RCD tripping

[Tinyotall]

Help Please!!

Had an issue today where a external DBs RCD in a garden shed / workshop keeps tripping. It only trips when high wattage items are used, otherwise its fine. The installation has been active and fine for the past 7 years. I have tested all circuit, all sockets / points but can still not find the fault. the SWA to the shed also tests fine. Any help would be good.......

 

[Deleted member 9648]

If all tests are fine it would suggest a faulty RCD,a ramp test might show something up...or just swap it and see.

 

[Guest123]

You mention "high wattage items".

Is there a possibility of accumulative leakage from these items???

Is it possible the RCD has deteriorated, have you tried ramp testing it to see at what value it is operating at???

 

[Tinyotall]

If all tests are fine it would suggest a faulty RCD,a ramp test might show something up...or just swap it and see.

Have replaced the RCD and it trips too. Could it be further back?

 

[topquark]

Have replaced the RCD and it trips too. Could it be further back?

Could be a faulty batch. Ramp test it and prove it's too sensitive. Then if it proves to be ok, check neutral connections in the CU. Neutral bar and all main neutral lead terminations in main incommer and RCD/RCBOs.

 

[Tinyotall]

You mention "high wattage items".

Is it possible the RCD has deteriorated, have you tried ramp testing it to see at what value it is operating at???

The items are a Heavy duty Vac and a Shower also sometimes trips with the TV turning on. Did change the RCD but no avail. have tried all circuits turn and tried the items in turn in each circuit. gone through every test my Fluke will allow. still scratching head.

 

[topquark]

You have showers and TV in the garden/workshop?

 

[Tinyotall]

You have showers and TV in the garden/workshop?

Dog grooming!

 

[Tinyotall]

Could be a faulty batch. Ramp test it and prove it's too sensitive. Then if it proves to be ok, check neutral connections in the CU. Neutral bar and all main neutral lead terminations in main incommer and RCD/RCBOs.

The power to the shed is fed from the meter into a 30amp fused switch then via the SWA to the shed DB.... The only neutral not checked is in on the switch before the SWA, but as this if fed direct from the meter did not want to open it up!

 

[Tinyotall]

anymore ideas?

 

[telectrix]

not the cheapest solution, but you could replace the MCbs with RCBOs, ditch the existing RCD. that should track the fault down to 1 circuit.

 

[pushrod]

Higher current makes me think more earth leakage. What were your IR values on those circuits?

Edit: have the appliances that are causing the tripping been tested?

 

[malcolmsanford]

Help Please!!

Had an issue today where a external DBs RCD in a garden shed / workshop keeps tripping. It only trips when high wattage items are used, otherwise its fine. The installation has been active and fine for the past 7 years. I have tested all circuit, all sockets / points but can still not find the fault. the SWA to the shed also tests fine. Any help would be good.......

That would say to me one or two things there as been a deterioration of the installation or there is something new that as been introduced.

As you say you have replaced the RCD with another and still the same. You have checked the terminations all ok, so is there a dampness issue, I assume the shed is also 7+ yrs old could there be a breakdown in insulation that is causing dampness, to check this you could for a temp test do away with RCD protection and see what happens, you will though need to make sure that your ZS for the protection devices are spot on.

Second then if all this is ok is anything new bought, or is there an intermittent fault on existing appliance ie is the shower element breaking down. If you have bought a new piece of equipment then maybe that is having a cumulative affect on protective conductor current so check that with an appropriate clamp meter. IF all Ok then start to PAT test the appliances.

 

[telectrix]

and if all else fails. --- wooden shed... bonfire night next month.......

 

[Tinyotall]

That would say to me one or two things there as been a deterioration of the installation or there is something new that as been introduced.

As you say you have replaced the RCD with another and still the same. You have checked the terminations all ok, so is there a dampness issue, I assume the shed is also 7+ yrs old could there be a breakdown in insulation that is causing dampness, to check this you could for a temp test do away with RCD protection and see what happens, you will though need to make sure that your ZS for the protection devices are spot on.

Second then if all this is ok is anything new bought, or is there an intermittent fault on existing appliance ie is the shower element breaking down. If you have bought a new piece of equipment then maybe that is having a cumulative affect on protective conductor current so check that with an appropriate clamp meter. IF all Ok then start to PAT test the appliances.

Many thanks for all input. Have narrowed down the issue to the shower, did pat test it and it failed on leakage.