Drayton MA1 3 Port Valve Actuator Head 230V, 27651

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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. 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.

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.Very frustrating and don't know what else to do with the damn things other than to have a different make and model installed. I don't do it myself. I get a professional to do it - thank god I have an all-singing-all-dancing central heating insurance cover to deal with it. I do know they have a circuit board and very flimsy, but normally reliable, micro-switches but why would I want to go replacing the whole actuator, as you suggested in the first place, or even the circuit board as you now suggest, when the excellent descriptions of correct operation given by both 'Jonhmdc' and 'flameport' show that my actuator was working correctly all along and the only thing at fault was my understanding of its correct operation. Digging so far indicates that if the controller calls for heating (with thermostat set above ambient temperature) nothing happens.

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. 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.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. If the valve was previously at Heating only, the result is the valve being held in that position, so finding the valve at H with no demand after using the heating is normal operation and exactly what you would expect. 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; Boosted HW MPV stays in W. Boosted CH and MPV moves to H. Turn the boosts off and MPV remains in H and after a short time pump stops.

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. So, it seems as though everything is working normally until there is a demand for Heating only, when, once it is satisfied, the actuator remains in H. This is repeatable! So, am I trying to fix a problem that isn't there, (other than not having any hot water yesterday morning)? Perhaps I've never noticed the actuator staying in the H (or the last selected) position before.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. If the boiler doesn't run when there is *only* a CH demand, it indicates either that the valve hasn't moved all the way to the CH position or that the microswitch isn't working. I assume if the 3 way valve was working properly and the heating side wiring wasn't requesting heating then the 3 way valve would be set to Heat and the central heating wouldn't work. However although I heard the main valve move and watched the plastic lever move, I haven't heard anything from the 3 way valve and the plastic lever seems to be floating. The default position of the valve is W, held there by the spring. Power can be applied to the white wire, grey wire or both white and grey.