combustion air

Unknown

as outlined in NFPA 54/ANSI Z223.1 National Fuel Gas Code.

First you must determine if room is a confined space.

It is stated two ways 20 BTU per hour per cubic foot of room or space

OR

50 cubic feet per 1,000 BTU's

Example a room 9 x 10 x 8 = 720 cubic feet

720 cubic feet x 20 = 14,400 BTU's maximum BTU's that can safely be in that area anything more as far as BTU's makes it a confined space.

If you use louvered doors it depends on whether the louvers are wood or metal. Problem often is that fire codes will require a solid core fire door so louvers in the door are out check with local code officials on that one.

As far as openings for combustion:

If all air is to come from inside the building it requires 1 square inch per 1,000 BTU's but not less than 100 Square inches. That is two openings each 100 sq inch one 12 inches from ceiling one 12 inches from floor.

Air from outdoors Method One

Again two openings same distance from floor and ceiling.
If using vertical ducts 1 square inch per 4,000 BTU's
If using horizontal 1 square inch per 2,000 BTU's

Method two

One permanent opening 12 inches from ceiling where equipment has clearances of 1" from sides and back and at least 6" from front. The opening shall communicate directly with outdoors or ducts horizontal or vertical that communicate directly with outdoors or space that communicate with outdoors. The opening shall be 1 square inch per 3,000 BTU's but not less than the sum of the areas in square inches of all the vent connectors in the confined space.

To find area of vent connector formula is A= 3.1416 x radius squared

Example:

A 4" flue radius is 2" squared is 4 x 3.1416 = 12.56 square inches

The newest code book change also have a new method which is the KAIR (Known Air Infitration Method). There are two formulas one for appliances other than fan assisted and one for fan assisted appliances. Space does not permit covering this method but my latest book "Fundamentals of Gas Volume II" covers this in detail.

It is debateable as to whether one method is better than the other. Air for combustion is better supplied by a forced method. This will provide a definite measured amount of air in and then the vent will do its job to remove flue products. Keep in mind that for every 1,000 BTU's 30 cubic feet of air is needed.

A formula to find air needed is

Total BTU equipment input x 30 divided by 60 minutes = CFM of the fan. Excluding pressurization problems from other sources it should be adequate. This does guarantee an amount of air however. This should then be verified by combustion testing.

curiousity kills

combustion air

Could anyone help me clarify the combustion air code? I have a calculation LxWxHx20=btu's allowed in room.Is this accurate? Also are luvered doors accepted? And if I am quoting this right two openings at one cubic inch per 1000 but if you only use one it is 3000 btu? Why is it less with one but more with two? Thanks for any feedback.

curiousity kills

Thanks Tim

Thank you Tim for your thorough answer and taking the time to explain it.Would you mind if I printed your response to keep in my truck for referance.I do have the gas code book but it is easier for me to interpet your answer.Thank you.....

Unknown

Copy all you

want. Enjoy!!!

curiousity kills

thanks

Thanks Tim happy thanksgiving.