I have several consumer units around the house
but before them all is a new 100ma 100ms RCD in a box,
so must only this box be insulated?

ukdiy wiki says:
"With a TT install you will need to use an insulated CU since this minimises the possibility of a phase to earth fault occurring inside the CU before the RCD (which due to the high earth fault loop impedance of the local earth spike, may result in a fault that would never be cleared). "
at http://wiki.diyfaq.org.uk/index.php/...ting_Equipment

[george]

On 17/10/2016 23:08, DICEGEORGE wrote:

I have several consumer units around the house
but before them all is a new 100ma 100ms RCD in a box,
so must only this box be insulated?

Subsequent boxes will have earth fault protection from the RCD, so they
can be any type. The RCD itself would traditionally have been in a
plastic box, but with the 3rd amendment of the 17th edition you may find
that harder to find.


ukdiy wiki says:
"With a TT install you will need to use an insulated CU since this minimises the possibility of a phase to earth fault occurring inside the CU before the RCD (which due to the high earth fault loop impedance of the local earth spike, may result in a fault that would never be cleared)."
at http://wiki.diyfaq.org.uk/index.php/...ting_Equipment

[george]



--
Cheers,

John.

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thats good news,
I can keep my plastic RCD consumer units and only replace the wooden ones,
thanks John.
[George]

On 18/10/2016 14:00, DICEGEORGE wrote:
thats good news,
I can keep my plastic RCD consumer units and only replace the wooden ones,
thanks John.

I think you may be conflating two issues here...

For TT installs, plastic used to be the norm to mitigate against the
potential for an earth fault before the type S RCD.

17th edition amendment 3 mandates that new CUs installed should be of a
non combustible material. Meaning that if you use a metal clad CU for a
TT install (and where there are multiple CUs; the CU that contains the
non RCD protected incomers) you would need to use a double insulation
kit for the incomers to reduce the possibility of an earth short before
the RCD.

Irrespective of that, you can keep what you already have. Just when
installing new CUs they need to be non combustible. If they are
downstream of an RCD anyway, then its a non issue at that point.


--
Cheers,

John.

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| Internode Ltd - http://www.internode.co.uk |
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| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 2016-10-18 13:48:48 +0000, John Rumm said:

On 18/10/2016 14:00, DICEGEORGE wrote:
thats good news,
I can keep my plastic RCD consumer units and only replace the wooden ones,
thanks John.

I think you may be conflating two issues here...

For TT installs, plastic used to be the norm to mitigate against the
potential for an earth fault before the type S RCD.

17th edition amendment 3 mandates that new CUs installed should be of a
non combustible material. Meaning that if you use a metal clad CU for a
TT install (and where there are multiple CUs; the CU that contains the
non RCD protected incomers) you would need to use a double insulation
kit for the incomers to reduce the possibility of an earth short before
the RCD.

Irrespective of that, you can keep what you already have. Just when
installing new CUs they need to be non combustible. If they are
downstream of an RCD anyway, then its a non issue at that point.

You could put a single time delayed rcd in a plastic box by itself in
front of everything. It can be in plastic rather than metal because
one rcd by itself does not meet the 7671 definition of 'switchgear'.

On 20/10/2016 16:51, bruce wrote:
On 2016-10-18 13:48:48 +0000, John Rumm said:

On 18/10/2016 14:00, DICEGEORGE wrote:
thats good news,
I can keep my plastic RCD consumer units and only replace the wooden
ones,
thanks John.

I think you may be conflating two issues here...

For TT installs, plastic used to be the norm to mitigate against the
potential for an earth fault before the type S RCD.

17th edition amendment 3 mandates that new CUs installed should be of
a non combustible material. Meaning that if you use a metal clad CU
for a TT install (and where there are multiple CUs; the CU that
contains the non RCD protected incomers) you would need to use a
double insulation kit for the incomers to reduce the possibility of an
earth short before the RCD.

Irrespective of that, you can keep what you already have. Just when
installing new CUs they need to be non combustible. If they are
downstream of an RCD anyway, then its a non issue at that point.

You could put a single time delayed rcd in a plastic box by itself in
front of everything. It can be in plastic rather than metal because one
rcd by itself does not meet the 7671 definition of 'switchgear'.

It sounds to me like that is what he already has...


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/