Worcester boiler limited heating

[stratplus]

Unvented set up, wireless room stat.
When programmer is set to once or continue the heating only seems to be on for a couple of hours then goes off.
The wireless stat says the room temp is nowhere near the target temp.
Programmer is set to be on all day, room stat target temp is higher than actual temp so the zone valve should open which it does but the boiler dosen't fire.
Select hot water on programmer and boiler fires up no problem.
Thought it may be the wireless room stat but the zone valve opens so would have thought that rules it out.
Any ideas?

 

[stratplus]

Once the hot water had been selected and the boiler fires if turn water off and select heating then the heating works.

 

[IDCHAPPY]

Some wireless stats seems to work in 10 minute periods mate, don't think cause it opens the ZV it isn't dropping out... the more i experience wireless the more i yearn for wired controls....

 

[bewsh]

Is it a mid pos or 2-port set up?

 

[stratplus]

Is it a mid pos or 2-port set up?

Two port set up.

 

[bewsh]

Are you getting 240vac on the orange when the valve is open?

 

[stratplus]

Are you getting 240vac on the orange when the valve is open?

Not really looked yet but are you thinking the micro switch may be sticking on the 2 port so when the valve moves over on a call its not actually opening?
Seems to be intermitent though, only seems to happen when you set programmer to once or constant ie a longer period of time.

 

[bewsh]

Well if the valve is opening, you are getting voltage from the controls. But if the microswitch isn't working, then it won't give power to the boiler/pump.

When you've got a c/h demand from programmer/stat, check you have 240vac on the 2-port brown wire, this will cause the motor to move and open the valve. Then if that's ok, check if you've got 240vac on the 2-port orange wire, this is the live to boiler/pump. Also check you've got 240vac on 2-port grey, which is permanent live.

Could just need a new synchron motor