Heating Controls

[derekdoolittle]

Hi guys, great site, but unfortunately cannot find the solution to my probs, so hope one of you can help, we cannot have central heating only on our timer control ( Honeywell st699 ) it lights up and something in the boiler stirs but not until i move the seperate hot water switch to constant will the boiler actually fire and heat the rads.
On looking in the airing cupboard i discovered right at the back the wires from what i have found to be a motorised valve laying on the carpet, also sniffing around i found there to be no cylinder stat, my question is why would someone take the valve wires from the wiring centre ? ( i love this site i have learnt all the proper names of these things) and should i have a cylinder stat, if not, what controls the cyl water temp?
Thanks in hopeful anticipation.

 

[gas4you]

Sounds like you have a gravity primary HW system. When these timers are fitted to these systems they should have had an extra sticker, supplied with it in the box, placed on the front covering the CH line I think, so the customer would know instanlty that they cannot have heating on without the HW.

Your hot tap water temperature is controlled by the boiler thermostat temp setting.

Often this would be turned to about 2 in the summer, then up to about 4 in the winter to allow for the radiators to heat up sufficiently to heat the rooms.

 

[derekdoolittle]

Thanks for the quick reply Dave, what you say appears to make sense, what a basic system, why on earth are the wires removed from the 3 port valve in the airing cupboard though, any ideas?

 

[gas4you]

None whatsoever I'm afraid