Down firing oil burners

Jack M

The two smallest Burnham Megasteam boilers (288 & 396) are basicly the same with different Reillo burners, the F3 and F5 (Becketts are an option as well). The Riello F3 and F5 burners have an adjustable range of outputs. There is an overlap in these burner outputs. The F3's range is from .5 to .95 gph while the F5 is from .75 to 1.65gph. So my question is "can a Megasteam 386 with a Riello F5 be downfired to .75 gph? or .85? To prefectly match a specific EDR on a one pipe steam system? How much wiggle room exists?

STEVEusaPA

Give it a whirl, see what your analyzer tells you. I dont think it will make much difference except that the boiler will run longer, using more oil.
Are you actually experiencing a problem? I would think with steam you want to follow the basics:
Steam up.
Air out.
Water back.
When you want to boil water on the stove, you put it on high right?
You may also have to add/remove/change the baffles.

Fred

I think the 396 has baffles and the 288 does not ???

New England SteamWorks

I'm with Fred: What problem are we attempting to address?

Also, if you downfire a MegaSteam check your stack temp and make sure it's not too low, which it frequently will be with the 3-pass design.

Baffles are removable in the event that the stack temp is too low, even when firing to spec.

Robert O'Brien

Triple pass boilers really can't be down fired.

Jack M

Fred said:

I think the 396 has baffles and the 288 does not ???

True (as RI_Steamworks mentioned) the 396 has baffles but they are optional and easily removed for low draft situations.

Jack M

Robert O'Brien said:

Triple pass boilers really can't be down fired.

I'm not following the logic here. Isn't a 288 just a downfired 396?
The F3 and F5 burners are running at the same pressure, same RPM.
The boiler chassis are identical (same size, same weight, same everything).
Downfiring would allow the installation to be better tuned to a specific EDR. "A few sizes fits most" leaves too much efficiency on the table.

spoon22

What type of chimney is it lined? Stack Temps may be too low if down fired too much which would cause draft problems and possibly destroy an unlined chimney

Jack M

Lined and insulated 6" stainless liner. 2 story house with excellent draft (not a tight envelope). Burnham calls for a 6" round or 8" rectangular flue on both the 288 and 396.

New England SteamWorks

I guess I am still missing what the problem is or the issue to be resolved? Are you trying to decide which boiler to install, or is it already installed and you have another issue?

Jack M

RI_SteamWorks said:

I guess I am still missing what the problem is or the issue to be resolved? Are you trying to decide which boiler to install, or is it already installed and you have another issue?

I don't understand why an F5 burner on the 396 could not be downfired to .75gph (the Riello spec). Wouldn't the smoke pipe temps be the same as the 288 with a .75 gph? (if that is the only issue)?

I'm a homeowner and not familiar with the details of burner tuning. The contention that "triple pass can't be downfired" leaves the question unanswered. Why can't boilers be fine tuned at the burner to match my EDR? To say that the manufacturer matches the burner to the boiler does not follow logic in this case. The 288 and the 396 are identical. So what's the rationale for not using the burner's gph/output range to match the desired load. A 386 with an F5 theoretically could cover an EDR range of 288 all the way up to 386. I'm sure that I'm missing something.

nicholas bonham-carter

I think the problem is oversizing of the boiler. We have no information about any symptoms which usually accompany an over fired situation.
It seems to be that the OP has actually calculated his EDR, and therefore realizes that his boiler is oversized?
He has studied the tables of output of the several boilers, from the same manufacturer on both sides of his needed EDR, and this is where his question comes from, "can I down fire my boiler?"
We will all be interested in the outcome.--NBC

New England SteamWorks

nicholas bonham-carter said:

I think the problem is oversizing of the boiler.

Well, honestly, we don't even know if the boiler even exists or if this is all still hypothetical.

Fred

RI_SteamWorks said:

nicholas bonham-carter said:

I think the problem is oversizing of the boiler.

Well, honestly, we don't even know if the boiler even exists or if this is all still hypothetical.

I guess, in my mind, it really shouldn't matter. If the OP has the unit installed and may need to try and down-size it or if the OP is considering a new boiler and wants to understand what he can or can't do with the 396 and a specific burner, I think it's a fair question. Maybe he definately wants a Megasteam but needs something inbetween the 288 and the 396. Who knows, but still a fair question.