Glowworm 15HXI F4 fault

[BertW]

All,

Before I call out a heating engineer I wondered if anybody here might have had a similar experience with a glow worm boiler or might be able to help. I like to have some idea of what the issue is before calling in the professionals.

I have a Glow worm 15HXI which has worked faultlessly for the last 5 years. Then last week, every couple of days it would stop working and show an F4 fault. A reset of the boiler would clear the fault, it would fire up and work correctly for a few days.
Then yesterday, it stopped firing completely, and shows the F4 fault continously, even after reset.

I looked in the boiler manual and it suggests that F4 is an ignition fault and lists a number of things to check.
So I have taken the cover from the boiler, and can see that when I reset it, the fan runs for a second or so first, then the gas flows and the ignition sprks away. The boiler always lights at this stage and a strong blue flame shows through the inspection window. Then after a second or so, the flame goes out. The boiler goes through this loop 3 times (each time the same result) and then displays an F4.

To my mind, the ignition circuit is obviously fine, and so either the boiler thinks that the flame has not lit correctly, or some other factor is causing the gas to switch off.

So tonight, I thought I would check any sensors / leads that tell the PCB if the flame is lit. I also saw something saying that I should check the condensation drain is not blocked. I have visually inspected the flue and air ducts and they both look clean.

Does anybody have any other ideas? If I don't have any success with these simple checks then I suspect that the main chamber of the boiler will need to be opened and I don't really want to go there.

Thanks in advance.

 

[newbie1]

my suggestion is stop playing with things you dont know about and get a qualified engineer,,sorry to be blunt but diy gas work is my pet hate

 

[BertW]

Hi,

Thanks for the reply. I agree entirely, which is why I have not done anything with the gas at all. I am an electrical engineer by trade and thought at the very least I could and should inspect the sensors and the PCB.
I have had one bad experience with a heating engineer before who simply replaced bits in order until the boiler started working, which has not filled me with confidence since. This is why I like to have some idea what is wrong before calling somebody in.

 

[quality]

I think F4 is flame failure
could be a few things
no gas
ignition electrode
ignition lead
gas valve
ignition circuit/transformer on pcb

as said get someone out who is registered , better of with a recommendation from someone else

 

[BertW]

Hi,

Thanks for taking time to reply.

Can anybody recommend somebody in the Bristol area? As I said before, I have had a couple of bad experiences before with inexperienced engineers.

 

[washer]

The burner seal might need changing which could cause that fault, quite a common problem on the Hxi, call a engineer in.

 

[BertW]

Further updates...

I gave Glowworm a call and they were surprisingly helpful given that the boiler is well outside of its warranty. In essence they suspect the gas valve, especially as the gas pressure at the cooker (not far from the boiler) is very good.
I checked the voltage at the valve, and at ignition it is 24v as it should be. I took the connector off and cleaned it all up and now the boiler is running nicely.
Thanks to those who took the time to reply.

Cheers

B

 

[ferret]

it,ll be ionisation the electrode just needs cleaning up with a bit of emery cloth . or replacing!

 

[BertW]

Ahh! The connectors inside the chamber did have a dull and slightly sticky finish to them, which I assumed had something to do with the combustion process going on.
I suspect that the valve will probably need replacing at some point but am happy to get that done now that I understand what the fault is.

 

[moony]

well if you do make sure that the engineer checks the burner pressures after replacement of the gas valve (not saying that you wont try to do it yourself or anything lol)

 

[BertW]

Thanks for the help.

 

[BertW]

A further update!

After the boiler working for a few weeks, me having a fiddle with the electrics, it working a bit longer etc etc it finally failed to start just after Christmas.
Called in a local heating engineer who eventually diagnosed a faulty gas valve (be warned that these things often need to be calibrated before they will work!).
All working nicely now and I can thoroughly recommend an engineer in the Bristol area if anybody needs one.