Trane Gas Unit Heaters Wartungshandbuch

19

GBNE-SVX001A-EN

Observe the following precautions when venting the unit:

1.  Use flue pipe of the same size as the flue connections 

on the gas unit heater (See Table #1). All heaters should 
be vented with double wall or single wall vent, a factory 
built chimney, or a lined brick and mortar chimney that 
has been constructed in accordance with the National 
Building Code. Type B vent should only be used for 
vertical rise portions of a Category I vent pipe system. 
Type B vent pipe should not be used for horizontal runs 
of vent pipe.

2.  Provide as long a vertical run of flue pipe at the gas unit 

heater as possible. A minimum of 5' (1.5m) of vertical 
flue is required. The top of the vent pipe should extend at 
least 2' (0.61m) above the highest point on the roof. Install 
a weather cap over the vent opening. Consideration 
should be made for anticipated snow depth.

3.  Slope horizontal runs upward from the gas unit heater at 

least 1/4" per foot (21mm/m) minimum.  Horizontal runs 
should not exceed 75% of the vertical height of the vent 
pipe, or chimney, above the flue pipe connection, up to 
a maximum length of 10' (3m). Horizontal portions of the 
venting system shall be supported at minimum intervals 
of 4' (1.2m). In Canada, support at minimum intervals of 
3' (1m).

4.  Use as few elbows as possible.
5.  Seal all vent pipe joints and seams to prevent 

leakage. Use General Electric RTV-108, Dow 
Corning RTV-732, or equivalent silicone sealant  
with a temperature rating of 500 degrees F, or 3M #425 
aluminum foil tape (or equivalent).

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.

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.

ANSI now organizes vented 
appliances into four categories. 

 

Non 

 

  

 

Condensing Condensing

 Negative
 

Vent 

    I  

II

 Pressure 

 

 Positive
 

Vent 

    III     IV

 Pressure 

 

Category I
Includes non-condensing appliances 
with negative vent pressure, like the 
traditional atmospheric unit heater.

Category II
Groups condensing appliances  
with negative vent pressure.
Category III
Appliances are non-condensing  
and operate with a positive vent 
pressure.

Category IV
Covers condensing appliances with 
positive vent pressure.

All unit heaters must be vented! All Venting installations shall be in accordance with the latest edition of Part 7, Venting of 
Equipment of the National Fuel Gas Code, ANSI Z223.1 (NFPA 54), or applicable provisions of local building codes. Refer to 
page 21 for Canadian installations. Refer to Figures 7, 8, 9A, 9B, 10A and 10B.

Do not damper or add heat recovery devices to the flue piping. Failure to open such a damper prior to operating  
gas unit will result in the spillage of flue gas into the occupied space.