G3B Conversion in Dunkirk

Long Beach Ed

Tim, your books have been incredibly helpful to us.  Thanks for making your experience available tot he Trade.  



We've recently installed a G3B Carlin in a 113,000 BTU Dunkirk Series 8 steam boiler.  The boiler is 40 years old but of efficient, modern design and good condition.  Perhaps you'd kindly advise if our numbers look good to you.  



We drilled a 15/64" orifice and have gas pressure of 3.8#. 



It took quite a bit of time to get stable CO.  We have CO of 10.19%, O2 of 2.7%, 3ppm CO. 



Our stack temperature is 470 net.  That translates to combustion efficiency of 81.6%. 



We've replaced the breech and installed a double acting draft regulator.  Our draft is a bit high at perhaps negative .08 with two regulators installed as the interior chimney is 45 feet tall. 



How does this all look to you?   Any suggestions would be so greatly appreciated!



Ed in NYC

Tim McElwain

Try reducing the draft by

adding a "neutral pressure point adjuster" in the flue. If you are not aware of what it is let me know by e-mail gastc@cox.net and I will get you some instructions. I might also ask if you installed any baffles inside the boiler sections? That can also help to lower the draft and at the same time get the stack down to maybe 350 degrees.



We drilled a 15/64" orifice and have gas pressure of 3.8#. BY MY CALCUALTIONS THIS SIZE ORIFICE AT 3.8" W.C. GIVES AROUND 165,000 BTU'S????  SOUNDS LIKE YOU ARE OVER GASSED. YOU SAID YOU ARE LOOKING FOR 117,000 BTU'S IS THAT CORRECT IF SO HOW DID YOU COME TO THAT FIGURE?

Long Beach Ed

My mistake

That Dunkirk is rated at around 165,000 BTU input.  The 113,000 is out. 



No, there's really no way I can see to put baffles in that boiler.  Unless you have a suggestion.  The inside looks like a regular tube iron radiator.  Wet base and top flue.  I removed the firebox refractory. 



Your book well explains the "neutral pressure point adjuster", though I thought it was a modification I would look at when installing an atmospheric burner.  Should I try that, between the boiler and damper on the basis of cutting down the draft?  When the draft's where I want it, I'll go from there?  



Thanks for the help Tim. 



-Ed  

Tim McElwain

I am different

than everyone else I want the NPP adjuster between the barometric or draft hood and the chimney. That way we control total draft. I also want it placed in the bottom of the flue not in the top. Adjust it up and down until you are satisfied with draft then scribe and secure. The NPP adjuster is good on really any application for adjusting draft.

Long Beach Ed

Great

Thank you Tim.  I'll let you know how I make out. 



Will we have to adjust the burner air shutter again after installing the baffle in the flue?

Tim McElwain

No you should not have to touch the

air unless you see a drastic change. Also what is the draft overfire?

Long Beach Ed

Draft

The draft over the fire was just about -.06.  Maybe higher.

Long Beach Ed

Dunkirk Numbers

Went to work on The House with the 40 Foot Chimney today. 



Got the draft down to -.02 +/-  over the fire and about the same in the flue. 



CO2 is at 9.3%,  02 at 4.2% (CO 17ppm) The net stack temp came down to about 425 degrees. 



We'd like to get the stack lower, but this old Dunkirk is wide open but not open enough for any baffles or bricks or anything that I can think of.   This seems to translate to 81% efficiency, so I guess I'm done here. 



What do you think?  Any suggestions? 



Thanks for the help and advice.



Eddie, Long Beach NY

Tim McElwain

Everything

looks good!

Long Beach Ed

Thanks, Tim

Your training manual is priceless.  Couldn't do this kind of work without it!