No hot water unless heating is on

[martziniuk]

I'm running a conventional potterton Netaheat boiler. The hot water won't warm up unless the heating thermostat clicks on. I flushed my heating about a month ago if it helps. The motorised valves both appear to work as they should.
Is it possible to get air in the hot water system causing the boiler to overheat with only hot water on?

 

[twgas]

HW valve is, more than likely, not opening fully to close the switch or switch is not working

 

[martziniuk]

The motorised HW valve turns on an off with the programmer, I have also tried it in manual mode too.

 

[oldbuffer]

As twgas.

The valve may appear to work on programmer, but may not be moving over far enough to make the micro-switch work, provide power to the orange wire and make the boiler fire. In manual mode its unlikely there will be enough travel to make the micro-switch close. Or the micro-switch itself may have failed.

 

[martziniuk]

As twgas.

The valve may appear to work on programmer, but may not be moving over far enough to make the micro-switch work, provide power to the orange wire and make the boiler fire. In manual mode its unlikely there will be enough travel to make the micro-switch close. Or the micro-switch itself may have failed.

I'll fit a new valve switch and update. Thanks.

 

[martziniuk]

As twgas.

The valve may appear to work on programmer, but may not be moving over far enough to make the micro-switch work, provide power to the orange wire and make the boiler fire. In manual mode its unlikely there will be enough travel to make the micro-switch close. Or the micro-switch itself may have failed.

Bang on! The lever never went as far as the new motors lever. Hot water is back working independently again

 

[martziniuk]

Update:
After I fitted the new motor it worked for 3 months then started to play up. I then fitted a genuine Honeywell motor which worked for a month or so before occasionally giving no hot water. I've found today that if I flick the controller between off and on a few times it will start the boiler. Is the actual valve seizing or is there another problem?

 

[jeff the gasman]

Replace the valve probably a faulty micro switch or partially seized valve
Jeff

 

[CombustionGuy]

Or a faulty controller

 

[martziniuk]

Or a faulty controller

That crossed my mind but the motorised valve does flick over when the hot water is turned on. That means the controllers requesting hot water right?

 

[pallen5000]

Did you change the complete valve and head?

 

[matt1e]

Replace the valve probably a faulty micro switch or partially seized valve
Jeff

I concur

 

[martziniuk]

Did you change the complete valve and head?

I replaced the syncron motor only. I'll have to get a plumber to change the valve then as presumably I'd have to drain the system down