Glow Worm Micron 50FF

[Dazzh]

Hi All, Sorry for the long winded post however looking for a bit of advice and to see if someone can point me in the right direction.

My son has a Glow Worm Micron 50FF in his house. Boiler has been fine and I recon it was fitted when the house was first built 13 years ago.

Two weeks ago he came home to no heating/hot water. Boiler was dead and wouldn't fire up, there was no lights showing on the boiler even after he tried to reset this however the fan was running constantly until the electricity to the boiler was turned off.

He has home emergency(not BG) through an insurance scheme. They called out an engineer who said it was a diverter valve. He got the boiler running and came the next day and fitted a new motorised head. The next day it cut out again. The engineer returned had a look at the programmer/timer and said he would submit report to Insurance company. They phoned and said the engineer stated there is a wire missing from the programmer. They were informed boiler had been fine for years so doubt a wire had just suddenly disappeared.

They send another engineer who states it's the boiler circuit board. Company stated £280 for board plus fitting.

They then send glow worm engineer under the fixed price repair as they thought this would be a better option. He diagnosed an air pressure switch and managed to get the boiler running. Part was not in stock and would take 3 days to get as it was over the weekend.

The next day the boiler cut out again I went and had a look at it as he stated it was the APS was the the problem. I turned off the electricity supply, removed the front case(not combustion case cover) the APS is at the top of the boiler, disconnected a clear plastic tube which runs to the fan and also branches to the top of the boiler and terminated in a black rubber stopper. I blew lightly into this which activated a micro switch in the APS. Put it all back together switched on electricity and the boiler started and ran without problem.

The glow worm engineer attended a few days later and fitted an new APS and tubing then left. An hour later boiler was off again. My son phoned Glow Worm who contacted the engineer he now states it will probably need a new circuit board and fan however didn't find any issues earlier. Glow worm no longer stock these parts because of the age of the boiler however did give me the part numbers which can be purchased online. I went over and blew through the tube to the APS activated the micro switch and got it working again. Glow Worm refunded money to Insurance company and they couldn't fix it.

So 3 engineers visited and different parts identified. Insurance only covers up to £150 in parts and call out plus 3 hours labour if the problem is fixed.

To cut a long story short what could the problem be if blowing through the tube to the APS gets the boiler working. Is it likely to be the fan which, continues to run when the boiler is not working until switched off at the mains, or the circuit board.

Thanks for taking the time to read this and all help appreciated.

 

[terryplumb]

Re fan running until mains electric to boiler is switched off. Can you please clarify this point. Do you mean when you got the boiler running by blowing into APS ,and subsequently when you don't want it to run any longer , you turn the boiler off but the fan continues to run permanently until electrics are isolated ? Or do you mean when you want the boiler to run ,and you turn it on ,the fan starts to run but ignition does not take place ( burner does not light ) and the fan continues to run permanently until you isolate electric supply ? Regards terry.

 

[Dazzh]

Thanks for the reply Terry.

Scenario 2 fits the bill however to clarify. When it stops working ie fault returns and will not ignite(even when reset), the fan will continue to run constantly until you turn the boiler off at the fused connection unit. When you turn the power back on the fan starts but it will not display the reset/burner light or make any attempt to reignite. So the fans running but nothing else is happening. The only thing turning the power on/off is the thermostat once it reaches temp. If I turn the room thermostat down the boiler will cut out as normal with no fan running.

However when the fault returns and it cuts out the only way to get it to come on is to isolate power at FCU, blow in to APS until micro switch trips, turn power back on and it will then reignite and lights for reset and burner on will both work.

The boiler is in the attached garage so its hard to tell when it has cut out other than you feel the house getting cold.

 

[terryplumb]

When the boiler " cuts out " ,and I assume by this you mean its been running central heating for a while ,then you realise house is cold ,radiators are cold and you go look at the boiler. At that point what are the two led lights lights doing. The combination of the two gives an indication of what's going wrong. For example if the left led (marked reset ) is flashing SLOWLY and the right led ( marked burner lit ) is lit but not flashing just permanently lit ,is indicating the PCB is at fault. Another mode .....left flashing RAPIDLY and right flashing slowly is indicating a problem with fan or APS . there are several other permutations of the LEDs to indicate other faults. I think yours will be one of the two outlined . have a look and report back.

 

[oldbuffer]

Had a similar problem with one of these some years ago. Memory is a bit hazy, but you might get your next engineer to check the earth connection that runs into the combustion chamber. This can come loose at the terminal.

 

[Dazzh]

Cheers Terry,

The light are not flashing at all when it has "cut out". Even turning the knob to reset doesn't bring any of the lights on.

However when I go through the procedure I have outlined to get it going again the "reset" and "burner" light both work as normal.

Its almost as if something is tripping in the boiler and cutting everything out(except the fan) and blowing into the APS(which has been newly fitted) appears to reset it.

 

[Dazzh]

Thanks @oldbuffer.

Just heard back from insurance company. Glow Worm are sending out an engineer on Saturday to fit a gas valve and PCB, which they have managed to source. They can't source a fan from their suppliers. I'll ask my son to see if the engineer will check this to make sure its working properly.

The only issue is originally they stated it just needed a APS, which they replaced, so find it difficult to understand why they now say it needs a PCB and gas valve without seeing and checking these.

However if it works he will be delighted as it been ongoing for over 2 weeks.

 

[terryplumb]

So the fault is intermittent then ? I take it the boiler works OK for a while ,hours ? Days ? And at some point it fails to ignite although fan will be running ? If so I would change the PCB.

 

[Dazzh]

Yes Terry that's exactly what happens.

Been running since yesterday afternoon. He has kept the heating on, not timed, as he fears that if it went off it may not restart. Hopefully PCB replacement will sort it out.

Thanks for all the replies and I'll report back if this solves the problem.

 

[terryplumb]

Good luck with it ,do let us know how you get on regards Terry

 

[terryplumb]

Cheers

 

[easyflow]

Bit worrying, An engineer should have found the problem pretty rapid with a multi metre instead of throwing parts at it.
Even if the problem is intermittent.

 

[Dazzh]

Yes @easyflow that's what I was thinking. However they appear to be able to get it going but soon afterwards it would cut out again.

1st engineer - replaced diverter valve head. Did not cure problem.
2nd engineer - stated pcb(did not replace)
3rd engineer - attended and stated APS, had to arrange for part to be delivered and fitted
4th engineer - attended and replaced APS. Did not cure problem
5th engineer - attending Sat to replace PCB and gas valve.

Thankfully it's the insurance company that's arranging and paying for the repairs however I think they only pay if the problem is fixed.

 

[picasso]

Needs a new fan would be my recommendation.

 

[John D v2.0]

We had almost the same problem, after the engineer replaced sensors and PCB due to an overheat light/trip coming on when the boiler wasn't running.
The boiler not fire up just left the fan running, fired up and then went out immediately. If the engineer blew in the pressure switch with the case off as it fired up it would stay running. The pressure switch was piped up wrongly, connected to the sample point and basically measuring the difference between room and fan blow side. Correcting that didn't help.
Eventually he decided faulty pressure switch contacts bouncing but the new digital circuit board was more sensitive and got a new switch.
After fitting that it wouldn't fire up at all.
Then he measured the pressure difference with the fan running, slightly below the spec of the switch.
Eventually discovered the flue was longer than the allowed length for concentric and was for every flat above in the block. Maybe the misconnection was to get around the issue.
The result was a new boiler.