Potterton

[raden]

In message , Andy Hall writes

... And Barcelonas

[raden]

?

[Malc]

Because it was a crap design basically. They used a capacitive dropper from each side of the output relay (i.e. from the NC and the NO contact but not the common) to provide power for the stat (both feeding into a common rectifier, zener and smoothing cap). In some modes of wiring a CH circuit it is possible for the power to arrive at the stat from the NC side of the relay, as I'm sure you know. In this case the power had to charge up the smoothing capacitor which kept power on the relay as it changed over. If the relay moved too quickly then there wasn't enough charge in the capacitor to power the relay across to the NO contact and it would oscillate and burn out the zener. If the circuit had been provided with bigger droppers and also a higher wattage zener then it would have been fine but in the interests of cheapness things were pared to the limit. As it was my job to analyse field returns I got to know the various failure modes by sight without having to test the stat. At one point we were running at 10% failure rate.

-- Malc

[Andy Hall]

Didn't anybody ever apply a brain to this?

Surely the cost of the returns in dealing with them would start to compare with the cost of a better design.......

.andy

To email, substitute .nospam with .gl

[Rob]

Houses/boilers built down to a price.....

[raden]

In message , Andy Hall writes

Andy you're on dangerous ground here, applying logic and such

[raden]

Ah, I see

"'ere y'are mate, I'll give you a deal on 10,000 " you mean

[Dave Plowman (News)]

An electronic one is probably cheaper to make. When you're making millions of the things, it nearly comes down to just the cost of the raw materials and energy.

[Malc]

Cloff.

Eventually they did but it was two years after I joined, and they'd set up their own electronics manufacturing facility (Enertech) in Redditch, that anything was done. And then the managing director had to step in and adjudicate between my boss and the director of Enertech who were playing politics over the design instead of pulling together. At one point my boss forbad me to talk to Enertech about the design which given that we were different parts of the same company I chose to ignore, which got me into more trouble.

[tony sayer]

In article , raden writes

IIRC Ford in the USofA had a car, the Pinto, that almost blew up in a rear end collision, apparently some bolts would tear the fuel tank apart.

It seemed at the time it was cheaper for Ford not to modify production but to argue the accident claims.

This was of course before litigation became the business it is today:(..

[tony sayer]

In article , Malc writes

Such is the best of British management. World class;(

[tony sayer]

In article , raden writes

Capactive droppers or wattless droppers, are nothing new, they were used in TV 's years ago to drop the voltage required to the heater chain. Not a bad idea really.....

[Dave Plowman (News)]

I've never seen this. All the ones I've had dealings with had series heaters with a series resistor. Some radios used special mains cord as the resistor.

[Andrew Gabriel]

This was the case which changed that. ISTR Ford argued it would have cost them $125M to change the design of the fuel tank so the cars didn't all burst into flames on rear-end collisions, in a case where they were being sued by someone who was badly burned. So the Judge turned to them and said, in that case, the damages will be $125M to make it clear you will not use finiancial considerations in deciding if it's worth fixing a faulty design to save lifes/injuries. Ford had been expecting damages of well under a $1M based only on the injuries, loss of earnings, etc. and had calculated it was cheaper to pay the damages to many victims than to fix the design fault. This case changed that from then on.

[IMM]

They were knowlingly prepared to allow people to be killed because it was financially beneficial to them. I hate that company, have a look at what they have done through history. Scum of the earth.

[Pete C]

:(((

In these situations it's best to marvel at the wonders of paid employment, but it's not easy to do as a graduate!

But they're still in business so it shows how bad things can get without being terminal.

What was the application? It sounds like it was designed for retrofitting if there was no provision for a separate mains feed to the circuit. Not easy to power a circuit from both sides of a relay alone.

cheers, Pete.

[Andy Hall]

Well.... they applied a brain at least, albeit not a heart.

I've always had the view that if the running of business is dominated by one discipline (e.g. accountants, marketeers, engineers, sales) to the point where the others have little influence, then it will probably ultimately fail.

.andy

To email, substitute .nospam with .gl

[Malc]

The controls were electronic equivalents of a standard bimetallic thermostat so they had to be retrofittable to an existing circuit and would not confuse a plumber who was not an electrician.

[Pete C]

Not the only example sadly:

Well.... they applied a brain at least, albeit not a heart.

I'd argue they have neither, it's those situations that corporate manslaughter laws and heavy fines on company profits are needed for.

Another example closer to home:

cheers, Pete.

[Pete C]

Hmmm, begs the question, why have an electronic equivalent of a standard thermostat, or was there something else to it.

cheers, Pete.