My condenser tumble dryer keeps tripping the main 80A switch on my CU.
It runs fine (on half heat setting) for about 40 mins, then trips.
The socket in use is in the garage approx 5 mtrs direct spur to the CU in the garage on a 16A circuit breaker which does not trip.
Nothing in the house except the fridge/freezer on the kitchen circuit is on (apart from Sky box on standby) no electric shower etc.
Any ideas?
TIA
Might that be an RCD type 80A?
Sounds like an RCD trip rather than a trip on over current.
"Switch"? I think you mean RCD as normally the "main switch" in an CU has now fault or overload function it is just a switch.
Assuming that it really is an RCD the the chances are that the dryer has an earth leakage fault, this is fairly commmon. Probably have to repalce the heating elements.
earth leakage issues.
Possibly damp electrics in the unit, or neutral/earth short on the ring. Or a slightly high impedance joint that puts a spike on the mains when it switches on or off, and allows transient earth currents through all the capacitors in the RFI filters around the house.
Fit a 100mA 60A trip if you have a 30mA, and fit RCBO's to the 13A sockets on the ground floor rings, and check for earth neutral shorts. If it still happens, fix the bloody drier! I had a washing machine like this. windings on a motor were shorted to the amarmature.
sorry yes, wrong term apols
yes RCD (sorry)
replace dryer is easier I think :-(
sounds like its the dryer, I will just throw it out. and get a new one
thanks for advice,
Vass presented the following explanation :
That could be be either damp causing leakage or probably even more likely the heating element on the point of failing/burning out. You could check the element for leakage to earth with a megger, but a rough check which might work is to disconnect just the element and then try running it - providing the machine itself doesn't then go into a fault condition and promptly shut itself down.
hmm found these elements
right, its running now without heater element connected, will report back in an hour
Replacing heater elements is usually fairly straightforward. The other thing to check is if it has a noise filter like
It's been a while since I've had to delve inside a tumble drier, but the ones I've come across have an open type heater, where the resistance wire is sprung between mica or ceramic supports.
How can a heater fail, apart from carbonised fluff bridging to an earthing point? Where perhaps a good blast of compressed air would solve the problem?
well, disconnecting it has stopped it tripping after an hour of use. i will pull the heater out and take a look. thanks
heater looks fine, clean and undamaged. However there is evidence of wet fabric particles all around the fan area small clumps of it but not near the elements.
Before going down that route, it might be worth noting that it sounds as if you have a "whole house" RCD which can be a PITA even with correctly working appliances if enough of them gang up on you. Dave's solution would be a good one to implement anyway to stop you losing all power on a trip.
Sounds a bit of fire risk with the amount of fluff that is about in a tumble drier. The one I took apart and cleaned(*) had a couple of coiled mineral insulated elements bit like those on an electic cooker but shaped like the coiled CFL lamps. Mineral insulated heaters are prone to leakage.
(*) The single shot over heat stat operated it was that going that prompted me to investigate. Both elements and the ducting where heavily caked in fluff and a couple of places said layer of fluff on the elements was decidedly charred...
This was a condensing dryer so the air is heated and circulated rather than a vented drier with heats the (relatively clean) incoming air then dumps it.
Ummm...
1 - Many driers now do use open-coil elements This I do not like re fluff & fire hazard - I too prefer mineral insulated.2 - One RCD may be sensititised by other appliances An RCD typically trips at 23mA - not 30mA. If enough appliances leak
1-2mA then they can get up to about 10-12mA earth leakage, only needs 12mA on the tumble dryer or anything for nuisance tripping.3 - If you have sockets without RCD, buy a plug-in RCD & test Stick the dryer on a plug-in RCD into non-RCD sockets. If you need to use an extension lead it MUST be 1.25mm and FULLY unwound because a dryer will turn it into a molten glued-together mess (or fire).
4 - If the CU is a split-load, add RCBOs on non-RCD side For example lights down, kitchen sockets, outside socket, etc.5 - If the CU is 1-RCD re whole-house or TT, again RCBOs Basically provide individual RCBO protection where possible. Particularly for kitchen or utility room - so they don't trip the rest.
It could be the AC fan with damp fluff, or the motor - thus far it sounds like the heater. Change the heater and see how things go - if you can strip the machine and get the fluff out of it.
The fluff is in fact lint and it is highly flammable, worth having a smoke alarm above any dryer because if the belt snaps there is a time before the overheat sensors kick in. I am not convinced the overheat thermostat will kick in before any lint around the heater has gone up in smoke.
Fredxx wrote on 15/11/2009 :
Ours use an element similar to an immersion heater element, except of course, not submerged in water. The element runs inside a copper tube mineral insulated, I think. The element can start to break down and become conductive to the earthed copper sheath.
To ensure discrimination the 100mA main RCD should be type S time delayed otherwise there is high likelihood that it will trip at the same time as the RCBO and you end up with the lights and other circuits out all over the house. If your RCD is your main switch do not reduce it from 80A to 60A. There are options for protecting the downstream circuits such as all circuits on RCBOs or splitting the board. into protected sub-groups. If you want to go down that route get hold of a copy of the on site guide to BS7671-2008
yep, there is a row of 4 open coil elements, but they all look pretty clean
I could move the garage sockets to the other side of the split CU
the non RCD side has 2 x 16 unused and a 32 (in use for shower)
Leaving it plugged in to the same socked with no changes at the CU disconnecting the heater and running it for an hour did'nt trip. So, can I be confident its the heater elements? or, could this just reduce the load when in fact it could be the combination of the motor etc ??
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