the Wylex box for a new CU with 2 x 20A radial
circuits with RCBOs or a RCD main switch. Don't consider a 2 way garage
CU as you have 25mmm tails. You might just squeeze a 4way with main
switch CU in there.

If it is a ring then

a) swap the sockets for sockets with RCD built into them. Job done in
minutes.


b) swap the Wylex unit for a 32A double width RCBO in a suitable
enclosure (going to be tricky with 25mm tails)

or

c) follow the advice for the radial circuit and have 3 spare ways and
one 32A RCBO.

Thanks for the advice!

I've looked, and now wish I hadn't! The MCB is connected to a 10mm
cable (could just be 6mm, but I think it is 10). However, by the time
it gets to the sockets they are each wired with single 2.5mm cable.
There is presumably some sort of junction box somewhere, but what he
used that takes one 10mm and two 2.5mm wire I don't know. You'd think
it would be big enough to spot! I presume branched radials are frowned
upon, even with a suitable MCB. Fortunately I can scrap one of the
sockets, as it is unused, being intended for running a washing
machine/tumble dryer on Economy 7.

Actually, I don't benefit significantly from Economy 7[1] so I may just
scrap the timeswitch[2] and connect the single storage heater to a spare
way on the main CU, with a timeswitch at the socket. I expect they will
charge me to change the meter.


[1] with my current supplier who I was allocated to when Iresa went
bust I think I am paying significantly more on Economy 7. More round
tuits needed.

[2] very few supplers will charge one on a flat rate tariff if one has
an Economy 7 meter, despite the simplicity of the arithmetic needed it
hasn't been programmed into most of their billing systems.




I thought that suppliers were falling all over each other in a rush to
fit meters for free?

No network signal.


It reminds me of a rewire I did some years ago when the customer had gas
CH fitted at the same time as the rewire. Some months later she called
back to say she was having problems with the electricity company and
could I tell her the date on which we disconnected the economy 7 meter.

I could give her the exact date. September the 11th 2001.


--

Roger Hayter

On 10/02/2019 23:41, Roger Hayter wrote:
ARW wrote:

On 10/02/2019 21:54, Roger Hayter wrote:
ARW wrote:

On 07/02/2019 23:27, Roger Hayter wrote:
snip

I've carefully avoided checking that the economy 7 circuit is wired as a
ring so far, but I suppose I could always use a smaller MCB.




A couple of options.

First of all find out if is a ring or not. Now is the time to find out!

If not a ring then swap the Wylex box for a new CU with 2 x 20A radial
circuits with RCBOs or a RCD main switch. Don't consider a 2 way garage
CU as you have 25mmm tails. You might just squeeze a 4way with main
switch CU in there.

If it is a ring then

a) swap the sockets for sockets with RCD built into them. Job done in
minutes.


b) swap the Wylex unit for a 32A double width RCBO in a suitable
enclosure (going to be tricky with 25mm tails)

or

c) follow the advice for the radial circuit and have 3 spare ways and
one 32A RCBO.

Thanks for the advice!

I've looked, and now wish I hadn't! The MCB is connected to a 10mm
cable (could just be 6mm, but I think it is 10). However, by the time
it gets to the sockets they are each wired with single 2.5mm cable.
There is presumably some sort of junction box somewhere, but what he
used that takes one 10mm and two 2.5mm wire I don't know. You'd think
it would be big enough to spot! I presume branched radials are frowned
upon, even with a suitable MCB. Fortunately I can scrap one of the
sockets, as it is unused, being intended for running a washing
machine/tumble dryer on Economy 7.

The branched radials are in your case called unfused spurs.

They are frowned upon by some but not by others (including me).

If it worries you then without a doubt the easiest and cheapest option
is to swap the MCB for a 20A MCB (you have to swap the back plate), fit
a RCD socket and blank off the other socket into a flex outlet plate or
into strip connector with a blank plate over it.

I am sure from your photos that this is the MCB you may need

https://www.screwfix.com/p/wylex-20a...g-in-mcb/80070

BTW If you do swap the MCB to a 20A the unfused spurs become branches:-)

--
Adam

ARW wrote:

On 10/02/2019 23:41, Roger Hayter wrote:
ARW wrote:

On 10/02/2019 21:54, Roger Hayter wrote:
ARW wrote:

On 07/02/2019 23:27, Roger Hayter wrote:
snip

I've carefully avoided checking that the economy 7 circuit is wired as a
ring so far, but I suppose I could always use a smaller MCB.




A couple of options.

First of all find out if is a ring or not. Now is the time to find out!

If not a ring then swap the Wylex box for a new CU with 2 x 20A radial
circuits with RCBOs or a RCD main switch. Don't consider a 2 way garage
CU as you have 25mmm tails. You might just squeeze a 4way with main
switch CU in there.

If it is a ring then

a) swap the sockets for sockets with RCD built into them. Job done in
minutes.


b) swap the Wylex unit for a 32A double width RCBO in a suitable
enclosure (going to be tricky with 25mm tails)

or

c) follow the advice for the radial circuit and have 3 spare ways and
one 32A RCBO.

Thanks for the advice!

I've looked, and now wish I hadn't! The MCB is connected to a 10mm
cable (could just be 6mm, but I think it is 10). However, by the time
it gets to the sockets they are each wired with single 2.5mm cable.
There is presumably some sort of junction box somewhere, but what he
used that takes one 10mm and two 2.5mm wire I don't know. You'd think
it would be big enough to spot! I presume branched radials are frowned
upon, even with a suitable MCB. Fortunately I can scrap one of the
sockets, as it is unused, being intended for running a washing
machine/tumble dryer on Economy 7.

The branched radials are in your case called unfused spurs.

They are frowned upon by some but not by others (including me).

About 20m of 2.5mm T&E isn't a problem from the fault current POV I
suppose? I could work it out but prefer the next solution.




If it worries you then without a doubt the easiest and cheapest option
is to swap the MCB for a 20A MCB (you have to swap the back plate), fit
a RCD socket and blank off the other socket into a flex outlet plate or
into strip connector with a blank plate over it.

I am sure from your photos that this is the MCB you may need

https://www.screwfix.com/p/wylex-20a...g-in-mcb/80070

BTW If you do swap the MCB to a 20A the unfused spurs become branches:-)

Are branches acceptable in the context, with the common cable being
bigger? I don't want one so that is an academic question. Thanks for
the MCB hint, I think I'll get that pending a permanent solution.

--

Roger Hayter

Roger Hayter wrote:
Mike Humphrey wrote:
It's something to be careful of in multi-rate installations that there's
often not a single switch to cut all power to the building. My house
used to have THTC, which meant there were *four* main switches
(general supply, 24 hour heating, water heating, timed heating). Unless
all four were off, something was still powered or could become powered
under timeswitch control.

That's complicated, did you have four separate incoming cables and main
fuses, or was it all done after the meter?

There's one incoming cable with a main fuse. This then fed a pair of
henley blocks, which split the supply to two meters. One was just a
single-rate mechanical meter, which did the "general supply" and fed a
consumer unit for everything that didn't involve heating. The other
meter included a radio timeswitch, with one continous output and two
switched outputs. Although this was actually a multi-rate meter it
only recorded one rate - all heating was charged at the same price.
The three live and one neutral tails from this meter fed a second
consumer unit with three independent main switches (each feeding their
own bank of MCBs) that powered all the heaters.

The two switched outputs turned on and off according to a schedule that
SSE set - it changed regularly, potentially being different every day,
and customers weren't told what the schedule was. So unlike Economy 7,
which is unlikely to turn on at a random point in the day, it's
extra important to make sure that the relevant main switch is off - as
you never know when the timeswitch will switch on!
Just to add to the confusion, the immersion heater and some of the
storage heaters had a boost facility - fed from a different circuit on a
different main switch.

Mike

Mike Humphrey wrote:

Roger Hayter wrote:
Mike Humphrey wrote:
It's something to be careful of in multi-rate installations that there's
often not a single switch to cut all power to the building. My house
used to have THTC, which meant there were *four* main switches
(general supply, 24 hour heating, water heating, timed heating). Unless
all four were off, something was still powered or could become powered
under timeswitch control.

That's complicated, did you have four separate incoming cables and main
fuses, or was it all done after the meter?

There's one incoming cable with a main fuse. This then fed a pair of
henley blocks, which split the supply to two meters. One was just a
single-rate mechanical meter, which did the "general supply" and fed a
consumer unit for everything that didn't involve heating. The other
meter included a radio timeswitch, with one continous output and two
switched outputs. Although this was actually a multi-rate meter it
only recorded one rate - all heating was charged at the same price.
The three live and one neutral tails from this meter fed a second
consumer unit with three independent main switches (each feeding their
own bank of MCBs) that powered all the heaters.

The two switched outputs turned on and off according to a schedule that
SSE set - it changed regularly, potentially being different every day,
and customers weren't told what the schedule was. So unlike Economy 7,
which is unlikely to turn on at a random point in the day, it's
extra important to make sure that the relevant main switch is off - as
you never know when the timeswitch will switch on!
Just to add to the confusion, the immersion heater and some of the
storage heaters had a boost facility - fed from a different circuit on a
different main switch.

Mike
That sounds confusing. But versatile for heating, I suppose. They
presumably had to trust you not to connect everything to the cheaper
heating always on supply.

--

Roger Hayter

On 11/02/2019 21:31, Roger Hayter wrote:
ARW wrote:



BTW If you do swap the MCB to a 20A the unfused spurs become branches:-)

Are branches acceptable in the context, with the common cable being
bigger? I don't want one so that is an academic question. Thanks for
the MCB hint, I think I'll get that pending a permanent solution.



They are well within regs even though you have a larger main cable.

Do you have access to the reg book? If so appendix 15 is the one to look
at (and laugh at when you see how badly worded it is).

You might find it on line (the 17th edition was out there due to the
mistakes in the printed edition).


--
Adam

ARW wrote:

On 11/02/2019 21:31, Roger Hayter wrote:
ARW wrote:



BTW If you do swap the MCB to a 20A the unfused spurs become branches:-)

Are branches acceptable in the context, with the common cable being
bigger? I don't want one so that is an academic question. Thanks for
the MCB hint, I think I'll get that pending a permanent solution.



They are well within regs even though you have a larger main cable.

Do you have access to the reg book? If so appendix 15 is the one to look
at (and laugh at when you see how badly worded it is).

You might find it on line (the 17th edition was out there due to the
mistakes in the printed edition).

I've got the on site guide somewhere, but disinclined to look when I
don't intend to leave the 32A MCB in anyway. I note Amazon are selling
the 18th edition, I didn't think they used to. I have no need for it
except light reading.

--

Roger Hayter

Roger Hayter wrote:
You might find it on line (the 17th edition was out there due to the
mistakes in the printed edition).

I've got the on site guide somewhere, but disinclined to look when I
don't intend to leave the 32A MCB in anyway. I note Amazon are selling
the 18th edition, I didn't think they used to. I have no need for it
except light reading.

As opposed to power reading no doubt! :-)

--
Chris Green
·

On 12/02/2019 20:21, Chris Green wrote:
Roger Hayter wrote:
You might find it on line (the 17th edition was out there due to the
mistakes in the printed edition).

I've got the on site guide somewhere, but disinclined to look when I
don't intend to leave the 32A MCB in anyway. I note Amazon are selling
the 18th edition, I didn't think they used to. I have no need for it
except light reading.

As opposed to power reading no doubt! :-)


If you read up on ring mains, do you end up just
going round in circles ? :-)

On Friday, 15 February 2019 13:06:34 UTC, Andrew wrote:
If you read up on ring mains, do you end up just
going round in circles ? :-)

If you read up on ring finals do you find out what happens to Hagen and see the interior of Valhalla?

Owain

On 15/02/2019 15:17, wrote:
On Friday, 15 February 2019 13:06:34 UTC, Andrew wrote:
If you read up on ring mains, do you end up just
going round in circles ? :-)

If you read up on ring finals do you find out what happens to Hagen and see the interior of Valhalla?

Owain

Those are Killer cycles.


--
In todays liberal progressive conflict-free education system, everyone
gets full Marx.