When I pulled the old one out it was very hot. But maybe that was because I'd reset it a number of times in the previous 15 mins.
Same brand and model number - both MK Sentry B16s. I'll try it tomorrow, when I've actually got some washing to dry!
16A MCB trips when tumble dryer is on
- Thread starter Jimbo
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When I pulled the old one out it was very hot. But maybe that was because I'd reset it a number of times in the previous 15 mins.
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Jimbo, do you have anything else which draws a substantial current, ideally approaching that of the dryer (maybe a fan heater or suchlike), that you could plug into this socket and see what happens?
Kind Regards, John
Kind Regards, John
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Or a 3kW kettle?
I considered that, but given that it apparently usually takes about 20 mins for the MCXB to trip with the dryer, I'm not sure a kettle would be workable. Unfortunately (for this test), other than tumble dryers, 3 kW plug-in loads are not common - which is why I suggested a (probably only 2 kW) fan heater.
Kind Regards, John
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Leave the lid open. 
If you're talking about a kettle, I think that most would take a lot less than 20 mins to boil (and then switch themselves off, unless one 'interfered' with the automatic switch-ff!), even without the lid on.Leave the lid open.
I know what I would probably do if I needed to have a 3kW load for >20 mins supplied through one plug, but I'm not going to describe it here!
Kind Regards, John
I don't think they know they're boiling with the lid open.If you're talking about a kettle, I think that most would take a lot less than 20 mins to boil (and then switch themselves off, unless one 'interfered' with the automatic switch-ff!), even without the lid on.Leave the lid open.
I suppose there may be different types.
As you say, they obvioulsy varies. My usual one certainly does discover that it's boiling with the lid off, although it doesn't make that discovery until a short time after boiling starts.
I wasn't thinking about anything particularly naughty (just 'the obvious', really)! On reflection, the simplest way would probably be to plug in a 2-way (or more ways) extension lead and then plug two loads totalling 3kW into it (e.g. two fan heaters, one running at 2kW and the other at its 1 kW setting).
Kind Regards, John
PROGRESS!!!
I put some drying on this evening, and the MCB tripped. I reset it, and almost immediately I noticed the sound of arcing within the RCD, on the neutral side where it screws into the busbar. Busbar is tight but when I switched it all off and undid the clamps, the busbar was too hot to hold. So clearly the arcing is heating the busbar, heat is being transferred to the MCB which is tripping.
So off to Screwfix tomorrow for a replacement RCD! Will let you know whether this fixes it, but I'm pretty confident!
Thanks all for you help and suggestions.
I put some drying on this evening, and the MCB tripped. I reset it, and almost immediately I noticed the sound of arcing within the RCD, on the neutral side where it screws into the busbar. Busbar is tight but when I switched it all off and undid the clamps, the busbar was too hot to hold. So clearly the arcing is heating the busbar, heat is being transferred to the MCB which is tripping.
So off to Screwfix tomorrow for a replacement RCD! Will let you know whether this fixes it, but I'm pretty confident!
Thanks all for you help and suggestions.
Before you rush off to Screwfix ... are you sure that, although the screws were tight, the RCDs terminal 'cage' (or whatever) was correctly gripping the busbar? With some makes, it's quite easy to tighten the screw without realising that the busbar 'lug' is not actually being gripped in the terminal cage!
Kind Regards, John
That was my first thought when I heard it arcing, but yes it's all clamped up properly.
Fair enough, although I imagine that it would be a pretty unusual fault for an RCD to develop - the L and N conductors essentially just go straight 'through' (straight through the sense toroid and the switch contacts), so the problem would have to be at the termination of one of those conductors or, possibly, a problem with the switch contacts.
I look forward to hearing the outcome. If it were me, and if replacing the RCD solved the problem, my next step would almost certainly be an autopsy on the RCD!
Kind Regards, John
Thanks for the update. That sounds very promising. I'd still be interested to know what the inside of the old RCD looks like!I replaced the RCD, dryer has been running for 45 mins now without a problem, no arcing from the RCD, all seems well!
Kind Regards, John
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