Diverter valve issues

[Surefire]

Chaps
I have been changing these mid position Myson MPE322 diverter valve actuator heads quite frequently and I know they are not the best design and suffer from overheating issues as they are just stalled and drawing current in the on position.

However on further investigation I have found that the valve is always in the CH position (except when hot water is called for then it drives to mid position). So for 24 hours a day 256 days a year this valve is in the CH position drawing current and remaining hot. Now wonder they aint lasting long!

The situation might not be helped because I have replaced the original with a Heat miser thermostat which is programmed to change the temperature setting for different times of the day. So on the controller the Central heating is set to continuous and the stat does the heating control. I just thought that when the stat goes off and there is no call for hot water, the diverter valve should loose all power and return under spring tension to it initial un-powered position but it doesn't, it remains powered in the CH position. Is this correct?

 

[oilhead]

This is the situation with most of the popular spring return valves. There are motor open/motor close valves, but you may need significant wiring changes to install one of these to accommodate the closing feed from the thermostat. There are also programmers that 'unlatch' the valves when powered off, but in your case with the programmable thermostat needing constant feed, they will not help.

 

[Surefire]

Thanks oilhead. Just for information Iv'e been watching an informative video on YouTube from Boiler boffin and it explains the operation quite clearly. Basically to stop the diverter motor from being held in the CH position 24/7 I just need to give it a call for hot water for a few seconds then that will allow the diverter valve to return to the rest position after the HW call is lost.