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Earth leakage fault - consider using an whole lab insolation traffo - discuss

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MadScientist:
Hi, IN my home lab/office I have the usual test gear , small CNC mills etc

Annoying my house which i bought three years ago , occasionally tripos its RCBO for no apparent reason , typically flicking the RCBO on again ,restores the status quo

Tracking down the issue is exceeding difficult , the RCBO protects essentially two mains rings and is not on the lighting circuits ( The house was built in 1995 and is coded correctly for the time  ).  This year in 12 months I have three-four trips

I will replace the RCBO soon  and Im considering putting a separate one on each main ring to start the process of segregating the problem

In the mean time I have two choices , Isolate  the whole lab on a 230-230 isolating traffo, ( to eliminate leakage currents from the lab  ) or putting the computing resources on a UPS ( which is what I am doing first ) The UPS isnt really a solution long term , the long term solution is no trips !

The isolation traffo isnt a long term idea, but would at least eliminate over 12 months is anything in the lab generating earth leakage currents, but I have had the RBCO trips when nothing was powered on in the lab . I am aware of the common mode issues with isolation , but putting the whole lab on one would generally eliminate issues of inadvertent grounding

After that Im not sure how to track down this elusive fault , due to the infrequency of its occurrence

ideas ?


Thanks

Dave

vk6zgo:
Some heavy domestic appliances have a bit too much leakage by design to be used on an RCBO, & in Australia are allowed to be driven from an unprotected source.
Maybe they aren't in your country-----where are you?

In this country, things like refrigerators, washing machines & dryers are all used from switched power sockets, & are used RCD/RCBO protected.

Hot water systems, stoves, etc are hardwired, & some of those may be in the group which will be marginal with an RCD/RCBO.

The problem could be a faulty RCBO though---- such things do fail, eventually, just as conventional circuit breakers do.

madires:
An isolation transformer for the whole lab is a bad idea because you wouldn't notice a bad device besides other issues. I'd install a dedicated RCD (plus mains) for the lab, one (plus mains) for the data center, and also one for each mains ring (UK?). This way you would have only a partial blackout if one of the RCDs is triggered.

MadScientist:
My next step is to consider putting the lab on a seperate RCBO , its not " too " awkward as , my lab is close enough to the main distribution board , but as always trying to run twin +earth wires through an existing decorated house is a PITA.

Im in ireland , and the practice here is as per the UK.  Heavy loads like Cookers etc are not on a RCBO , ( in 1995) , newer houses now have all house RCBOs however

Ill replace the RCBO as a first step , thats the easiest and a have a 500W UPS coming to at least protect the computers

its a bugger of a problem to track down

MadScientist:

--- Quote ---because you wouldn't notice a bad device besides other issues
--- End quote ---

There is nothing to stop me fitting a local RCBO to my safety transformer , which would detect local  leakages to the PE wire on equipment connected

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