Glowworm Flexicom Sx18

[haway]

The subject may be explanation enough ? My boiler has, like many others, exhibited a fault which is displayed as "F9"; it is common, but seemingly impossible to cure ? Each morning, it shows F9, I can start the boiler by injecting a shot of water, and away it goes, all day, no problem- until tomorrow!
I had the same fault last winter, the pressure switch was changed then, it got through the winter until a few weeks ago. Can anyone possitively define the fault ? Even my heating engineer is struggling with it.

[The Builder]

This boiler is known for it, haway. Expensive to maintain as well. If it's old enough, I would seriously consider replacing it with something sensible.

Faulty pressure switch usually, also ......... pressure sensor; stuck circulating pump; bunged-up pump filter; plus the inevitable possibility of circuit board fault.

F9 seems to be a catch-all fault code when something is wrong (or wrongly sensed as faulty) on the water pressure side.

I'm afraid that no one (probably even Glowworm) can give you a definitive answer. I would check the pump and filter, and maybe try another pressure switch.

When it's drained down, the pressure gauge should read "0". If there is still a reading of some sort, then that would indicate a faulty pressure sensor.

[dekkypoo]

I've seen this many times before, if the pressure keeps dropping there is a leak somewhere

[The Builder]

........ often, dekky, but not necessarily. A faulty pressure switch/sensor will cause the system to "blow off" the pressure, thus expelling water.
A faulty pressure vessel, or one that need re-charging (pumping up) will have the same result.

[dekkypoo]

T B ..Very true but if it is the pressure valve"blowing off" there will be a stained/wet patch where the pipe comes out of the wall.

[Hymie]

Since you are increasing the system pressure each morning, this would suggest to me that you have a leak somewhere in the system – and that the displayed F9 is a genuine low pressure fault/indication.

What is the pressure reading before you add a ‘shot of water’ to fix the problem? The system has a minimum pressure of 0.7bar and recommended at 1.0bar.

[haway]

Thank you all for your input; as for questions on pressure, as I said, it's the only way to get the boiler to fire up, there are no leaks, I have to drain off water as the pressure builds up; it works at anything up to 2.5 bar, at which point, I get nervous and bleed pressure off. I tend to agree with the suggestion of a replacement, this one is only 6 years old, however, I would like to hang on until warmer weather before anything drastic.....

[jpcastellino]

Hey haway,

Did you finally manage to cure that f9? (guess why I ask...)

[benaj]

F9 error on SX18 means Low water pressure sensor detected a drop in water pressure and the boiler wouldn't start. https://www.glow-worm.co.uk/trade/service-support/fault-finding-codes/subsites/betacom-a-range-9-233377.html


This may help:-
http://heatingforce.co.uk/blog/boiler-losing-pressure/