Glow Worm 80F - thermal cut off tripping

[AH1972]

I am first time poster to these forums and am hoping for some advice for the central heating system of the house we moved into in August. I have had a heating engineer round who has resolved some of the issues we had, but the thermal cut off switch on the underside of the boiler continues to trip on a regular basis.

System comprises Glow Worm Fuel Saver 80F boiler in the kitchen, hot water tank in the upstairs airing cupboard and cold water supply tank in the loft (2 tanks, the smaller one I believe feeds the CH system?). System does not have a room thermostat and relies on boiler thermostat and TRVs on all radiators. The radiators and the hot water tank all work very efficiently assuming the boiler is operating.

The following summarises all the issues which we had:
1 - Boiler still firing up after the timer unit supposedly had switched it off.
2- The burner taking up to several minutes to light after the system being switched on (although the fan operated).
3 - Occasional loud banging coming from the boiler like a bag of bolts had been tipped into it (usually some hours into operation).
4 - Occasional tripping of the thermal cut off switch – usually after a couple of hours of operation and often accompanying the banging noises.

The heating engineer has:
1 - Tightened the casing – burner now operates quickly.
2 - Increased pump speed – seems to have cured worst of the banging noises.
3 - Replaced the timer unit – made no difference.
4 - Replaced boiler circuit board – system now turns off correctly when prompted by the timer unit.
5 - Replaced thermostat on front of boiler.
6 - Partially opened valve (in airing cupboard) to a separate circuit from the CH and HW circuits - not sure what this was about??

Whilst 3 of our 4 issues have been resolved, the thermal cut off switch is still tripping and on a more regular basis than before. I don’t know if this is a reaction to the work already done or a symptom of the recent cold weather. I am currently re-setting the cut off switch around 4 times between 4pm and 10pm.

Provided we keep re-setting the switch we have a functioning CH and HW system which is very effective, but it’s annoying and I would be concerned about what should happen if the thermal cut off switch was to fail (can this happen?). In the future we will probably have the boiler replaced with something more efficient but, in the meantime, if anyone has experienced similar issues with this boiler and was able to cure it, I would be grateful for your advice.

Thanks

 

[pumps100]

Hi there,I know your post was a long time ago but did you ever find a solution? We have had the Fuelsaver 80f for many years and it has been incredibly reliable.In November we started to have the thermal reset issue you had. Your description exactly the same as ours but completely random. Changed the pump. No difference. Sometimes it will work fine for a week without tripping out. Nowadays it maybe trips one to two times a day but sometimes it will go for 2-3 days OK - mind of its own. Lot of banging and clatter when it shuts down.About 5 years ago the fan assembly failed and was replaced with a new one. Apart from annual servicing and a few pump changes over the years its been a great system and has been very reliable.Most gas engineers dont want to even contemplate what could be causing it; the fan (again), PCB, a blockage. Could spend a fortune and not get anywhere.If you found a solution I would be most grateful to know what it was.ThanksIan

I am first time poster to these forums and am hoping for some advice for the central heating system of the house we moved into in August. I have had a heating engineer round who has resolved some of the issues we had, but the thermal cut off switch on the underside of the boiler continues to trip on a regular basis.

System comprises Glow Worm Fuel Saver 80F boiler in the kitchen, hot water tank in the upstairs airing cupboard and cold water supply tank in the loft (2 tanks, the smaller one I believe feeds the CH system?). System does not have a room thermostat and relies on boiler thermostat and TRVs on all radiators. The radiators and the hot water tank all work very efficiently assuming the boiler is operating.

The following summarises all the issues which we had:
1 - Boiler still firing up after the timer unit supposedly had switched it off.
2- The burner taking up to several minutes to light after the system being switched on (although the fan operated).
3 - Occasional loud banging coming from the boiler like a bag of bolts had been tipped into it (usually some hours into operation).
4 - Occasional tripping of the thermal cut off switch – usually after a couple of hours of operation and often accompanying the banging noises.

The heating engineer has:
1 - Tightened the casing – burner now operates quickly.
2 - Increased pump speed – seems to have cured worst of the banging noises.
3 - Replaced the timer unit – made no difference.
4 - Replaced boiler circuit board – system now turns off correctly when prompted by the timer unit.
5 - Replaced thermostat on front of boiler.
6 - Partially opened valve (in airing cupboard) to a separate circuit from the CH and HW circuits - not sure what this was about??

Whilst 3 of our 4 issues have been resolved, the thermal cut off switch is still tripping and on a more regular basis than before. I don’t know if this is a reaction to the work already done or a symptom of the recent cold weather. I am currently re-setting the cut off switch around 4 times between 4pm and 10pm.

Provided we keep re-setting the switch we have a functioning CH and HW system which is very effective, but it’s annoying and I would be concerned about what should happen if the thermal cut off switch was to fail (can this happen?). In the future we will probably have the boiler replaced with something more efficient but, in the meantime, if anyone has experienced similar issues with this boiler and was able to cure it, I would be grateful for your advice.

Thanks

 

[Agile]

Hi there,

Most gas engineers dont want to even contemplate what could be causing it; the fan (again), PCB, a blockage.

Thanks

[/quote]

Are you trying to get free diagnosis from engineers?

I dont see why a competent engineer would not be able to diagnose your fault.

But that would be a chargeable visit costing perhaps £84 and perhaps you dont expect to pay?

Tony

 

[pumps100]

I am sorry Tony but I don't think perhaps I fully explained the history.

I have taken the following advice using proper firms I have used before.

First the fan. Called an establisheed firm which I have used before and previously paid over £2.8k for a boiler for a rental property. When he came the boiler was having a good day. He took the cover off did a few checks and could not find anything wrong. Said it was probably just dampness in the flue.

I paid £85 call out charge.

Two weeks later I got trusted and reliable registered engineer from my local village. Lets call him Bob. He came removed the fan and tested it - you could visibly see it was arcing out to earth. replaced the fan. Everything fine.

In November we were having problems with heat circulation and the occasional trips. Called local guy Bob again. Probably the pump. Paid £160. Heating in house much better. Asked him about the trips. Could be anything; fan again, APS, PCB...

Bob said really I should get a new boiler. I am keen to do this and replace with a condensing boiler.I have chased for a price twice and I am still waiting. I actually first asked for a quote before last summer and as recently as November when he put the new pump in.

In the interim I actually called Glowworm. I cannot recall exactly but the deal with them is you have to sign up for a monthly contract for 12 months which was circa £360 before they grace your door.

If the original poster got a solution I would be interested to know what it was. This would help me in my discussions with local Bob or whoever to do the work. What I dont want is to get someone in who says its the PCB, and its not, or the fan or whatever and so on.

And lastly Tony, and forgive me if I have misinterpreted what you were implying, I am not an idiot.

Regards

Ian

 

[pumps100]

Thought I would post an update on the problem with intermittent thermal cut-out with our Gloworm Fuelsaver 80f.

I have had this boiler for 20 years or so with absolutely no issues.Fan had been replaced once and a new canopy seal fitted. Had been very reliable until the intermittent trip issue.

So, we decided to bite the bullet and go for a new boiler, and also change some radiators. I wrote up a schedule of work and gave it my local plumbing and heating Engineer. He said that because he is nearing retirement he had given up his gas accreditation - because of this could not do all the work. He recommended another heating Engineer. Spoke to him. Promised to come over but did not. I gave up with him.

I then decided to omit the new boiler from the job and do it in two stages. I could get the boiler done later by an accredited Engineer. Spoke to my known local guy about doing the work excluding the new boiler. He was keen to do it. He would come back to me with an estimate. Despite chasing he never did.

The reason for doing the work in two stages was that I had an inkling that the thermal tripping was related to a flow or circulation issue. The pump had been changed only a few months before. I had taken the opportunity to remove the casing and the impeller was completely choked with sludge and debris - no wonder it was not pumping!

To cut a long story short during the summer I removed and replaced six radiators. I calculated and resized the radiators for each room as some were too small and others to big. I removed all TRV's and replaced with standard valves. I also removed choked drain valves. I cleaned and drained the system repeatedly. I thoroughly cleaned the expansion tank.

I did this work over two weeks during the heatwave in the summer. The work took a little longer as I had to paper and decorate when the rads were off.

I bought Stelrad Compact radiators online and got a very good price even though they were supplied via a local branch of PSS. I bought the valves, cleanser & inhibitors and other bits from Toolstation and the SR fittings via ebay. I spent about £440 which included a £50 blowtorch.

Surprisingly, I had no leaks when the system was filled. Balancing the flow was trickier than I expected but I got there in the end.

I have had the system on since the beginning of August. I have tested both DHW & CH thoroughly. I have had no trips whatsoever and the system is so quiet you do not know it is running.

Early days yet but I believe the issue I had with intermittent tripping out is to do with a restriction or blockage and/or sludge in the system. Changing a few radiators and cleaning out your system is much much cheaper than resorting to changing boilers.Do this first before doing anything else.

Regards

Ian