Thank you! A mechanical engineer here... just needed to do a quick estimate. This helped. We didn't do furnace combustion air requirements when I was in school.
Hi Paul: To start with you would need to know the BTU rating of the appliance you are dealing with. Once you find that you would follow the formula (30 cubic feet or air per 1000 BTU's if the appliance has draft control and 15 cubic feet of air per 1000 BTU's if the appliance does not have draft control) to find the amount of air required per hour. The size of the opening is then calculated through either tables or a formula from our gas codebook. If you don't have access to a codebook with those tables then you're going to need to figure out the total air required, then take into account the draft speed (usually 600 feet to 1600 feet per minute) for natural draft appliances. After which those numbers will be used in the flow rate formula to get your size needed. All in all its a fairly lengthy calculation. I'm not sure if I'm on the right track here with my answer but I hope this helps somewhat. Take care
So a heating system rated at 125,000 btu is located in a confined space , all the combustion air is to be taken from the outside through horizontal duct a gritle is to cover 40% of the area
HI Liz: This sounds like a combustion duct sizing question to me. You would need to the codebook to figure out the size of the combustion duct free area before you could add the grill on at the end of the run to outdoors. You won't need to do an air requirements calculation here as the tables in the codebook already account for the btu rating of the appliance. It would also depend what codebook (depending on country) you are using.
it would apply dame for diesel engines? otherwise how does this would work if you know the amount of oxygen on the air interacting on the combustion? i mean how you calculate POC if you know the oxygen amount.? (hopping be clear)
Hi Ruben: This would apply to diesel engines as well. You would have to know the input rating of the engine (BTUH). You would also have to know the oxygen content that you are sending in. I would assume that it's just air you are using with the diesel engine so the oxygen in the air would be 20%, similar to the numbers I used in the video. The POC's are another story. They are based on the flow rate of the fuel that you are using. You would have to figure that out based on the engine you are dealing with and then also the type of fuel mixture you are dealing with (hydrogen and carbon). I hope this helps. Take care Mark
Hello, I work with Altierus Career College to develop online course content. In developing our HVAC Program, we came across your RU-vid videos - Gas Furnace: Component Identification - and would like to include a link to it in the online course for student viewing. Please respond whether permission is granted or otherwise. Thank you!
