micron 30ff cuts out after "successful" lighting sequence

[daveburton1]

Hi,

I have a trusty 2 year old Micron 30FF that is causing me some grief. It successfully lights on every firing sequence (I have the front off and can see the blue glow of the flames) but at the end of the sequence the gas is cut and obviously it doesn't stay lit!

I had a professional come and have a look (a friend) who squeezed one of the pipes to the air switch for 40 seconds during the lighting sequence - causing the fan to turn for much longer, and this caused it to light once he'd let go. He said replace the air switch.

I've done this to no avail - same problem. It nearly always fires if the fan is turning for 40 seconds before the rest of the lighting sequence carries on.

The fault is one that says "software error" in the manual - great info. Micron say dodgy earth or PCB. But why does it light when the fan is forced to turn for longer?

Once warm it always lights on demand. Should I replace the thermistor / give up and get a new PCB?

Many thanks

Dave

[6]

Start with the cheapest option

[Ed Sirett]

The symptoms suggest that the flame detection process is faulty.

Looking at the manual and reading between the lines it looks as if there is a two stage ignition (there are three wires + earth) going to the gas valve. The first stage is happening but probably requires confimation of the flame before going to full rate using the second solenoind on the valve.

Problems with flame detection:

Dirt and crud and misposition of the ignition/sensing electrode. Polarity of supply. Earthing to and within the boiler. Spark electrode (also used to detect the flame on this boiler) and its lead. NB a small break will transmit a spark to lit the gas but fail to detect the flame. Also check the gas supply.

I think the APS stuff was a complete red herring.

Only when you have exhausted the low tech stuff then you should obtain a recon'd PCB.

[daveburton1]

To me, the fact that once it's warm it works no problem seems to point towards the spark and its lead. There is a service part of the manual and I have followed the procedure to clean and realign the electrode properly.

However the fact Micron also mentioned the earth could easily put this at the top of the list! How would I go about checking this - I have a multimeter to hand.

Many thanks for your help,

Dave

[Dave Burton]

1) Dirt and crud and misposition of the ignition/sensing electrode.

Checked position - approx 4mm from burner surface

2) Polarity of supply.

Not sure on this - I am guessing it is OK if the burner lights after the fan turns for a longer time

3) Earthing to and within the boiler.

Seems fine - checked, max 7 ohms

4) Spark electrode (also used to detect the flame on this boiler) and its lead. NB a small break will transmit a spark to lit the gas but fail to detect the flame.

Not replaced although seems like a cheap option - therefore good. Also where's the best place to get a lead - I guess it's fire-proof?

5) Also check the gas supply.

Again, is this likely to be fine if the burner works all evening once lit? Can anyone shed any more light on the fact it will stay lit if the fan turns for 40 seconds before the ignition sequence?

Many thanks for all your help

Dave

[delta925]

replying to daveburton1, delta925 wrote: The OP never updated this thread with the final solution.

I have a Micron 50FF that was fitted in 2004 and been 100% reliable until a month ago.

With no warning or symptoms the indicators were Reset ON, Burner Lit Flashing Slow indicating a software error. No combination of totally removing power and the control knob would clear this.

The fan and pressure switch were tested by independently applying power to the fan and monitoring the switch with a multimeter. The thermistor was measured with the multimeter. As the temperature was more like 5C than 20C a reading of 14K ohm was reasonable. The overtemperature switch was measured and confirmed to be closed. The control valve solenoid coils both measured around 900 ohms.

An advance exchange control board was ordered. The original was a Pijnenburg type 227134 . The exchange was ordered under the same code but a Ritter type labelled

2000227134 was received. The Glowworm website conforms that the original Pektron 801990, Pijnenburg 227134 / 2000227134 and Ritter 2000227142 are interchangeable. It would seem that the Ritter ( the final version ) has been boxed and labeled as 2000801990, 2000227134 and 2000227142 .

Once the control board was swapped the burner lit first time but failed to stay alight. After 3 attempt it locked out. It seems that regardless of the power and control know sequence at least these later boards lock out for a period of time. When the lockout finally could be cleared at the second attempt ( 5 in total ) the burner stayed alight.

While the system was hot the burner turned off then relit controlled by the thermistor without any problem.

However once off for a couple of hours the burner would not stay alight again.

It was at this point a search found this thread.

An electrode had already been ordered in case needed but was delivered a day later. Once fitted the burner lit at the second attempt and has not locked out since.

What this appears to show it that just because an electrode will create a spark it may have deteriorated beyond the point where the burner flame can be detected.

Also possibly the Ritter control board flame detection is less sensitive than the Pijnenburg and / or the electrode deterioration actually caused the control board failure as flame detection errors and lockouts were occurring but not noticed.

While the Glowworm manual fault finding chart can not cover every possibility not showing the burner igniting then the burner being lit as two stages is a major omission. For ' Does burner lit indicator come on ' > no it could say check electrode and wiring, faulty electrode, control board fault.

I hope this helps others with a Glowworm Micron 30FF, 40FF, 50FF and others too e.g. 60FF, 70FF, Halstead Buckingham that use these or a similar control board / circuit board / PCB.