rcd test picking up faulty appliance??

[chrisreid186]

evening all

just before i start this thread i would like to point out that rcd tests should be carried out at the load side of the rcd

got a call out to a fault where the a 30ma rcd kept blowing to the stage where it wouldn't reset, there were only 2 circuits involved one 6a lighting and one 16amp radial, all the wiring i did from new about a year ago

1st thing i did was turn the power off and swap the rcd for a new one, power on and the rcd never tripped.
did a full auto rcd test on load side of rcd with breakers off and the results were good

ok so i've got the power working again but haven't found the fault that originally blew the rcd,
out of curiosity i wondered if doing a full auto rcd test at each mcb would highlight any problems
tested the light circuit and the results were good
tested the radial circuit and at x1 my fluke tester gave a error 4 message which is a earth error

wasn't sure if i was on to anything here so i unplugged everything from the radial and insulation tested it, all fine,
then when everything was disconnected i also rcd tested from the mcb which gave a good results no error 4
then i decided to start plugging in appliances one by one to see if effected the rcd test
got to a fridge freezer and the error 4 came back,

still not totally convinced this appliance was faulty i decided to put the fridge freezer on a different rcd and wait to see if this rcd trips

hopefully find out if it was the fridge freezer on Tuesday

would be handy to know if this method of testing does pick up faults in the appliances ????

the best thing to do would be to pat test the appliance or attach a clamp meter to the cpc and record any earth leakage, but didnt have those tools on me

 

[GLENNSPARK]

Did you not do a ramp test on the rcd to find out what the actual tripping current was?

 

[chrisreid186]

yeah ramp tested the rcd and the result was good, i think because they re setted it so many times the old one just gave up

 

[Sav]

I think that most fridge/freezers have some small kind of earth leakages due to the thermostat or pump ?????
Do a pat test maybe to clarify.
Best regards,
Sav

 

[GLENNSPARK]

Chances are it`l be that fridge freezer as they are known to develop earth leakege problems with age. Do you know anyone who can pat it for you. If the rcd is staying in without that appliance connected then you may have found the problem however, it might be a combination of several appliances that just tipped it over the edge...........

 

[chrisreid186]

when i plugged the fridge freezer in it didn't trip the rcd so i expect that the fault only becomes apparent after a few hours of the fridge freezer being in use, would pat testing pick this up?

 

[chrisreid186]

also he did say he defrosted it recently so maybe something got a bit damp and caused earth leakage?

 

[GLENNSPARK]

As the fridge warms up then the earth leakege will become more pronounced until eventually the RCD wont stay in.......

 

[chrisreid186]

so would pat testing pick up the fault straight away?

 

[GLENNSPARK]

Good question chris. Best to try and see: its a process of elimination. It seems to me that you have decided it was the fridge so i would go for that. Plug it in, get it warmed up then pat it......see what you get......

 

[MarkieSparkie]

Hi chris, I'm not sure what your "test method" has told you because I think your interpretation may be based on a false premise. I leave that to you to decide in light of the following information.
Error Code 4 on a Fluke 165x series MFT actually indicates the test has been inhibited because the MFT has detected a Fault Voltage equal or greater than the preset level. Only two preset levels are able to be set, 25V or 50V, for nearly all installations, including domestic, it should be set to 50V. To check the setting look at the top right hand corner of the MFT display, it should read U[SUB]L[/SUB]=50V, if it reads U[SUB]L[/SUB]=25V press F4 to toggle the setting.
You like many others interpret Error Code 4 as an "Earth Fault" it's an easy mistake to make. If the green lead ("earth") has a poor connection (or is disconnected) the MFT thinks that the green lead is at some potential in excess of the preset Fault Voltage and therefore inhibits the test. Often remaking the green connection and retesting allows a reading to be obtained because now the MFT sees a normal safe voltage on the green lead. However, with a sound connection, if the test is still inhibited (Error Code 4) the MFT has detected a true excessive Fault Voltage. In this case you will need to check the installation, in particular, the voltage between N-E.

 

[GLENNSPARK]

Hi chris, I'm not sure what your "test method" has told you because I think your interpretation may be based on a false premise. I leave that to you to decide in light of the following information.
Error code 4 on a Fluke 165x series MFT actually indicates the test has been inhibited because the MFT has detected a fault voltage equal or greater than the preset level. Only two preset levels are able to be set, 25V or 50V, for nearly all installations, including domestic, it should be set to 50V. To check the setting look at the top right hand corner of the MFT display, it should read U[SUB]L[/SUB]=50V, if it reads U[SUB]L[/SUB]=25V press F4 to toggle the setting.

Touch voltage.......

 

[chrisreid186]

would it be reasonable to assume that the fridge freezer is creating the 50v fault voltage ? as it only appeared when the fridge freezer was plugged in>

 

[GLENNSPARK]

would it be reasonable to assume that the fridge freezer is creating the 50v fault voltage ? as it only appeared when the fridge freezer was plugged in>

What do you think?:cheesy:

 

[chrisreid186]

has to be