RCBO fails trip time. Causes? How to speed it up?

alphonse mephisto

This is a brand new installation. Its small but there are plenty of circuits. All wiring is 100% and everything works as planned. ALL pre-connection tests were perfect. I havent done Zl ohms yet. My RCD trip time fine. But I have 5 fixed appliance powerd by 5 RCBO and these fail RCD max operating time. tripping at 0.46sec.

:rolleyes:What are your thought on this?

Causes?

Solutions?!

frankmul

alphonse mephisto wrote: »

This is a brand new installation. Its small but there are plenty of circuits. All wiring is 100% and everything works as planned. ALL pre-connection tests were perfect. I havent done Zl ohms yet. My RCD trip time fine. But I have 5 fixed appliance powerd by 5 RCBO and these fail RCD max operating time. tripping at 0.46sec.

:rolleyes:What are your thought on this?

Causes?

Solutions?!

just wondering if your rcd tester is in calibration. any chance of getting a second tester to retest the circuit.

M cebee

they can't all trip at 0.46 sec on the 30mA tests anyway

frankmul

M cebee wrote: »

they can't all trip at 0.46 sec on the 30mA tests anyway

true, strange that they all had the same time. never thought of that

2011

frankmul wrote: »

true, strange that they all had the same time. never thought of that

+1
Very good point.

frankmul

Might it be 46msec instead of 0.46 sec. I have seen a few caught out by that

alphonse mephisto

Sorry it is 46msec but its still a fail? Its strange that its all of them, fair enough one or two but its five different circuits. Only thing they have in common is the same make and type of rcbo. Ive been doing the tests at the circuits spur on the feed side with the load disconnected.

alphonse mephisto

I can try the test across the rcbos terminals and see what happens,
Any other thoughts other than rewire the board?

frankmul

Disconnection time is 0.3 seconds or 300msecs for the rated current. 46msec is well inside that.

M cebee

yes
46ms is a pass anyhow for 30ma test

alphonse mephisto

I am in fact a cabbage. Was just looking at the manual off use rcd tester. It gives readings in milli seconds I miss read the regs! Worked out alright so! Zl Monday morning and hopefully an early drink so! :-)

alphonse mephisto

Can't believe that was so foolish! Even stranger now the times being. The same! A lot of stress relieved there!

2011

frankmul wrote: »

Disconnection time is 0.3 seconds or 300msecs for the rated current. 46msec is well inside that.

Correct me if I'm wrong, but I think that the disconnection time is 0.2 seconds.

M cebee

wasn't it always 300ms

and 40ms i think for 5x

has it changed?

2011

M cebee wrote: »

wasn't it always 300ms

and 40ms i think for 5x

has it changed?

I am not aware of any change. It has been a while, I thought it was 0.2 sec

M cebee

2011 wrote: »

I am not aware of any change. It has been a while, I thought it was 0.2 sec

i've had a few beers and don't have rules handy so i'm not much use:)

Bruthal

M cebee wrote: »

i've had a few beers and don't have rules handy so i'm not much use:)

Dont be blaming the beers on that:pac:

frankmul

p5 section 3.6
http://www.etci.ie/docs/ET214.pdf

alphonse mephisto

From et 101 2008 max operating times for general type rcds 1x In 0.3 sec.
5x In 0.04sec

frankmul

Did you test in both half of the cycle

alphonse mephisto

I did indeed, my higher readings seemed to be on the 180side! Ill do couple more anyway to be sure but looks like a pass now anyway! :-)

alphonse mephisto

What would cause an rcd fail its tripping time anyway?

frankmul

Mechanical part of rcd slow to act could be one reason