Table II
No. of seconds required to consume 1 cu. ft. of gas. |
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INPUT | NATURAL GAS | PROPANE |
BTU/HR. | 1000 BTU/CU. FT. | 2500 BTU/CU. FT. |
58,000 | 62 SEC. | 155 SEC. |
90,000 | 40 SEC. | 100 SEC. |
135,000 | 27 SEC. | 67 SEC. |
160,000 | 22 SEC. | 56 SEC. |
180,000 | 20 SEC. | 50 SEC. |
200,000 | 18 SEC. | 45 SEC. |
225,000 | 16 SEC. | 40 SEC. |
270,000 | 13 SEC. | 33 SEC. |
315,000 | 12 SEC. | 29 SEC. |
360,000 | 10 SEC. | 25 SEC. |
VENTING
To carry off the products of combustion, a vent pipe must be attached to the drafthood of the heater and connected to a chimney vent of adequate height and area. Venting connections should be made in accordance with all codes and ordinances which apply.
Ensure that the vent pipe is securely fastened to the draft hood and that the draft hood is properly attached to the heater. For a single heater installation the vent pipe must be sized no small- er than the flue size of the heater. Horizontal runs of vent pipe should be installed with a rise of at least 1/4” per foot of length. The vertical connector rise of vent pipe above the draft hood, before any fittings, should be as great as possible.
When more then one heater is installed and the vents are combined, the area of the horizontal manifold and common vent should be at least equal to the area of the largest single vent, plus 50% of the area of all other vents joining it (see Vent Size Chart below) (For example, to combine two 6” vents with a 5” vent, the area of the combined vent would be equal to 28 + 28/2+20/2 equals 52 square inches - use a minimum 9 inch common vent and manifold). Units with larger inputs must be vented below others. When using a common vent connector, it shall be at the highest practical level.
VENT TOP
OR CAP
COMMON
CHIMNEY VENT
MANIFOLD
VENT CONNECTOR
TEE
CONNECTORCAPPED RISE
The chimney vent must be extended at least two feet higher than any obstruction located within 10 feet.
Where a back draft exists, the cause must be determined and corrected. A flue cap on the chimney vent may correct the sit- uation. However, if the back draft cannot be corrected, if long horizontal vent pipe runs are necessary, or if a suitable flue cannot be obtained, a mechanical exhaust may be required to ensure proper venting and combustion.
DIA. | AREA | DIA. | AREA |
| Some local codes prohibit connecting a gas heater to a flue or | |
IN. | SQ. IN. | IN. | SQ. IN. |
| chimney with coal or oil fired equipment. Therefore, these | |
| connections should be avoided. However, where a separate | |||||
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5 | 20 | 10 | 79 |
| chimney is not available, the flue pipe from the water heater | |
| should enter the common flue or chimney at a point ABOVE | |||||
6 | 28 | 12 | 113 |
| the flue pipe from the coal or oil fired equipment. | |
7 | 38 | 14 | 154 |
| Improper venting may result in poor combustion, sooting and | |
8 | 50 | 16 | 201 |
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| serious damage to the heater. | |||||
9 | 64 |
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| Page 5 |
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