3 way valve faulty or not ?

[bennetm3]

I'm having problems with our CH system.

The basic problem is that the HW will switch on when required. ( I can see the actuator move to the required position on the 3 way valse)
However, when I switch on the CH nothing happens and the actuator does not move at all.

I assumed the Synchronous motor was faulty, so replaced it with another unit from Screwfix. However the fault still remains.

I can make the heating come on by manually pulling the lever over to the CH position and it then fires up. The CH stays on and seems to work fine, and the room thermostat switches it on and off at the desired temperature.

The problem happens when the HW switches on and the valve moves over to HW. Afther the HW has swicthed off the valve does not return to the CH position.

Any ideas what could be wrong ?

I would be very grateful for any ideas on this.

( The valve is a Danfoss 3 position )

 

[D_Hailsham]

Fault finding procedure is in How a mid-position valve works.

 

[Murf520970]

if you have 240 volts at the white wire of the 3 port valve with a heating demand & the motors not moving the valve & you have replaced the synchron motor correctly , the valve may be siezed up . Remove the head off the valve (if its a removable head) & move the spindle back & forth to release it . If the valve head cant be be relaced it will need to be replaced as a whole .

 

[bennetm3]

I have removed the head and I can move the spindle freely. I can move it around with my fingers quite easily.

I will check I have 240V at the white wire. (are they always white ?)

I noticed the motor had two wires but neither seemed to be marked.
Does it matter which way they are wired up ?
I did try both ways around, but it didn't make any diffrence.

Is it possible that one of the micro-switches inside the head is faulty ??

 

[Murf520970]

Basically the programmer when ch is selected sends 240 v to the room stat which will then ( if turned up & calling for heat) sends 240 to the white wire of the 3 port mid postion divertor valve which should then supply the 240 to the motor moving it over to ch. The motor has to move to close the microswitch which fires the boiler . Im presuming it is a y plan set up with a 3 port mid position divertor valve & it isnt a hot water priority set up in which case it will not supply ch until the hw demand is satisfied . If in any doubt go to honeywell controls site & look at the controls wiring downloads section & compare the wiring between yours & the y plan wiring lay out & the w plan wiring