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Older Burnham boiler/Beckett AFG technical question nozzle type/size

bpedrant Member Posts: 1
Hello all,

My house has a Burnham boiler model: RSA85RH-TB

The boiler does run very reliably, but a previous tech installed an "A" nozzle (which worked OK) and it got me going on helping to verify the setup for my new HVAC guy and if there are ways to make it more efficient.
(Replacing the boiler is not an option at this point.)

The technical/install manual says to use a .75 x 80B nozzle at 140psi. This is a solid cone type pattern. After reading/researching, I have found that these are recommended more for larger commercial type systems and also have a louder burn volume. I can confirm that it has a loud burn sound.

Is there any updated technical info for this boiler? Or, is it "use a type B" because Burnham said it 20 years ago type of situation? :)
(I have seen other heating techs comment that using a S-S is preferable over the B for sub-1GPH firing rates. They are quieter and maybe more efficient.) I have no clue why the previous guy installed an "A" type.....

The boiler does generate plenty of BTUs to keep the house and hot water warm, even in MA's 0 degree days. But, my HVAC guy went against the book and installed a .65 nozzle. His thinking is that it would burn longer and thus be more efficient. Is this OK? Should I recommend him change it back to the higher one (or go even lower)?

More info on the system:
Beckett AFG burner. Nozzle at .65 x 80B
Low Firing Rate Baffle is installed
Pump pressure is 140psi
Beckett Cleancut and Beckett AquaSmart 7600 controller installed
First circulator pump runs the 2 zones with zone valves
Second circulator pump heats up the indirect hot water tank



  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,817
    edited January 2023
    The factory nozzle specification is where I always start if I am running into problems with a Job. That said, I carried 3 nozzle boxes on my truck and usually had every possible combination of nozzle available, however by the end of the week, if there were a lot of oil burner calls, there were times that I did not have the factory specified nozzle available. There were some tricks that I could do to make what I did have work at the time. Changing the fire rate lower and increase the pressure was the most common. Changing to a W or SS nozzle of a wider angle (like from 60° to 70°) in place of a hollow might work too.

    There was one boiler that required only one nozzle and there was no substitute. So I placed a spare under the transformer (where the wire connections were) just in case I was caught short on that burner. Never had to use it though. I think it is still there because my son does that customer's tune up as a side job in the summer. (He no longer works in the trade full time)

    If I knew that a boiler or furnace was grossly oversized for the job, I might be inclined to lower the firing rate by about 15% This helped sometimes. The bottom like is that when ever I changed out a nozzle, be it the OEM specified nozzle or a substitute nozzle, there was a Smoke Test, Draft Test, and Combustion analyzer to check the flame quality. (back in the day it was a stack thermometer and Fyrite CO2 % bottle). That is how I was taught... That is how I wanted all my technicians to do it. I wanted the numbers on the job ticket too.

    So Brian, Did your tech have a combustion analyzer? Did he use it? What were the numbers?
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
    EBEBRATT-Ed Member Posts: 15,513
    Bottom line is no matter what nozzle the boiler MFG specs (and what they spec sometimes doesn't work well or is not the best choice) the only way to know is combustion test then come back in a month and check it again.

    Every boiler is different
    every burner is different
    every job burns different fuel
    the temperature of the fuel may be different (underground versus indoor tank)
    The draft and condition of the chimney varies (inside or outside chimney)
    The temperature of the combustion air varies
    and the fuel pressure may be different

    That being said you should start with the nozzle the mfg recommends.

    Frequently if the boiler is oversized (which many are) you can size the nozzle down and get longer run times=less short cycling and cleaner combustion. The stack temp must remain above 330 or so to prevent condensation.

    testing is the only way to tell for sure.

    I have had identical boilers in the same boiler room run different.

    It's not a washing machine or a dishwasher. There are too many variables with combustion to have a one size fits all.

    Your looking for the burner to operate in a safe range.......not shooting for exact combustion numbers
  • Steamhead
    Steamhead Member Posts: 16,826
    There's another version of that boiler, here is the spec for it:

    RS-AH85 Model: AFG; Nozzle: 0.65 X 80°B* (Hago); Alt. Nozzle: 0.65 X 80°A (Delavan); Pump Pressure: 140 PSI. Air tube assembly and head are the same.

    This would give a slightly lower firing rate- 0.77 GPH as opposed to 0.89.

    As long as this setup satisfies the house's heating needs, I'd be inclined to keep it.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    EBEBRATT-Ed Member Posts: 15,513
    For my money most jobs I have seen with small fire work better with anything Delevan than other brands