I have a Beckett AFG model WL-4504 burner, Weil-McLane WTGO-4 oil boiler that runs a f4 head. The specs call for a 1.25X80B nozzle with 100psi pump pressure. What I found in my boiler was a .75X80A nozzle. I have not verified pressure yet. The shutter is set to 2 and the band to 0. Specs call for shutter of 10 and band of 0 for the original larger nozzle.

What are the pros and cons of running a smaller nozzle? Looks like the f4 head has a firing rate of .85-1.35. Do I need to change the electrode adjustments? Should pump pressure be increased? If I run a smaller nozzle to save on fuel I presume will it heat the boiler properly, meaning not to rated BTU but large enough flame to firebox ratio? Also the nozzle that is in there is a nozzle and not a B, will this have a drastic effect? Lots of questions but thanks for any input in advance. I arrived home to a boiler tripped out and opened the top up and found the entire unit stuffed with soot. I'm kind of trying to reinvent things here from scratch since I'm cleaning it etc. I bought the house a year ago and remember something about a smaller nozzle to save on fuel. #1 in Haines, Alaska was about $5/gal a couple of months ago. We run the limits on the cool side anyway, so maybe this is why the original owner switched nozzles?

I'll throw in my two cents' worth (and that's about its worth)... Given a fixed/constant pump pressure (100 PSI is typically standard), the GPH rating of the nozzle dictates BTUH input. In a pinch, and using proper methods, the pump pressure can be adjusted to compensate for an undersized or oversized nozzle, within reasonable limits. Stay within the GPH range specified on the burner rating plate. Sounds like the burner calls for a nozzle with a solid spray pattern, and someone has put in a hollow, as well as changing the combustion air settings. Cleaning out that soot will give you a level of appreciation for system care that you never wanted to know. Be sure to wear a good dust mask or respirator, and use care not to damage the refractory chamber. Canary optional. Hopefully you will get additional input/suggestions from other pros, perhaps with more fuel oil experience/knowledge than myself.

Thanks for your comment. I've heard of guys putting in smaller nozzles and bumping up the pressure for a more atomized spray.
Aside from the fact that they put in a hollow nozzle vs a solid, what about sizing? I have to burn #1 up here in Alaska and all specs are always for #2 which has a higher BTU content. I'm wondering how this plays into the game.

Hopefully you will get additional input/suggestions from other pros, perhaps with more fuel oil experience/knowledge than myself.That makes two of us... ;)

Well, I'm into day 2 of the cleaning and yes a respirator is a must with this level of "overhaul". We have had some cold temps and we recently installed a wood stove and have been running that primarily for heat. (Due to the cost of #1 up here) Since the demand on the boiler is about 4 times less now, it didn't run much and since I have the boiler room vents directly at a outside wall the room began to get very cold. One of the pipes had started to freeze up so I had to plug the lower of the 2 vents up completely and restrict the upper so that the room would warm up a bit. This was about 3 weeks ago. I'm sure this had something to do with it plugging with soot the way it did. I see Beckett offers a outside kit 51747 and I will be looking into this as well. Does anybody know of motorized louvers that are interlocked with when the burner fires?

I have seen some power louvers used in commercial applications, primarily laundromats with very large water heaters. The ones I have seen were quite large (at least 24" x 24"). I am not sure of the manufacturer, but you can probably find them quite easily on the web.