Ariston 27 RFFI failing to ignite.

[Agile]

I was wondering about that Geoff too but did not dare say it!

Having said that modern electronics design is so convoluted and with so many essential feedback paths that it becomes difficult to use a logical fault diagnosis. Line output timebase which drives the switch mode supply etc.

Tony

 

[Gasguru]

Yep gave up repairing TV's when IC's came in, spent many Saturdays as an electronics student repairing them in the back of the local TV shop.

Grundigs were great - huge holes burnt through the boards makes Puma's look tame in comparison.

 

[Agile]

I also did radio and TV repairs for a shop when I was a student!

Same pricing process as I now use for boilers! Fixed price for radios and a fixed price for TVs.

The really good thing was that was for a bench repair as then people would bring their sets to the shop to be repaired. Most radios took about 25 minutes and most TVs about 55 minutes.

Tony

 

[Gasguru]

They don't make them like they used to

 

[TheFamousPoohBear]

Hi all,
Thanks for the reply.
I am merely the customer at the end of the day using the corgi as the primary engineer to solve a problem.
I found the documentation you referred to but it is blank, not having been completed either by the installing company or the service one.
There was no further follow up as regards future service or advice as to requirement for such from the installing company.
Yes, I have been an electronics engineer all my life and fully appreciate the necessary attributes towards logical problem solving.
The gas pressure at the inlet on fire-up only drops by an almost immeasurable amount indicating to my mind the valve is barely opening, if at all.
There is no pressure measurable at the valve outlet also indicating the control system is not really opening the valve to any extent.
The decision making has primarily been on the advice of the corgi but the fault, given these parameters, seems logically to lie either with the valve or it's control system. As referred to before when the replacement board was fitted it came up with a completely unrelated fault where the fan did not even attempt to run at all.
The corgi did not check the flue restrictor ring. I would assume this would be the responsibility of the installing engineer at the time of installation.
The remaining item is the ignition burner pressure.
While there has been no adjustment to the pots I know from experience to normally leave such adjustments well alone if you lack the proper information or leave any alteration to an expert.
The corgi has not, to the best of my knowledge, made any changes in this area.
Soft light setting was also checked indicating 32%, within limits as indicated in the manual.
While the problem is a failure to ignite the gas there must be gas passing through the valve to ignite in the first place. Hence, as this did not seem to be the case, the ignition electrode was changed anyway followed by the valve assembly and finally the control board.
Non of these approaches came up with a solution. The gas valve continued to behave in exactly the same way with all these attempts although with the replacement board, as it indicated a completely different and unrelated fault condition, would also prevent ignition as the sequence would likely terminate anyway but for a different reason entirely.
I think if I had been the actual engineer working on this fault I would have adopted very similar reasoning in seeking a solution.

 

[gas4you]

What other gas appliances have you got? Turn them all on and check the working pressure at the meter.

 

[Agile]

They don't make them like they used to

Thats an 1155 receiver as used together with the 1154 transmitter in early wartime aircraft.

Hopefully the Pooh Bear will be familliar with them.

Tony

 

[Gasguru]

The flue restrictor rings are often not fitted by installers due to

1. they can't be bothered to read the instructions and

2. the instructions (esp. Ariston) are not always that clear and sometimes require clarification by the manufacturer.

3. they get lost

Suffice to say if you have a standard flue (straight out the wall) it will require the ring. Boilers can often funtion for several years before a missing ring results in lockouts.


When the gas valve was replaced was it actually setup correctly with a manometer? The maximum and minimum burner pressures are adjusted on the valve. If this was not done its quite possible no gas will pass through the new valve.

Soft light pressure at 30%...what does this mean? The softlight (ignition burner pressure) should be set to 5mbar. Maximum and minimum pressures are probably 11.4 and 2. Also many Aristons require the pressures to be measured with the compensation tube disconnected. As I said the pots on the board can drift and require re-adjustment.

Ariston like to confuse everyone and produce a multitude of boards for their boilers - you must check the serial number of the boiler when replacing a board. Some suppliers (eg HRPC) are renowned for sending out incorrect pcb's.

Confirm the boiler GC number from the manual since there are a few versions of the 27RFFI (system boiler).

 

[TheFamousPoohBear]

Hi All,
It's the bear again.
Yes, I know the R1155 and the T1154. An 813 output valve running with around 1250V on its anode, requiring a fairly beefy psu. I was at an electronics fair in the university a couple of years ago where it was all talk of microprocesors and most of these guys had never even heard of 807's, 811's or 813's! What are they teaching them these days? Not the proper men's stuff at all by the sound of things!
I used to have a 1155 a number of years ago but it had been badly treated probably by a previous owner looking for spares. It worked after a fashion but had been too badly mauled to be worth fully repairing.
I still run two 19 sets, a Mk2 and a Mk3 but need new variometers. After 65 years they still function which is 63 years more than this boiler!
You're right when you say they don't make them like they used to.
The other more modern transmitter is an icom 7400 into a folded dipole. Call sign is MM3RHA.

About the gas valve replacement. I wasn't actually present when the corgi did this so I don't know what adjustments he made, if any. He merely said he had replaced the valve and it didn't work. I'm fairly sure no manometer measurements were carried out.
About the 32% softlight setting. (pot E) It lists the setting in the manual in % terms as the % difference between the minimum and maximum burner levels. It lists the value should be set to 33%
Such a measurement would translate into mb pressure but on what this actually is the instruction book is not stated. The other pots on the control board are to adjust the max power setting 70% and ignition delay (2 mins).
These can be checked by examining the operating variables monitor accessed by holding the reset button for 10 seconds. Ensuring these settings are within the limits would be a start at least so that will be the next job.
The corgi made no mention of attempting any reset of these controls.
There are two GC numbers. 47-116-23 and 41-116-08
I got transco to check the gas meter governor yesterday and it's all in order.
I think the answer if I am going to get this working at all and hold off on renewing the boiler it is to follow your advice and get in a corgi who knows more than the first one.

 

[gas4you]

If the working pressure is correct at the meter govenor then the pie sizing must be incorrect to get a drop of this magnitude.

Get a good corgi to check this with standard calculations.

 

[Gasguru]

Aha your GC number indicates the boiler is an ecoSystem or microcondens - a condensing fully premixed burner. Unfortunately few will have any experience of this particular model - I've yet to see one.

As I said before Ariston like to confuse everyone with their ridiculous boiler naming conventions and there are several versions of the 27 RFFI. We all assumed you had a non condensing boiler (having been installed a couple of years ago and living in Scotland (different regs.)).

Therfore much of what has been suggested before can be ignored since it doesn't apply to this type of burner.

Was the air/gas mixture setup (with a flue gas analyser) when the boiler was installed? Perhaps the mixture became too lean and resulted in the original lockout problem. When the new gas valve was installed it should have allowed the boiler to initially light, however its possible the initial settings on the valve were incorrect causing a lean mixture and failure to ignite. Others eg Tony have more experience of setting up these valves from scratch and can offer more advice.

(From my experience some merchants club together and buy gas valves from other sources (grey market). These may not have been calibrated by the manufacturer to suit a particular boiler and hence don't work out the box).

Have you checked the small tube from the gas valve to the burner? This is used to modulate the gas valve as the fan varies in speed. Perhaps the spigot on the fan/burner assembly the tube connects to is partially blocked.

Using the procedure in the manual check the softlight setting incase it has become corrupted.

 

[gas4you]

Still should be 20mBar at inlet though.

 

[Gasguru]

Still should be 20mBar at inlet though.

Ariston state 17-25 is acceptable.

21 at meter plus/minus 2 minus 1 = 18mbar minimum acceptable. Often loose anonther mbar through the GV isolating valve etc so down to 17 mbar.

 

[gas4you]

If I ever have less than 20mBar WP with a combi on a long run of pipe I always get NG out to set it to around 22mBar.

As you will guess I know most of them personally round my way and I am known for wanting everything set spot on