I have a Potterton Suprima 60 with an EP2001 programmer fully pumped system with 2 MVs,the problem is that when the HW is on and the heating is off at the programmer the rads get hot even though the MV is closed,the same happens when heating is on and the HW is off.I have changed the cylinder stat to no avail,could it be the programmer at fault.
Thanks in anticipation for any help.

Bob P., April 2009

the mv is closed but the ball inside the body can still let by and allow water through to the rads. if your saying its closed but the rads still get hot this is the most likely fault.

aa, April 2009