Drayton 3 Port motorised Valve MA1 Actuator only.

Product Information

Anyway having diagnosed this far I'm going to leave it with the central heating and the water heating on full time to see if I can get the temperature in the bungalow up to the expected level. Last night my partner heard a very strange buzzing whiring noise coming from what i now know is the "mid position actuator" .

However, turning off the system power causes the actuator to return immediately to the W, relaxed, position under spring pressure. Turn on the system power and everything works as it should, until the Heating-only demand is satisfied when the actuator remains in H. It seems to have two functions; an open/close switch and a three position switch for Heat Mid and Water. I assume that the logic is roughly; With power applied to the white wire only, it will move to the mid position for hot water and heating. I was ready to go buy a new actuator as I believed this was the problem, however it appears to operate as described in the above discussion. For some reason later in the day, with the hot water off and the heating on, twiddling the thermostat does not cause the boiler to fire and the pump to run; I assume causing the pump to run is the critical test because the boiler usually fires a bit after the pump runs.

Specification

The system is a conventional gravity-fed system with gas condensing boiler, Lifestyle LP522 programmer, Drayton RTS1 room-stat, Honeywell tank-stat, Drayton MA1 MPV and ACL Lifestyle Wiring Centre. The problem I am having though is even after the temperature set by thermostat has been reached, and after the scheduled CH OFF, my pump continues to operate, my radiators continue to heat and the temperature continues to increase.

With the head unit removed from the valve body, turning on the system and demanding Heating causes the actuator to move to the H position. Turning down the room stat satisfies the demand and the system shuts down the boiler and the pump but the actuator remains in the H position. Cycling the demand fires the boiler and pump but satisfying the demand with the room-stat has no effect on the actuator which stubbornly remains in H. I turned off the power to the system and immediately the actuator returned to the relaxed, Water, position under spring pressure. The problem with the cold shower remains a mystery, appears to be a one-off and it has not happened again.

formatting link When there is a HW demand but not a CH demand, the valve is un-powered and sits in the HW position. The boiler and pump are powered directly from the cylinder stat.

When there is a CH demand but no HW demand (tank stat satisfied or HW off at programmer) the valve moves to the CH position. A microswitch in the valve actuator switches a live supply to the orange wire - which then powers the boiler and pump. One year ago (almost to the day) the Drayton MA1 mid-position actuator was replaced (4 years old) on my central heating system as it wasn't operating correctly. It was replaced with another MA1 and the problem was solved. However, I have just switched on my central heating for the first time this year and find that I always get CH with HW even when the CH timer is off. I looked at the MA1 and can see that the valve position is in the middle (HW+CH). If I unsnap the actuator from the valve I can turn the valve manually. I then tried the following with the MA1 removed: That is, there is a shared (flow) valve which has to open to allow any water to flow, then a second 3 way valve which decides which way the water will flow.When HW and CH are calling for heat at the same time, the valve moves to the mid position. The boiler and pump are still powered directly from the cylinder stat. That was why I came here and my misunderstanding has now been corrected thanks to John and flameport! I have looked up the model and found it to be a "drayton mid position actuator MA1" and wanted to know what i need to do to replace it . The MPV actuator is a BGMVSP-23. The control and thermostat is a Hive system. Boiler is a Worcester Greenstar Ri. System is gravity fed open vented system, tanks in the loft and HW cylinder in airing cupboard. From what you say, does the actuator stay in the H position when the demand is satisfied when the timer is still on (as well as when the timer shuts off) and if so, what is keeping it 'actuated' there and thus stopping the spring pressure from returning it to the W position?