If the installation area meets the definition of "Unconfined Space" and does not have additional air requirements as described, the furnace may be installed without making special provisions for combustion and ventilation air.
Whenever this furnace is installed in an area along with one or more gas appliances, the total Btu/hr input of all appliances must be included when determining the free area requirements for combustion and ventilation air openings.
Do not block the combustion or ventilation air openings in the furnace. Any blockage will result in improper combustion and may result in a fire hazard or unsafe condition.
If ventilation and/or combustion air must be supplied to the "Confined Space" from inside the building structure, two permanent openings to an additional room of sufficient volume as to combine the volumes of the spaces to meet the criteria for an "Unconfined Space" must be created. Each opening must have a free area of not less than one square inch per 1000 Btu per hour of total input of all appliances within the "Confined Space" (but not less than 100 square inches). These openings must be located 12 inches from the top and bottom of the furnace area respectively and must be at least 3 inches long on the smaller side of the opening (See Figure 2). Neither opening can be blocked at any time.
Figure 2 | CONFINED SPACE / INDOOR AIR |
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| TOTAL INPUT | MIN. FREE AREA | ROUND DUCT |
| (Btuh) | (Sq. In.) | (Dia. In.) |
| 40,000 | 100 | 12 |
| 60,000 | 100 | 12 |
| 80,000 | 100 | 12 |
| 100,000 | 100 | 12 |
| 120,000 | 120 | 13 |
| 140,000 | 140 | 14 |
| 160,000 | 160 | 15 |
| EXAMPLE: |
|
|
| 50,000 Btuh Furnace & 10,000 Btuh Water | ||
| Heater = 60,000 Btuh Total Input = 12" | ||
| Dia. Round Duct. |
| |
If ventilation and/or combustion air must be supplied to the "Confined Space" from outside the building structure, two permanent openings to the outdoors must be created. Each opening must have a free area of not less than one square inch per 4000 Btu per hour of total input of all appliances within the "Confined Space". These openings must be located 12 inches from the top and bottom of the furnace area respectively (See Figures 3, 4, and 5). Neither opening can be blocked at any time.
Figure 3 | CONFINED SPACE / OUTDOOR AIR |
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| TOTAL INPUT | MIN. FREE AREA | ROUND DUCT |
| (Btuh) | (Sq. In.) | (Dia. In.) |
| 40,000 | 10 | 4 |
| 60,000 | 15 | 5 |
| 80,000 | 20 | 5 |
| 100,000 | 25 | 6 |
| 120,000 | 30 | 6 |
| 140,000 | 35 | 7 |
| 160,000 | 40 | 8 |
| EXAMPLE: |
|
|
| 50,000 Btuh Furnace & 10,000 Btuh Water | ||
| Heater = 60,000 Btuh Total Input = 5" Dia. | ||
| Round Duct. |
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20571201 | Issue 0527 | Page 9 of 28 |