Tumble drier interference suppressor.

[Jeff Layman]

Four years ago I had to replace the interference suppressor in our then

4-years-old Beko tumble drier as it tripped the RCD when cooling down. It's the one shown here:

It's just gone again, so it seems there is a design fault. I could just replace it, but wondered about using a different suppressor such as this one:

It looks like it could do the job, as it seems to have X and Y-class capacitors and is said to be rated at 20A. It's not drop-in, but there's plenty of space to fit it.

Any comments?

[RJH]

I had the same problem - but failure after about 10 years of the component shown in your first link.

I gathered from google searches that an improved version - similar to that in the 2nd link - was available. In the end I ordered one from Beko which did indeed look similar to that 2nd one, and it was effectively drop in ISTR. Fitted it and no problems in the 3 or 4 years since. But then I only used the thing a few times, maybe 10, a year.

[The Natural Philosopher]

Looks good to me

[nothanks]

You could leave it out ... the drier won't notice and I would be VERY surprised if even the most sensitive local radio amateur noticed either.

[Harry Bloomfield Esq]

Yep, it will be fine.

[Fredxx]

The suppressor you show will inherent have a leakage current to earth. It Y capacitance of 27nF suggests a small earth current of 2mA. Also at switch-on there will be a current spike to earth.

I wouldn't have thought either could trip the RCD unless overly sensitive or faulty.

Your second filter is more sophisticated and has a very low leakage path to earth.

I might be tempted to run the tumble drier without the suppressor, but I wouldn't want to rule out any other leakage path in the tumble drier that could pose a greater danger. I'd recommend taking it apart and giving it a very good clean.

[John Walliker]

Definitely. When I took mine apart I found damp fluff in all sorts of places outside the main air path. It lives in a damp garage, so this is no great surprise. I also noticed that one of the mica supports for the heating elements was broken so I replaced the heater as well. The only problem with this replacement was that the connectors on the replacement were slightly different to those on the original, but that was quickly fixed with a soldering iron and some cannibalisation. John

[Jeff Layman]

We clean out the filter after each use, and the condenser every couple of months. There's always a bit of wet fluff there but nothing major which could pose a fire hazard. I'm going to get into the tumble drier later today and have a nose around.

I've never been able to understand why the suppressor trips the RCD when the tumble drier has finished its cycle and has started to cool down. At that stage, I've already turned off the double-pole mains switch so that it's only the suppressor which is connected across the mains (it's just inside where the mains cable enters the tumble drier); the rest of the drier is isolated by the main switch. Somehow, one of the 27nF Y2 capacitors is short-circuiting to earth.

[The Natural Philosopher]

Only have to leak a bit

[alan_m]

Suppressor terminals (or area between) getting damp during cool-down?

Possibly high humidity inside the case just after a cycle with fairly rapid cooling of some metal parts.

[Jeff Layman]

That's a possibility, but it might be the suppressor after all.

I just took it out to find a sticky transparent fluid over part of it. Looks like the potting or something in it is leaking. However, as it's mounted upside-down, the fluid didn't seem to be getting on the spade terminals.

Looks like the "non-Beko" filter will fit with a bit of fiddling, so I think I'll try one of those.

[Fredxx]

30mA @ 240V is 7W. I don't think a Y2 capacitor would last very long with that sort of heat being generated?

Any leakage is bound to be elsewhere in the machine, or a earth-neutral short. The earth-neutral can be elsewhere but under those faulty wiring conditions the RCD would normally only trip under a load so not relevant if the RCD only trips when the drier switches off.

[Custos Custodum]

But the current and voltage are in quadrature, shirley?

[Fredxx]

Yes, but the capacitive reactive current of a 27nF will be around 2mA.

I = V / Xc

Xc = 1 / (50 * 2 * Pi * 27nF)

Where's the other 28-30mA going? I can only assume it will be dissipative. Either way I would be opening up the tubule drier and giving a good clean and once-over.

[Animal]

3 caps + resistor. £18 is steep

far more effective at suppressig interference. Do you actually need to suppress any interference? In many cases such filtering isn't necessary.

[alan_m]

If the manufacturer could have saved a few pennies by not fitting suppression they would have done so :)

[Animal]

Mfrs are legally required to fit it. Sometimes it's functionally semi-necessary, more often not.

[The Natural Philosopher]

Classic cheap mains capacitor leaking.

Yup.

I think that will fix your problems perfectly

[The Natural Philosopher]

Of course.

Fredxx is displaying his ignorance again

[The Natural Philosopher]

Well, that is in fact a moot point.

brushed motors generate sparks, and a good filter keeps that out of the mains so that the electrical certification is *guaranteed*.

No manufacturer wants to faff around measuring a thousand units to see if they all pass when a cheap POS chinesium filter module *guarantees* that they will...

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