Pressuretrols

Paul48

      I find it amazing that they are still using the pressuretrols with the micro-switch in them. It is a horribly outdated technology. They are inconsistent, and unreliable.Using them in control circuits 35 yrs ago, they proved useless for repeatability.

        I guess unreliable is a wrong description. They will shut the system off, at some point. With the technology today, why don't they use something else?

nicholas bonham-carter

One more improvement to be made

I wish they had tell-tale lights to show when the switch was open or closed, on all the safeties.--NBC

Jamie Hall

That would be brilliant

and would save a lot of hassle.  Not that they couldn't be wired up easily enough, by someone who knew what they were doing, but one does wonder why they aren't standard (well, millivolt systems would be sort of a bear, but anything else...).



There are many times when I am very thankful for my wonderful old mercury switch vapourstat!



There are reasons for microswitches, however -- they are cheap, they are pretty reliable, and perhaps most important they can be used without modification on anything from millivolts to 120 vac.  Not that one can't make an all solid state switch which would do the same thing, but by the time you got done making it idiot and surge proof it would cost a good deal more than a microswitch.