George (dicegeorge) wrote:

In my house there's an old grey RCD box with no writing on it
which I cannot identify
which has been inserted before the old fuseboard
many years ago.

The test switch doesnt work but it does trip on faults.
It's very dusty from the old lime plaster above it.

So What to replace it with?

I guess a 100amp RCD box with 100ma trip current..
Or should I try a 30ma trip current one,
and be prepared for more trips?

What are you seeking to protect? If you want adequate protection from
electrocution then you need a 30mA device. A 100mA device is only really
designed to protect the installation ins situations where the earth loop
impedance is too high to reliable trip MCBs etc.

I have a second 2007 consumer unit which powers a few sockets
which power my computers and electric heaters etc
so a trip on the old wiring circuit isnt that catastrophic..

You could also say, if the old wiring is leaky enough to trip a RCD then
it needs fixing anyway.



--
Cheers,

John.

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John wrote:
You could also say, if the old wiring is leaky enough to trip a RCD then
it needs fixing anyway.

ok, thanks, so i get a 30ma RCD box
and put it before all the old fuse boxes
and if one of them trips often I pull out it's fuse and
investigate,further.

Perhaps this:
Wylex Garage Board 2 Way 63a 30mA RCD Metal
http://www.gil-lec.co.uk/products/Ci...tal/3371847927

(or the plastic version, for a tenner more)

and in it two these:
Wylex MCB SP 1 Module 40A 6kA

http://www.gil-lec.co.uk/products/Ci...6kA/1743830342



On Nov 19, 5:38*pm, John Rumm wrote:
George (dicegeorge) wrote:
In my house there's an old grey RCD box with no writing on it
which I cannot identify
which has been inserted before the old fuseboard
many years ago.

The test switch doesnt work but it does trip on faults.
It's very dusty from the old lime plaster above it.

So What to replace it with?

I guess a 100amp RCD box with 100ma trip current..
Or should I try a 30ma trip current one,
and be prepared for more trips?

What are you seeking to protect? If you want adequate protection from
electrocution then you need a 30mA device. A 100mA device is only really
designed to protect the installation ins situations where the earth loop
impedance is too high to reliable trip MCBs etc.

I have a second 2007 consumer unit which powers a few sockets
which power my computers and electric heaters etc
so a trip on the old wiring circuit isnt that catastrophic..

You could also say, if the old wiring is leaky enough to trip a RCD then
it needs fixing anyway.

--
Cheers,

John.

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

dicegeorge wrote:
John wrote:

You could also say, if the old wiring is leaky enough to trip a RCD then
it needs fixing anyway.

ok, thanks, so i get a 30ma RCD box
and put it before all the old fuse boxes
and if one of them trips often I pull out it's fuse and
investigate,further.

fraid that wont work. Pull the fuse and N&E are still connected.


NT

wrote in message
...
dicegeorge wrote:
John wrote:

You could also say, if the old wiring is leaky enough to trip a RCD
then
it needs fixing anyway.

ok, thanks, so i get a 30ma RCD box
and put it before all the old fuse boxes
and if one of them trips often I pull out it's fuse and
investigate,further.

fraid that wont work. Pull the fuse and N&E are still connected.


NT

I will turn off the new isolator as well so I should be out of danger,

Bu yes, if there is a leakage from N to E
even pulling out the live of that circuit
would mean the RCD will still trip out,
if i understand it correctly.

With lots of things (computers etc) leaking a few m.amp each
the cumulative leakage can trip the RCD:
I havent yet got a way of measuring each circuits leakage.




[g]

dicegeorge wrote:
John wrote:
You could also say, if the old wiring is leaky enough to trip a RCD then
it needs fixing anyway.

ok, thanks, so i get a 30ma RCD box
and put it before all the old fuse boxes
and if one of them trips often I pull out it's fuse and
investigate,further.

Depending on the actual nature of the fault that may or may not clear
the trip.

Perhaps this:
Wylex Garage Board 2 Way 63a 30mA RCD Metal
http://www.gil-lec.co.uk/products/Ci...tal/3371847927

Depends on whether you want one RCD protecting all the circuits. (given
this is a second CU that may be less of a problem)

(or the plastic version, for a tenner more)

Not required unless you are TT




--
Cheers,

John.

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