ferroli modena 102 shuts down

The simple answer is that YOU do not !

The signal sent to te gas valve is varied so that the valve sends the right amount of gas to provide the required power at any moment.

By having to even ask these questions it is obvious that you do not have the training and skills to safely measure the gas pressures and set up the gas valve and pcb correctly.

If you wish to study the subject you could enrol on an NVQ2 gas course at your local college. This will include core gas safety !

Tony

klapaucius said:

thanks raden.

would you be so kind to explain, how do I check modulation ?

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You will have to ask a jobbing fitter, not me. I just repair the boards

Agile said:

The signal sent to te gas valve is varied so that the valve sends the right amount of gas to provide the required power at any moment.

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the valve is controlled by an electric signal. the gas valve used in this boiler has two solenoids, one of them is used to modulate. what I gathered so far is that the amount of gas coming through the valve depends on the duty cycle of the PWM output of the controller.

what I was asking is what is the procedure of checking the modulation without actually getting into the gas circuit. I know it is not possible for me to measure the pressure, but I can check the driving signal and see how it depends on input conditions.

also I guess the large variations in gas pressure should be visible.

Agile, you are less than helpful, as usual.

what I was asking is what is the procedure of checking the modulation without actually getting into the gas circuit

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There isn't one. The outputs from the pcb aren't published.
"We" would simply take temp measurements around the boiler and monitor the burner pressures, knowing what sort of changes should be happening to both, from general experience, if not that particular boiler.

If you can get a steady state for long enough you could measure reduced gas usage at the meter, but none of us would go that way. It can be hard to see much difference at the flames.

It isn't brain surgery, once you've done it on a few boilers there's no big deal. But it would be difficult to convey without a lot of writing. Even with the full instructions you often have to read between the lines.

"""Agile, you are less than helpful, as usual."""

I think that I have been very helpful to you already although when you say things like the above that is hardly any encouragement for me to help you any further! Please just stop reading my advice if you dont find it helpful.

I have a professional duty to NOT give advice which could be dangerous to someone trying to DIY without the appropriate training and experience.

You have demonstrated a complete misunderstanding of how a gas valve functions!

It has mechanical settings on the valve which set the minimum and maximum gas pressures at the output.

Only when the valve is correctly set up as above can it respond to a modulation control signal. That is an analogue voltage applied and I am not aware of any boiler using PWM for this purpose. Its either totally analogue or uses a DAC.

When more that half of CORGI registered people cannot even set up a gas valve properly then I am not going to give you detailed instructions because if you blew yourself up then your neighbours and family might blame me.

I post here in my own name unlike most of the others who may give wrong or dangerous advice and want to keep their identities hidden.

Tony

Agile said:

It has mechanical settings on the valve which set the minimum and maximum gas pressures at the output.

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I know, I can read the manual. I did not adjust these settings. why would I ? installation is the same.

Agile said:

That is an analogue voltage applied and I am not aware of any boiler using PWM for this purpose. Its either totally analogue or uses a DAC.

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RTFM:
http://europe.hbc.honeywell.com/downloads/EN2R9025.PDF

as you can see, the valve is indeed controlled by PWM.
the higher PWM duty cycle is, the more current is applied to the solenoid, the more gas flows through the valve. digital ends when the PWM output is applied to the inductive load. in most PWM applications passive filters are used to recover the analog signal. PWM is widely used in many applications to perform digital-to-analog conversion.

I am not going to send you to a college, self-learning rules:
http://en.wikipedia.org/wiki/Pulse-width_modulation

Agile said:

You have demonstrated a complete misunderstanding of how a gas valve functions!

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we're even now. you have demontstrated a complete misunderstanding of electrics and electronics, I don't understand how you can be allowed near a half-electronic device.

sorry for the rant everyone.

ChrisR said:

It isn't brain surgery, once you've done it on a few boilers there's no big deal. But it would be difficult to convey without a lot of writing. Even with the full instructions you often have to read between the lines.

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thanks very much ChrisR, for the explanation. I will have to call the specialist to check modulation then.

I do agree that this particular ignition circuit does use PWM to generate the modulating signal although as you correctly imply the coil inductance will integrate the PWM signal to perform a D-A conversion. You probably remember the Sinclair audio amplifier with PWM which was a complete flop.

This is luckily quite rare and only a very small number of boilers use the second solenoid for modulation. Most modulate with a third solenoid incorporating the min/max mechanical settings which makes the setting easier for most people as thats the normal method.

The description of the gas valve operation seems to be misleading!

It says:-

""This maximum regulator is parallel to the integrated modulating regulator. This means that the lowest of both settings will determine the actual outlet pressure.""

I think that most people would expect the highest pressure to be obtained with a parallel arrangement and the lowest with a series arrangement.

Tony

WHere did you find the link to

http://europe.hbc.honeywell.com/downloads/EN2R9025.PDF

klapaucious? I tried a search from the root directory but couldn't find one.

Agile said:

I do agree that this particular ignition circuit does use PWM to generate the modulating signal

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are you sure this is an ignition circuit ? I thought ignition circuit provides spark for lighting, and gas supply is something different.

Agile said:

You probably remember the Sinclair audio amplifier with PWM which was a complete flop.

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I honestly don't understand what this had to do with it the original subject. are we going to dispute usefulness of PWM now ? going completely OT, switching amplifiers do exist and have use in certain applications, especially where high power is required.

while searching for the datasheets, many of the valves I found were controlled with PWM.

Agile said:

This is luckily quite rare and only a very small number of boilers use the second solenoid for modulation. Most modulate with a third solenoid incorporating the min/max mechanical settings which makes the setting easier for most people as thats the normal method.

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I don't really understand why would you need a third solenoid. min/max mechanical setting exists on the valve we are discussing here.

Agile said:

The description of the gas valve operation seems to be misleading!

It says:-

""This maximum regulator is parallel to the integrated modulating regulator. This means that the lowest of both settings will determine the actual outlet pressure.""

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I can't see anything misleading here. surely the mechanical regulator should limit the maximum output. the other way would be simply dangerous. the first malfunction of the controller producing 100% DC would open the valve completely and potentially blow everything up.

Agile said:

I think that most people would expect the highest pressure to be obtained with a parallel arrangement and the lowest with a series arrangement.

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you seem to have misread the datasheet. the sentence that you quoted only mentions maximum pressure, there is nothing about the lowest pressure in that sentence. afais, the highest of minimum settings will determine the minimal flow. logically, the inversion applies to the maximum.

ChrisR said:

WHere did you find the link to

http://europe.hbc.honeywell.com/downloads/EN2R9025.PDF

klapaucius?

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just googled for the part number. google indexes PDF documents.