Sterling RF-75 Vertically Vented Unit Heaters Category, Venting Categories, Within this manual

VENTING

ANSI now organizes vented appliances into four categories.

Venting Categories

	Non
	Condensing	Condensing
Negative
Vent	I	II
Pressure
Positive
Vent	III	IV
Pressure

Category I	Category III
Includes non-condensing	Appliances are non-condensing
appliances with negative vent	and operate with a positive vent
pressure, like the traditional	pressure.
atmospheric unit heater.	Category IV
Category II
	Covers condensing appliances
Groups condensing appliances	with positive vent pressure.
with negative vent pressure.	NOTICE: Category II and IV do
	not apply to equipment specified
	within this manual.

VERTICALLY VENTED UNIT HEATERS

(CATEGORY I)

Observe the following precautions when venting the unit: The unit heater shall be connected to a factory built chimney or vent complying with a recognized standard, or a masonry or concrete chimney lined with a lining material acceptable to the authority having jurisdiction.

Venting into an unlined masonry chimney is prohibited.

1.Use flue pipe of the same size as the flue connections on the gas unit heater, 4 inch (102mm). All heaters must be vented with UL Listed Type B vent, or single wall pipe.

2.Provide as long a vertical run of flue pipe at the gas unit heater as possible. A minimum of 5 feet (1.5m) of vertical flue is required. The top of the vent pipe should extend at least 2 feet (0.61m) above the highest point on the roof. Install a weather cap over the vent opening.

3.Slope horizontal runs upward from the gas unit heater at least 1/4-inch per foot (21mm/m) minimum. Horizontal runs should not exceed 33% of the vertical height of the vent pipe, or chimney, above the flue pipe connection, up to a maximum length of 10 feet (3m). Horizontal portions of the venting system shall be supported at maximum intervals of 4 feet (1.22m). (See Figure 12)

4.Use as few elbows as possible.

5.Tape flue pipe joints with high temp, RTV or foil face tape.

6.Avoid running vent pipe through unheated spaces.

7.When this cannot be avoided, insulate the pipe to prevent condensation of moisture on the walls of the pipe. Insulate vent pipe runs longer than 10 feet (3m). Insulation should be a minimum of 1/2 inch (12.7mm) thick foil faced fiberglass, 1-1/2# density insulation.

8.Do not damper the flue piping. Failure to open such a damper prior to operating the gas unit heater will result in the spillage of flue gas into the occupied space.

9.Avoid installing units in areas under negative pressure due to large exhaust fans or air conditioning. When required, a flue vent fan should be installed in accordance with the instructions included with the fan.

10.Vent connectors serving Category I and Category II heaters shall not be connected into any portion of mechanical draft systems operating under positive pressure.

11.Also refer to Figures 17 and 19 for additional requirements.

Figure 12

12