Glowworm flexicom heat only - F22 Fault - A puzzle

[dishman]

I'm getting an F22 fault when heating hot water only on a glowworm flexicom.

It's a fully pumped open vent system with a three way valve.

It seemed to heat the hot water tank fine and kept firing up now and then to maintain the set temperature for a good few hours.

Then, it suddenly had an F22 fault. The pipes made a bit more of a bubbling noise after this.

I worked out that the only way to resolve this is to open the three way valve to manual.

The downside of this is that it starts to heat the radiators as the pump still runs.

So...any thoughts?

The problem seems to lie in the fact it does not like being stuck heating the tank only after a while, I'm not sure why that would be. Surely it should be happy to just maintain a set temperature for that loop.

F22 code shows up as meaning - pressure loss or not enough water in the system.

 

[picasso]

Usual fault is the water moving to quickly through the heat exchanger, the software looks for a certain rise in temp over a set time, if the water is moving too fast the software interprets this as slow pump or no water and throws f22.

 

[dishman]

Interesting.

Is there an easy resolution to this? Set the pump to a slower speed?

Are there any other ways to exclude other possible issues.

The three way valve seems to be working fine. I have tested the motor and valve seems to operate fine.

Could the tank thermostat be an issue?

 

[dishman]

Hmm, the issue seems to have been caused by an snag in the internal flexihose condensate drain.

It must have caused condensate blockage.

It caused a few other ignition faults, which made me realise what it was. The f22 may have been related or it may reappear. I shall wait and see.