5. PRE-EXISTING COMMON VENT CHECK
If the installation of the combination unit involves removing
an existing furnace from a common vent with other
appliances, the existing venting system will probably be too
large for the remaining appliances and they will not vent
properly. The existing venting system MUST be checked by
a qualified technician to ensure it is properly sized and
vents properly.
6. GAS SUPPLY AND PIPING
NOTE: Because there are many types of liquified petroleum
(LP) gases, the term LP as used in this manual refers to
propane gas. Ifyou intend to use any type of LP gas, proper
precautions MUST be used inthe handling, piping, and use
of such gas. NOTE: In Canada, installations MUST be
performed by licensed LP installers.
The UL/CSA Rating Plate located on the side panel on the
unit contains the model number, type of gas and gas input
rating, and other important information.
FIRE AND/OR EXPLOSION HAZARD
Failure to follow this warning could result in property damage,
_ersonal injury, and/or death.
Make certain the unit is equipped to operate on the type of gas
available. Models designated as natural gas are to be used with
natural gas only. Models designated for use with liquefied petro-
leum (LP) gas are shipped with orifices sized for commercially
pure propane gas. They MUST not be used with butane or a mix-
ture of butane and propane unless properly sized orifices are
installed by a licensed LP installer.
GAS PIPING
The gas supply line MUST beofadequate size to handle the
Btu/hr requirements and length of the run for the unit being
installed. Determine the minimum pipe size for natural gas
from the table in FIGURE 4 or FIGURE 5. Base the length
of the run from the gas meter or source to the unit.
Gas Pipe Size
Btu ratings of all other gas appliances MUST beconsidered
for sizing of main gas line. Check gas line to installation for
compliance with local codes or, in the absence of local
codes, with the National Fuel Gas Code ANSI Z223.1 or in
Canada the National Standard CAN/CGA B149-1 or
current editions.
FIGURE 4
Gas Pipe Size, Length and Btu/hr Capacity
for Schedule 40 Iron Pipe/En_llish)
NATURAL GAS
Pipe Length Btu/hr (in thousands)
(Includes
Fittings) 3/4" 1" 11/4" 11/2" 2"
20' 190 350 730 1,100 2,100
40' 130 245 500 760 1,450
60' 105 195 400 610 1,150
LP GAS
Pipe Length Btu/hr (in thousands)
(Includes
Fittings) 1/2" 3/4" 1 " 11/4" 11/2"
20' 189 393 732 1,496 2,299
40' 129 267 504 1,039 1,559
60' 103 217 409 834 1,275
Gas Pipe Size, Length and Btu/hr Capacity
FIGURE 5
for Schedule 40 Iron Pipe (English)
Pipe Length
(Includes
Fittings)
6.1m
3/4" 2"
56 615
12.2m 38 425
18.3m 31 337
Pipe Length
(Includes
Fittings) 1/2" 11/2"
6.1m 55 674
12.2m 38 457
18.3m 30 374
**kW (Kilowatts) is the metric equivalent of Btu/hr.
NATURALGAS
kW**
1" 11/4" 11/2"
103 214 322
72 147 223
57 117 179
LP GAS
kW**
3/4" 1" 11/4"
115 215 438
78 148 305
64 120 244
PIPING AT UNIT
Connections
NOTE: The rules listed apply to natural and LP gas pipe
installations.
1. If installation is for LP gas, have LP gas installer use
TWO-STAGE REGULATION and make all connec-
tions from storage tank to unit.
2. Use black iron or steel pipe and fittings or other pipe ap-
proved by local code.
3. If copper tubing is used, it MUST comply with limitation
set in Fuel Gas Code.
NOTE: If a gas connector is used, it MUST be acceptable to
local authority. Connector MUST NOT be used inside the
furnace or be secured or supported by the furnace or
ductwork.
FIRE AND/OR EXPLOSION HAZARD
Failure to do so could result in property damage, bodily injury
or death.
Gas connector MUST be properly installed and can NOT be
used inside the furnace.
4. Use pipe joint compound on external (male) threads
ONLY. Joint compound MUST be resistant to any
chemical action of LP gases. Do NOT put pipe com-
pound on last 2 threads of pipe.
5. Use ground joint unions and install a drip leg no less
than 3 inches (76 mm) long to trap dirt and moisture be-
fore it can enter gas valve.
6. Use a wrench on gas valve when making connections
to prevent gas valve from turning. Do NOT use a pipe
wrench on the gas valve body.
7. Provide a 1/8 inch (3mm) National Pipe Thread (NPT)
plug for test gauge connection immediately upstream of
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