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Posted By Topic: Drinking water fountain

shuffleboy
Nov 22 2019 19:13

Hi forum members.

Attended a call out for a drinking water fountain, that had been recently installed by a plumber. We are the service agents.

The fountain contains 2 parts - a bottom unit with a 'Bubbler tap'. This part contains the coming compressor system.
And a top part, which sits on top and contains a push button/switch/solenoid system for filling bottles. The cold water is fed by the bottom unit.

Both unit components have their own single phase power supply, IEC leads. .

The call-out was because the top unit(which contains a little bottle counter display) had blown its main PCB.

I replaced the PCB.

Whilst my colleague was at the van collecting some parts, I decided to inspect the bottom part of the unit. This unit had a separate earth wire run to its chassis, over and above the earth in the socket.

I performed a leakage test and also clamped around this extra earth bonding wire and both times found approx 60mA leakage current. This result also showed when the socket switch was Off. Both on a suicide lead and on the separate earth bond the sparky has added to the unit frame.

How, with the socket switch in the off position, can a leakage current so high exist in the earth conductors?

I tried a nearby hoover on the wall socket and the leakage current dropped to almost zero. So it only affects the fountain.

DO you have any thoughts?

   

shuffleboy
Nov 22 2019 19:16

Am trying to add a photo but file size xe too big. Working on it...
   

shuffleboy
Nov 22 2019 19:19

Photo
   

SaintAlan
Nov 23 2019 21:26

You can get all sorts of circulating currents when you join two earth systems together. If power is leaking to one earth and the other earth has lower impedance to neutral (eg an MEN) then the current takes the easiest path.
I take it that the metalwork of your fountain is already grounded to the power earth and the second earth is complicating the situation. There might not be anything wrong with your fountain.
   

benben
Nov 25 2019 08:04

I find earthing and/or bonding on commercial jobs these days are always done way over the top, usually due to and electrical engineer specifying way to much.

If an appliance has a supply lead with an incorporated earth, why have additional bonding? or at least disconnect the earth if bonding with larger cable.