" of water columns @ 5000 feet above seal level

bagelboy

Hi...I am setting up bakery ovens using natural gas at 5600 feet above sea level.  I purchased derated orifices for one of the ranges and the tag states 5 inches of WC.  I still cannot get the ovens to rise above 400 degrees.  They should easily go to 500.  My question is...do you increase inches of water columns when you go from sea level to approx. 5600 feet above sea level or do they remain at the 5 as the manufactures id plates shows?

Thanks,

Eric

Mark Eatherton

Altitude matters...

but 5" at sea level is the same as 5" at 10,000 ASL.



Is the flame running continuously or is it shutting down? If it is shutting down, it sounds as if it is a control issue, and not a combustion issue.



Do you have a combustion analyzer?



Are you near Denver Colorado?



Our gas here is actually intentionally de-rated by pumping air into it, and most manufacturers assume we have 1,050 gas available.



The formula I have used successfully over the years is to derate the appliance at the normal rate (4%/1000 ft ASL) Then divide the required derated input by the caloric content of the gas (830 btu/cu ft here in Denver, less at higher altitudes) and size the orifices based on that input. Appliance burns clean and gets good and hot.



If you are not in the Denver area, I would suggest you check with the utility purveyor to determine the caloric content of the gas you are dealing with, and don't take the answer of a front line customer service rep. They have no idea what you are talking about. Talk to the guys in the lab. THEY know what you are talking about.



And be certain to check your work with a combustion gas analyzer. Ovens are notorious for generating excess CO.



HTH



ME