What does fault code F22 & F25 mean for a Flexicom 18hx mean?

my 18hx boiler this morning, no heating or hot water. Having read all the posts I started checking the condensate pipe. Whilst the weather is cold, it’s not freezing. My condensate pipe is not badly bent so I decided that it was not likely to be blocked. I took the front off and lowered the electrical display box. On the left there is a filter and I could clearly see ‘black’ granular stuff at the bottom. I unscrewed the left side of the cabinet at bottom only to allow me to pull the whole filter assembly down and pulled off condensate pipe, unscrewed filter assembly, pulled it off. You twist off filter bowl and cleaned it out thoroughly. the black granular stuff was a bit sticky and the filter is narrow so I used a screed to scrape bits off the float and inside filterand replaced. This is going to happen again for sure. - it worked, 30 minutes in total, thanks guys for giving me the confidence to have a go.

Vic
December 2017

Had F22 on my glow worm
It was down to an air block but worth cleaning the float out as my float was full of rubbish. Fixed by bleeding air from system make sure you run the boiler with ch and how on as it seems to help.
It's easy to clean the float out
Remove the 2!screws holding front cover at the bottom
Remove the screw holding the float, detach the hose from the overflow
Pull down
float assemble
Remove hose from bottom
Remove float
Unlock float chamber by turning it
Clean it out clean float refit
Job done

Chris j
May 2017

Hi there, I know this is an old question, but I'm sure there will still be people experiencing this fault, seeing as we just had it, and so I thought I would share our experience.

We've had the boiler for 7 years with no issues. Then recently we turned off the CH to leave on only the HW and suddenly started getting the F22 Fault Code (Low Water Pressure or Ignition Temperature Rise Too Slow).

After changing the settings back and trying all combination of CH and HW, and also changing the pump, we still had the error. We were next going to change the thermistor(s) as it seemed this was probably the only obvious cause after the pump, however first we took off the cover to inspect the Condensate level.

If you take the front cover of the boiler off by removing a couple of screws, then fold down the electronic control panel, you will see on the bottom left a dark grey plastic cylinder (Sump) with a light grey plastic part (Trap and Drain) connected to the top of it.

If you remove one silver locating screw that holds the Trap/Drain in place, you should be able to wiggle the whole thing out to inspect. Once you have it out, twist the Sump to remove it and check how much water/dirt is built up in it. There is a line to show the max level it should be at.

When we checked it, it was much higher than the line. The line is roughly 5-10% of the cylinder, and ours was about 70-80% full of water, with some dirt and grit in it. We also discovered that the float that goes in the top of the Sump was upside down! After emptying it, rinsing it out and reconnecting it, and putting the float the right way up, the boiler fired up and has been working fine since!

So I would recommend that anyone with a F22 fault code or similar checks the Condensate Trap/Drain/Sump and empties it out. There are instructions in the manual, under servicing, but they are not that clear. It is an easy job, if a bit fiddly and dirty!

OJ
April 2017

Hi all. I had the same problem with my glow worm flexicon 12hx. Fault codes f11,f22,f25. The house is approx 7 years old. Had a plumber friend have a look and said it could of been one of a few things. I didn't want to spend on numerous attempts to fix so I contacted glow worm and they put me onto a service deal, £299.88. Covered all boiler and system parts Inc. Pump and valves but did not cover blockages. However if they didn't fix fault I could claim money back.

Engineer arrived and stated it would not be a boiler fault with these codes, as they indicate circulation issues. He then:
Bled rads
Checked header tank was full
Emptied a radio to check refill

He then thought it was a flow valve at top of airing cupboard. Most systems don't have this he said, they have a simple H pipework. Just to make sure he changed pump. Said old pump was working but maybe not as efficient as should be but this was not the fault.

He thought it was a blockage in the valve and said this was not covered and I should get my plumber friend to remove valve and put H pipework in and this would solve issue. I was not convinced.

He said the boiler is working because it was showing 72° so was hit. But when he felt boiler he realised it wasn't hot. He went to van and came back, then changed a thermistor in the boiler, took 2 mins.

This fixed the fault immediately and it has been fixed since. This was one of the things my mate said it was likely to be. We thought we would have to remove a lot of parts to get to it. The engine eerie did it by understanding clipping original one, sliding it across and leaving it there and putting new one in.

This part is approx £10.

Worth a try for you all. For us we just needed it fixed immediately as it was unable liveable with baby in house.

Ieuan dobbs
January 2017

Hi I have the same with f25 is there any think I can do re point me in the right direction to look at many thanks

Chris
October 2016

A couple of things to consider.... Are your systems fairly old? Is the water quite hard in your areas? Is the FE tank clean of debris?
Sometimes scale, rust, iron etc can build up in the system and water flow becomes restricted.... Hence the f22 code 'not enough water in system' also bringing into play faults regarding Thermistor, as these would be d erecting too high temperatures on flow or return if the water isn't circulating properly. Air may be dragged into system due to poor circulation also, through expansion pipe. Heat exchangers can become blocked due to scale build up, rust etc.
I'd recommend topping up your FE tank with sentinel x800 and running the system for a few days and see how it goes. It's a cheap option and worth a go, trust me.
Also, go on the sentinel website, they have other products to suit your individual systems.
Best of luck.

PlumbLad78
August 2016

Had same problems with flexicom 15hxi. F22/f25 for almost 18 months after having pipe work done by British Gas
Ran boiler at low temps for several weeks and air that was not present in any radiator started to bubble out naturally through expansion pipe,gradually increasing the temp of the boiler and reducing the temp if the fault came back
If you have your boiler serviced annually and it's given the ok the fault must be air in the system which can affect the circulation

John c
May 2015

Actually, looking at my previous update, I can report that the F22 and T25 did eventually cease and we had an uneventful winter of heating. Great. Except that recently (April 2011) its all started again. The thing is, that every time I release the vent on the pump, air can be heard and seen spattering out from the small amounts of water released. In the end I've replaced the pump (Grundfos Selectra 15-50) as it was also sounding a bit rough (been in 20+years I think) and am hoping that will make some difference, but where can air be getting in. I can't see any leaks.

TJB
June 2011

We recently had an engineer visit as our flexicom 18 was failing. Eventually an electrode and heat exchanger were replaced, but on leaving, the engineer warned us that we might get F22 and F25 codes appearing due to air in the system. Sure enough this has started happening (about 4 weeks after visit). We are doing as advised currently (i.e. keep resetting). The codes return sometimes after an hour sometimes after just a few seconds. The suggestion was that trapped air would eventualy come out thru the header tank - as its taken about 30 resets so far, I'm beginning to doubt it and may need to get the engineer back to drain air from the pump.

TJB
July 2010

Hi tom
F22 means
Not enough water in the system.
CH flow or return thermistor wire loose, faulty or trapped.
CH flow or return thermistor not connected to pipe correctly.
Air in the system. Faulty pump or pump speed to fast.

and F25 means
Check thermistors are connected to pipes correctly
Air in the system.
System is too restrictive.

The first thing I would suggest would be checking the water pressure in the system and bleeding the radiators.
If this doesn't help I would recommend getting someone in to have a look.
Hope this helps!

Peter Verity, Verisafe Plumbing & Heating. www.verisafeplumbing.co.uk
April 2010