hoping for some help understanding numbers

JusB

Hi Lovely people

I'm chair of governors at a very small rural school and about to go to a meeting with the council appointed facilities management company about our boiler.

It's a 1998 Potterton NRX3 oil boiler which has been rather unreliable over the past couple of years but I still think I might have a fight on my hands to get it replaced under the FM co budget rather than ours.

I have just been sent the last engineers report, carried out last summer, and realise that although I have a general idea what the tests etc are I have absolutely no idea whether the numbers are good, bad or indifferent and was hoping that some lovely person here could give me a quick explanation.

The figures I have been given are

pump pressure 150 psi (converts to 10.34 bar)
co2 reading 8.7%
flue gas temp 136 C
efficiency nett 92.1%
smoke no 0-1
co2 43ppm
excess air 64%
nozzle size 3.5, angle 60, pattern solid

From what I have found on the manufacturers site

Flue gas temperature should be 160 - 170
Max operating pressure 6 bar
Co2 13%
efficiency when new 84 - 86%

Any help to understand what the figures actually mean would be really appreciated.

This has already been posted in heating hell - not sure why it went to that discussion - so apologies for the double post.

Thanks

ETA - many thanks everybody, we had the meeting with the facilities management company who have taken away our concerns, the main issues we have had are reliability, availability of parts (had a 12 week wait for parts last winter just with electric fan heaters to warm a school with) safety and efficiency - will wait to hear the results of the meeting.

JStar

Those numbers are your combustion analysis results. They can change depending on a few factors such as adjustments at the burner, cleanliness, and draft settings. At first look, the burner seems slightly underfired/lean, but that can be fixed by a qualified technician. It's not so much a problem with the whole boiler, but of setting up the burner properly.

Has the system had a history of problems?

JusB

Thanks JStar, yes there have been lots on ongoing problems and I think the control panel is kaput as we cannot control when the heating is off - so running all the time even when the school is shut, not able to control temperature of etc- we have also had to have an extra tank of oil delivered up to what we would normally have used by this time of year

newagedawn

whens the last time you had a professional clean it, maintain it and change the nozzle? burners need love to sir,lol

JusB

newagedawn said:

whens the last time you had a professional clean it, maintain it and change the nozzle? burners need love to sir,lol

Newagedawn it was last serviced in June/July time and has been regularly serviced and maintained for all of its 22 years

newagedawn

then someone changed something to make it run like krudd,lol
maybe someone should come back

JusB

newagedawn said:

then someone changed something to make it run like krudd,lol
maybe someone should come back

I have the premises management company manager coming in this afternoon for a discussion with the governors about it, we don't feel it is reliable, safe or efficient, but wanted to understand the figures not just take his word for what it means x

newagedawn

not to take away from your manager good sir, in practical application sir, the numbers are not right and in my experience this means the tech (weather new or old) that serviced the boiler change something to make it run like this, usually a wrong nozzle size and a change in the air settings will do this, good luck to you sir and your meeting

nicholas bonham-carter

Is this a hot water heating system, or steam?
As others have said, the burner can be adjusted to have a better and more efficient burn.
What sort of control system is in charge of the boiler? All these separate parts can be fixed/adjusted/replaced without necessarily changing out the boiler itself, which may have still a long lifespan to go. Hopefully, there is expert help available in your area.—NBC

Grallert

Those numbers don't seem terrible. not great but with a little service seems they would come around. What exactly is the issue here. The boiler not that old for a modern cast iron boiler. Not sure what burn it has but that shouldn't be an issue. Is there some kind of control issue? You might not need to toss the baby out with the bath water.

STEVEusaPA

I think it's underfired and probably too much draft. And of course a real proper cleaning.
After that's corrected I'm sure the combustion numbers will look better.

EBEBRATT-Ed

@JusB

I agree with @STEVEusaPA

Your "false" high efficiency" is caused by you low stack temperature of 136C which if I did the math right converts to 276F which is way too low. The mfg stack temp converts to 320F

Minimum stack temperature is considered to be 100F over boiler water temperature.

You Co2 (carbon dioxide) is a measurement of how well the fuel and air is mixed and burned.....like a carburator in and old car this is primarily the burners job. The boilers job is to absorb the heat and transfer it to the water,

0-1 smoke is good we strive for 0-a trace of smoke

1 reading that is missing is C0 carbon monoxide. It must be under 100ppm and should be below 50ppm. Most burners can get dow to 10-20ppm

The low stack temp means the boiler is likely underfired...too small a nozzle or wrong pump pressure