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Discuss RCD tripping when switching oven isolator off in the Electrical Forum area at ElectriciansForums.net

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Hi all.
I was called to a house recently where the occupier reported that when they turned the oven isolator off the RCD would trip.
So I tried it and that's exactly what happened. There was nothing switched on on the oven at the time. When the oven is on it works fine.
It is an integrated oven on a dedicated 16 amp circuit. Circuit tested fine in all respects and a ramp test on RCD showed it tripping at 24 mA.
They have to turn the isolator off when not using the oven as they have a son with learning difficulties who sometimes turns the controls on the front of th oven.
Any ideas what the cause might be?
Thanks.
 

Matthewd29

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Arms
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Did you try an earth leakage clamp.on the circuit? It is possible that there is a spike when turning it off which is pushing an already close RCD over the edge, it's a long shot but I have seen it happening
 

telectrix

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Mentor
Arms
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as post #4. try replacing the isolator before the head scratching.
 

marconi

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Mentor
Arms
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Replace the DP switch with one which makes the neutral before the line and breaks the line before the neutral. I think MK cooker switches operate this way.
 
  • Thread Starter Thread Starter
  • #13
Hi folks, sorry for not getting back with the outcome. Changed the 20 amp double pole switch and problem solved. Thanks for all your replies.
 
B

Bobster

Replace the DP switch with one which makes the neutral before the line and breaks the line before the neutral. I think MK cooker switches operate this way.
Understandable for a 3ph DB main switch for example.

However, this shouldn't in theory effect a single phase load. There isn't a difference in current draw, by switching line or neutral.

Unless the switch is faulty and is sending some current elsewhere.
 

Midwest

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Arms
Esteemed
Understandable for a 3ph DB main switch for example.

However, this shouldn't in theory effect a single phase load. There isn't a difference in current draw, by switching line or neutral.

Unless the switch is faulty and is sending some current elsewhere.
Beama talk about 'Double pole switching within the fixed wiring is known to produce a strange phenomenon whereby switching OFF a double pole switch supplied through an RCD can cause the RCD to trip.' in their RCD Handbook.

So there must be some substances to it.
 

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