Tumble Dryer woes - Page 1
Forum section: electronics / general

author: Wilksey
author_rank: Super Contributor
timestamp: September 28, 2021, 07:34:20 pm
content: Hi All,My house wiring is typical - 2 RCDs and a few MCBs running to the side of them, lawnmower used to occasionally trip the RCD but has stopped doing that for some unknown reason, nothing has changed.Anyways, my condenser tumble dryer has started to trip the main RCD to the sockets, but not all the time, every now and then it'll just trip, most of the time it'll complete the cycle and it'll be fine, seems to be worse when there are heavy items such as towels in there, as it was tripping the entire house I decided to get a plug in RCD and plug the tumble into that instead, well, it trips the main RCD still.So why would it not trip the inline RCD in the first place? The dryer seems to get very hot so I am thinking it might have some vents blocked or it could be a thermal switch, do they trip short cct?Any ideas? I'd like to keep the machine as it works fine when it doesn't trip but if it is cactus then it'll have to get replaced, I don't really know much about dryers , but it seems to spin OK and the rest of the time it works and everything comes out dry, no puddles of water anywhere, as I say it is a condenser so the water is contained and emptied after each cycle.Other than replacing it which I don't really want to do, if I can fix it and avoid landfill I will, I am a bit stuck for ideas.Any suggestions much appreciated.Cheers.

author: Monkeh
author_rank: Super Contributor
timestamp: September 28, 2021, 07:53:28 pm
content: House RCD is either more sensitive or just faster operating. You can't put two in series like that and expect discrimination without a time delay.The heater in the dryer is probably full of fluff. Clean all the filters, pull it forward and remove the rear covers and clean back there.

author: Wilksey
author_rank: Super Contributor
timestamp: September 28, 2021, 08:42:46 pm
content: Yeah I figured the house RCD was more sensitive than the plug in one, the plug in one is quite old now, so I might get a new one and see if that helps, the fuse board isn't exactly new, I can't see from the deck what is written on it so i'll have to pull out the steps and see what is written on it.I have cleaned all of the filters in the front, but not taken the back off, I shall have a look.Is there anything that you know of (I am in the UK) that I can get like an RCD that is more sensitive than the house RCD? I think from memory the plug in RCD has 30mA written on it, I am guessing the house RCD is either the same or better, i.e. 10mA or just faster, I think the plug in says 40ms but not sure.I read a post on another forum that states their machine (different model) was tripping all the time, but when he removed the earth connection it worked, that was an interesting read, I didn't see any posts after that from said person mind you- I mean it would stop the RCD tripping

author: antenna
author_rank: Frequent Contributor
timestamp: September 29, 2021, 06:18:48 am
content: Make sure you clean the vent in the back and clean the vent pipe/tube to the outside of the house. A plugged dryer vent will burn your house down faster than you can find a fire extinguisher!Disconnecting the earth connection will prevent the RCD from tripping, but that isreally dangerous, especially if the RCD is telling you there is current on the machine chassis. If you disconnect that ground and get between the dryer and another source of earth ground, you might not need a dryer afterward. If a sketchy bypass is really what you want, just replace the RCD with a plain receptacle and keep the ground connected. It will not be up to code and the fire inspector will mess up that insurance claim... but, ground with no RCD is safer than keeping the RCD and disconnecting the ground to avoid the trip. I would recommend taking a look inside and try to track down what is dumping current on the ground andnotbypass anything.

author: BrokenYugo
author_rank: Super Contributor
timestamp: September 29, 2021, 06:42:36 am
content: Take it apart and clean all the lint out of it, a surprising amount makes it past the filter over time. Being that this is a condenser dryer, also look for evidence of water leaks.

author: themadhippy
author_rank: Super Contributor
timestamp: September 29, 2021, 07:06:58 am
content: QuoteNot in the uk,all the sockets are "plain" the rcd is in the consumer unit and protects the entire circuit. Also the fault current is then going to be on anything thats connected to electrical earth ,if the fault isnt passing enough current to blow the fuse its going to be sitting there waiting to biteQuoteIf your 100% certain of what your doing then yes disconnecting the earth to get elements dried out can work,however you need to be aware of the risks involved and not use it as a permanent "fix"

author: Wilksey
author_rank: Super Contributor
timestamp: September 29, 2021, 12:12:05 pm
content: It is a condenser so it does not have a vent pipe that goes outside.I was not suggesting I would for one second consider removing the earth, I was just pointing out some common responses on other forums....I'll take the back off and clean every orifice I can see at the weekend see if that helps, didn't realise there was filters in the back.Thanks for all of your comments / suggestions.

author: G7PSK
author_rank: Super Contributor
timestamp: September 29, 2021, 01:25:36 pm
content: I had the same problem a few years back, turned out the RCD was the problem had it replaced and no more problems.

author: Wilksey
author_rank: Super Contributor
timestamp: September 29, 2021, 04:15:40 pm
content: Yeah that would be my next suspect, although I wonder would the washing machine not trip the RCD if it was faulty?

author: ajb
author_rank: Super Contributor
timestamp: September 29, 2021, 04:36:42 pm
content: There's often a small amount of leakage between the line conductors and ground in devices, either via filter capacitance which is deliberately placed across line/ground, or parasitic leakage that can increase as devices age/get filled with dust--the latter is particularly likely in motors, since you have a bunch of closely packed windings in a grounded frame that go through frequent thermal cycles.Any sort of breaker can start to wear or age in a way that will make it more sensitive to tripping after a while, so replacing the RCD is probably the best thing to try after cleaning the dryer. If that doesn't solve the problem, then you might start digging deeper into the dryer, and test things like the motor/compressor for leakage faults if you have the equipment for that available.Depending on the age/sophistication of the dryer, it might use an 'electronically commutated' motor, which is really the same thing as a brushless DC motor, for the compressor or drum. That will be more complicated to troubleshoot because you could have a fault in the driver or the motor itself, and it will likely be more difficult to do things like run the dryer with the compressor disconnected to see if that's the cause of the problem.

author: Wilksey
author_rank: Super Contributor
timestamp: September 30, 2021, 04:55:16 pm
content: Thanks all, certainly got a few things to try / consider.

author: Alti
author_rank: Frequent Contributor
timestamp: September 30, 2021, 07:40:57 pm
content: Test your RCD for sensitivity. It must not trip with indefinitely long 15mA leakage and must trip with 30mA within specified time. So 253V/15mA=16k9, this should never trip. If it trips, you have problems with either RCD or the wiring, or both.Putting second RCD in series is doable but that requires selectivity.QuoteAlso, your "condenser tumble dryer" sounds like sth modern. If you have AC type RCD then it is not designed and tested to trip in case the leak is something different than 50Hz AC.If the leakage happens in between phase and protective earth, cleaning electrical wiring might help here. If the leakage is in between neutral and protective earth then this is unlikely you can clean that up.

author: SteveyG
author_rank: Unknown
timestamp: October 01, 2021, 09:03:42 am
content: Quote from: Wilksey on September 28, 2021, 07:34:20 pmBecause the RCD in the consumer unit is seeing the cumulative leakage of the entire circuit plus every appliance on that RCD. It's normal to have some level of leakage and portable appliances can leak anywhere up to 4 mA under normal operating conditions without being considered faulty. Bear in mind things like condenser dryers and washing machines with inverter drives will have some kind of filter network on the AC supply which specifically diverts current to the CPC.For example, the differential current between phase and neutral on my supply is about 19 mA steady state, but it varies considerably as appliances are used. It's likely just that the high integrity consumer unit just isn't suited to your particular usage anymore.I would try to measure the earth leakage on the dryer in isolation if possible. If it tests OK then consider an RCBO based consumer unit.

author: SteveyG
author_rank: Unknown
timestamp: October 01, 2021, 09:05:54 am
content: Quote from: Alti on September 30, 2021, 07:40:57 pmThe failure mode of type AC RCDs is NOT to trip in the event of saturation of the current transformer, which is why it is considered a safety issue and the correct RCD type should be used for certain loads. The false tripping should not happen no matter what the nature of the differential current.

author: Alti
author_rank: Frequent Contributor
timestamp: October 01, 2021, 09:29:51 am
content: Quote from: SteveyG on October 01, 2021, 09:05:54 amYes, well AC type is designed and tested only for AC 50Hz-60Hz leaks. Whether it trips at DC, 1Hz or 1kHz is not specified. It is NOT a failure mode, it is the expected property of this device.

author: SteveyG
author_rank: Unknown
timestamp: October 01, 2021, 11:20:52 am
content: It absolutely is a failure mode.It's fine for it not to trip if there is DC bias exceeding the trip current on it's own, but the device will inherently be unable to trip under it's designed fault conditions whilst there is DC bias present.The analogy would be a car with automatic emergency braking, but the system is not designed to detect pedestrians. However when a pedestrian is present, the brakes no longer work...

author: themadhippy
author_rank: Super Contributor
timestamp: October 02, 2021, 02:15:18 pm
content: Quote50v surely,as that's the maximum voltage permitted on the earth before automatic disconnection kicks in

author: Alti
author_rank: Frequent Contributor
timestamp: October 02, 2021, 05:01:28 pm
content: Quote from: themadhippy on October 02, 2021, 02:15:18 pmThe resistor value given is the smallest value that should work OK when connected in between L and PE, with any compliant AC type 30mA RCD, for indefinitely long. If the RCD trips with this value resistor in between L and PE, then there is a problem somewhere. Voltage out of range, wiring leakage, faulty tumble dryer, RCD too sensitive, etc.

author: ajb
author_rank: Super Contributor
timestamp: October 02, 2021, 05:30:21 pm
content: Quote from: themadhippy on October 02, 2021, 02:15:18 pmIf you can get 50V on the earth conductor with only 15mA then you have bigger problems than just a faulty RCD. That would imply an earth impedance of 3k3.I'm not sure why the earth voltage matters here anyway, though, because what reference would a device have to measure the ground voltage against anyway?Maybe this is a difference between wiring practices and devices in other countries from what I'm familiar with in the US. Here GFCIs don't care about the equipment ground at all, partly because they're the only legal way to fit grounding receptacles on ungrounded circuits (they have to be marked as 'GFCI protected' and 'No equipment ground' as well). Standard breakers don't have a neutral or ground connection at all, but GFCI and AFCI breakers do have neutral connections, since they can't work otherwise. The only device I can see going into a breaker panel that would have a ground connection at all would be some in-panel surge protectors that fit in breaker spaces.I've seen photos/videos talking about consumer units from the UK but am pretty much wholly ignorant of how other places do their residential wiring. I'd be interested in learning about them.

author: Gyro
author_rank: Super Contributor
timestamp: October 02, 2021, 05:40:25 pm
content: Quote from: Wilksey on September 28, 2021, 07:34:20 pmFocussing back on the actual appliance...Firstly, is it one of the affected Whirlpool manufactured ones that are known to cause fires, which has slipped through the recall process?https://www.gov.uk/government/news/update-on-whirlpool-tumble-dryer-recall-progress. If so, discontinue usage immediately.Secondly, is the element one of the enclose tubular types, as also used in electric ovens, washing machines etc.? The most common failure mode in these is increased leakage in the alumina powder insulation between the element wire and sheath when hot (which could tie in will long run time heavy loads). This is a common cause of RCD trips.

author: NiHaoMike
author_rank: Super Contributor
timestamp: October 02, 2021, 11:41:39 pm
content: If the heating element is not accessible with the covers in place (and thus its casing becoming live wouldn't be a safety issue), perhaps it might be worth a try using Kapton tape or mica sheet to isolate it from ground?

author: james_s
author_rank: Super Contributor
timestamp: October 03, 2021, 03:31:08 am
content: Is there a heating element? I thought those condensing dryers used a compressor based dehumidifier instead of a heating element.

author: NiHaoMike
author_rank: Super Contributor
timestamp: October 03, 2021, 04:47:27 am
content: There's usually one to get it up to temperature quickly.

author: Gyro
author_rank: Super Contributor
timestamp: October 03, 2021, 08:51:17 am
content: Quote from: james_s on October 03, 2021, 03:31:08 amUnless these appliances are radically different in the US, I think you're overestimating the dedication of white goods manufacturers.Condensing tumble dryers are very similar to the ducted ones. The only difference is that, instead of being directed through a duct in the wall, the exhaust air is simply passed across a very light Aluminium heat exchanger, warming the incoming air and condensing out exhaust moisture in the process. This increases its thermal efficiency. The exhaust air is still quite warm, but dry enough to be discharged back into the room without causing condensation issues.The element size is probably a little smaller than non-condensing dryers, but they are still fairly high energy consumers. The element is either a closed tube type, as I mentioned previously, or a bare expose type, as used in fan heaters. Replacements for these tend to be more expensive, presumably due to the increased hand assembly required in manufacture.Some examples, a quick look indicates that tube elements are probably used in about 30% if dryers...https://www.elementman.co.uk/elements/tumble-dryer/?p=3A cynic might think that (apart from the comparatively lower power consumption) the main marketing reason for the initial introduction of condenser dryers was to overcome the customer resistance to having to drill a big hole in their wall!The closest I know to a compressor based heat exchanger type drying solution is to hang the wet washing in a closed room with a compressor based room dehumidifier. In both cases, the room gets pretty warm. For domestic reasons, I keep meaning to calculate which is the cheapest solution in energy terms, the relatively shorter multi-kW burst in the dryer, or the longer drying session at a couple of hundred watts with the dehumidifier.Quote from: NiHaoMike on October 02, 2021, 11:41:39 pmUnfortunately, looking at the mechanical mounting arrangements of the tube type elements in the above link, it seems unlikely that this would work without significant modification.

author: richard.cs
author_rank: Super Contributor
timestamp: October 03, 2021, 09:43:39 am
content: Both condensing driers with conventional heating elements, and ones with compressors exist in the UK, the latter are normally called "heat pump driers" and are considerably more expensive.

author: Gyro
author_rank: Super Contributor
timestamp: October 03, 2021, 11:15:05 am
content: Quote from: richard.cs on October 03, 2021, 09:43:39 amI'm clearly a bit behind the times then, I must have bought a reliable one.EDIT: Looking back, the OP clarified that he has a condensing one, so at least we know what we are dealing with in this case. A make and model number would pin down the element style.

author: james_s
author_rank: Super Contributor
timestamp: October 03, 2021, 09:20:45 pm
content: Quote from: Gyro on October 03, 2021, 08:51:17 amCondensing dryers aren't really a thing here, I mean I'm sure you can get one if you look hard enough but I've never personally seen one so I'm quite ignorant as to how they are actually designed, I can only contemplate how I would design one. Our dryers are about 80% electric and 20% natural gas and vented through the wall with a flexible hose, all virtually identical inside whether built in 2015 or 1965. Our washing machines have traditionally been radically different than what you see in the UK and Europe, the traditional dryers I think are fairly similar but the US ones are much larger.

author: Wilksey
author_rank: Super Contributor
timestamp: October 03, 2021, 10:38:49 pm
content: Wow, so much information to digest, thank you all for your replies!It is not a Whirlpool, it is a cheap-ish Beko, i.e. not one of the cheapest ones, but mid priced Beko, but still a "budget" make.I did check a few years ago that it was not one of the recalled ones, and I checked a few months back too when I saw a notification about Beko models being recalled, and mine is not on the recall list.I took all of the front filters out and I didn't know that behind one of the filters was another filter type looking "thing" so I took that out and it was a bit fluffy, and gave them all a thorough soaking / cleaning, dried it out put them back and so far it hasn't tripped, so I didn't get as far as to take the back off yet, but I shall if it gives me more grief!Thanks again all!