Help Required ... 3 Way Valve not always switching to Hot Water

[Ray1000]

Thank you MB
I've always had them separate until this week.
Just observing the radiator and HW temperatures by touch I'd be surprised if it were using more energy in the combined 1 hour than the previous 2 hours.

Before HW 6am to 7am and CH 7am to 8am
After HW and CH 7am to 8am
The HW doesn't come on again until the following morning at 7am


Ray

 

[Johntheo5]

I think one of the main reasons Ray is that you may find that a very low boiler flow temperature down to 40C may be quite sufficient for CH purposes (with greater boiler efficiencies) but won't for HW heating, the trend now is weather compensated CH and priority DHW where the boiler flow temperature is increased to max of say 80C to give very rapid cylinder reheating and then back to economical CH.

 

[Ray1000]

Thank you John, I'm hearing that for the first time.
I hadn't realised the boiler temperature could be so low for CH ... but not surprised now you've explained it.
I thought we had our boiler on relatively low and the radiators are still almost untouchable.
Presumably you need an elaborate control system for switching from 40 CH to 80 HW?