Post
by htg engineer »
Mon May 05, 2008 3:25 pm
The oblong silver box will be the actuator, probably a Honeywell V4073 or similar.
Remove the actuator, check the 3 port valve turns freely, and check the actuator turns when HW or CH selected. If it's not turning - replace.
I think you might have to change the whole three port valve though, normally if the actuator fails, all of the radiators will heat up when hot water only selected. If only upstairs radiators heat up it sounds like the valve is turning but not fully closing off the heating side. Therefore letting water/pressure through but not enough to reach downstairs.
Hope this helps