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A resistance is measured in Ohms!!!
You were apparently measuring a CURRENT in µA
You dont seen to know the difference between current and resistance!
You also talk about "sensors" when obviously you are meaning the flame detection electrode!
I do understand what these things mean and I am someone who has the skills to assist you! Unfortunately you prefer to be rather rude to me! Thats not likely to encourage me to help you!
I dont see why you think thats to your advantage!
Tony
Have you been able to measure the flame detection current when the the reignition attempts are going on?
Even bofore that, you might have been able to see the current dropping?
It's possible that the electrode/flame sensor is moving as it warms up and coming out of the flame.
Check the earths too, the currents are small so a little resistance will stop it. If you have a resistance going up when it gets hot, that could be your problem. Wires and conducting probes shouldn't have any resistance!
Also eyeball the flame when the reigniton starts - is it very small? That could be due to a maladjusted gas valve - corgi zone.
Even bofore that, you might have been able to see the current dropping?
It's possible that the electrode/flame sensor is moving as it warms up and coming out of the flame.
Check the earths too, the currents are small so a little resistance will stop it. If you have a resistance going up when it gets hot, that could be your problem. Wires and conducting probes shouldn't have any resistance!
Also eyeball the flame when the reigniton starts - is it very small? That could be due to a maladjusted gas valve - corgi zone.
niannorth.
While following is for explanation only and I urge you not to go 'in there' to poke about, it will put you on a better footing in understanding the ignition process on your boiler.
When pump and fan run is established, gas valve opens and spark (alternating voltage like you would get from a mains voltage) will be seen coming from the spark electrode. The spark will be discharging from the spark electrode, jump across some 4mm of air gap to burner.
As soon as the gas appears at the burner, the gas ignites. At this point, the voltage travels through the flame to the sense electrode. This voltage flow through burner flame modifys the voltage to DC (as found on batteries and power supplies). This voltage is seen by the electronics and spark is 'removed' and burner flame increases in size.
To carry out 'dry' tests will not tell/ help you any. You do not even need to know about ohms, microamps electron flow or any such thing. But you do need to know system sequence to be able to pinpoint the defect.
Chris has already suggested the burner flame needs to be a certain size. Have you ensured the polarity of mains wires and socket is as should be? In the end it may well be the PCB. PCB seems to be one component everyone and his uncle wants to replace without solid foundation.
While following is for explanation only and I urge you not to go 'in there' to poke about, it will put you on a better footing in understanding the ignition process on your boiler.
When pump and fan run is established, gas valve opens and spark (alternating voltage like you would get from a mains voltage) will be seen coming from the spark electrode. The spark will be discharging from the spark electrode, jump across some 4mm of air gap to burner.
As soon as the gas appears at the burner, the gas ignites. At this point, the voltage travels through the flame to the sense electrode. This voltage flow through burner flame modifys the voltage to DC (as found on batteries and power supplies). This voltage is seen by the electronics and spark is 'removed' and burner flame increases in size.
To carry out 'dry' tests will not tell/ help you any. You do not even need to know about ohms, microamps electron flow or any such thing. But you do need to know system sequence to be able to pinpoint the defect.
Chris has already suggested the burner flame needs to be a certain size. Have you ensured the polarity of mains wires and socket is as should be? In the end it may well be the PCB. PCB seems to be one component everyone and his uncle wants to replace without solid foundation.
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niannorth
Niannorth,
It sounds like a PCB fault. I have a similar boiler which died just before Xmas with the same failure mode you’ve described. I could also see the spark now and then after the flame was lit. I also noticed gas modulation was unstable. Red light would come on a few minutes after start-up. I replaced the PCB. Boiler works fine now.
Replacing the PCB is a rip-off, I agree. MTSgroup (Ariston is part of Merloni TermoSanitari) don’t offer any repair service. The fault is probably just a resistor/capacitor/diode etc just out of spec in the flame detection circuit and scrapping the whole PCB for the failure of a penny component is eco-unfriendly. BUT it needs electronic skill and a test kit to fix this type of fault properly. Flame detection is VERY important.
MTS make a range of boilers, sold throughout Europe, all using the same technology. As far as I can tell, they use a Flame Ionization Detector (FID) rod to establish whether the burner has been lit properly by a spark generated at two similar rods next to it. A FID, is analogous to a cathode in a TV tube, when heated it gives off a stream of electrons. In a boiler, these charged particles flow into the burning gas. It’s this current flow which is detected by the PCB circuitry. It looks as though you were measuring the current change OK and the PCB was seeing the current drawn. The PCB is just not throwing the “detected switch” properly.
Generally, in this type of boiler technology, you can rule out the probe as the likely fault. Provided there’s no obvious resistance measured from the end of the probe to the PCB connector.
(From this thread, you’d think a flame detection problem is rocket science!)
I’m still looking for somebody who can properly fix my old board. (I’ll keep it as a spare.) CET (I assume this is where you saw the reconditioned offer) told me they’re a bit busy this month but they’ll look at mine later. Any other suggested repairers would be an useful post?
It sounds like a PCB fault. I have a similar boiler which died just before Xmas with the same failure mode you’ve described. I could also see the spark now and then after the flame was lit. I also noticed gas modulation was unstable. Red light would come on a few minutes after start-up. I replaced the PCB. Boiler works fine now.
Replacing the PCB is a rip-off, I agree. MTSgroup (Ariston is part of Merloni TermoSanitari) don’t offer any repair service. The fault is probably just a resistor/capacitor/diode etc just out of spec in the flame detection circuit and scrapping the whole PCB for the failure of a penny component is eco-unfriendly. BUT it needs electronic skill and a test kit to fix this type of fault properly. Flame detection is VERY important.
MTS make a range of boilers, sold throughout Europe, all using the same technology. As far as I can tell, they use a Flame Ionization Detector (FID) rod to establish whether the burner has been lit properly by a spark generated at two similar rods next to it. A FID, is analogous to a cathode in a TV tube, when heated it gives off a stream of electrons. In a boiler, these charged particles flow into the burning gas. It’s this current flow which is detected by the PCB circuitry. It looks as though you were measuring the current change OK and the PCB was seeing the current drawn. The PCB is just not throwing the “detected switch” properly.
Generally, in this type of boiler technology, you can rule out the probe as the likely fault. Provided there’s no obvious resistance measured from the end of the probe to the PCB connector.
(From this thread, you’d think a flame detection problem is rocket science!)
I’m still looking for somebody who can properly fix my old board. (I’ll keep it as a spare.) CET (I assume this is where you saw the reconditioned offer) told me they’re a bit busy this month but they’ll look at mine later. Any other suggested repairers would be an useful post?
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niannorth
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niannorth
Niannorth,
Glad to see you fixed it, I hope you did get CORGI help to set up the PCB potentiometers (safety/efficiency/legal reasons). These control “soft-light” and “max heating” gas pressure settings and I suspect the PCB came with natural gas settings. (For butane/propane these gas pressures settings are higher.) Your installation manual will document these exact values.
I just spotted the other post. Combi systems are a pain and Ariston are well up the list when it comes to hassle. When I had two low cost Ariston boilers installed at our farm, it was suggested that I buy a THIRD just for spares! My spare is now well cannibalised!!!!
Glad to see you fixed it, I hope you did get CORGI help to set up the PCB potentiometers (safety/efficiency/legal reasons). These control “soft-light” and “max heating” gas pressure settings and I suspect the PCB came with natural gas settings. (For butane/propane these gas pressures settings are higher.) Your installation manual will document these exact values.
I just spotted the other post. Combi systems are a pain and Ariston are well up the list when it comes to hassle. When I had two low cost Ariston boilers installed at our farm, it was suggested that I buy a THIRD just for spares! My spare is now well cannibalised!!!!
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niannorth
your problem could also be the air pressure switch breaking down for various reasons its a cheaper option but you are not allowed to fix it unless you are corgi registerd so you would be better off finding a gas engineer sorry
Happy New Year, Frank.
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