A few months ago this splendid boiler (1997, and still performing excellently), intermittently, but with increasing frequency, started failing to light the burner. There was a repeated clicking sound. This was similar to the noise made by the igniter relay on the gas side of our caravan fridge until the gas reaches the fridge (eg, if the gas was not turned off at the cylinder before turning the fridge fuel selector to off).
So I wondered if the clicking noise made by the boiler meant that it was trying to light the pilot burner, but failing to do so.
I called in an engineer, who had no idea what the noise betokened. He spent a long time on the phone with Ideal, who advised him to check the sealing strips between the (removable) case front and (fixed) back, and repair/replace as necessary. He found a small gap in the strip where the sensor tube for the boiler thermostat passes into the control box area below the bottom of the back case and glued a new piece of seal into the gap.
I was sceptical that this would make any difference, as the engineer also was, but the boiler then lit and ran normally. He agreed that having repaired the gap in the seal made no sense in relation to the problem because the cavity between the two halves of the case is under negative pressure from the flue fan. And, although there is a warning on the boiler not to run it with the front case removed, it started and ran just as well with this removed as with it in place. He agreed that the function of the seal was probably to deter any CO from leaking into the interior of the house.
After a fortnight, the same lighting up problem returned. I called him, but he said he was too busy to come and had no idea what the cause of the problem could be.
So I called another engineer. He very quickly traced the clicking sound to the gas valve. It's a dual solenoid valve (pilot jet and main jet) and, he said, after long service, the actuator moved by the second stage solenoid can start to stick.The solenoid armature strikes the actuator. If this fails to move, so the next stage in the ignition process does not start, the PCB switches the solenoid back on to try again, and so on.
He ordered a new valve. This was not a cheap "compatible" part but the one supplied by Honeywell as the current part for this application (£200 for valve and fitting). It was identical in appearance to the old valve, and fitted the various connections (gas and electrical) without any problems.
At first the performance of the new valve was excellent, but, after about a week, although the boiler always lights first time and achieves full flame height, the actual ignition process in the main burner is intermittently noisy. Often, it makes a variously loud/not so loud "woof". At other times it lights smoothly and quite quietly (as the boiler had always done with the old valve before this failed).
I have tentatively identified a pattern to the "woofing", which, at times, is almost a loudish bang. It seems to happen only when the boiler has been on, and when it-relights as it cycles. The shorter the "off" part of the cycle, the louder the re-lighting noise.
We also notice sometimes, after an instance of noisy lighting, a faint smell of gas around the boiler.
I reported this new problem promptly to the engineer who fitted the new valve. He came, and heard the "woofing", and one instance of a "bang". He said other factors might be responsible - e g, the burner gas injector bore might have worn slightly oversize with age. But he agreed, because there were different levels of lighting noise, that the most likely cause was that the new gas valve was faulty. As it was under warranty he agreed to order a new one.
After about a month he texted us to say that he had the new valve, and would come to fit it asap. Since then he has responded to our reminders by again promising to let us know as soon as he has time to come, but he has neither texted us back nor come.
My suspicion is that the new valve is opening slightly earlier than it should in relation to the timing of the start of the ignition process, meaning that gas starts being delivered to the main burner slightly sooner than it should be. When this happens, a varying proportion of the gas inside the burner/emerging from its jets is not ignited (because there is too much gas for the amount of oxygen supplied by the air draught), and, aided by the residual heat of the main burner metal, heats up when the rest ignites, creating a small but noisy explosion- like low-speed detonation in a petrol engine put under load when the ignition timing is over-advanced, or if the fuel has too low an octane rating for that engine.
Why is the ignition quiet when the boiler is cold? Possibly because there is no residual heat to ignite any excess gas after ignition has taken place?
The fact that the new valve worked well at first seems to rule out the possibility that it is not as identical to the old one as it looks. I believe that it is on a supersession part number, which (at least on older cars), can mean that it has been passed by the car manufacturer as "close enough" in spec to the original part, but is actually different in certain respects - which may affect its performance to some degree.
Can anyone cast light on this problem? I wonder if the engineer is being coy about returning because he suspects that the new valve varies sufficiently in spec from the original one to create the ignition problem that I had told him about, and that a further new example of the same valve would make no difference? He may consider the ignition problem to be insignificant (he hasn't said this), but the occasional slight smell of gas surely forbids such a verdict?
So I wondered if the clicking noise made by the boiler meant that it was trying to light the pilot burner, but failing to do so.
I called in an engineer, who had no idea what the noise betokened. He spent a long time on the phone with Ideal, who advised him to check the sealing strips between the (removable) case front and (fixed) back, and repair/replace as necessary. He found a small gap in the strip where the sensor tube for the boiler thermostat passes into the control box area below the bottom of the back case and glued a new piece of seal into the gap.
I was sceptical that this would make any difference, as the engineer also was, but the boiler then lit and ran normally. He agreed that having repaired the gap in the seal made no sense in relation to the problem because the cavity between the two halves of the case is under negative pressure from the flue fan. And, although there is a warning on the boiler not to run it with the front case removed, it started and ran just as well with this removed as with it in place. He agreed that the function of the seal was probably to deter any CO from leaking into the interior of the house.
After a fortnight, the same lighting up problem returned. I called him, but he said he was too busy to come and had no idea what the cause of the problem could be.
So I called another engineer. He very quickly traced the clicking sound to the gas valve. It's a dual solenoid valve (pilot jet and main jet) and, he said, after long service, the actuator moved by the second stage solenoid can start to stick.The solenoid armature strikes the actuator. If this fails to move, so the next stage in the ignition process does not start, the PCB switches the solenoid back on to try again, and so on.
He ordered a new valve. This was not a cheap "compatible" part but the one supplied by Honeywell as the current part for this application (£200 for valve and fitting). It was identical in appearance to the old valve, and fitted the various connections (gas and electrical) without any problems.
At first the performance of the new valve was excellent, but, after about a week, although the boiler always lights first time and achieves full flame height, the actual ignition process in the main burner is intermittently noisy. Often, it makes a variously loud/not so loud "woof". At other times it lights smoothly and quite quietly (as the boiler had always done with the old valve before this failed).
I have tentatively identified a pattern to the "woofing", which, at times, is almost a loudish bang. It seems to happen only when the boiler has been on, and when it-relights as it cycles. The shorter the "off" part of the cycle, the louder the re-lighting noise.
We also notice sometimes, after an instance of noisy lighting, a faint smell of gas around the boiler.
I reported this new problem promptly to the engineer who fitted the new valve. He came, and heard the "woofing", and one instance of a "bang". He said other factors might be responsible - e g, the burner gas injector bore might have worn slightly oversize with age. But he agreed, because there were different levels of lighting noise, that the most likely cause was that the new gas valve was faulty. As it was under warranty he agreed to order a new one.
After about a month he texted us to say that he had the new valve, and would come to fit it asap. Since then he has responded to our reminders by again promising to let us know as soon as he has time to come, but he has neither texted us back nor come.
My suspicion is that the new valve is opening slightly earlier than it should in relation to the timing of the start of the ignition process, meaning that gas starts being delivered to the main burner slightly sooner than it should be. When this happens, a varying proportion of the gas inside the burner/emerging from its jets is not ignited (because there is too much gas for the amount of oxygen supplied by the air draught), and, aided by the residual heat of the main burner metal, heats up when the rest ignites, creating a small but noisy explosion- like low-speed detonation in a petrol engine put under load when the ignition timing is over-advanced, or if the fuel has too low an octane rating for that engine.
Why is the ignition quiet when the boiler is cold? Possibly because there is no residual heat to ignite any excess gas after ignition has taken place?
The fact that the new valve worked well at first seems to rule out the possibility that it is not as identical to the old one as it looks. I believe that it is on a supersession part number, which (at least on older cars), can mean that it has been passed by the car manufacturer as "close enough" in spec to the original part, but is actually different in certain respects - which may affect its performance to some degree.
Can anyone cast light on this problem? I wonder if the engineer is being coy about returning because he suspects that the new valve varies sufficiently in spec from the original one to create the ignition problem that I had told him about, and that a further new example of the same valve would make no difference? He may consider the ignition problem to be insignificant (he hasn't said this), but the occasional slight smell of gas surely forbids such a verdict?
