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Hot Tip #4 – Combustion Air

As the cold weather arrives, we frequently start closing doors in and around our boiler room.

This blocks off the needed combustion air to the boiler. The required make-up air opening is:

5 square feet per 1,000,000 BTU’s per hour.

A 300 BHP boiler would require:             300 * 33,000 /1,000,000 * 5 = 49.5 square feet

THIS IS 49.5 SQUARE FEET OF UNRESTRICTED AIRFLOW

If the air make-up opening is restricted (which it always is), with louvers or screens, then a larger opening is required.

Typical devaluation factors caused by these restrictive devices are 40 to 70 percent.

So, the required opening of 49.5 square feet can approach:  49.5 / (100% -70%) = 165 square feet.

Since the cold weather places a larger load on boilers, it becomes more vital that we monitor boiler efficiency closely.