Code Required Combustion Air
Code Required Combustion Air
(OP)
My situation falls under Chicago Code, but I would appreciate input from anyone who has run across this. I am sizing up combustion air for a large boiler plant - probably eight (8) 700BHP boilers. It will be an N+1 design. Two questions:
1. Do I need to size the combustion air for that "Plus 1" boiler even though it is not supposed to run unless another one fails?
2. The boilers will run on natural gas; however, they also have oil as a backup. I am delivering combustion air by mechanical means. The Chicago code requires 0.35 CFM per 1,000 BTUH for gas, and 0.4167 CFM per 1,000 BTUH for oil. Do I have to size the combustion air for oil (which is larger) even though the oil will only be used in an emergency if the gas supply fails?
Thank you for you help.
1. Do I need to size the combustion air for that "Plus 1" boiler even though it is not supposed to run unless another one fails?
2. The boilers will run on natural gas; however, they also have oil as a backup. I am delivering combustion air by mechanical means. The Chicago code requires 0.35 CFM per 1,000 BTUH for gas, and 0.4167 CFM per 1,000 BTUH for oil. Do I have to size the combustion air for oil (which is larger) even though the oil will only be used in an emergency if the gas supply fails?
Thank you for you help.





RE: Code Required Combustion Air
What are you relaly saving otherwise? Some inches on a louver, the next size up heater?
The worst case scenerio would be a big change becasue an inspector can always say "someone" can turn all boilers on, even though their not supposed to.
knowledge is power
RE: Code Required Combustion Air
RE: Code Required Combustion Air
Sorry, not sure of a specific code section. But I relate this to the gas code. You need to size gas piping for all equipment running at max at all times. Even if the equipment runs just in emergencies.
Another option is you can potentially use transfer air as a portion of the combustion air (as allowed by code) If you locate the transfer above the main entrance door, at least you can keep that area conditioned, even if other portions are not.
Im going to stick with my original thought. Ive been burnt to many times in CA, trying to save chump change (again relative) in first cost, and then pay 5x that to fix it later.
Good luck
knowledge is power
RE: Code Required Combustion Air
RE: Code Required Combustion Air
Obvioulsy you have to size for all boilers. Safety and common sense requires there will always be a point whne the +1 boier could be on.
As for NG or oil, will you have oil tank and oil piping isntalled and ready to go in case you need it? then yes you shoudl size for oil. If the boilers are jsut made to use oil, but you don't isntall any oil-piing and tank, I assume JHA woudl allow NG sizing. You shoudl ask them for clarification.
RE: Code Required Combustion Air
I'm not specifically cooling the "combustion" air, but I am trying to maintain 85 deg in the boiler room. I may have on the order of 100,000 CFM of OA required, which could be 95 deg. That, plus the heat rejection of the boilers will be a significant cooling load. They only way to temper the room is to cool the makeup air.
I don't think sealed combustion is an option, but I will ask Cleaver.
Thanks all for your help.
RE: Code Required Combustion Air
How many boilers are running when it's 95 degrees outside?
RE: Code Required Combustion Air
RE: Code Required Combustion Air
RE: Code Required Combustion Air
I have the feeling whoever is helping you on this gives you bad advice. I have never heard of someone proposing to cool the combustion air. I've seen it in power plants fro gas-turbines to boost power (at expense of efficiency), but not for boilers. and boilers would love warmer air.
RE: Code Required Combustion Air
RE: Code Required Combustion Air
RE: Code Required Combustion Air
Anyways, to answer the question, size for worst case on your intake sizes and airflow. But for cooling, I think it's insane to cool boiler rooms to 85 in Chicago. If you must do something, I like Drazen's idea of only sizing for heat rejection for expected summer operation (your four 700 HP boilers plus whatever else is in the room).
RE: Code Required Combustion Air
Not familiar with Chicago area codes, but I'd bet that full capacity burning #2 will be basis for the air permit.
RE: Code Required Combustion Air
RE: Code Required Combustion Air
heat comes with the job in a boiler room, just like cooks in a kitchen.
You could give them may be an air washer on the OA intake (evaporative cooling) - and you get what you get - www.munters.com
Especially since cooling form 95 to 85 will occur only a few hours in the year in Chicago, does not make sense to cool 100,000 CFM for a few hours.
RE: Code Required Combustion Air
As far as combustion air requirements, this was also an N+1 plant, and the owner's practice was to run N+1 at all times, because you don't just flick a switch and get steam out of even a warm boiler. This plant could stand no more than a 10% pressure sag due to process requirements. That doesn't mean all the installed boilers are ever drawing full air requirements, but as stated above, the AHJ's assertion was that nothing prevented them running all 8 flat out. Similar situation for emissions permits, they were based on all 8 running.