Hot water only works when heating is not running

[Davis]

Have an issue with heating/hot water system. It's conventional system with potterton precision boiler (3 years old) and expansion tank in loft. Issue is that heating and hot water run fine independently but when both are scheduled to be on at the same time, the heating works but the hot water does not. If I turn the heating off then water seems to heat up quickly. I've tried to replace the 3 way valve head unit as this was cause of similar problem about 5 years ago albeit on the old boiler (but other way round i.e. no heating).


Am currently running the timer on different schedules so there is water in the tank for showers etc when the heating is not on but would appreciate any advice on what to look for.

 

[ShaunCorbs]

does it work in manual mode on the 3 port valve?

 

[Unregistered]

haven't tried that but set all combinations and could see the lever moving to each position correctly.

 

[ShaunCorbs]

haven't tried that but set all combinations and could see the lever moving to each position correctly.

was it fine before this problem came to light?

 

[Davis]

Yes, although to be honest this weekend is probably the first time that both have been running in parrallel so the last time they were both running would have been the end of last winter

 

[jtsplumbing]

What 3 port valve do you have ? sounds as if its not going to mid position, for what it costs for just the head , your better to replace complete valve.

 

[Davis]

its a drayton ma1 and I did actually get the valve and head together - i just thought I'd get away with doing the head only as the valve was turning ok by hand

 

[jtsplumbing]

its a drayton ma1 and I did actually get the valve and head together - i just thought I'd get away with doing the head only as the valve was turning ok by hand

Never pays to just replace the head,