Air Ducts; General Requirements - Carrier 58MCA Installation, Start-Up, And Operating Instructions Manual

FRONT FILLER
PANEL
Fig. 20—Removing Bottom Closure Panel
Gas valve shutoff switch MUST be facing forward or tilted
upward. Failure to follow this warning could result in
property damage or death.
Never purge a gas line into a combustion chamber. Never use
matches, candles, flame, or other sources of ignition for
purpose of checking leakage. Use a soap-and-water solution
to check for leakage. Failure to follow this warning could
result in fire, explosion, personal injury, or death.
Use proper length of pipe to avoid stress on gas control
manifold. Failure to follow this warning could result in a gas
leak resulting in fire, explosion, personal injury, or death.
Table 3—Maximum Capacity of Pipe*
NOMINAL
IRON INTERNAL
PIPE DIAMETER
SIZE (IN.)
(IN.)
1/2 0.622 175
3/4 0.824 360
1 1.049 680
1-1/4 1.380 1400
1-1/2 1.610 2100
* Cubic ft of gas per hr for gas pressures of 0.5 psig (14-in. wc) or less, and
a pressure drop of 0.5-in. wc (based on a 0.60 specific gravity gas).
Ref: Table 10-2 NFPA 54-1999.
Install a sediment trap in riser leading to furnace. Trap can be
installed by connecting a tee to riser leading to furnace so
straight-through section of tee is vertical. Then connect a capped
nipple into lower end of tee. Capped nipple should extend below
level of gas controls. Place a ground joint union between gas
control manifold and manual gas shutoff valve. (See Fig. 21.)
BOTTOM
CLOSURE
PANEL
A93047
LENGTH OF PIPE (FT)
10 20 30 40 50
120 97 82 73
250 200 170 151
465 375 320 285
950 770 660 580
1460 1180 990 900
GAS
SUPPLY
MANUAL
SHUTOFF
VALVE
(REQUIRED)
SEDIMENT
TRAP
UNION
Fig. 21—Typical Gas Pipe Arrangement
If a flexible connector is required or allowed by authority
having jurisdiction, black iron pipe shall be installed at gas
valve and extend a minimum of 2 in. outside furnace casing.
An accessible manual shutoff valve MUST be installed upstream
of furnace gas controls and within 6 ft of furnace. A 1/8-in. NPT
plugged tapping, accessible for test gage connection, MUST be
installed immediately upstream of gas supply connection to
furnace and downstream of manual shutoff valve.
NOTE: The gas valve inlet press tap connection is suitable to use
as test gage connection providing test pressure DOES NOT exceed
maximum 0.5 psig (14-in. wc) stated on gas valve. (See Fig. 44.)
Piping should be pressure tested in accordance with local and
national plumbing and gas codes before furnace is attached. In
Canada, refer to current edition of NSCNGPIC. If pressure
exceeds 0.5 psig (14-in. wc), gas supply pipe must be disconnected
from furnace and capped before pressure test. If test pressure is
equal to or less than 0.5 psig (14-in. wc), turn off electric shutoff
switch located on gas valve before test. It is recommended that
ground joint union be loosened before pressure testing. After all
connections have been made, purge lines and check for leakage.
Step 1—General Requirements
The duct system should be designed and sized according to
accepted national standards such as those published by: Air
Conditioning Contractors Association (ACCA), Sheet Metal and
Air Conditioning Contractors National Association (SMACNA) or
American Society of Heating, Refrigerating and Air Conditioning
Engineers (ASHRAE). Or consult factory The Air Systems Design
Guidelines reference tables available from your local distributor.
The duct system should be sized to handle the required system
design CFM at the design static pressure.
When a furnace is installed so that the supply ducts carry air to
areas outside the space containing the furnace, the return air must
also be handled by a duct(s) sealed to the furnace casing and
terminating outside the space containing the furnace.
Secure ductwork with proper fasteners for type of ductwork used.
Seal supply- and return-duct connections to furnace with code
approved tape or duct sealer.
Flexible connections should be used between ductwork and
furnace to prevent transmission of vibration. Ductwork passing
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AIR DUCTS

A93324