I have inherited the [unpaid] care of some amateur electric pottery
kilns. The house has wire fuses and no RCD. The supply appears to be TN-
S. There are Henley blocks between the meter and the consumer units.
There is a MET near the main incomer.
One way of a Wylex plastic fuse box has a 40A plug in MCB. This feeds a
10mm csa T&E which is connected to a big metal junction box on the end
of a plastic underground conduit about 45mm dia and about 27 metres
long. I believe it was installed over 40 years ago. The conduit contains
11 individual conductors which appear to be PVC sheathed, not rubber.
They are about 6mm csa, so I guess they are 7/.044; 5 red, 5 black, 1
green and yellow. Two red and two black have been paralleled to feed the
kilns. Is this permitted? Others are not used.
The conduit runs into another big metal junction box in a concrete
sectional garage with the kilns in. Here 10mm csa T&E feeds a small
consumer unit with an 80A RCD, and a 40A MCB which feeds a Henley block.
It has a 6mm csa connection from the earth bar to an earth rod. Should
this be removed?

Each of the 4 kilns is hard wired into the Henley block with modern T&E,
some 10mm csa and smaller kilns with 6mm csa. Each kiln has a small
Wylex consumer unit nearby with an isolator and a MCB, either 40A or 32A
to suit. Each kiln has a 'door open' interlock switch which prevents the
contactor from energising. Each has a programmer which controls the
temperature rate rise by turning on and off the whole kiln, which it
monitors with a thermocouple pyrometer.
The highest load kiln draws 38A. When the mains was 237v there was a
voltage drop of 7 volts when this turned on.
I am not going to modernise the house wiring, [not my job squire] but
I'd like to bring the kiln room up to something like spec. I'll start by
printing laminated instructions about isolating the kilns before loading
them with pots, and having only one firing at a time.
There are 2 questions hidden in this long message, and I'm seeking
advice.

--
take the dog out to email me.

Did the previous owner survive? If yes then no problem .. grin.
Brian

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"Mike" wrote in message
...

I have inherited the [unpaid] care of some amateur electric pottery
kilns. The house has wire fuses and no RCD. The supply appears to be TN-
S. There are Henley blocks between the meter and the consumer units.
There is a MET near the main incomer.
One way of a Wylex plastic fuse box has a 40A plug in MCB. This feeds a
10mm csa T&E which is connected to a big metal junction box on the end
of a plastic underground conduit about 45mm dia and about 27 metres
long. I believe it was installed over 40 years ago. The conduit contains
11 individual conductors which appear to be PVC sheathed, not rubber.
They are about 6mm csa, so I guess they are 7/.044; 5 red, 5 black, 1
green and yellow. Two red and two black have been paralleled to feed the
kilns. Is this permitted? Others are not used.
The conduit runs into another big metal junction box in a concrete
sectional garage with the kilns in. Here 10mm csa T&E feeds a small
consumer unit with an 80A RCD, and a 40A MCB which feeds a Henley block.
It has a 6mm csa connection from the earth bar to an earth rod. Should
this be removed?

Each of the 4 kilns is hard wired into the Henley block with modern T&E,
some 10mm csa and smaller kilns with 6mm csa. Each kiln has a small
Wylex consumer unit nearby with an isolator and a MCB, either 40A or 32A
to suit. Each kiln has a 'door open' interlock switch which prevents the
contactor from energising. Each has a programmer which controls the
temperature rate rise by turning on and off the whole kiln, which it
monitors with a thermocouple pyrometer.
The highest load kiln draws 38A. When the mains was 237v there was a
voltage drop of 7 volts when this turned on.
I am not going to modernise the house wiring, [not my job squire] but
I'd like to bring the kiln room up to something like spec. I'll start by
printing laminated instructions about isolating the kilns before loading
them with pots, and having only one firing at a time.
There are 2 questions hidden in this long message, and I'm seeking
advice.

--
take the dog out to email me.

In article ,
says...

Did the previous owner survive? If yes then no problem .. grin.
Brian

Yes the owner has survived, so far.

HI Mike

I'm not sure about the 'official' position on the wiring - it sounds
like one of those "I wired this up and I know how to operate it.." type
of things..

Does sound as though firing more than one kiln at a time would pop the
40A MCB.. You could probably arrange some kind of interlock system to
ensure that only one kiln is fired at a time.... though it's not going
to be an enormous problem if the MCB needs to be reset.


As far as voltage drop - my glass-fusing kiln pulls about 32 Amps, and
the few incandescent lights in the house dip slightly when it fires -
but, as we're on the end of a long cable back to a shared pole
transformer, I've not worried particularly about it.

Are the kilns 'shared' by members of the public (you talk about writing
instructions for their use)?
I'm not sure what the insurance situation might be, should somebody get
injured or killed by these kilns - if you're 'caring' for the kilns then
might you be liable?

There are aspects of the wiring in my workshop that would probably make
an insurance assessor blink - but only I get to work in there, so I'm
not unduly worried..

Adrian

On 11/12/2019 19:53, Mike wrote:

I have inherited the [unpaid] care of some amateur electric pottery
kilns. The house has wire fuses and no RCD. The supply appears to be TN-
S. There are Henley blocks between the meter and the consumer units.
There is a MET near the main incomer.
One way of a Wylex plastic fuse box has a 40A plug in MCB. This feeds a
10mm csa T&E which is connected to a big metal junction box on the end
of a plastic underground conduit about 45mm dia and about 27 metres
long. I believe it was installed over 40 years ago. The conduit contains
11 individual conductors which appear to be PVC sheathed, not rubber.
They are about 6mm csa, so I guess they are 7/.044; 5 red, 5 black, 1
green and yellow. Two red and two black have been paralleled to feed the
kilns. Is this permitted? Others are not used.
The conduit runs into another big metal junction box in a concrete
sectional garage with the kilns in. Here 10mm csa T&E feeds a small
consumer unit with an 80A RCD, and a 40A MCB which feeds a Henley block.
It has a 6mm csa connection from the earth bar to an earth rod. Should
this be removed?

Each of the 4 kilns is hard wired into the Henley block with modern T&E,
some 10mm csa and smaller kilns with 6mm csa. Each kiln has a small
Wylex consumer unit nearby with an isolator and a MCB, either 40A or 32A
to suit. Each kiln has a 'door open' interlock switch which prevents the
contactor from energising. Each has a programmer which controls the
temperature rate rise by turning on and off the whole kiln, which it
monitors with a thermocouple pyrometer.
The highest load kiln draws 38A. When the mains was 237v there was a
voltage drop of 7 volts when this turned on.
I am not going to modernise the house wiring, [not my job squire] but
I'd like to bring the kiln room up to something like spec. I'll start by
printing laminated instructions about isolating the kilns before loading
them with pots, and having only one firing at a time.
There are 2 questions hidden in this long message, and I'm seeking
advice.

--
take the dog out to email me.

If you're asking all these questions are you sure you're in a position to be responsible for the system?
"A man's got to know his limitations" Harry Callahan

On Wednesday, 11 December 2019 19:54:02 UTC, Mike wrote:
I have inherited the [unpaid] care of some amateur electric pottery
kilns. The house has wire fuses and no RCD. The supply appears to be TN-
S. There are Henley blocks between the meter and the consumer units.
There is a MET near the main incomer.
One way of a Wylex plastic fuse box has a 40A plug in MCB. This feeds a
10mm csa T&E which is connected to a big metal junction box on the end
of a plastic underground conduit about 45mm dia and about 27 metres
long. I believe it was installed over 40 years ago. The conduit contains
11 individual conductors which appear to be PVC sheathed, not rubber.
They are about 6mm csa, so I guess they are 7/.044; 5 red, 5 black, 1
green and yellow. Two red and two black have been paralleled to feed the
kilns. Is this permitted? Others are not used.
The conduit runs into another big metal junction box in a concrete
sectional garage with the kilns in. Here 10mm csa T&E feeds a small
consumer unit with an 80A RCD, and a 40A MCB which feeds a Henley block.
It has a 6mm csa connection from the earth bar to an earth rod. Should
this be removed?

Each of the 4 kilns is hard wired into the Henley block with modern T&E,
some 10mm csa and smaller kilns with 6mm csa. Each kiln has a small
Wylex consumer unit nearby with an isolator and a MCB, either 40A or 32A
to suit. Each kiln has a 'door open' interlock switch which prevents the
contactor from energising. Each has a programmer which controls the
temperature rate rise by turning on and off the whole kiln, which it
monitors with a thermocouple pyrometer.
The highest load kiln draws 38A. When the mains was 237v there was a
voltage drop of 7 volts when this turned on.
I am not going to modernise the house wiring, [not my job squire] but
I'd like to bring the kiln room up to something like spec. I'll start by
printing laminated instructions about isolating the kilns before loading
them with pots, and having only one firing at a time.
There are 2 questions hidden in this long message, and I'm seeking
advice.

How many kilns are there? What's the current draw of each? AIUI a 40A way is at the limit of an old Wylex's ability, so if just one kiln eats 38A and you have several.... erm, well, that could be a problem. Lack of RCD is unlikely to meet current standards.

A 40yr old interlock system also might not meet modern requirements, but usually old wiring doesn't need to. But several kilns suggests it probably does. More info needed really.


NT

On 11/12/2019 19:53, Mike wrote:

I have inherited the [unpaid] care of some amateur electric pottery
kilns. The house has wire fuses and no RCD. The supply appears to be TN-
S. There are Henley blocks between the meter and the consumer units.
There is a MET near the main incomer.
One way of a Wylex plastic fuse box has a 40A plug in MCB. This feeds a
10mm csa T&E which is connected to a big metal junction box on the end
of a plastic underground conduit about 45mm dia and about 27 metres
long. I believe it was installed over 40 years ago. The conduit contains
11 individual conductors which appear to be PVC sheathed, not rubber.
They are about 6mm csa, so I guess they are 7/.044; 5 red, 5 black, 1
green and yellow. Two red and two black have been paralleled to feed the
kilns. Is this permitted? Others are not used.
The conduit runs into another big metal junction box in a concrete
sectional garage with the kilns in. Here 10mm csa T&E feeds a small
consumer unit with an 80A RCD, and a 40A MCB which feeds a Henley block.
It has a 6mm csa connection from the earth bar to an earth rod. Should
this be removed?

Each of the 4 kilns is hard wired into the Henley block with modern T&E,
some 10mm csa and smaller kilns with 6mm csa. Each kiln has a small
Wylex consumer unit nearby with an isolator and a MCB, either 40A or 32A
to suit. Each kiln has a 'door open' interlock switch which prevents the
contactor from energising. Each has a programmer which controls the
temperature rate rise by turning on and off the whole kiln, which it
monitors with a thermocouple pyrometer.
The highest load kiln draws 38A. When the mains was 237v there was a
voltage drop of 7 volts when this turned on.
I am not going to modernise the house wiring, [not my job squire] but
I'd like to bring the kiln room up to something like spec. I'll start by
printing laminated instructions about isolating the kilns before loading
them with pots, and having only one firing at a time.
There are 2 questions hidden in this long message, and I'm seeking
advice.



I have no idea why you have an earth rod if there is no RCD and it is a
TN setup.

Parallel conductors are allowed.

Some info here for you on that.

https://www.voltimum.co.uk/articles/...lel-conductors

Remember that a sheet of laminated instructions will not stop the stupid
from getting it wrong.

Some photos might help.

--
Adam

In article ,
says...

Remember that a sheet of laminated instructions will not stop the stupid
from getting it wrong.

The stupid won't bother to read it either!

--

Terry