Actuators (motorised valves)
Reasons an actuator will fail to operate:
- Burnt out synchronous motor windings
- Valves spindle seized /sludge contamination
- Auxiliary switch (end switch) burnt out
- Gearing worn out
- Loose mountings
- Poor terminal connection
Two port valves are either in the open or closed position via the internal ball (shoe or paddle).
3 port mid-position valves control both circuits at the same time or independently from one another, (depending on demands). When these valves are de energised “at rest” it defaults in hot water position (port B for hot water will always be open). This is why “blocker valves” (an additional two port zone valve) must be installed after port B on a mid position valve when installed on an unvented hot water cylinder system, to prevent the stored water from overheating / over pressurising.
Should the synchronous motor burn out, it is possible to replace the motor, however, if the end switch fails, a complete actuator must be replaced.
The manual override lever should only be used for draining and refilling purposes and not as a solution to heat the hot water and/or central heating, in case of the actuator failing.
Should the manual override lever fail to move or too much resistance is felt, the valve and actuator should be replaced and investigate the condition of system water (magnetite maybe present).
Some very old actuator heads require the system to be drained first, before separating from the brass valve body.
Experience has shown that actuator covers not having a raised pip (reversed dimple) on top of the cover, are the type which will leak if separated from the brass body, prior to draining.
To test an actuator: (proving the room stat, cylinder stat and programmer is working ok
Should boiler / pump not respond, the auxiliary switch may be faulty (new actuator needed)
Should boiler / pump respond, the syncron motor will be faulty (new motor needed)