Fault finding issue/help!

[isparky]

Hi all. Just been to look at a job that was recently done by another electrician, can't fault the work other than he has yet to provide the client with any certificates and no fly lead on the armoured cable supplying a sub mains board! It's a summerhouse being used as a gym/storage. It has a sub mains consumer unit with one ring final and one lighting circuit. Basically the ring final circuit and the RCD at the main consumer unit in the house is tripping when the lights are switched on and the treadmill is running. The treadmill is from the US and has a litefuze lt5000 step up/down voltage transformer to power it up. Other than the treadmill there is only a fan plugged into the ring main. What I am wondering is could it be the transformer that is causing the breakers to trip, anyone else encountered this issue? Also to note is it does not trip when the lights are switched off, only when both the lights and treadmill are on, which has got me slightly baffled. I have carried out a Zs test but no insulation tests thus far.

Any suggestions appreciated!

Ben

 

[Guest111]

I would try a leakage current test as it sounds as though it may be a combination of leakage currents causing it to trip.

 

[drew35]

Plug something else in instead of the treadmill, that will rule out the treadmill quickly wouldn't it???

 

[KFH]

My 110V transformer often trips RCDs, one day I will test it to find out why. I would suspect the transformer, get testing

 

[telectrix]

is it MCB tripping or RCD?

 

[isparky]

is it MCB tripping or RCD?

When I first arrived it was both rcd's, main switch on sub-mains and rcd at on split load board in house. But later on it was mcb at sub-mains and rcd in house.

What they were originally doing was turning the transformer on v

 

[isparky]

they were originally turning the transformer on via the socket, so I tried leaving the transformer on and turning the treadmill off via the on/off switch on the treadmill. Tried this several times with the lights on and seemed ok. Client is going to report back but I'm sure it will need a revisit.
Maybe there is a spike in earth leakage when the transformer is first turned on?