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I've been experiencing problems with my central heating system recently, usually seems to be the heating not working - as opposed to hot water - although not as easy to notice if the hot water is off for a while.

I switched off the heating on the programmer and turned up HW thermostat and the boiler fired up OK.

Did the same with the HW and turned up the CH thermostat and nothing happened.
I removed the 3-way actuator and set the valve position manually, using the HW stat to fire the boiler up and pump water to the radiators. After maybe an hour I set the programmer back to normal - i.e. CH priority - and refitted the actuator and the CH worked fine, until the next day.

2nd day I left the actuator off all day, although I had managed to get the CH priority to work I adjusted the 3-way valve manually for the rest of the day. One thing I noticed is that the actuator body was very hot - even though it hadn't been any where near the CH pipework.
Assuming the motor was burned out, I sourced a new Synchron motor and replaced it. Refitted actuator and everything seemed to work fine - that was yesterday.

Woke up today and it was obvious that the heating had been on first thing - around 6am - but was no longer working. As the HW kicks in about 7am I'm assuming that when the valve switches from CH to HW and then back again this is where the problem occurs.
Could this be something jamming the valve? Could it be a problem with the micro-switches?

Any other ideas?

My next step would be to replace the whole actuator, then maybe the valve, but I don't want to go down that route without some advice first.

One other comment - it is possible to turn the valve spindle all the way around. I'm not sure if this is relevant, but I did see on another site that this isn't supposed to happen.

Any help would be greatly appreciated.

Many Thanks, Ian.

Could be stuck or not receiving a signal from somewhere.

As always, makes and models, of all the controls including the boiler is a good starting point.

I'm in and out all day so will check in as and when

Hi Scruff, details as follows:

Danfoss HSV3 valve body
Danfoss HSA3 actuator
Grundfoss UOS 15-60 pump
Danfoss AT cylinder stat
Danfoss RMT230 room stat
Ideal Classic FF360 boiler

All main pipework (except that to boiler and around pump/valve etc.) is speedfit.

Thanks, Ian.

The HSV3 is a shoe valve, so I would take the actuator off and check the shaft turns ok, for the first job.

Whilst you have it off you can check the movement of the actuator.

Actuator moves OK, although quicker in one direction than the other - maybe against the spring.

Valve moves OK, but as I said above, the spindle turns all the way around - is this right?

Yes it turns all the way round, but there's a right and wrong way it should be be.

If you get it wrong, the wrong port opens

The heating has failed again, so I've started from this point and run some tests to see what happens. These tests were all done with the actuator head removed from the valve body.

Start point - actuator is pointing almost fully to HW, but not quite - say 85deg out of 90.

step 1 - turn up room stat - no response on anything.

step 2 - start moving manual lever on actuator - boiler fires up, actuator continues moving on it's own to CH position.

step 3 - turn down room stat - boiler shuts down.

step 4 - turn up cyl stat - boiler fires up, actuator moves fully to HW position.

step 5 - turn down cyl stat - boiler shuts down, actuator doesn't move.

step 6 - turn up room stat - boiler fires up, actuator moves (slowly) fully to CH position.

step 7 - turn up cyl stat (while still calling for CH) - actuator moves about 85deg towards HW, boiler stays on.

step 8 - tyrn down cyl stat (room stat still calling for heat) - actuator does not move, boiler shuts down.

from this point I have to go back to step 2 to make things work again.

To me this points maybe to one of the micro-switches in the actuator, but would welcome some professional advice.

Sounds like the new motor, have you got a good connection.

I would just fit a new actuator and be done.

Sounds like the best option. I wanted to make sure it wasn't the valve before I buy a new actuator.

I'll go with that option and let you know how I get on.

Thanks for advice.

You say the valve turns ok, so it should be alright.