Ravehnheat Csi85 720 series FLA reading

[nowucit]

Hi guys,

can anyone give me a bit of guidance, conducted a FGA on the above and a couple of the readings are throwing me. I can't find any guidance in the MI destructions or on their website.

FGA as follows

O2% 12.4
CO2% 4.8
CO PPM 12
CO/CO2 0.0002

Ratio seems fine <0.004
PPM seems fine <100
O2% I thought should be between 3-5% so the reading is considerably higher, while the CO2 I thought should be around 8-10% or there about (if I remember rightly).

Appliance was on full heat when I took the reading, can anyone tell me what the figures are trying to tell me. :banghead:

cheers

 

[nowucit]

OK ... Next attempt!! This time with hot water on full and ensuring leads are connected to FGA properly!

FGA as follows

O2% 7.8
CO2% 7.4
CO PPM 41
CO/CO2 0.0005

Ratio seems fine <0.004
PPM seems fine <100
O2% Better but still high, CO2% 7.4 which a bit healthier.

If anyone can tell me what the figures are trying to tell me you are more than welcome

 

[AmritPedersen]

What do the mi's call for.

 

[GrahamM]

Is this not a standard aerated appliance?
Not a zero governed condensing boiler that requires CO² figures etc.
Maybe I have the wrong boiler but think you are looking for something that is not there.
Check BP and ratio bellow 0.004. Thats all that's all you need look at.

 

[Blake]

Make sure you check min and max burner pressures also

 

[nowucit]

Is this not a standard aerated appliance?
Not a zero governed condensing boiler that requires CO² figures etc.
Maybe I have the wrong boiler but think you are looking for something that is not there.
Check BP and ratio bellow 0.004. Thats all that's all you need look at.

thanks GrahamM looks like I've been overlooking the obvious

thanks Blake I will recheck

 

[Reg Man]

Burner pressure 10.5mbar 22.6kW Gas rate 2.3m3/hr. O2 reading don't look quite right. Have you checked the integrity of the flue and ensured the heat exchanger is clean. Ratio looks fine but could be improved.

 

[nowucit]

Hi Reg Man, flue is fine, i will check and clean heat exchanger and burner, and check burner pressure and gas rate again. I am right in thinking that as these have a modulating gas valve and no service mode to establish high burn that I simply put the DHW on full and run the bath tap giving the applience 5 or so minutes to reach working temp?

I know they boilers are factory default to mid on the CH side via the potentiometer on the pcb. so persumably I would only want to adjust should I want to to increase or decrease the output of the boiler to suit the system.

thanks for your time fellas I'm new to servicing (well the industry generally) so 'learning all the time' :smile:

 

[GrahamM]

Hi Reg Man, flue is fine, i will check and clean heat exchanger and burner, and check burner pressure and gas rate again. I am right in thinking that as these have a modulating gas valve and no service mode to establish high burn that I simply put the DHW on full and run the bath tap giving the applience 5 or so minutes to reach working temp?

I know they boilers are factory default to mid on the CH side via the potentiometer on the pcb. so persumably I would only want to adjust should I want to to increase or decrease the output of the boiler to suit the system.

thanks for your time fellas I'm new to servicing (well the industry generally) so 'learning all the time' :smile:

Spot on. Give the H/E a light brush if looks like it may need it and give a good hoover out.
Put on tap(or 2 taps) at a good flow so will not modulate down and check the BP and gas rate. Remember the ratio although not required by manufacturer is still good practice to take in my opinion and may be a bit off after cleaning, that is why the limits change to 0.008.
The CO² and O² mean nothing at all on this boiler.
Pull off connector on modulator and check the min BP as well.
Job done!

 

[nowucit]

Thanks very much GrahamM I will look at it over the weekend and report back... is it only appliances with zero goveners that CO2 and O2 are critical during FGA?

Also what is the range for CO2% I have in my head somewhere around 7-10% but cant put my finger on where that came from.

 

[Reg Man]

Ratio is the most imortant reading. Co/Co2. O2 normally 20.9% in atmosphere.

 

[GrahamM]

Thanks very much GrahamM I will look at it over the weekend and report back... is it only appliances with zero goveners that CO2 and O2 are critical during FGA?

Also what is the range for CO2% I have in my head somewhere around 7-10% but cant put my finger on where that came from.

Only really zero governed appliances that require these figures.
CO²%, Ratio and Gas rate are critical to how each appliance model functions.
There is no general range for CO²%. Every appliance model is different. This is why you must have the MI's to hand.
Some will allow you a range of 9-10 CO²%, others say it must be 9. If it says CO²% of 9 required you must have that or as near as. If it is only creeping up to 8.9 I am not going to try altering any settings for sake of 0.1 CO²%

 

[Reg Man]

Only really zero governed appliances that require these figures.
CO²%, Ratio and Gas rate are critical to how each appliance model functions.
There is no general range for CO²%. Every appliance model is different. This is why you must have the MI's to hand.
Some will allow you a range of 9-10 CO²%, others say it must be 9. If it says CO²% of 9 required you must have that or as near as. If it is only creeping up to 8.9 I am not going to try altering any settings for sake of 0.1 CO²%

Ratio applies to all gas boilers zero governed or not. As Graham said 9%-10% CO2% on most common high efficiency boilers with max 200ppm CO = 0.0002 ratio

 

[nowucit]

Thanks fellas that great help

 

[GrahamM]

Ratio applies to all gas boilers zero governed or not. As Graham said 9%-10% CO2% on most common high efficiency boilers with max 200ppm CO = 0.0002 ratio

Think you are wrong there Reg Man!
There is no regs in place that states the ratio MUST be taken on a standard, non-condensing boiler. Unless the MI's specifically mention it obviously.
A lot have no flue test point and the flue term 3 stories up would be inaccessible.
It is good practice to FGA every boiler that you can though, as I do.

Only a select few mention the max CO PPM as well, Worcester for one which states 200ppm CO max. Again, as far as I am aware there is no general set figure for this unless MI's state it.