Specifications

035-17377-000 REV A (0201)
Unitary Products Group 27
NOTE: Maximum capacity of pipe in cubic feet of gas per
hour based upon a pressure drop of 0.3 inch W.C. and 0.6
specific gravity gas.
NOTE:
There may be a local gas utility requirement specify-
ing a minimum diameter for gas piping. All units require a 3/4
inch pipe connection at the entrance fitting. Line should not
be sized smaller than the entrance fitting size.
GAS CONNECTION
The gas supply line can be routed within the space and roof
curb, exiting through the unit’s basepan. Refer to Figure 9 for
the gas piping inlet location. Typical supply piping arrange-
ments are shown in Figures 17 and 18. All pipe nipples, fit-
tings, and the gas cock are field supplied or may be
purchased in UPG accessory kit #1GP0404.
Gas piping recommendations:
1. A drip leg and a ground joint union must be installed in
the gas piping.
2. Where required by local codes, a manual shut-off valve
must be installed outside of the unit.
3. Use wrought iron or steel pipe for all gas lines. Pipe
dope should be applied sparingly to male threads only.
4. All piping should be cleaned of dirt and scale by ham-
mering on the outside of the pipe and blowing out loose
particles. Before initial start-up, be sure that all gas lines
external to the unit have been purged of air.
5. The gas supply should be a separate line and installed in
accordance with all safety codes as prescribed under
“Limitations”.
6. A 1/8-inch NPT plugged tapping, accessible for test gage
connection, must be installed immediately upstream of
the gas supply connection to the unit.
7. After the gas connections have been completed, open
the main shut-off valve admitting normal gas pressure to
the mains. Check all joints for leaks with soap solution
or other material suitable for the purpose. NEVER USE
A FLAME.
VENT AND COMBUSTION AIR
Venting slots in the heating compartment access panel
remove the need for a combustion air hood. The gas heat
flue exhaust is routed through factory installed exhaust piping
with screen. If necessary, a flue exhaust extension may be
installed at the point of installation.
ACCESSORIES
ELECTRIC HEAT
Electric heaters are available for field installation. Refer to
electric heat instructions for installation. These heaters
mount in the heat compartment with the heating elements
extending into the supply air chamber. All electric heaters are
fused and intended for use with single point power supply.
TABLE 24: GAS PIPE SIZING - CAPACITY OF PIPE
Length of
Pipe (ft.)
Nominal Iron Pipe Size
3/4 in. 1 in. 1-1/4 in.
10
278 520 1050
20
190 350 730
30
152 285 590
40
130 245 500
50
115 215 440
60
105 195 400
70
96 180 370
80
90 170 350
90
84 160 320
100
79 150 305
Natural gas may contain some propane. Propane
is an excellent solvent and will quickly dissolve
white lead and most standard commercial com-
pounds. A special pipe dope must be used when
assembling wrought iron or steel pipe. Shellac
based compounds such as Gaskolac or Stalastic,
and compounds such as Rectorseal #5, Clydes’s
or John Crane may be used.
The furnace and its individual shut-off valve must
be disconnected from the gas supply piping sys-
tem during any pressure testing at pressures in
excess of 1/2 PSIG.
Pressures greater than 1/2 PSIG will cause gas
valve damage resulting in a hazardous condition.
If it is subjected to a pressure greater than 1/2
PSIG, the gas valve must be replace.
The furnace must be isolated from the gas supply
piping system by closing its individual manual
shut-off valve during any pressure testing of the
gas supply piping system at test pressures equal
to or less than 1/2 PSIG.