Central heating timer: old rotary type

If the existing timer works as a simple on / off switch, then it's a simple job to replace it.

Only you know your capabilities in this department. The job is normally pretty simple as these things go, although sometimes some nutter of an installer has done something weird with the wiring.

Christian.

As far as I remember, the timer has a 3-position rocker switch (Hot Water Only/Off/CH + Hot Water) and the rotary dial, which can be rotated to "click" the system on or off or you can use the plastic markers to set up a basic timing sequence.

Looking on the web, I see that the rotary type are still being produced by Randall, Honeywell etc....

Obviously I'll know more when I actually move in -- timer manufacturer and model no., type of boiler etc.

Bruce

Replacing the timer with an electronic one shouldn't be too much of a problem. They all have more or less the same connections - mains feed, N, E, CH on, HW on - and maybe HW off depending on the system it's controlling.

If the clock is old, the rest of the control system is probably old too. It may even use gravity (convection) circulation for the primary hot water circuit. In the spring, I would seriously consider bringing it up to date - to ensure that the boiler only runs when there is a demand, and that most rooms have TRVs on the radiators. It's well worth using a programmable room stat too. That will both give more intelligent control than a mechanical stat and will also enable you to have independent control over the timing of the CH and HW.

It sounds like the system might be a gravity hot water circulation type. If so, a complete overhaul of the controls may be beneficial, allowing fully independent control of heating and water, room and cylinder thermostats etc. Otherwise, the system will be very inefficient and the hot water dangerously hot from the tap.

Christian.

They are still a popular means of central heating control, mainly, I think, because they are so simple to use.

In message , bruce snipped-for-privacy@my-deja.com writes

It depends ... some old Horstmann time clocks incorporate a pump over run

What is it ?

In message , bruce snipped-for-privacy@my-deja.com writes

Sounds like a Randall

(sharp intake of breath for dramatic effect)

In message , bruce snipped-for-privacy@my-deja.com writes

Randall 102 or 103 at a guess

Is it white with the dial at the top and the rocker switch on the side ?

If so, then e.g a Randall (now Danfoss BTW) 105E is a plug in replacement

In message , Set Square writes

But widely varying backplates

I have now moved in to the house. The timer is a Randall Model 102 mini-programmer. Can this be easily "swapped out" with an electronic type?

Thanks Bruce

In message , bruce snipped-for-privacy@my-deja.com writes

I think I already answered that yesterday

"Randall 102 or 103 at a guess

Is it white with the dial at the top and the rocker switch on the side ?

If so, then e.g a Randall (now Danfoss BTW) 105E is a plug in replacement"

Just been looking at some Randall instruction manuals on the web.

Looks like I can easily replace my 102 electro-mechanical timer with a

Bruce

In message , bruce snipped-for-privacy@my-deja.com writes

Yup - simple as that

undo the retaining screw underneath, slide it up, replacement is the reverse of the above