vaillant ecoTec Plus - Hot water no heating

We have a three year old Vaillant ecoTec Plus which producing plenty of hot water but no heating. Water pressure is 1 bar. The control unit is a wifi VR 66. I have changed the batteries in the control unit and the thermostat seems to be working. Neither the boiler nor the control unit are showing any error messages.

I have vented all the radiators, the towel rails and the Fernox filter a couple of times. I can't find any external pump to vent and I am wary about opening up the boiler to see if I can vent the internal pump. I have flushed out the filter. Nothing so far has got the heating going.

One thing that I have noticed is that the pipe above the filter is very warm and the filter itself is warm but the pipes below the filter is cold. Both valves above and below the filter are set to on (parallel with the pipe) Is this how it should be?

Is there anything else that I can try before calling in the heating engineer?

Let me quest which ecotec plus you have

Was anything touched on the boiler or filter before it stopped working?

It is pretty hot today!

Are you sure that the thermostat is set to give a room temperature higher than the current ambient? Like setting it to 30 C ?

Tony

The model is a Vaillant Ecotec Plus 624.

Nothing was touched or changed on the system. It just stopped heating the towel rails one day. For testing I have the thermostat set as high as it can go (30 C) and I have the controlled in a cool place so that it is recording an ambient temperature of 24 C.

Can you hear the boiler firing up when it is cold and a demand is put on the controller for CH ?

Yes the boiler is firing away.

A lot of valiant controls are hot water priority systems. This means the heating will not come on until any hot water demand is satisfied

gazdaz36 said:

A lot of valiant controls are hot water priority systems. This means the heating will not come on until any hot water demand is satisfied

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Can you explain this a bit more? I am not aware of a demand for hot water that might override the heating. I have been trying to get the boiler heating the radiators when there has been nobody else in the house and -so - no hot taps running or dishwashers etc running. Is this what you mean?