Is this article a Red Haddock ???

[JohnW2]

Over the years, the most troublesome part of our heating system, has been the 3-port valve actuator. A basically simple device, but under tremendous strain, from a spring, wound up by a constantly powered, stalled clock type motor, to retain the valve open. Such a daft idea, I had it in mind to design something better, and more reliable, to operate the valve.

Indeed. It's always seemed totally daft to me - to the extent that I initially told people that they surely couldn't be right in saying that that is how they work. To have a motor which spends the vast majority of its life 'stalled' seems just plain crazy - and, as you say, it surely would be possible to design something more sensible?

 

[ericmark]

Seem to remember there was a sequence of events which could leave it activated even with heating off?

 

[ebee]

"a spring, wound up by a constantly powered, stalled clock type motor, to retain the valve open. Such a daft idea,"

I must admit that when I first came across it I thought the same and in the heating fraternity it is thought of as normal.
It mightjust be that it keeps the cost down and therefore not too relevant.
Someone might know the answer, I do not.

 

[Harry Bloomfield]

I must admit that when I first came across it I thought the same and in the heating fraternity it is thought of as normal.
It mightjust be that it keeps the cost down and therefore not too relevant.

I, numerous times, cursed the whole idea.

 

[JohnW2]

I must admit that when I first came across it I thought the same and in the heating fraternity it is thought of as normal.

Indeed - as I recently wrote:

Indeed. It's always seemed totally daft to me - to the extent that I initially told people that they surely couldn't be right in saying that that is how they work. To have a motor which spends the vast majority of its life 'stalled' seems just plain crazy ...

It mightjust be that it keeps the cost down and therefore not too relevant.

Maybe, at least the initial cost. However, I'm not so sure about the long-term 'cost over time', since I can't help but think that a motor which spends so much of its life 'powered but stalled' is probably going to need to replaced appreciably more often/frequently than one which is used more sensibly?

Someone might know the answer, I do not.

Same here!

 

[Harry Bloomfield]

which spends so much of its life 'powered but stalled'

They are simply stalled, by the insertion of a diode, once the desired position is obtained.