I'm changing the case on the consumer unit - replacement for broken one guv,
honest - and in replacing all the original internal bits it may
coincidentally become a full 17th edition box.

Before I reconnect everything I want to do a sensible set of circuit tests,
that I can record. I have a query or two re insulation testing.

For rings and single function radials (oven, immersion etc) I can be fairly
confident that nothing sensitive is connected, and insulation test at 500V
for L-E, N-E, L-N. For lighting circuits, which include electronic items
like microprocessor dimmers and 12v halogen PSUs, disconnected only by
single pole switches, I'm a bit wary about using 500V testing. Other options
would seem to be to test just at 250V, or to temporarily connect line and
neutral and test to earth at 500V. Any thoughts?

Finally, I have mains/battery smoke detectors on their own single 6A
circuit. The mains feed in 1mm T&E goes to the first detector, and thence
onward in 3&E. Should there be an isolator (FCU or similar) before the first
detector, and if not what are the implications here for insulation testing?

Thanks for any advice,

Charles F

I just wonder how old the cabling is that you are of course not fitting to a
new box.. grin.

Some of the old pvc seems to crumble.

Brian

--
--
From the sofa of Brian Gaff -

Blind user, so no pictures please!
"Charles Fearnley" wrote in
message ...
I'm changing the case on the consumer unit - replacement for broken one
guv, honest - and in replacing all the original internal bits it may
coincidentally become a full 17th edition box.

Before I reconnect everything I want to do a sensible set of circuit
tests, that I can record. I have a query or two re insulation testing.

For rings and single function radials (oven, immersion etc) I can be
fairly confident that nothing sensitive is connected, and insulation test
at 500V for L-E, N-E, L-N. For lighting circuits, which include electronic
items like microprocessor dimmers and 12v halogen PSUs, disconnected only
by single pole switches, I'm a bit wary about using 500V testing. Other
options would seem to be to test just at 250V, or to temporarily connect
line and neutral and test to earth at 500V. Any thoughts?

Finally, I have mains/battery smoke detectors on their own single 6A
circuit. The mains feed in 1mm T&E goes to the first detector, and thence
onward in 3&E. Should there be an isolator (FCU or similar) before the
first detector, and if not what are the implications here for insulation
testing?

Thanks for any advice,

Charles F

Hope this is OK for Brian - I'm not at home, and on google groups....

Cable almost all now less than ten years old. Some done just before we bought the house as an upgrade for the sale, a lot done as part of an extension project, and signed off by the council, a little since.

Incidentally, the house is 40 odd years old, and was mostly wired in copper clad aluminium cable. I wasn't happy about this, and have cleared it all, mainly becuse the bared ends had a tendency to break off, and because the larger size (than copper) meant getting three cables into a fitting was pretty much impossible. There were no signs of overheating at joints though.

However, there were no signs at all of problems at all with the PVC. If it's out of the sun, and not one of the dodgy formulations, it seems to last extremely well.

Charles F

On Friday, July 6, 2012 6:23:05 PM UTC+1, Brian Gaff wrote:
I just wonder how old the cabling is that you are of course not fitting to a
new box.. grin.

Some of the old pvc seems to crumble.

Brian

--
--
From the sofa of Brian Gaff -

Blind user, so no pictures please!
"Charles Fearnley" wrote in
message ...
I'm changing the case on the consumer unit - replacement for broken one
guv, honest - and in replacing all the original internal bits it may
coincidentally become a full 17th edition box.

Before I reconnect everything I want to do a sensible set of circuit
tests, that I can record. I have a query or two re insulation testing.

For rings and single function radials (oven, immersion etc) I can be
fairly confident that nothing sensitive is connected, and insulation test
at 500V for L-E, N-E, L-N. For lighting circuits, which include electronic
items like microprocessor dimmers and 12v halogen PSUs, disconnected only
by single pole switches, I'm a bit wary about using 500V testing. Other
options would seem to be to test just at 250V, or to temporarily connect
line and neutral and test to earth at 500V. Any thoughts?

Finally, I have mains/battery smoke detectors on their own single 6A
circuit. The mains feed in 1mm T&E goes to the first detector, and thence
onward in 3&E. Should there be an isolator (FCU or similar) before the
first detector, and if not what are the implications here for insulation
testing?

Thanks for any advice,

Charles F

Charles Fearnley wrote:
I'm changing the case on the consumer unit - replacement for broken
one guv, honest - and in replacing all the original internal bits it
may coincidentally become a full 17th edition box.

Before I reconnect everything I want to do a sensible set of circuit
tests, that I can record. I have a query or two re insulation testing.

For rings and single function radials (oven, immersion etc) I can be
fairly confident that nothing sensitive is connected, and insulation
test at 500V for L-E, N-E, L-N. For lighting circuits, which include
electronic items like microprocessor dimmers and 12v halogen PSUs,
disconnected only by single pole switches, I'm a bit wary about using
500V testing. Other options would seem to be to test just at 250V, or
to temporarily connect line and neutral and test to earth at 500V.
Any thoughts?
Finally, I have mains/battery smoke detectors on their own single 6A
circuit. The mains feed in 1mm T&E goes to the first detector, and
thence onward in 3&E. Should there be an isolator (FCU or similar)
before the first detector, and if not what are the implications here
for insulation testing?

I suggest doing the test at 250V to start with. That way if you get a
reading of zero you know something is still plugged in. I do not know what
500V would do to the PCB of an oven! Remember that if anything is connected
no matter how sensitive then the LN reading will be very low.

You suggestion for the lights is correct. Although you can also do a 500V
test if all the lights are turned off - it just means you are not fully
testing the switch wires.

As for the smokes. I see no reason for them to have an isolator.

--
Adam

"ARWadsworth" wrote in message
...
Charles Fearnley wrote:
I'm changing the case on the consumer unit - replacement for broken
one guv, honest - and in replacing all the original internal bits it
may coincidentally become a full 17th edition box.

Before I reconnect everything I want to do a sensible set of circuit
tests, that I can record. I have a query or two re insulation testing.

For rings and single function radials (oven, immersion etc) I can be
fairly confident that nothing sensitive is connected, and insulation
test at 500V for L-E, N-E, L-N. For lighting circuits, which include
electronic items like microprocessor dimmers and 12v halogen PSUs,
disconnected only by single pole switches, I'm a bit wary about using
500V testing. Other options would seem to be to test just at 250V, or
to temporarily connect line and neutral and test to earth at 500V.
Any thoughts?
Finally, I have mains/battery smoke detectors on their own single 6A
circuit. The mains feed in 1mm T&E goes to the first detector, and
thence onward in 3&E. Should there be an isolator (FCU or similar)
before the first detector, and if not what are the implications here
for insulation testing?

I suggest doing the test at 250V to start with. That way if you get a
reading of zero you know something is still plugged in. I do not know what
500V would do to the PCB of an oven! Remember that if anything is
connected no matter how sensitive then the LN reading will be very low.

You suggestion for the lights is correct. Although you can also do a 500V
test if all the lights are turned off - it just means you are not fully
testing the switch wires.

As for the smokes. I see no reason for them to have an isolator.

--
Adam

Thanks Adam - really useful to have a comment from someone who does this all
the time.... I'll start with 250v on everything to confirm nothing has been
missed or left switched on.

As for the lights - not dealing with new installations it had not occurred
to me that with no lamps installed the switches can all be on and all
cables tested. In an existing installation I can't see many people wanting
to completely de-bulb, so testing at 500v would be just the "backbone"
wiring with switches off - this is how the electrical contractor who tested
my earlier work for the council did it.

Charles F