split post: biasi boiler

[Paul Barker]

No u haven't altered anything to affect co2. Agree that many corgi registered and non registered installers don't set up co2.

Corgi inspectors are probably spread too thin to address this issue. The need for fga is now such it is bound to become mandatory.

Eventually tests for competence will reflect the appliances we work on today, instead of the 10pc we hardly ever encounter.

Maybe your installer would have a m8 with the equipment and ability to check it. I do these favours locally.

 

[Paul Barker]

To explain you have simply set maximum power during heating mode.

co2 is adjusted for your boiler at the gas valve only for low power, which is always lowest possible output regardless where it is range rated. Biasi expect high oower co2 to then stay within certain maximum (they tolerate a little over) but no adjustment can be made, if maximum too high start looking for faults like flue integrity and lengths.

All manufacturers have their slant. Some gas valves permit co2 adjustment for max and min. Some manufacturers control fan speed to adjust, some a combination. Some just offer you a test to confirm ok but no means to adjust, set it for lowest output and cgeck it's within defined limit at highest.

But relevant to you

 

[Agile]

The meter regulator should be checked for correct operation. That means less than 1 mB reduction in output pressure between min and max power.

Correcting that, if it were wrong, might improve the problem a little. It only needs a water manometer to check it.

However, before the boiler is set up correctly using an FGA, its essential that the meter regulator is working properly.

Anyone installing a pre-mix boiler without the facilities to test for CO² is not equipped to do the job properly.

Tony

 

[dsinclair999]

To explain you have simply set maximum power during heating mode.
Do you mean MINIMUM power during heating mode? I lowered it to the lowest setting from a much higher setting.
Scratch this, I misunderstood you.

co2 is adjusted for your boiler at the gas valve only for low power, which is always lowest possible output regardless where it is range rated. Biasi expect high oower co2 to then stay within certain maximum (they tolerate a little over) but no adjustment can be made, if maximum too high start looking for faults like flue integrity and lengths.
So... you're saying that this CO2 level doesn't need adjusting! When the installer was last here he set the levels to the Biasi recommended levels.

All manufacturers have their slant. Some gas valves permit co2 adjustment for max and min. Some manufacturers control fan speed to adjust, some a combination. Some just offer you a test to confirm ok but no means to adjust, set it for lowest output and cgeck it's within defined limit at highest.

But relevant to you

 

[dsinclair999]

The meter regulator should be checked for correct operation. That means less than 1 mB reduction in output pressure between min and max power.

Correcting that, if it were wrong, might improve the problem a little. It only needs a water manometer to check it.

However, before the boiler is set up correctly using an FGA, its essential that the meter regulator is working properly.

Anyone installing a pre-mix boiler without the facilities to test for CO² is not equipped to do the job properly.
Give the installer his due, he did have the kit for testing the CO2 ratios etc, but I don't think he was an 'expert' on this make of boiler!!! I guess there is some quirks about this make of boiler he doesn't know about!

Tony

 

[dsinclair999]

I dunno, this is sooo annoying

If I have the heating up full, no noise, turn on a hot tap, no noise

However, if the heating is turned down to any lower level, the noise is heard intermittently, turn on a hot tap and you get the noise straight away, every time!


Regards

DS

 

[Agile]

Anyone installing a pre-mix boiler without the facilities to test for CO² is not equipped to do the job properly.

Give the installer his due, he did have the kit for testing the CO2 ratios etc, but I don't think he was an 'expert' on this make of boiler!!! I guess there is some quirks about this make of boiler he doesn't know about!

I was not specifically referring to your installer but just to installers in general.

There is no need for an installer to be an expert on a boiler. He does need to be an expert in setting up boilers using his FGA correctly. The MI give him all the information he needs for any particular model.

All I can say is that your problem always turns out to be because the gas pipe size or regulator is wrong or the installer has not really measured and adjusted the boiler correctly.

Some premix boilers require setting up on maximum power while others like the Biasi should be adjusted on mimimum. Some installers dont realise and set up all boilers at maximum.

Tony

 

[dsinclair999]

Some premix boilers require setting up on maximum power while others like the Biasi should be adjusted on mimimum. Some installers dont realise and set up all boilers at maximum.

I think that's the problem Tony. So for my case the CO2 content should be in the range 8.8-9.0 as per the manual for minimum heat input of 11.0kW?

It's quite bad tho as he went thru most of this stuff with Biasi tech support who should have told him all this!!!!
Tony

Regards

DS

 

[Opel Fruit]

I have exactly the same problem, same boiler. Range rated down to 21kW on CH, so no foghorn sound.
Once the DHW flow causes the boiler to modulate up, the bellowing begins.
Biasi immediately said "if it sounds like a foghorn, the CO2 is not set correctly". OK - it WAS set when it was fitted in October. So it's moved then??
The foghorn sound only started a couple of weeks ago. Not sure why it's suddenly started. Not sure what makes the boiler resonate like this....

Does this indicate too much or too little air? Does more air increase or decrease the CO2 level in the flue?

Will have to find someone local with a FGA - though none of the heating engineers seem to have them!

On another note, my old gas meter (1993) sits at 24mB when no gas is being consumed, and drops to 19mB when the boiler is at full firing. The installer adjusted the governor initially because the original pressure was 27mB. I have checked the pressure with a WG and it is still as he set it.
Do I need a new Meter? Why would the foghorn sound start, all things remaining as is?

 

[Agile]

The meter regulator should be checked for correct operation. That means less than 1 mB reduction in output pressure between min and max power.

Anyone installing a pre-mix boiler without the facilities to test for CO² is not equipped to do the job properly.

Tony

The correct pressure at the meter on part load should be around 21 mB. Its irrelevant what it is with no load ! On full load it should still be at 20 mB as I explained before. The Gas Transporter will replace the meter regulator free ( 0800 111999 ) if requested.

Whilst you say the pressure at the meter is only 19 mB at full load but you dont quote this at the boiler. If its more than 1 mB pressure loss as demanded by the regulations then the boiler can be difficult to set up correctly.

If its the normal foghorn sound then its only produced at minimum power. Thats on startup or when the heating modulates back after ( in your case ) about 10-15 minutes.

Its caused be a weak mixture and usually measures less that 8.7 % CO².

The average three bed semi has a heat loss of 10-12 kW. Unless you have a six bedroom detached house with poor insulation your boilers is set way too high for CH at 21 kW. The only loser is you as the efficiency falls due to less operation at a higher condensation and a slightly less constant room temperature.

Its difficult to guess whats the main problem from the info you have given. You say "it was set correctly last October". One assumes this is by your installer but you also say your local installers dont have FGAs? Why are you apparently unable to call him back to check it again?

The thermal cycling and the ageing of components like the meter regulator will cause the exact operating conditions to vary slightly with time and this is one reason why boilers need servicing anually and resetting to the optimum manufacturer's operating parameters.

However, the above relates to the normal situation of the noise at minimum power! Yours as you have written it is only on higher power! That would imply a flue fault perhaps a failing flue seal allowing combustion gasses to recirculate. Thats assuming the inlet gas pressure is correct !

Tony Glazier

 

[Opel Fruit]

Thanks for the reply. I will try and clarify!
The supply pressure is 19mB at the boiler inlet test point. If the gas fire or stove is lit, this drops more. The lowest seen is 17mB, which is the bottom of the allowed range in the Biasi spec. The gas supply does seem to vary off load between 24 and 25mB. I assume this is normal supply variation in to the property.

The noise is present at high powers. There is nothing wrong or different about the flue in terms of inlet or outlet. I have thoroughly checked the flue and the seal at the boiler outlet. The inside of the sealed chamber is spotless. Biasi Technical fully recognise the "fault" being present at high power, not low power.

I have never had any wetside issues.

The original installer (only the "benchmarking" bit - whom I monitored fairly closely due to him being the third pillock who knew the square root of bugger-all about heating, but everything about tap-washers) did get someone else to come and set the CO2 - he had a Testo meter that was in calibration. The offset adjustment wasn't far out - about 1 half turn. The final CO2 readings were 9% at the minimum setting, and 9.3% at the higher setting. So spot on then.

The droning/hammer sound (perhaps not foghorn) only happens if I adjust the boiler to fire at above 25kW (initially) on CH, i.e. setting 5 on the B control. Or when drawing more than 8-9L/min of DHW - Quiet whilst showering, racket whilst running a bath!

The only other variable, by the way, was I added Purimachos inhibitor a couple of weeks ago - I previously used F1. Just chucked that in for interest....

Any ideas welcomed.

 

[chrishutt]

I have never had any wetside issues.

Your time will come...

I added Purimachos inhibitor a couple of weeks ago

That could be the problem. I used to stick Purimachos Protex into systems with C&M Britonys but kept getting aircraft type noises from the main heat exchanger near the top of the temperature range. I flushed out the Protex and replaced with something decent - end of problem.

 

[Opel Fruit]

Oh pooh!
It was a Litre of Purimachos Protex.... which I bought on "sale" from Screwfix before they dropped the brand....
Unbelievable (or not) that a Litre of inhibitor in a 15 rad system might cause noise....
The only reason I added it was that I had added the 15th rad to a new room a couple of weeks back - and the noise started around the same time... perhaps. I hadn't connected the two events - I have used Protex before (on numerous oil fired systems in France) and not had any noise issues. Those were the days - set the burner up for a nice yellow flame! And do it again the next year! Everytime Total Fioul changed the mix....

 

[chrishutt]

Protex seems OK on traditional high water content boilers, but on the low water content ones (at least on the Britonys) it causes these noises, probably due to frothing. You'd think the inhibitor manufacturers would have to test their product on a wide range of boilers before unleashing it on the public. Mind you there are so many boilers out there now...

 

[Opel Fruit]

Interesting you mention frothing.

I checked the two boiler bleed points earlier - just in case - the warm (not over hot) water in the pump and the nipple at the top of the H/E was distinctly aerated..... and "fizzy" after being run at high power some minutes earlier.

Sounds like a full drain is on the cards