connected. After all connections have been made, purge lines and
check for leakage at furnace prior to operating furnace.
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 furnace gas valve and accessible
manual shutoff valve before test.
The gas supply pressure shall be within the maximum and
minimum inlet supply pressures marked on the rating plate with
the furnace burners ON and OFF.
ELECTRICAL CONNECTIONS
See Fig. 30 for field wiring diagram showing typical field 115-v
and 24-v wiring. Check all factory and field electrical connections
for tightness.
Field-supplied wiring shall conform with the limitations of 63°F
(35°C) rise.
Blower access panel door switch opens 115-v power to
control center. No component operation can occur. Do not
bypass or close switch with panel removed. Failure to follow
this warning could result in personal injury or death.
Furnace control must be grounded for proper operation or
control will lock out. Control is grounded through
green/yellow wire routed to gas valve and burner box screw.
Failure to follow this caution will result in mior unit opera-
tion.
Step 1—115-v Wiring
Before proceeding with electrical connections, make certain that
voltage, frequency, and phase correspond to that specified on unit
Fig. 26—Bottom Filter Arrangement
A00290
WASHABLE
FILTER
FILTER
SUPPORT
FILTER
RETAINER
17
1
⁄2-IN. WIDE
CASINGS ONLY:
INSTALL FIELD-SUPPLIED
FILTER FILLER STRIP
UNDER FILTER.
1″
24
1
/
2
″
3″
21-IN. WIDE
CASINGS ONLY:
SUPPORT RODS (3)
EXTEND 1/4" ON EACH
SIDE OF FILTER AND
REST ON CASING FLANGE
Fig. 27—Removing Bottom Closure Panel
A93047
BOTTOM
CLOSURE
PANEL
FRONT FILLER
PANEL
Fig. 28—Typical Gas Pipe Arrangement
A93324
UNION
SEDIMENT
TRAP
MANUAL
SHUTOFF
VALVE
(REQUIRED)
GAS
SUPPLY
Table 3—Maximum Capacity of Pipe
(Cu Ft Per Hr)*
NOMINAL
IRON
PIPE
SIZE
(IN.)
INTERNAL
DIAMETER
(IN.)
LENGTH OF PIPE (FT)
10 20 30 40 50
1/2 0.622 175 120 97 82 73
3/4 0.824 360 250 200 170 151
1 1.049 680 465 375 320 285
1-1/4 1.380 1400 950 770 660 580
1-1/2 1.610 2100 1460 1180 990 900
* 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 9.2 NFGC.
21
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