Reducing Nozzle size Beckett AF II


Old 02-06-13, 08:37 AM
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Reducing Nozzle size Beckett AF II

I have searched and there is a lot of great info, but looking to zero a question with additional info. I know there is no love for the AF II, but it has been faithful for 19 years

I have a Vailliant boiler model F70 W50 PP , serial number 291 3677 1.0 GPH, 121 MBH. It came with a Beckett AF II 150 burner, other info on burner AH837296, MP1192, 0.75-1.5. Due to the high cost of oil I have been monitoring the system and find it frequently firing for 4 to 6 minutes, which is considered a short cycle . The longest burn, When two ambient temperature zones open together is about to 12 minutes.

I recently had the burner serviced and told them about the problem, asking if they could install a smaller nozzle . The technician advised that a .85 was the smallest nozzle recommended . But looking at Beckett’s information it appears that I could install a .65 nozzle which at the 140 pound pump pressure would give an effective, 0.77 GPH Oil consumption rate. Would this be recommended , I have the feeling that the technician did not have the smaller nozzle available so he just replaced the old one with the same size.

Thank you
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Old 02-06-13, 10:25 AM
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I just replaced my Vaillant this fall... had it for about 25 years or so... GOOD RIDDANCE to it...

I did have the AFG burner but I can tell you that you will probably find no joy at all in trying to downfire that boiler. I was never able to get it running properly with anything smaller than the stock nozzle... and believe me, I tried every possible combination of static plate, head, adjustment that are known to man...

Honestly, I wouldn't even try if I were you.

4-6 minutes I would not really consider a short cycle.

While a burner might be rated for a wide range of firing rates, that does not mean that the COMBUSTION CHAMBER is the correct size for that range... in fact, it will NOT be.

The burner itself is only PART of the 'equation'

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