Central heating timer question.

[Dan S. MacAbre]

Mum and dad's Randall 102 seems to stick on the last 'off' actuator, so that it doesn't move after 11PM, and the heating stays on all night. I'm considering whether to try and repair it, or replace it. Has anyone here seen one with the same problem, and managed to fix it? Or will the motor now be nackered? My first instinct isn't to go and buy a new digital one, since I've had a few of these where the display just fades away, that I wouldn't automatically expect it to last anything like as long as this old Randall thing. If the best thing is to buy a digital one, because of the timing flexibility, are there any makes to look for, or to avoid?

If this was at home, I'd already have dismantled the thing, but it's not so easy to try things out when there's a journey involved.

[tabbypurr]

Unlikely to be a motor fault. Only opening it will show what's sticky or damaged. Unfortunately you're right about reliability. I might get a used mechanical one if needed.

NT

[Bob Minchin]

Lubricating the pallets might help but you can still get smiths type rotary ones but the cost more than a digital LCD one.

[Dan S. MacAbre]

What I was wondering about the motor is might it have been damaged by not being allowed to turn. Once pushed past the point where it stopped against the actuator, it turns okay, even past the other three actuators. It's just the last one that stops it. I can't notice anything when turned by hand, though.

It looks like you can get NOS ones, which will save a bit of rewiring. Unless they're still actually making them, and what I'm looking at are actually new ones?

[Dan S. MacAbre]

Okay, thanks. I'll see if there's anything in there that might benefit from lubrication. I had a quick look on eBay, and was surprised to find that the rotary ones are more common. And there are plenty of direct replacements still available.

[DerbyBorn]

A gear tooth could have worn away otherwise a clean and lube might fix it.

[tabbypurr]

I wouldn't lube any part unless it was lubed from new, that's a classic way to cause such equipment to fail.

NT

[Dan S. MacAbre]

Okay, I'll look for those dried-up black oily marks on anything that might rub together. The back is held on with small starlock washers on plastic posts, which is a bit of a nuisance.

[Dan S. MacAbre]

I've sometimes seen (e.g. in old zone valves) motor drive wheels that sort of go concave over the years. If it's gone like that, I'll just replace it.

[spuorgelgoog]

My experience of dismantling clockwork is to buy a new one first. At least that way you can have heating while you're crawling around on the floor trying to work out how many pingfuckits are now inside the dog.

Owain

[John Rumm]

I have found that once the mechanical ones get to the point of unreliability there is not usually much you can do for them. Either the cams wear and fail to properly engage with the switch so you miss on or off events, or they just get caught up and jam as yours does.

That tends to be a particular Honeywell unit rather than a generic problem affecting them all. I have found the Centaurstat ones quite good

- I had one in my last place that showed now indication of failure after

7 years or so.

The main advantage of the digital ones is that you can have programmed temperatures. So they in effect replace a time switch, and the stat. plus you get the ability to preselect different temperatures at different times of day - say warm when you wake up, cooler later, warmer in the evening etc.

Some have an "optimising" capability where they learn the characteristics of the house and switch the heating on early so as to actually hit your demanded temperatures at the time you spec (so say you say 20 degrees at 7am, a normal prog stat will turn the heating on at 7 and it will reach 20 some time later. The optimum start ones will work out they need to turn it on so as to have it at 20 for 7am. Some people find this handy, other find it irritating that it runs the heating at unexpected times.

Its going to be less hassle to fit a known working one in that case.

[Dan S. MacAbre]

I think I'll just get a new one, and be done with it.

[Dan S. MacAbre]

I think I'll get a new one, so that they can advance, boost, etc. 5/2 day timing won't make much difference to them, but you never know.

I've actually got a Grasslin QE2 that's lasted for about ten years. And it was second-hand when I got it (I was fed up of buying new ones every few years). It's just that before that, I always seemed to be replacing them.

Bloody luxury :-) When I was a lad, we had a coal fire in the front room and a back boiler. Strange, but I don't remember ever feeling cold. Our little boy's the same - never wears pyjamas, even in winter, and always kicks the covers off in his sleep. Weird.

[spuorgelgoog]

Modern programmers often have a 'holiday' setting which might be useful.

Owain

[tabbypurr]

One problem with digitals is they can be far from trivial to operate. Add people with no willingness to learn to program them and they're a (minor) disaster.

NT

[Dan S. MacAbre]

I think it's because it's one of those things you only do every five years, or something. I'll have to set it for them, and hope they leave it alone.