300ma RCD tripping randomly

[Bradley6969]

Distribution unit 100A 300ma 3phase RCD with four 60A BS88 each fuse feeds 4 boxes on one circuit with 2X16 socket outlets with own individual 30ma RCBOs but there ok and all being plugged into
The RCD keeps tripping? Have tested the distribution unit and all the boxes with IR test and RCD I’ve the earth leakage with all loads connected and disconnected can’t see a problem but there saying it’s nuisance tripping at vary periods within a month for instance,
Can this be an imbalance on the phases?
Or overload of 100A??

 

[telectrix]

an overload will not trip a RCD. have you tested the RCD? try a RCD test with circuits connected and then again with circuits dissed. also ramp test in both situations. if readings are different, then the problem is in the circuits. e.g. if a ramp test gives 275mA with no circuits connected, and 140mA with them connected, then you have somewhere around 135mA leakage on the circuits.

 

[Bradley6969]

an overload will not trip a RCD. have you tested the RCD? try a RCD test with circuits connected and then again with circuits dissed. also ramp test in both situations. if readings are different, then the problem is in the circuits. e.g. if a ramp test gives 275mA with no circuits connected, and 140mA with them connected, then you have somewhere around 135mA leakage on the circuits.

Thanks will try that, what I mean is over current or inrush? I know the over current has protection with the 60A fuses

 

[suffolkspark]

Is it an old wylex one? Ive had so many of them over the years trip randomly yet test out fine

 

[Bradley6969]

Is it an old wylex one? Ive had so many of them over the years trip randomly yet test out fine

Nope it’s not, they’ve had Board out to check there end as it’s over head supply and possibly thought it was a spike in voltage as it’s really random like could trip off for a few hours then be alright and then not trip for say a month but all cables IR tested all ok just gotta go back to ramp test

 

[Bradley6969]

What typical earth leakage reading would it cause it to trip say I had a 30ma rcd anything more than 30ma of leakage cause it to trip?

 

[Bradley6969]

Over so many circuits or even one circuit?

 

[Toneyz]

Is this a TT supply or any particular regulation that having the 300mA RCD has been installed to comply with?

 

[suffolkspark]

What typical earth leakage reading would it cause it to trip say I had a 30ma rcd anything more than 30ma of leakage cause it to trip?

Huh?

 

[Deleted member 9648]

How long are the distribution circuits? Capacitance on very long runs can cause RCD's to trip, sometimes when a load is switched on or off.

 

[Bradley6969]

Is this a TT supply or any particular regulation that having the 300mA RCD has been installed to comply with?

Yes TT install as it feeds some power bollards on a marina

 

[Bradley6969]

How long are the distribution circuits? Capacitance on very long runs can cause RCD's to trip, sometimes when a load is switched on or off.

Max run 30m ish cable is 16mm in and out each bollard

 

[Toneyz]

I’ve the earth leakage with all loads connected and disconnected can’t see a problem but there saying it’s nuisance tripping a

If I am reading this correctly what was the leakage with all the loads connected and disconnected? Also, have you done a ramp test on the 300mA RCD?

 

[gazdkw82]

Need to test the rcds thoroughly. Good suggestion about about doing tests on load and off load.