Venting Requirements and Outside Air Combustion
Outside Combustion Air
This design (U.S. Patent No. 5,421,774) allows dual venting of two Model VR heaters. The concentric design of the vent allows each of the two heaters to be safely operated totally independent of the other. Heaters vented through the op- tional dual vent do not have to match in capacity, length, or configuration and may be controlled by the same or differ- ent thermostats.
Model VR heaters may be operated with combustion air from the heated space or with combustion air piped from outside. If out- side combustion air is selected, a Reznor outside combustion air kit must be installed, Outside combustion air may be supplied in any vented application but should always be supplied (1) if the building atmosphere has negative pressure; (2) if the building atmosphere is dirty or dusty; (3) if the building atmosphere con- tains substances that will cause toxic gas when combined with flame or flue products; (4) if the heater is installed in a tightly closed room that does not provide required air for combustion. The outside combustion air kit for Model VR heaters includes a section of 4” (5” on sizes 175 & 200) flexible pipe expandable to three feet, a special designed inlet air cap, an air inlet cover with collar, relay with wiring, and two clamps. The maximum length of the field-supplied combustion air pipe depends on the size and length of heater and the type of pipe.
Combustion Air Inlet Length Table
NOTE: Do not install an outside combustion air inlet on an unvented heater.
MAXIMUM LENGTH OF OUTSIDE COMBUSTION AIR INLET PIPE
TYPE OF INLET PIPE
Corrugated or Flexible
125 150 175 200 50 75 100
125 150 175 200
SIZE MBH 50 75 100
80 24.4 10 3.0 5 1.5
Feet Meters Feet Meters Feet Meters
EQUIVALENT LENGTH FOR
A Assumes the use of three feet of flexible pipe at the combustion air inlet on the burner/control box