RCD's wont TRIP!

[Marie-Claire]

I changed a distribution board on a TT system to a new one but both RCD's won't trip when i have pressed test. Is it possible both RCD's are faulty? Everything is installed correctly

 

[cagedanimal2010]

could we have a bit more info please!
what type of db?
is power getting to rcds?

Danny

 

[Dunc]

Have you checked there is power going to the RCD and polarity is correct?

 

[Marie-Claire]

Yes the power is definately there, the ring main and lights work when i powered up, even when i have disconnected all circuits and pressed the test button, the RCD will not trip,

 

[nickblake]

As above have you switched the main isolator on as well as the RCD's, sorry to be patronsing on that but seen it before

 

[Marie-Claire]

yes everything is on, i have checked there is power and proved it by boiling a kettle on the ring circuit, even so, the rcd's will not trip when i press the test button or when i created a deliberate fault

 

[cagedanimal2010]

have you tried a ramp test?

 

[telectrix]

try disconnecting all loads and test. but sounds like they are faulty.

 

[Marie-Claire]

i disconnected all loads and tested, i haven't tried a ramp test, without sounding dumb, i have never heard of one, what does this involve. Also the distribution board was provided by the customer who was given it by a builder, it was new and boxed but where it was purchased from is unknown so we can't check if it was a bad batch

 

[cagedanimal2010]

a ramp test is a function on some testers, in which it test the current needed to trip rcds. have you the make of the board?

 

[kevh]

When you said pressed test, do you mean rcd test button or rcd tester ?

 

[telectrix]

a ramp test is wher the MFT puts fault currents on the RCD starting at 5mA, increasing in 5mA increments till the rcd trips and then tells you the trip current. not all testers have this function.

 

[Marie-Claire]

no, i don't have the make, the incoming supply i measured at 230v and i put a line to neutral fault on the ring so i would have thought that should have tripped out in any case, i pressed the test button with all circuits connected and then unconnected, i have a new board to install on monday so i'll let you know if i have the same problem, im pretty confident the RCD's are faulty but was a bit thrown that that both of them are. Thanks boys

 

[Silly Sausage]

the incoming supply i measured at 230v and i put a line to neutral fault on the ring so i would have thought that should have tripped out in any case,

That's a short circuit and should have taken your mcb out.
I assume you meant say Line to Earth fault!

 

[Mark_Burgess]

What was the Ze reading?