Atmospheric barometric conversion

SWEI

So are we. Keep the data coming...

JStar

Yes and no. With the draft control in place, our draft was around -0.03inWC. Looks acceptable. But our O2 was up at 13%. So, it looked like we no longer had a draft problem. I figured at that point that the boiler and burners were consuming too much air (probably by design). That lead us to the baffling. Our O2 dropped to 5%. So, the original draft hood is in place, with the barometric acting as an extreme draft relief damper. The baffle is reducing the airflow through the boiler and allowing the combustion products to remain between the sections longer.

SWEI

JStar said:

So, the original draft hood is in place, with the barometric acting as an extreme draft relief damper. The baffle is reducing the airflow through the boiler and allowing the combustion products to remain between the sections longer.

Forgive me, but I've gotten just a tad lost on this one. Original being the old EG-45 hood or the new(er) EG-40 hood?

thanks~

ChrisJ

SWEI said:

JStar said:

So, the original draft hood is in place, with the barometric acting as an extreme draft relief damper. The baffle is reducing the airflow through the boiler and allowing the combustion products to remain between the sections longer.

Forgive me, but I've gotten just a tad lost on this one. Original being the old EG-45 hood or the new(er) EG-40 hood?

thanks~

Original as in proper, EG-40 hood.
The EG-45 hood is what we blocked to use with the barometric.

SWEI

Thanks.

Tim McElwain

Joe with everything in place as original I am sure the O2 was not 13% so something is not right especially if you had to put a baffle in a design boiler. What did you use for a baffle and how is it placed?

There are other alternatives that can be used to increase slightly the efficiency of a design piece of equipment.

Tim McElwain

I looked up some figures I had on an EG 40 boiler from a test done about a year ago.

7.5% O2

7.8% CO2

50% excess air

Draft -.02

400° Net Stack

78.5% Efficiency

47 PPM CO AF

This was with the designed draft hood in place with a 3 foot rise off the top of the boiler. It was vented into a relined chimney 20 feet tall.

Tim McElwain

Those numbers are very typical of an atmospheric burner. As for stack temp what are you looking for with that boiler?

Keep in mind with a built in draft hood you have to test each section and average out the readings. Also the draft reading has to be taken after the draft hood not before which is preferable, that is one of the down sides of built in draft hoods.

Per Weil McLain on this style boiler a stack temperature below 350 is likely to cause too long a wet time.

After testing this style of boiler for many years these are very typical numbers. It is very difficult to get less than 50% excess air on an atmospheric burner set up.

There are things that I will some times do such as a draft adjuster in the drat hood or in the flue pipe especially if you have excessive draft.

JStar

Atmospheric boilers always give horrible combustion numbers. That's why I'm so interested in experimenting with them. They are designed to use a lot of excess air.

ChrisJ

The barometric alone with blocked drafthood was a complete failure from what I saw.

The barometric wasn't doing anything during our test, it was the stock drafthood + brick + 4" manifold pressure.

JStar

I'm going to fabricate some more sturdy, metal baffles to replace the brick at some point. It may be colder out at that point, too. At the rate of my current schedule, I might have free time in March.

ChrisJ

Hatterasguy said:

So, the barometric did not have sufficient authority to limit the draft. It would need to be lager with a more sensitive door.

But the brick significantly reduced the airflow in combination with an increase in fuel

This takes the efficiency from the high '70s into the low 80's.

The question that begs is whether pushing toward reduced air will be acceptable throughout the operating range.

In theory, any atmospheric boiler could be pushed with more fuel and restricted air to get its efficiency up into the '80s...........the question is whether the risk is worth the reward.

My slight understanding of all of this is that would only be true if we can get the barometric to regulate the draft 100%. Since the drafthood is still in use my draft overall isn't being controlled any better than normal.

@JStar Bringing a Megasteam with you in March?

ChrisJ

Hatterasguy said:

ChrisJ said:

My slight understanding of all of this is that would only be true if we can get the barometric to regulate the draft 100%. Since the drafthood is still in use my draft overall isn't being controlled any better than normal.

Then you must ask yourself a question............

Why did Weil-McClain provide it with considerable excess air using the drafthood when they could have just as easily restricted the air and obtained the same efficiency that you currently have?

Bricks are cheap.

Re-read my comment.
" that would only be true if we can get the barometric to regulate the draft 100%"

That draft regulator + spill switch retails for around $100, not sure what it'd cost WM. Compare that to the sheet metal drafthood.

Not to mention the drafthood requires absolutely no skill or knowledge to setup.

I still think Jstar's initial thought was correct. The EG-40 is essentially a downfired EG-45 and they cheated using a baffled drafthood. By connecting even a small amount of draft to it the flue passages in the block behave way too big for the 5 burner setup.

Just to be clear, both the EG-45 and EG-40 run great in stock configuration with their supplied drafthoods.