rcd not tripping

[michufc]

hi to all i need a bit of help as i dont normally deal with 3 phase i have come to carry out a periodic inspection and carried out a rcd test on varrious circuits and it wont trip at 1x test

the system has a old mem d/b with a rcd as a main switch
what would cause the rcd not to trip out

thanks mike

 

[telectrix]

does it trip at x5? are you sure it's 30mA.? if so, it's duff and needs replacing.

 

[michufc]

it says on the rcd 0.03ma on it and in fairness i carried out a auto test and it stopped at 1x due to it detecting a non trip

 

[telectrix]

try it on manual. if it don't trip, press the test button. sometimes, if they've not been used they stick. if in doubt, replace.

 

[michufc]

well thats what i thought so i pressed the functual test botton but still no good do i only need to carry out the testing at 5x then

 

[telectrix]

if it don't trip at X1 and don't trip off the test button, it'e deffo faulty. replace it.

 

[Marnik]

Why test at 5x? If the functinal test button fails, there is no point at all! Replace the RCD

 

[SimpleSimon]

Test needs to be done at x1/2 x1 and x5 and a ramp.

 

[michufc]

that was my conclusion the problem is is a really old board so i think i would be easier to replace the whole thing it has 10 circuits at prescent but i have no idea how much to charge to replace it as its a church it has to go to a comittee for the go ahead

 

[telectrix]

looks like his RCD is due for the hammer test.

 

[michufc]

what do you mean by hammer test mate

 

[telectrix]

place rcd on floor, whack it with a hammer. then you are certain its duff. seriously, though, if you're considering replacing the whole board, cost out your materials, estimate the hours involved ( including testing) and multiply the hours by what you think is a reasonable hourly rate. then add on 25% for materials mark-up and snags.

 

[Risteard]

Test needs to be done at x1/2 x1 and x5 and a ramp.

No need to ramp test. The 1/2 test ensures that it doesn't operate at half its nominal rated residual operating current which is what is required.