no heating till dhw satisfied?

[rego]

i have what i believe is a y plan fully pumped system with a baxi bermuda back boiler. all controls ie programmer, room stat, cylinder stat and diverter valve are honeywell. programmer fairly new but others old, metal covers on cylinder stat and diverter valve. problem is this-if i switch controls to heating only it takes about one hour for valve to switch over to heating ie it appears as if it is satisfying dhw 1st even though i am not calling for water. if i turn down cylinder stat it immediately switches to heating. cylinder stat is set at 120. any ideas?

 

[HarrogateGas]

Sounds like you have an old Priority system, these can be wired up to give hot water priority or central heating priority. Yours sounds like the former. If thisd is the case your sytem is working fine and to the best it can. You need to set the timer to come on an hour or so before you want your heating to come on. this gives it chance to heat your water before switching over to do heating.

You can have it converted to a full Y plan but this can be fairly costly as few plumbers have the electrical know how to re-wire.

 

[rego]

thanks for that. is 120 about right for cylinder stat?

 

[chrishutt]

The usual temp for the cylinder stat is 60 C = 140 F, but make sure your boiler flow temp is about 10 C higher than this - say 70 C = 158 F.

 

[Lectrician]

But, if HW is not called for by timeclock, the CH should come on straightaway (as it does when the stat is satisfied).

A wiring fault I think...




Beware of simply swapping the system over - usually, a priority system is used when the boiler is not capable of serving both HW and CH at once.