B. INDIRECT VENTING (UNVENTED HEATERS) — This heater requires ventilation in the building to dilute the products of combustion and provide fresh air for efficient combustion. Where unvented heaters are used, gravity or mechanical means shall be provided to supply and exhaust at least 4 CFM per 1,000 Btu/hr input of installed heaters. Exhaust vents must be located at the highest point above and in the vicinity of the heaters, and the inlet vents must be located below the level of the heaters. An exhaust hood (Part #42924000) must be placed on the flue adapter collar located on the end of the last body section when used unvented and must be mounted only in an downward position as shown.
#10
Screws
| Exhaust Hood |
Flue Adapter | (mount in a downward |
Collar | position) |
Exhaust Hood Attachment (for UNVENTED use)
17.0) AIR FOR COMBUSTION
If indoor combustion air is to be supplied for a tightly enclosed area, one square inch of free area opening shall be provided below the heater for each 1,000 Btu/hr of heater input. Adequate clearances around the air inlet screen must be maintained at all times. In larger open areas of buildings, infiltration normally is adequate to provide air for combustion.
17.1) DIRECT OUTSIDE AIR FOR COMBUSTION
Outside combustion air should be supplied directly to the heater when the building is subject to negative pressure, or when contaminants or high humidity are present in the building air. These contaminants include paints, solvents, corrosive vapors or any other foreign particles that may cause damage to the heater or result in poor combustion.
Outside combustion air can be brought directly to the heater by a 4” diameter duct less than 50 ft. long or equivalent (see table in Section 16). This is attached to the 4” diameter starting collar (supplied with heater). The starting collar is fitted to the rear of the burner box cabinet as shown below. An approved vent cap must be placed directly on the end of the outside combustion air inlet pipe. The combustion air inlet should be not less than 3 ft. (0.9m), either vertically or horizontally, from the flue vent termination. The air intake terminal must be located not less than 1 ft. (30cm) above grade. It is good installation practice to supply combustion air from the same pressure zone as the vent outlet. Avoid bringing combustion air to the heater from an attic space. There is no guarantee that adequate combustion air will be supplied.
If the heater is installed less than 2 ft. from the ceiling, a combustion air inlet kit PN 44129510 must be provided to allow for expansion/contraction of straight tube heaters (PTS series).
In colder climates, where necessary, insulate the outside combustion air duct. In high humidity applications, the burner box should be sealed with silicone sealer.
| Form #43343330 |
May 08 |