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Combustion Readings

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  • 20-01-2021 10:23am
    #1
    Mickeroo
    Administrators, Computer Games Moderators, Sports Moderators Posts: 32,145 Admin ✭✭✭✭✭


    Pretty sure our boiler is the one that was installed when the house was built so it must be about 22 years old or so (it's had the odd bit replaced since we moved in 5 years ago). Had it serviced at the end of autumn, now I wasn't at the house when it was done but the guy did some sort of test on it and it printed out a little report that said the efficiency was 90% or so, so basically like new. I thought boilers that old were more like 70% efficient even when they were new so I'm a bit skeptical of the figures :confused:


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    #2
    Wearb
    Moderators, Home & Garden Moderators Posts: 6,213 Mod ✭✭✭✭Wearb


    Mickeroo wrote: »
    Pretty sure our boiler is the one that was installed when the house was built so it must be about 22 years old or so (it's had the odd bit replaced since we moved in 5 years ago). Had it serviced at the end of autumn, now I wasn't at the house when it was done but the guy did some sort of test on it and it printed out a little report that said the efficiency was 90% or so, so basically like new. I thought boilers that old were more like 70% efficient even when they were new so I'm a bit skeptical of the figures :confused:

    Pop up a copy of printout here. Redact any id.

    Please follow site and charter rules. "Resistance is futile"



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    #3
    Mickeroo
    Administrators, Computer Games Moderators, Sports Moderators Posts: 32,145 Admin ✭✭✭✭✭Mickeroo


    Probably be as easy to just type it out:

    FUEL L OIL

    02% 7.1
    CO2% 10.3
    CO PPM 49
    FLUE °C 69.5
    INLET °C 8.6
    NETT °C 60.9

    EFF (G) 90.7
    LOSSES 9.3
    XAIR % 51.4
    Cal. due on 13/01/21
    CO/CO2 0.0004

    PR5 mbar 0.00

    No issue with the service btw, guy was a gent and will get them again. Just curious about the print out.


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    #4
    Wearb
    Moderators, Home & Garden Moderators Posts: 6,213 Mod ✭✭✭✭Wearb


    Mickeroo wrote: »
    Probably be as easy to just type it out:



    No issue with the service btw, guy was a gent and will get them again. Just curious about the print out.
    Whats make and model of boiler?
    Date of service?

    Please follow site and charter rules. "Resistance is futile"



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    #5
    Mickeroo
    Administrators, Computer Games Moderators, Sports Moderators Posts: 32,145 Admin ✭✭✭✭✭Mickeroo


    Wearb wrote: »
    Whats make and model of boiler?
    Date of service?

    23rd sept. It's a Riello 40 G3B, just had a quick look at it there.


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    #6
    Wearb
    Moderators, Home & Garden Moderators Posts: 6,213 Mod ✭✭✭✭Wearb


    Mickeroo wrote: »
    23rd sept. It's a Riello 40 G3B, just had a quick look at it there.

    Thats the burner make not boiler make.

    However it wasn't tested nor setup properly. I elaborate later when I've time.

    Please follow site and charter rules. "Resistance is futile"



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    #7
    Mickeroo
    Administrators, Computer Games Moderators, Sports Moderators Posts: 32,145 Admin ✭✭✭✭✭Mickeroo


    Wearb wrote: »
    Thats the burner make not boiler make.

    However it wasn't tested nor setup properly. I elaborate later when I've time.

    Ah my bad, showing my lack of knowledge there, didn't realise there was a difference :o

    PM me later if you can, would be interested in what you have to say but don't want to hijack this thread anymore :)


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    #8
    John.G
    Registered Users Posts: 3,466 ✭✭✭John.G


    That's a condensing boiler, pretty good for a 22 year old.


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    #9
    John.G
    Registered Users Posts: 3,466 ✭✭✭John.G


    Wearb or Jimf might answer this the below readings would seem to be (IMO, correctly) based on the gross heating value of the fuel "EFF (G) 90.7", I'm sure I have seen efficiencies of 98% or so on some condensing boilers analysis which, again IMO has to be based on the Net fuel heating value but any boiler with a flue gas temperature of 60C is condensing nil?.

    FUEL L OIL

    02% 7.1
    CO2% 10.3
    CO PPM 49
    FLUE °C 69.5
    INLET °C 8.6
    NETT °C 60.9

    EFF (G) 90.7
    LOSSES 9.3
    XAIR % 51.4


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    #10
    Mickeroo
    Administrators, Computer Games Moderators, Sports Moderators Posts: 32,145 Admin ✭✭✭✭✭Mickeroo


    I looked again and the boiler is a Firebird Heatpac 90 which I did not think was a condensing boiler?


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    #11
    John.G
    Registered Users Posts: 3,466 ✭✭✭John.G


    You can't get a flue gas temperature of 70C with a non condensing boiler, mine (same as yours) is ~ 230C, maybe who ever took the readings didn't wait long enough for the boiler to heat up.


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    #12
    Wearb
    Moderators, Home & Garden Moderators Posts: 6,213 Mod ✭✭✭✭Wearb


    FUEL L OIL

    02% 7.1
    CO2% 10.3
    CO PPM 49
    FLUE °C 69.5
    INLET °C 8.6
    NETT °C 60.9

    EFF (G) 90.7
    LOSSES 9.3
    XAIR % 51.4
    Cal. due on 13/01/21
    CO/CO2 0.0004

    PR5 mbar 0.00

    Unless there was a really good reason the O2 level should have been set a lot lower. That setting is suitable for an ambient temperature of below freezing. This was done in September.

    Flue temperature is indicative of the boiler not having been given time to heat up to operating temperature. A big no no for any tech. The other reason (unlikely but possible) is the the boiler is way underfired, by having the incorrect nozzle and/or pump pressure.

    The above will give inflated efficiency figures and doesn't reveal much about how well the boiler is running.
    The guy might be a nice guy, but I'd be reluctant to have him back.

    Please follow site and charter rules. "Resistance is futile"



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    #13
    John.G
    Registered Users Posts: 3,466 ✭✭✭John.G


    Is the analyser (see post 9) set differently for condensing/non condensing boilers.


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    #14
    Wearb
    Moderators, Home & Garden Moderators Posts: 6,213 Mod ✭✭✭✭Wearb


    John.G wrote: »
    Is the analyser (see post 9) set differently for condensing/non condensing boilers.
    Yes John. For condensing the settings assume complete condensing, giving inflated eff figures, except in exceptional circumstances.

    Please follow site and charter rules. "Resistance is futile"



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    #15
    John.G
    Registered Users Posts: 3,466 ✭✭✭John.G


    Can't remember the exact name but boilers now have to give something like seasonally adjusted readings or something like that, so is that also based on the Net heating value?, hopefully not.


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    #16
    Wearb
    Moderators, Home & Garden Moderators Posts: 6,213 Mod ✭✭✭✭Wearb


    John.G wrote: »
    Can't remember the exact name but boilers now have to give something like seasonally adjusted readings or something like that, so is that also based on the Net heating value?, hopefully not.
    Seasonal figures are different than combustion figures.



    Seasonal figures are made up of the efficiency of a boiler over an annual period (with boiler running at designed output) with all the ups and downs of temperature and periods of use and must be a complicated procedure.



    What you get with combustion figures is how well the fuel is being burnt with some assumptions made about efficiency at that time.

    Please follow site and charter rules. "Resistance is futile"



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    #17
    jimf
    Registered Users Posts: 3,950 ✭✭✭jimf


    John.G wrote: »
    Wearb or Jimf might answer this the below readings would seem to be (IMO, correctly) based on the gross heating value of the fuel "EFF (G) 90.7", I'm sure I have seen efficiencies of 98% or so on some condensing boilers analysis which, again IMO has to be based on the Net fuel heating value but any boiler with a flue gas temperature of 60C is condensing nil?.

    FUEL L OIL

    02% 7.1
    CO2% 10.3
    CO PPM 49
    FLUE °C 69.5
    INLET °C 8.6
    NETT °C 60.9

    EFF (G) 90.7
    LOSSES 9.3
    XAIR % 51.4

    boiler is way overaired
    02 should be around 5.5 co2 approx 11.5 % excess air 35%

    flugas temp needs to be up to operating temp before been set up eff of boiler somewhere in the region of 83% gross

    all the above need to be done with the boiler in its operating state ie burner cover on and boiler door on


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    #18
    jimf
    Registered Users Posts: 3,950 ✭✭✭jimf


    John.G wrote: »
    Can't remember the exact name but boilers now have to give something like seasonally adjusted readings or something like that, so is that also based on the Net heating value?, hopefully not.


    the figures we see with he boilers are based on any given reading at any given time

    lets say 98% nett will probably adjust to about 94% across the season this allows as well for when boiler is not running in condensing mode


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    #19
    John.G
    Registered Users Posts: 3,466 ✭✭✭John.G


    But condensing mode doesn't even begin until the flue gas temperature reaches ~ 50C, from your own experiences Jimf what kind of typical flue temps are you seeing and what has been the lowest?.


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    #20
    K.Flyer
    Registered Users Posts: 8,565 ✭✭✭K.Flyer


    But the boiler in question is Non Condensing, I think it's best not create confusion with the op discussing the technicalities of condensing boilers.
    I agree with Jim and Wearb, the figures are off and the boiler needs to be looked at again.


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    #21
    jimf
    Registered Users Posts: 3,950 ✭✭✭jimf


    John.G wrote: »
    But condensing mode doesn't even begin until the flue gas temperature reaches ~ 50C, from your own experiences Jimf what kind of typical flue temps are you seeing and what has been the lowest?.

    flue gas temps can vary across different makes

    the lowest by far is the grant vortex usually around 65


    the highest would be the firebird silver boilers not to be confused with the enviromax

    the silver series can be as high as 125 this is because of the more open airways through the secondary heat exchanger compared to the enviromax

    as a rule with me anyway i usually dont hang around too long once i have the boiler up to minimum stat temp i am happy to then do the fga get paid and on to the next victim sorry i mean customer

    thats not to say we wont have the fga in the boiler earlier usually you can spot an overaired boiler before it reaches operating temp all this of course once you ae happy the boiler is burning clean with no soot residue

    rule of thumb the proper nozzle and set pressure to mi and you are usually not far off

    sometimes it better to fine tune it on the pump pressure than the air damper


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    #22
    John.G
    Registered Users Posts: 3,466 ✭✭✭John.G


    So, it looks like there are very few, if any, oil fired HE boilers that ever run in condensing mode, non the less there are still savings of around 7/8% based on my flue gas temps of 230/235C. Gas fired boilers can probably achieve partial condensing as the heat exchanger duty decreases as they modulate down when house up to temperature.


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