RCD Conundrum

[morph]

Hi morph,

What I would be doing (in the absence of a EL clamp), would be to start disconnecting (both L and N) of individual circuits one at a time, and repeating the Ramp test, to see where it improves, then IR test the suspect circuit/s, average readings on ramp tests for 30mA RCD's tend to be around the 20-25mA mark IME,

Or do as above but IR test each individual circuit to find the culprit/s.

agreed , i have now been asked to sort up stairs socket issue so i will fix that and then look at I/R
it was just the fact that with other circuits isolated and most things unplugged on down ring that the ramp was 8 and 19 at board that seemed odd
if nothing is on how does the ramp result vary so much ?

 

[PC Electrics]

Issue a danger notice.

Appliances will work fine with reverse polarity, but that does not diminish the danger. Such is the danger that modern electronically controlled boilers are designed to detect reverse polarity and will go straight into lock out, thus forcing the owner to call in expert help.

 

[netblindpaul]

It varies because the meters we have to test it can't cope with testing in this manner.

 

[spark 68]

if nothing is on how does the ramp result vary so much ?

The Cables were not isolated at the CU, so if it is a cable or JB or accessory that is breaking down, it would still allow enough leakage to affect your readings.

Don't forget that MCB's are single pole (in the UK at least) and don't in general isolate the N.

 

[morph]

It varies because the meters we have to test it can't cope with testing in this manner.

thanks for the reply , could you expand a little please

 

[morph]

The Cables were not isolated at the CU, so if it is a cable or JB or accessory that is breaking down, it would still allow enough leakage to affect your readings.

Don't forget that MCB's are single pole (in the UK at least) and don't in general isolate the N.

have some more time tomorrow to investigate , just did nt think the conductor insulation would have any bearing if not under load, thanks for the replies..

 

[netblindpaul]

morph,
This has been done recently, it is a function of the meter.
They are basic.
You are testing a capacitor in parallel with the RCD at the sockets, not the RCD itself.

 

[morph]

morph,
This has been done recently, it is a function of the meter.
They are basic.
You are testing a capacitor in parallel with the RCD at the sockets, not the RCD itself.

true indeed had not thought of that ,
generaly though the variance is not so significant

 

[Engineer54]

In other words the only meaningful values on a RCD test, are those taken at the CU. Tests taken at the socket outlets only basically prove the RCD is functioning, NOT the operating values of the RCD device!!!