Discuss RCBO socket circuit tripping. in the Electrical Forum area at ElectriciansForums.net

GBDamo

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I'm stuck here fellas.

I have a radial with only one double socket outlet in 2.5mm T&E on a 20A RCBO running five meters in surface mounted trunking. TN-S, R1 and R2 good, 243V measured, Ze 0.12, Zdb 0.29, Zs 0.36, IR all +200MOhms.

RCD trip tests all ok at 0 and 180 and ramp 24mA.

Now these sockets are only used for one thing, two 580W water distillers.

Both have been clamped during operation and are drawing 2.4-2.6A as expected.

Both have been IR tested L-E & N-E and +200MOhms.

I am stumped to the point where I may run in a new socket on a new RCBO, cost not an issue the customer just wants it stopped.

My concern is the issue could be with one or both the distillers units and not the circuit.

I don't have a low current clamp meter so cannot measure earth leakage directly.

Any ideas where to look next, I'm still on the job by the way.
 
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GBDamo

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  • #3
First thoughts are towards faulty distillers..
Have you tried plugging in other appliances?
I'm leaning that way too but cannot think of any definitive way of proving it.

I think it's happening when there thermal overload kicks in, i.e. when they're run dry as they often trip overnight.

I don't want to test that as it may damage the kit but it's the only theory I have at the moment.

I think the customer knows this as they have had them put on a dedicated circuit so as not to take down other areas.
 
O

Octopus

As a "controlled test" replace the RCBO with a MCB for a couple of nights and see what happens?
 

SparkyAndGeorge

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Arms
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Most likely faulty appliance. How often is it tripping, instantly or randomly? Seen something like this before even though it recently "passed" all its PAT tests. As above swap rcbo for mcb and replace socket for T earth and mark up.
 
Defiantly points to a faulty appliance. A PAT wouldn't necessarily pick this up though, the equipment is likely 'safe' to pass PAT. Could be worth contacting the appliance manufacture.
 

GBDamo

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Most likely faulty appliance. How often is it tripping, instantly or randomly? Seen something like this before even though it recently "passed" all its PAT tests. As above swap rcbo for mcb and replace socket for T earth and mark up.
What's a T earth? Auto correct fail?
 

GBDamo

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  • #11
Most likely faulty appliance. How often is it tripping, instantly or randomly? Seen something like this before even though it recently "passed" all its PAT tests. As above swap rcbo for mcb and replace socket for T earth and mark up.
Defiantly points to a faulty appliance. A PAT wouldn't necessarily pick this up though, the equipment is likely 'safe' to pass PAT. Could be worth contacting the appliance manufacture.
Just passed PAT test..:D
 

Charlie_

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Arms
Nothing wrong with removing sealed plugs, happens all the time with washing machines, etc.
Are the units easily serviceable?
Do they have spare parts?
 

GBDamo

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  • #14
Turn them off overnight and see what happens.
If only they'd listen.

I am looking for a manual as we speak as I cannot see how they control other than thermal trip.

Aquadist Euronda
 

GBDamo

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  • #15
As there any other temperature control apart from the thermal cut-out?
Not that I can see, no.
 
D

Deleted member 105166

Wire a manual time switch into the circuit, so you can see what time it trips. Reset the time switch and repeat for a couple of nights. May give some clues.
 
Just passed PAT test..:D
A proper PAT with a mains voltage tester, testing for a true earth leakage, or a pass/fail simulated tester? Big difference.
 

GBDamo

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  • #21
Hi,

With your ramp test was the readings consistent?
Yes.
 

littlespark

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Is it one of the appliances, or both?
Is it conceivable to run another dedicated circuit, RCBO controlled and see which of the 2 are causing the problem.

It could be as simple as the socket being faulty
 

GBDamo

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  • #25
I'm going home.

Will get in touch with the manufacturers and discuss further and if necessary fit using FCUs.

Cheers guys.
 

GBDamo

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  • #27
Is it one of the appliances, or both?
Is it conceivable to run another dedicated circuit, RCBO controlled and see which of the 2 are causing the problem.

It could be as simple as the socket being faulty
There are already three circuits there, the new dedicated circuit, the old ring main and a random MIC metal clad single.

All three circuits have tripped but they "manage" it by keeping them on the recently installed dedicated circuit.

They are not the most helpful, like I said will try the manufacturers and look to FCU them.
 

freddo

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Insulation fault when something heats up and expands? Clears again when cool.
 

Wilko

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So - a “plug in” appliance that has degraded over time and likely has 20mA or more earth leakage is to be kept in service by adapting the electrical installation to remove the RCD ?
Just checking I’ve understood this correctly :) .
 

Charlie_

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Arms
Asked on the forget information you have given I would say that the equipment is faulty, elements may appear to be fine and test ok but as soon as they get hot the resistance to earth diminishes..
The fault current might even be high enough to take out an mcb
 
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