Delay off timer required

Looking for an inexpensive run-on timer, which will keep my CH pump active for about two minutes after the boiler has switched off. I'm currently experiencing problems when the whole system stops just as the boiler has reached its setpoint.

Several cheap timers around with 30 seconds max, others with a £90 price tag. Another option is to by a £25 pound bathroom extractor fan (with timer), and throw the fan away- hardly ideal.

Not ready yet to fit a modern boiler with all its advantages!

A twenty minute Google was not very fruitful.

TIA

GrahamC

Reply to
Graham C
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RS have numerous ones to do this job but they are going to be £30 plus so however wasteful the fan solution might be It is possibly the cheapest unless you are going to make something from scratch - then there is the cost of your time.

One type to think about is the thermal delay door release from an old washing machine. Not normally as long as two minutes but you might have some luck if you wrap it up in some insulating fireproof medium like glass fibre which should extend the time. You still have to get it to operate a microswitch as at the end of the delay the result is a mechanical movement and you need an electrical difference.

Bob

Reply to
Bob Minchin

Graham, you can use a Manrose 1351 bathroom extractor fan timer. We will be publishing a wiring diagram for this application on the wiki in the next day or so. Watch out here for the announcement from me or John Rumm.

I'm told this is the Manrose 1351 although it doesn't say so anywhere in the description: -

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Reply to
Dave Osborne

Indeed - I use one of these for just this purpose. It's slightly fiddly to adjust the delay - a little to screw to turn, covering a range of 1-45 (or is it 60?) minutes. It's best to adjust it on the bench, switching (say) a light bulb off - and fiddle until you get the desired delay. It seems fairly consistent once set. Mine is set to about 4 minutes - which seems to be enough to stop the boiler overheating under the circumstances which the OP described.

Reply to
Roger Mills

An afterthought for Graham. . . . If the pump keeps going after the boiler stops, the water *does* have somewhere to go, doesn't it? This is not always the case! For example, on S-Plan systems, the motorised valves will all be closed in these circumstances, so there needs to be a bi-pass circuit - preferably using an automatic bi-pass valve.

Reply to
Roger Mills

Graham C submitted this idea :

Just an half formed thought....

How about a thermostat which closed on rise in temperature?

You fix the 'stat on the flow pipe, its output feeding the pump - which should ensure the pump runs until all of the heat has been drawn out of the boiler.

Reply to
Harry Bloomfield

In message , Graham C writes

I think that the Ideal pcb no 28 might be correct for the task, no idea how much they cost new though

Reply to
geoff

There's a Deta one here, £5.32

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Reply to
Andrew Gabriel

Thanks very much for some very useful suggestions guys. Not sure which one I'll adopt at the moment, but I'm sure a sensible solution will be found.

Thermostat on the feed pipe is interesting, but needs an awkward cable run, as the sensor must be close to the boiler, and the pump is several rooms away.

I don't have any motorised valves, so no problem there.

Thanks again.

GrahamC

Reply to
Graham C

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