Combustion Readings

Mickeroo

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

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

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

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.

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?

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.

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.

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

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

John.G

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

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

Mickeroo

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

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.

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.

John.G

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

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.

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.

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.

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

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

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?.

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.

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

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.