Is your VMC not working or lazy?

[Chancer]

I posted a question regarding this a couple of years ago it seems, IIRC Gluestick also had a similar problem.

I have 2 VMC's and they both have gradually failed within +/- 3 years of service.

Initially they start running slower on the low speed until eventually they only run on the fast speed, its not at all obvious as they get quieter while this happens, eventually they will not start up on the second speed without a kick.

I bit the bullet today and removed the one here (the other is in the UK) and did some testing, I had suspected that the motor run capacitors could be to blame and by cannibalising one in stock waiting to be fitted to an apartment I was able to swop over the capacitors as they were the same rating.

The problem definitely is the capacitors as the motor sprung into life with gusto and I now realise that both had slowed considerably within the first 6 months, they use just as much leccy when running slow or at a standstill so it is worth repairing at the first sign.

Mine were the hygrostat type and when the first speed fails they are pretty ineffective as vapours from the kitchen or bathroom do not get sucked through to the hygrostat. I also noticed after the first year that when spring cleaning their was always grease/dust on top of the kitchen cabinets which was not apparent in either property in the first year.

I have a friend with several houses rented out, he tells me that on average he has to renew the VMC's every 2-3 years, being French he believed 100% the electricians claim that they burn out in that time unless serviced every year, I was sceptical.

I hope that this saves some of you some money.

Capacitors, especially electrolytic ones are often the source of failures of electric and electronic equipment, Sky boxes and boiler control boards being especially fragile, the manufacturer saves a fraction of a penny on each capacitor by using one rated to the supply voltage, going up one rating often means they would last for centuries.

If you replace the capacitors on your VMC (a 2 microfarad and a 3) try to get ones with a higher voltage rating if available.

[crossy67]

Good info.  As I remember from collage days it's the paper ones that will give the most problems and have the shortest lifespan, the paper absorbs moisture through time, this moisture degrades the insulating properties of the paper (yeah right, a paper insulator, wonder why they don't make plugs form old News of the Worlds lol)

[Pierre ZFP]

Timely advice indeed - I have a bathroom extractor fan that has just decided not to turn anymore.  I had assumed it had 'burnt out' as I've had it for a good many years but now I'll check out the capacitor and maybe save myself a replacement

I think I owe you a [B]  [:D]

 

[Alan Zoff]

When the clock/timer on our otherwise perfect Stoves cooker packed up last year, the supplier said Stoves no longer made the unit and suggested we bought a new cooker. However, the proprietor of a small electronics shop (in England) told me the timer/unit is the same as on a later Stoves model but now has a new part number and could be had for £115. But before ordering it, he suggested I tried replacing a capacitor on the timer circuit board, for which he charged me 30p!!!

When I told him that it had worked immediately (as it does still), he wouldn't take anything extra for his time and advice so I dropped in a bottle of something instead, leaving both of us very satisfied.

Nothing to do with your VMC of course, but bears out your point about checking capacitors before shelling out big money.

[Gluestick]

Good times and easy money created an environment where consumers were invariably prepared to junk lots of stuff and simply buy or pay for fitment of a replacement. Bit different now perhaps.

Various realities have conspired to elevate replacement parts to stratospheric cost levels! One of these has been take-overs, mergers and acquisitions. For example, Electrolux now covers a staggering field of endeavour thanks to takes overs. And their service and parts facility are pretty useless once any product reaches circa 3 years old

Fortunately, search engines (Mainly Google) are evermore powerful and inclusive: not only for sources of "Pattern" parts and substitutes, but also for service and repair data.

Recently, the central control unit of my wireless intruder alarm went duff: serial false alerts. A component on the main PCB has died, failed or shorted.

Now I dug into this system via Google and found (By the simple expedient of using the model number on PCB and case) that the system was actually manufactured by a leading Taiwanese security outfit: it had been "Badged" by  a French outfit in Antibes. A French replacement unit was quoted at between         € 200-300.

Ouch!

By searching and ferreting I found a complete new system in New Zealand at a price including air carriage of £78! So I now have two more detectors too.

As you know, from various postings over the years, I don't chuck things out until they are without doubt definitely irreparable!

Call me mean if you like: I would rather say, economical.[:)]

Small power synchronous AC motors are the epitome of simplicity: with little to burn out and go wrong.

Pays to scope out why they refuse to rotate!

[BIG MAC]

I am not sure my skills extend to capacitor replacement..it's my brothers who are sparks...I wouldn't know what a capacitor looked like albeit I have changed CDI units on cars and bikes and PCBs on boilers...I guess it will look like a little cylindrical jobbie soldered onto the board?

[pachapapa]

Lovely things and one gets power factor correction as well.[:)]

[Chancer]

[quote user="BIG MAC"]

I am not sure my skills extend to capacitor replacement..it's my brothers who are sparks...I wouldn't know what a capacitor looked like albeit I have changed CDI units on cars and bikes and PCBs on boilers...I guess it will look like a little cylindrical jobbie soldered onto the board?

[/quote]

No circui boards, you cannot miss them as they are large and the only components other than the motor and hygrostat if you have one.

A piece of pi55 to change even for the mechanically challenged, they have spade terminals and the wires just clip on, no soldering [;-)]

[Alan Zoff]

I realise that you are referring to a particular application, Chancer, but just in case anyone is in doubt, Mac's description is correct for many other applications - and he will need to get polarity right as well.

[Théière]

[quote user="Alan Zoff"]I realise that you are referring to a particular application, Chancer, but just in case anyone is in doubt, Mac's description is correct for many other applications - and he will need to get polarity right as well.[/quote]

Only if it is an electolytic capacitor, regular capacitors do not have a polarity

[Chancer]

And electrolytic ones are not used for motor start/run applications.

[Gluestick]

And mains supply changes its polarity circa 50 times/second...............'cos it's AC supplied at around 50 Hz.

[pachapapa]

Maxwell says, at 110 volts it is 60 Hz.

[IMG]http://www.cksinfo.com/clipart/animals/frogs/frog3.png[/IMG]

 

[Gluestick]

110 volts in France??

I think not.

One presumes this forum is concerned with mainly France and the UK, since a majority of members will be using equipment designed for both territories.

The choice of frequency of the alternating current was dependent upon the type of generator and its drive; however, this was back in circa 1890 so I feel it is not of overmuch concern now.[Www]

The actual supply frequency is as with 99.9999999% of all realities in engineering, a compromise. It is, however, a function set by the generator (The supply company not the equipment) and is not a function of voltage.

There are anomalies in utility frequency around the globe: some generators supply the grid at 230V @60Hz.

Frequency and why:

World mains electricity Supplies:

[pachapapa]

Thanks for info.[:)] Reminds me of synchronising 8 generators at 60 Hz before restarting mine and mill operations after strikes.

Until the 80s some old appartment blocks in the poor quarters of paris were still on a nominal 110....actually 127.

[LangeHaas]

Three years later... thanks!

I remembered reading this when it was posted and looked it up again because my vmc stopped working (I spins slowly when you help it first). I will be replacing the capacitors, that should sort it!

PS I have one of the capacitors out and it says "30000h" which, if h means hours, is 3.4 years... which is exactly how old the vmc is!

[Chancer]

Glad you found it from the search facility!

3 years on and the VMC's of which I changed the capacitors are still running at full speed, since then I have installed a few more in the flats and most of them are in the throes of death.

I got my capacitors at a high street Maplin store, they certainly outlast the OE ones!

[idun]

Our first VMC we had installed in our french house was costly well over £100 maybe a lot more than that. It lasted about 15 - 18 years and was on low 24/7, I rarely increased the speed as I also had a cooker hood. The next was less than £50 as far as I can remember and I cannot remember changing that.

Our neighbour used to turn theirs on and off all the time and it soon stopped working.

I should have had a VMC put in this house, but we have an air recouperation system that is not yet all fixed up and I'm not sure whether it will really work well for us. To be seen.

[f1steveuk]

Just curious, but I know that VMCs are designed to run 24/7. We seem to be spending less time in France currently, and I turn the thing off when we go back to the UK, so I am wondering now if I should leave it going, fit a timer, or continue to switch it off when not here??  Also, I recall reading these cost less to run than a light bulb, is this true? How much per month say, would the running costs be? As I say, just curious.

[Cendrillon]

We can be away for months at a time but we leave our VMC switched on all year long .

[Pierre ZFP]

Depends of course what your VMC is rated at.

Assuming a normal tarrif of .122 €/kW

VMC of 25 Watts will cost a smidge over €2  per month and a 40 Watt  one is close to €3.5 per month

[idun]

 I would never have dreamt of turning ours off, even when we left France before we sold the house, it was on......and for a long time.

Keeps the house 'aired' and I like a well aired house.

[Loiseau]

I leave mine on all the time too. I feel it's probably even more important to keep the air moving when the house is closed up than when it's inhabited.

Angela

[Chancer]

I have 3 running here and one in the UK, cost per year €25-30 per year.

My UK place is a timber outbuilding, think shed! Before the VMC it was riddled with damp whenever I returned, none at all now with a VMC.

I have always had a VMC running here in France but this summer made a mistake which again showed me how much good they do. The VMC is above the kitchen and extracts from it and the bathroom, the salon is open plan with the kitchen so gets aerated but the bedroom has no sortie (ceiling height problems) but until now with the door opened has always been OK.

I was away for June, July and August and left the VMC on but the bedroom door was closed, now this is summer and I believe it was a dry one and the only way for humidity to get into the flat is through the tiled floor, the salon and bedroom I tiled over the old tiles which were laid on sand over terre battu, the salon was dry but I have mould in several places in the bedroom, my leather belts and shoes are all covered in it and a pack of foilwrapped Tesco stock cubes (like OXO/Viandox) had drawn in so much humidity even through the wrapping that they had leaked a grungy ooze all over the bottom of my wardrobe which is my overflow store cupboard.

IMHO the running cost of a VMC is a small price to pay for the benefits it brings,  I have to wach every penny very carefully but the VMC will be the last thing for me to scrimp on.

[f1steveuk]

Thanks, I shall be taken note of the comments, and leaving the VMC on!!!