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?

 

[Machra]

Johntheo5 - Could you expand on the use of an SPST please. My three way valve 'switch' gets very hot and I think this is why I have had to replace them every 2 to 3 years and this sounds like it may sort out this problem. Would something like this be OK

https://uk.farnell.com/schneider-electric-legacy-relay/9as3a240/power-relay-spst-no-240vac-30a/dp/3665694

 

[Johntheo5]

Are you talking about the switch on your programmer getting very hot or the 3 way valve actuator getting quite hot?,
A SPST is basically a on/off switch., its a single point, single throw, one way switch, or something like that.

 

[Machra]

Sorry I am talking about the 3 way valve actuator getting very hot. They way I have my programmes set CH is the last setting in an evening (goes off at 1030pm) and therefore the actuator stays ‘charged’ all night until the HW comes on at 0700 the next morning. I have looked at setting a short 15 mins cycle of HW late evening as that would set the actuator back to HW and power it off thus reducing the temperature but that only works when the hot water cylinder has reduced in temp enough for the cylinder stat to call for the boiler to fire up and in my case this hasn’t happened even when I set the HW to come on at 0100. Thus the SPST sounds like a great idea, or am I just overthinking this. I am an avid diy er but not an electrician hence why I asked about a suitable SPST

 

[Johntheo5]

You mean install a relay like in post #37?, you dont require anything remotely as powerful as a 30A, the actuator motor runs at around 10 watts max so something like a 2 to 3A, say 5A if easier to source.

 

[Machra]

Yes that is what I mean. I assume I need a 230v relay?

 

[Johntheo5]

Yes, 230V.

 

[Ray1000]

If I’m keeping up, you seem to be talking about an additional wired in item that would stop the 3 way valve actuator using power and creating heat while it’s waiting hours for the next call for DHW … if so what would the wiring diagram look like. Thanks Ray