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Plastic vent pipe types listed below have been certified by the American Gas Association for use in furnaces classified as Category 4.
These particular types of furnaces use positive pressure vent systems (exhaust gas temperature less than 1400F above the dew point temperature) and are always equipped with an induced draft motor which removes exhaust gases from the appliance and discharges them to exterior.
The dewpoint temperature is the temperature at which the air can now longer hold all of its water vapor, and some of the water vapor must condense into liquid water. (definition by weatherquestions.com)
Proper installation of the vent system is essential for the condensing furnace (that’s another name for category 4 type furnace) to achieve maximum efficiency and to drain condensate efficiently from the system.
Make sure that your installation complies with National, State and Local codes. Some of the furnace installation guides may be available online or obtained directly from the manufacturer.
There are 3 plastic types of pipes certified by the American Gas Association for use in high efficiency, condensing, category 4 furnaces: PVC, CPVC, and ABS
PVC pipe
| ASTM Standard | Type of the Pipe | max Allowable Temp | Marking on pipe surface |
| F891 | Cellular Core | 158o | ASTM F891 |
| D2665 | DWV Pipe | ASTM D2665 | |
| D1785 | SCH 40, 80, 120 | ASTM D1785 | |
| D2241 | SDR Series | ASTM D2241 |
CPVC Pipe
| ASTM Standard | Type of the Pipe | max Allowable Temp | Marking on pipe surface |
| D2846 | CPVC 41 | 212o | ASTM D2846 |
| F441 | SCH 40, 80 | ASTM F441 | |
| F442 | SDR Series | ASTM F442 |
ABS Pipe
| ASTM Standard | Type of the Pipe | max Allowable Temp | Marking on pipe surface |
| D2661 | SCH 40 DWV | 180o | ASTM D2661 |
| F628 | SCH 40 DWV Cellular Core | ASTM F628441 |
About Dariusz Rudnicki
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My Rinnai Tankless water heater usings a pipe inside a pipe for venting and fresh air intake. Why don’t any high efficiency furnaces do that?
Hi Chris,
High efficiency furnaces do that as well (http://www.kvmtools.com/products/Vent-Termination-Kit-%7BDAYTON-6MC43%7D.html), but in most cases it’s only the final section of the 2 pipe system, at wall or roof penetration. Maybe because of the double wall PVC vent pipe cost… It’s significantly cheaper to run two single pipes and I’m not even sure if there are any manufacturers making 10′ long sections.