My old White Knight gas tumble dryer played up the other day and I found that the earth electrode (immediately above the main electrode) had eroded and sagged until it was touching the central electrode. I bent it back and all was well (briefly - but that's another story).
I thought I ought to order a new electrode but White Knight tell me that my type (with integral earth electrode) has been superceded by one without an earth electrode.
I'm sceptical that this will work in my machine (in the absence of an earth) but I could be wrong.
Here's what mine looks like.
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The replacement is just the same but without the "hockey stick" earth electrode.
I'm waiting to hear from the technical adviser at the moment.
Should I just try it or is my scepticism justified?
Looks exactly like the ignition electrode in my Keston boiler. They failed as the earth electrode drooped and the gap became too big (it's mounted up the other way in the boiler's downward pointing burner). They then modified them, and so far, the new type has been OK (I can't remember what changed - I think the ceramic sleeve became longer, but it still has the two electrodes).
I did repair the old ones a couple of times by bending the electrode back, but this has to be done with it hot - if you try bending it cold after it's had lots of heat treatment in the boiler, it's brittle and usually snaps.
Usually, the contact gap is resonably critical for proper ignition; too small or big reduces chance of successful ignition (and too big can also damage the spark coil). So it depends what the ground electrode will be and how far away it is.
Um no, not in this case. There is a seperate flame detector elctrode.
Pilot light in a tumble dryer? I think not. ;-)
Anyway, for anyone who is interested, the technical bods from Crosslee have been on the phone and tell me that as long as the tip is within 22mm of the base of the burner, it will work without the earth electrode. Seems a little odd given that the old gap was 1-2 mm. I'm not in a hurry to change the electrode now though seeing as it's working.
My first experience with tumble driers was a gas one (in my university hall of residence). Full washing load dry in 5 minutes (and that was probably after a spin at no more than 500RPM in top loading washer). Also used similar ones in the US more recently. Just have to be careful to check no one's melted a pair of trainers in them beforehand.
Electric ones were a tremendous disappointment when I first tried one. That's why I've never owned one.
No Harry, stick to your solar panels, you are completely wrong
It ABSOLUTELY doesn't measure the resistance, a flame acts like a lossy rectifier and the flame sense circuit is looking for that rectification effect in the flame - its a very safe way of flame detection since it depends on a parameter that can't easily be duplicated in the way that a resistance can
As long as the jet from which the gas issues is well earthed, then there is a circuit when there is a flame (assuming that the sense electrode is also in the flame)
But this isn't the case, is it? he said so
No - he's shown the old one as a single electrode, not a junction
And you were prolly as incompetent then as you are now. I have vastly more experience on modern domestic gas appliances than you do
It's not industrial gas equipment, is it - we're talking about modern domestic gas appliances here. They don't use UV / IR , they rarely use thermocouples (and if you had a clue, it would be obvious from the sketch that it wasn't)
This "One implementation of a gas burner with auto reignition senses the electrical conductivity of the flame."
and this " There are also ionisation flame detectors, which use current flow in the flame to detect flame presence, ... " while not incorrect, are misleading and written by someone who doesn't understand the process - I do
Flame sense electrodes (in modern domestic gas appliances) work on detecting a rectification effect produced by the flame, they do NOT work on resistance
for example
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"Flame rectification has become the primary means of flame sensing in virtually all new residential and commercial gasfired HVAC equipment. The days of the mercury filled autopilot and bimetal warp switch are long gone. Be it an intermittent pilot system, direct spark ignition, or a hot surface system, manufacturers have chosen flame rectification for their means of flame verification.
Why flame rectification? It may be the safest form of flame sensing available. It's virtually impossible to fool the ignition module with anything short of an actual flame simulator. It's very fast, with no cool down time such as with a thermocouple or autopilot. The gas flow can be stopped almost instantaneously. Any sensing circuit failure will result in a system shut down rather than an unsafe ignition."
So - you can piss off with your outdated and inaccurate claptrap. Half of your input to the thread was wrong, the other half (thermocouples and such) was just irrelevant
Hi, I don't know if this thread is still open but I have a problem with my White Knight Eco43A gas tumble dryer. When it is switched on from cold, the gas comes on and ignites and runs for about 4 minutes in a clockwise direction. The gas then turns off, the drum reverses (anticlockwise) and then starts up again in the clockwise direction. The gas ignites but now only runs for about 8 seconds. It will continue to do this for the rest of the cycle until it finishes. I have cleaned out all the air ducts, both inlet and exhaust thoroughly, the flexible exhaust pipe and outlet vent, inside is spotless. I initially suspected the gas failure electrode but it will allow it to fire up for 4 minutes initially. Could this be failing once it got hot? I have changed the inlet thermostats thinking that these could be the problem for a second hand pair from e bay. After fitting these, it did two cycles of 4 minute gas runs then went back to cutting off after 8 seconds on subsequent cycles. Has anyone else encountered and solved this problem? It's an old (but normally good) machine and I don't want to change it if there's a relatively cost effective fix. My thoughts following the inlet stats were:-
Flame failure electrode
Exhaust Stats
Gas control unit I was also struggling with sourcing parts, hence getting second hand stats from e bay. Is there anyone who keeps these bits or would have suitable replacements? Thanks in advance.
If you can find a thead, it's open. Most people block the site you're posting from, you'll get far more feedback if you get here a saner way. Here is news:uk.d-i-y
8 seconds sounds like too quick for it to be overheating and tripping a stat, more like a failure to detect a flame on subsequent ignitions or a fault with the gas control unit that is causing a failure to detect a flame once the unit has warmed up perhaps.
As it happens I have a control unit sitting in my garage but my machine predated your (1990) and didn’t have a reversing function so I suspect it wouldn’t be a straight swap. It was erratic ignition that finally forced me to retire my White Knight so I could be that my control unit is faulty too.
Thanks for your replies gents. Tim, I'm not sure that changing the exhaust stats would fix it or not? (Changing the inlets didn't) If I've read it correctly, the manual seems to indicate that the exhaust stats control the high/low heat setting? You wouldn't by any chance have the flame failure electrode? Or know where I could find one please? Many Thanks
I have the one in my burner, but it looks a bit like a bit of sucked toffee. It’s eroded over the years and identical replacements are unobtainable. Maybe it’s possible that a similar electrode from a gas boiler could be made to work but I was never brave enough to try. Have you tried cleaning up your electrode with emery cloth or similar?
The whole ignition sequence seems to be very “fail-safe” so I don’t think using a different manufacturer’s electrode would be dangerous (assuming you could fit it). Maybe have a look on eBay for “flame failure electrodes” and maybe go for the closet visual match?
I would perhaps have tried in my machine if it hadn’t been for the fact that the paddles in the drum were also disintegrating.
What other gas devices do you have? This strange behaviour is eerily similar to somebody in a nearby street where they had a water main burst. Water somehow got into the gas pipe and the pressures were all over the place. I believe British gas is now hoping to redo the area earlier than planned. The soil is clay and most of the old pipes have gone rusty and the clay has retained the gas until the upheaval of the water burst. Brian
Thanks for your replies gents, Tim, I'll have a go at cleaning the electrode this morning and continue my search for one. Brian, I have a gas boiler which is working fine. I have heard of people getting water in gas appliances but I don't think this is the problem in my case. Thank you for the suggestion though.
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