I've seen it suggested that the Suprima gas valve has two coils but I can't find any detail on how it works.
I wondered if one is for start and one for run?
Our boiler is lighting, but then immediately dropping out - as if it's not detecting a flame. However once it's running it's fine until it reaches temp. If there was an intermittant flame detection issue I'd expect the drop-outs to be much more random.
Any thoughts welcome.
You have replaced the thermocouple? I'd replace it again with a good quality one before looking for another fault.
Assuming this is a fairly modern modulating boiler, one coil is notionally Start and the other is for modulation of the gas flow to turn the wick up and down.
Suprima doesn't have one.
Suprima isn't a modulating boiler.
En el artículo , Rory snipped-for-privacy@hotmail.com escribió:
You do know the Suprima is notorious for PCB failures?
BBC Watchdog did an item on it a few years ago and Poxy Batterton had to pay up. They reimbursed me for the cost of a replacement PCB.
In message , Mike Tomlinson writes
+1 Dry soldered joints where the mains connector pins are too heavy to be properly wetted by the solder bath. Fault follows a service visit as the engineer *wriggles* the connector to disconnect the supply. (Ancient Profile model). >
OK. Digging further, it does seem that the Suprima name with various suffixes covers a wide range of boilers and newer ones modulate, old ones don't.
I cannot explain why a non modulating boiler has two coils.
Hopefully some one can???
Bob
Just showing my ignorance then! But it must have some sort of flame detector?
Yes - it does it via the ignition lead. The old red ones are a known weak point but mine has been replaced by the later white one.
However if that was faulty I'd expect the drop outs to happen randomly. In practice, once the boiler gets going, it runs fine until the it reaches the boiler 'stat limit. Then it mostly won't restart, going through three ignition cycles then locking out.
It may well be the PCB (again) but I'm wondering if the gas valve has separate ingnite and run coils and the run coil is failing when hot.
En el artículo , Rory snipped-for-privacy@hotmail.com escribió:
Counting the number of wires to the gas valve may be your answer. If it's only two, there can only be one coil.
I'd still whip out the pcb and check it carefully fro dry joints, especially where wires plug into the board. As someone else said, the headers (sets of pins mounted on the pcb) are often poorly soldered and develop dry joints.
Well (excluding earth) there's two wires from the PCP to the boiler - but 4 connections on the gas valve, as two of them are linked together. Not sure if they're numbered, but effectively 1 and 4 are wired back to the boiler and 2 and 3 are linked.
I have a feeling it starts on AC then switches to DC once flame is detected. So I'm not sure if I've got an intermittant flame detection failure or an intermittant DC gas valve coil failure. NB: This assumes my guess on how it works is correct.
The odd thing is that if it can get itself running it'll run until it hits the boiler stat - I'd have expected more random shut downs.
En el artículo , Rory snipped-for-privacy@hotmail.com escribió:
I'm not an expert so can't offer more advice, sorry. But I have the installation manual and user manuals here. The installation guide includes troubleshooting. Happy to make them available for download if you want.
The Profile (its predecessor) has two valves in one unit. The spark ignites a pilot light first, and only when the sensor senses a pilot flame will it open the second valve for the main burner. It has
3 wires from the control board - a common, and one for each valve.On the Profile, I had a case of it lighting and then going out. Caused by lack of fanned air flow, due to a bird having somehow jammed itself in the flue terminal grill (which I didn't find until having taken much of the boiler apart, tested the differential air pressure switch, etc).
Appreciate the offer but I still have the original hard copy.
My parents' suprima had too little solder on much of the board, although what did for it eventially was a LV supply capacitor going high ESR, presumably causing the microcontroller to crash with too much ripple on its power supply. Did a swap for a refurbished one from Geoff (CET Ltd).
Just to close this - had a discussion with Geoff at CET. On the gas valve, he explained it does have two coils but they're in series (hence it only has two wires going to it). So it either works or it doesn't.
It seems the default position is to change the PCB first. So he sent me a refurb one and sure enough all is well now.
The board does seem to have an issue connected with flame detection - the green LED would continue to flash after the gas lit, then close the gas valve. If it was going to keep going OK then the green LED went solid immediately the gas lit.
Very random issue - today it had worked fine from 6Am to 2PM, when I swapped the PCBs. Yesterday it was a nightmare, constantly going into lock-out.
I did a bit of reading up on the gas valve and it seems it's actually two valves in one, each having a different class of shut-off.
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