Category Ii/Iv Flue Gas Exhaust Vent Planning - Patterson-Kelley P-K MACH CM300 Installation & Owner's Manual

2.5.3 Category II/IV Flue Gas Exhaust Vent Planning

Several codes and standards have categorized appliances in accordance with the flue gas temperature
and pressure produced by the appliance. The applicable categories are defined as follows:
•
Category II: An appliance that operates with a non-positive vent static pressure and with a vent
temperature that may cause excessive condensate production in the vent.
•
Category IV: An appliance that operates with a positive vent static pressure and with a vent
temperature that may cause excessive condensate production in the vent.
•
Direct Vent: An appliance that is constructed and installed so that all air for combustion is
derived directly from outdoors and all flue gases are discharged to the outdoors.
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All P-K MACH boilers are dual-certified as Category II or IV appliances, as defined in ANSI
Z21.13/CSA 4.9, latest edition. The P-K MACH
negative to slightly positive exhaust pressure. It is critical to ensure the flue vent material is certified for
Category II or IV operation.
N : For Category II installations, ensure the flue venting system is designed to maintain a
OTE
slightly negative exhaust pressure between -0.01" W.C. and -0.05" W.C.
N : For Category IV installations, ensure the flue venting system is designed to maintain a
OTE
slightly positive exhaust pressure which MUST BE in the following ranges:
•
+0.01" W.C. and +0.22" W.C. (Direct Vent / Sealed Combustion)
•
+0.01" W.C. and +0.4" W.C. (Exhaust Only)
The vent material to be used for US and Canada is listed in the Table of Acceptable Materials for
Venting Systems located in Section 2.5.4.
Vent installations shall be in accordance with NFPA 54/ANSI Z223.1, the National Fuel Gas Code, or
CAN/ CSA-B149.1, the Natural Gas and Propane Installation Code, or applicable provisions of the local
building codes.
Vent Sizing for Category II / IV Operation
The vent must be sized in accordance with the
30) or according to the vent manufacturer's recommendations. When using manufactured venting
systems, consult your vent supplier for correct sizing and structural support requirements.
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P-K MACH Boiler Model
CM300, CM399, CM500,
C750, C900, C1050
CM300, CM399, CM500,
C750, C900, C1050
CM300, CM399, CM500,
C750, C900, C1050
Revised: January 3, 2020
Released: January 3, 2020
®
series boilers are capable of operating with slightly
ASHRAE
Draft Stack Temperature
Category II
-0.01" to -0.05" W.C.
Category IV
(Sealed Combustion)
+0.01" to +0.22" W.C.
Category IV
(Exhaust Only)
+0.01" to +0.4" W.C.
 Patterson-Kelley 2020
All Rights Reserved.
P-K MACH
Technical Service 1.877.728.5351
Systems and Equipment handbook (Chapter
Natural Gas
210 °F (gross)
210 °F (gross)
210 °F (gross)
1004905980 P-K MACH CM300-CM500&C750-C1050
Installation and Owners Manual (Rev F Jan-2020).docx
®
Gas Fired Boiler
CO CO
2 2
Propane Gas
9.0% 10.4%
9.0% 10.4%
9.0% 10.4%
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