Digital Timer which can be set to come on 15mins per hour ?

[self builder 123]

Hi

Could anyone tell me if they have come across a digital timer than can be set to come only for 15 mins in an hour throughout the day ?

I have a secondary return hot water system. Rather than circulating the water all day every day via the bronze pump, I was thinking that it might be smarter to circulate it every now and then.

The pipes are insulated with Climaflex foam, covered with fibreglass wool, but the water will still cool down at the end of the day.

Many thanks.

 

[JohnD]

Must it be digital?

 

[BS3036]

Isn't is more sensible to base the circulation on temperature measurements?

 

[self builder 123]

I agree temperature would be a better way of doing it, but I am confused as to how best to do this ?

Any comments / help would be much appreciated.

 

[TicklyT]

A pipe stat monitoring the circulation return, set, say, 20 degrees lower than the hot water temperature should do the job.

Maybe with the supply fed from the heating or hot water timer to switch the thing off overnight?

 

[333rocky333]

You would need a timer with 48 settings which is rare.

You could use a 2 channel timer and loop your supply through both sets of contacts and with some clever time setting achieve this,

 

[londonboy]

Personally I'd use the pipe stat method, at the furthest point in the loop.

You could connect this pipe stat to the HW ON terminal of your timer so it only circulated when waters cold and calling for heat.

 

[ericmark]

There are 100's of timers see here and also PLC's that will do the job.

I considered more than 4 timers then use a PLC and I have considered fitting a PLC to my own central heating.

However most will require some enclosure and will require some wiring or programming for them to work.

I have no idea of your ability. Maybe your better than me and could program a PIC and wire it into a relay. Which is beyond my ken.

However likely that would also be beyond you as well? And this is where we get to the real world and what one can buy.

If we take the simple time switch

I am sure you could make extra pins and get one of these to do the job. Not sure if 15 minutes may be 20 mins would be needed but it would do the job.

However it all depends on you. Two timers could easy trigger each other standard system in PLC programming.

However you have also been given some advice on temperature control which seems sound.

So over to you. How clever are you. Hats off to those you can recognise their own limits. Shame to admit it but I have often bitten off more than I can handle many times.

 

[JohnD]

as long as you are willing to accept an electromechanical timer instead of a digital one, a 24-hour Segment Timer (no pins to lose) has 48 on/off periods per day. This one is an Immersion heater timer.

http://www.screwfix.com/prods/89388/Electrical-Supplies/Timers/Mechanical-24-Hour-Immersion-Timer

You could even set it to run the pump less often at night.