Goodman GMP Installation & Operating Instructions Manual page 33

EXAMPLES USING SINGLE APPLIANCE VENTING TABLE
Single Fan Assisted Appliance
Suppose an installer has an 80,000 Btu / hr. input fan assisted appliance that must be
installed using 10 ft. of lateral connector attached to a 30 ft. high Type B vent. Two 90° elbows
are needed for the installation. Can a single wall metal vent connector be used for this
installation?
Solution -Table 2 refers to the use of single wall metal vent connectors with Type B vent. In the
first column find the row associated with a 30ft. height and a 10 ft. lateral. Read across this
row, looking at the "Fan Min" and "Fan Max" columns, to find that a 3" diameter single wall
metal connector is not recommended. Moving to the next larger size single wall connector (4")
we find that a 4" diameter single wall connector has a recommended maximum vent capacity
of 91,000 Btu / hr. and a recommended maximum vent capacity of 144,000 Btu / hr. The
80,000 Btu / hr. fan assisted appliance is outside this range, so we conclude that a single wall
connector cannot be used to vent this appliance using 10ft. of lateral for the connector.
However, we see that if the 80,000 Btu / hr. input appliance could be moved within 5ft. of the
vertical vent, then a 4" single wall metal connector could be used for this appliance. Table 2
shows the acceptable range of vent capacities for a 4" vent with 5ft. of lateral to be between
72,000 Btu / hr. and 157,000 Btu / hr.
If the appliance cannot be moved closer to the vertical vent, then Type B vent could be used
as the connector material. In this case, Table 1 shows that for a 30ft. high vent with 10ft. of lat-
eral, the acceptable range of vent capacities for a 4" diameter vent attached to a fan assisted ap-
pliance are between 37,000 Btu / hr. and 150,000 Btu / hr.
Common Venting a Draft Hood Water Heater with a Fan Assisted Furnace
In this case, a 35,000 Btu / hr draft hood equipped water heater with a 2ft. connector rise is to
be common vented with a 100,000 Btu / hr fan assisted furnace with a 3ft. connector rise. The
common vent consists of a 30ft rise of type B vent. What are the recommended vent diame-
ters for each connector and the common vent? Solution-TABLE 4
Water Heater vent connector diameter - Let us assume the installer would like to use a sin-
gle wall metal vent connector. Using table 4, Vent Connector Capacity, read down the total
vent height "H" column to 30ft. and read across the 2ft. connector rise "R" row to the first Btu /
hr rating in the "Nat Max" column that is equal to or greater than the water heater input rating.
The table shows that a 3" connector has a maximum input rating of 37,000 Btu / hr. Since this is
greater than the water heater input rating, a 3" vent connector is adequate. Furthermore,
since the water heater is equipped with a draft hood, there are no minimum input rating re-
strictions.
Furnace vent connector diameter - Again, let us assume the installer would like to use a sin-
gle wall vent connector. Using table 4, Vent connector capacity, read down the total vent
height "H" column to 30ft. and across the 3ft. connector rise "R" row. Since the furnace has a
fan assisted combustion system, find the first Fan Max column with a Btu / hr
rating greater than the furnace input rating. The 4" vent connector has a maximum input rating
of 119,000 Btu / hr and a minimum input rating of 85,000 Btu / hr. The 100,000
Btu / hr furnace in this example falls within this range, so a 4" connector is adequate. If the
furnace would have had an input rating of 80,000 Btu / hr, than a type B vent connector (see
Table 3) would have to be used to meet the minimum capacity limit.
IO-137H 33