Tripping Problem

[Paul FA]

I have garden lights in the front and back gardens. They are on a timer.

When the garden lights are on and the indoor house lights are also on, everything is fine.

When I turn on the oven or other large heating appliances the entire property electrics trip.  When I isolate the the garden lights (ie isolate them on the main switch board) everything works completely normal.

 

[Murdoch]

my guess is that you have cumulative leakages that are tipping the RCD to trip

 

[Paul FA]

Thanks for your response Murdoch.  Apologies, I am a novice and have no idea what "cumulative leakages" means.  Be great if you could perhaps spell it out for me please.

 

[Murdoch]

Thanks for your response Murdoch.  Apologies, I am a novice and have no idea what "cumulative leakages" means.  Be great if you could perhaps spell it out for me please.

I'm guessing that each of the circuits on the RCD are leaking to earth - once you get to about 22 ma then it will trip - so depending on whats being used on these circuits then either trips or doesn't trip the RCD

Tricky to say much else really without using proper test kit ....

 

[Fleeting]

Why should it trip at 22ma. Product standards dictate 30ma rcds are manufactured to trip at around the 27-28ma mark.

 

[SPECIAL LOCATION]

Why should it trip at 22ma. Product standards dictate 30ma rcds are manufactured to trip at around the 27-28ma mark.

BS7671 states the must not trip at 15ma,   but must trip at 30ma.

the real world means it is actually permissible for anything 16ma or higher to cause an RCD to trip...

But that said it is also a poor design having multiple circuits sharing the same RCD..

as BS7671 also says you should design installations to avoid nuisance tripping.   

 

[Fleeting]

BS7671 states the must not trip at 15ma,   but must trip at 30ma.

the real world means it is actually permissible for anything 16ma or higher to cause an RCD to trip...

But that said it is also a poor design having multiple circuits sharing the same RCD..

as BS7671 also says you should design installations to avoid nuisance tripping.   

I don't understand @Murdoch saying at 22ma it will trip.

 

[Paul FA]

Thank you Murdoch, Fleeting and Special Location.  Its great to have you guys discussing my problem.  I am more than happy to get in an Electrician to solve the problem.  However, it would really help if I could give him a steer as the last time I had a different type of problem I felt I was being taken advantage of.

Any thing to guide whoever I employ.  Better still if you guys can solve!  Thank you all.

 

[Murdoch]

Why should it trip at 22ma. Product standards dictate 30ma rcds are manufactured to trip at around the 27-28ma mark.

let’s just say that’s a figure based on many years of hands on experience ...... and reality at the coal face

 

[Fleeting]

let’s just say that’s a figure based on many years of hands on experience ...... and reality at the coal face

That doesn't explain why you stated a 30ma rcd will trip at 22ma.

 

[UNG]

That doesn't explain why you stated a 30ma rcd will trip at 22ma.

To explain

The British Standard requirements for RCDs states that the RCD should operate between 50% and 100% of its rated tripping current. That is 15 mA and 30 mA for the 30 mA RCD. Most 30 mA RCDs operate at levels between 18 mA and 23 mA.

For a more in depth explanation

https://www.tlc-direct.co.uk/Technical/Distribution/RCD.htm

 

[Murdoch]

That doesn't explain why you stated a 30ma rcd will trip at 22ma.

tripping times are a bit like car manufacturers claimed MPG - optimistic 

the lowest I’ve seen recently was 17ma and a typical value is low 20’s

 

[Andy™]

That doesn't explain why you stated a 30ma rcd will trip at 22ma.

because, from real life experience, thats when they start to trip. sometimes a bit lower, sometimes a bit higher

 

[Paul FA]

Thanks Murdoch, Ung, Andy, Fleeting, & Special Location.

Where do I go from here?

 

[Andy™]

start with some IR testing...

 

[Murdoch]

Where do I go from here?

ask around for a competent spark and get them to do some proper tests

in the meantime keep a diary of when it trips and what was on / being used at the time

 

[Paul FA]

Good advice.  Thank you everyone

 

[binky]

Thanks Murdoch, Ung, Andy, Fleeting, & Special Location.

Where do I go from here?

The other possibility is to separate garden lighting onto a mini board, so it no longer shares the RCD with internal house ccts.

 

[Murdoch]

@Fleeting

Test results from a brand new out of box RCBO today



22.5mA

 

[Paul FA]

Thanks everyone. Is putting the garden lights onto a separate board costly?