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Topic Title: "Leaky circuits"
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Created On: 14 October 2016 06:38 PM
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 14 October 2016 06:38 PM
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Sammyh20

Posts: 157
Joined: 18 March 2012

Hi all I have come across a about 3 installations this last 6 months where there seems to be a unwanted amount of earth leakage from different appliances.One of these was a new install ,but when a certain amount of appliances had been switched on the rcd unit would trip.Another instance was a older house but with new tenants with plenty of tech gadgets again causing the rcd to trip .Is this just coincidence or is technology giving us more earth leakage .All three properties had good insulation resistance readings .Any thoughts ,are you lot expierencing anything similar,maybe it is time to start using individual rcbos?.
 14 October 2016 07:27 PM
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mikejumper

Posts: 2408
Joined: 14 December 2006

I think people are learning to live with nuisance tripping as long as it's not too frequent.
 14 October 2016 07:41 PM
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broadgage

Posts: 2380
Joined: 07 August 2007

I think that many appliances are tending towards greater complexity and poorer quality with a consequent increase in earth leakage.

A few examples come to mind, an electric toaster with only a very few mm between the live element and earthed metalwork, carbonised toast crumbs are slightly conductive.

A washing machine with minute clearance between the crimp terminals on the water inlet valve and earthed metal, a trace of condensation resulted in a trip. EVEN IF THE MACHINE WAS TURNED OFF because one side of the solenoid was always live.

A freezer with the mains pilot lamp connected between live and earth, adding a permanent 1ma of leakage.

Trendy light switches with "always on" neon or LED lights also connected between live and earth, adding another 1ma or so, continually.

In all but the lowest budget installations I would favour an RCBO for each circuit, in most cases.
 14 October 2016 08:53 PM
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sparkingchip

Posts: 9953
Joined: 18 January 2003

How many multiple socket adapters with built in surge protection do they have?

Andy
 14 October 2016 11:24 PM
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stateit

Posts: 2668
Joined: 15 April 2005

Two days ago I was called to my local dental practice to investigate an intermittently tripping circuit.

Unfortunately that intermittently tripping circuit took out:

Reception area: PCs, server, comms, coffee machine, socket outlets (with heater or fan plugged in depending on season)

3 no. treatment rooms, each containing: Dental 'drill stations' (I don't know what else to call them), suction machines, socket outlets with PCs and other IT equipment.

3 no. X-Ray machines (one for each treatment room)

All on a single 32A 30mA RCBO.

Poor 'Flossie' (for that's what I mentally called her) was the dental receptionist fielding my call out that had to view me sucking air through my teeth when she asked me if I could 'fix the problem now' while there was a room full of patients waiting for treatment.

I suggested I might need a few hours and the supply would need turning off. She was most surprised it couldn't be 'seen to' quickly with no disruption.

The thing is: I'd worked on the property before it was a dental practice and it was a house. The original 12-way 'house board' was still there but there was a new board added with four circuits that had subsumed the whole installation for the downstairs floor (reception & treatment rooms).

Bad design or what? I asked why the electrician who had installed the new installation hadn't been called, but that drew a blank look. I left my number asking for the owner to call me so I could talk through the situation with them. I'm still waiting for that call...

-------------------------
S George
http://www.sg-electrical.com
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