Can I down fire my System 2000?

[vincenzo]

I just has my annual tune-up done on my 1 year old System 2000 and I noticed that it is firing at 90,000 btu's. I read through the burner's owners annual and saw that it can take a smaller nozzle size. I also saw the sticker in front of the boiler that say's the same thing. My house is 2 story colonial about 1550 sq. ft in size and was built in the 1930's, not completely insulated, (no wall insulation). My question is can I go to a smaller nozzle size and still have the burner operate normally, and if so how small. This boiler runs beautifully and I don't want to damage it . Also, will this void the warranty in any way? These are the test results that the oil burner tech took .
StackTemp:330
Net Stalk Temp:270
CO2: 10%
Smoke: 0
breech Draft: -20
Overfiredraft: 01
Efficiency: 86.6%
I posted the boiler sticker and the nozzle size from my burners owner's manual.

 

[Dana]

If a nozzle size is recommend in the EK-1 manual (not the burner manual) it can be re-jetted to the lower firing rate without screwing up the warranty as long as it's done by a qualified tech with a combustion analyzer.

It looks like you can bump it down to 83K for sure, but below that it becomes questionable. An uninsulated house that size would have a heat load of 40-50,000 BTU/hr, but with the heat-purging controls on the System 2K being 2x oversized doesn't have a huge effect on efficiency the way a dumber boiler that doesn't utilize an indirect water heater tank for heat purging purposes.