SECTION C: Installation
Venting
CAUTION: Proper installation of flue venting is criti- cal for the safe and efficient operation of the heater.
General
CAUTION: Condensate drains for the vent piping are required for installations of the MVB. Follow vent manufacturer instructions for installation and location of condensate drains in the vent. Condensate drain must be primed with water to prevent gas flue leak and must be routed to an appropriate container for neutrali- zation before disposal, as required by local codes.
Appliance Categories
Heaters are divided into four categories based on the pressure produced in the exhaust and the likelihood of condensate production in the vent.
Category I – A heater which operates with a non- positive vent static pressure and with a vent gas tem- perature that avoids excessive condensate production in the vent.
Category II – A heater which operates with a non- positive vent static pressure and with a vent gas tem- perature that may cause excessive condensate production in the vent.
Category III – A heater which operates with a positive vent pressure and with a vent gas temperature that avoids excessive condensate production in the vent.
Category IV – A heater which operates with a positive vent pressure and with a vent gas temperature that may cause excessive condensate production in the vent.
See Table J for appliance category requirements.
Note: For additional information on appliance catego- rization, see appropriate ANSI Z21 Standard and the NFGC (U.S.), or B149.1 (Canada), or applicable provi- sions of local building codes.
WARNING: Contact the manufacturer of the vent material if there is any question about the appliance categorization and suitability of a vent material for application on a Category IV vent system. Using im- proper venting materials can result in personal injury, death or property damage.
Use only the special gas vent pipes listed for use with Category IV gas burning heaters, such as the
Support of Vent Stack
The weight of the vent stack or chimney must not rest on the heater vent connection. Support must be pro- vided in compliance with applicable codes. The vent should also be installed to maintain proper clearances from combustible materials.
Use insulated vent pipe spacers where the vent passes through combustible roofs and walls.
Combustion | Exhaust | Heater Venting | Certified |
| Combustion Air |
Air Supply | Configuration | Category | Materials |
| Inlet Material |
|
|
|
|
|
|
| Vertical |
|
|
|
|
From Inside Building | Venting |
|
|
|
|
|
|
|
|
| |
Horizontal Through- |
| Stainless Steel |
|
| |
| IV |
|
| ||
|
|
| |||
| Vertical |
|
| Galvanized Steel | |
|
|
|
| ||
From Outside Building | Venting |
|
|
| PVC |
(Direct Venting) | Horizontal Through- |
|
|
| ABS |
|
|
|
| CPVC | |
|
|
|
|
|
|
Table J: Venting Category Requirements
21
