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18-CD22D1-8 29
Installer’s Guide
TWIN
TWIN
R1
R1
TWINNING CONNECTION DIAGRAM
FOR TWINNING 1 STAGE FURNACES WITH
SINGLE WIRE TWINNING FEATURE
1 STAGE HEAT / 1 STAGE COOL THERMOSTAT
1 STAGE
HEATING / COOLING
THERMOSTAT FURNACE NO. 1
FURNACE NO. 2
BLOWER OPERATION OF
UNIT NO. 2 IS SYNCRONIZED
WITH UNIT NO. 1 VIA SIGNALS
FROM TWIN CONNECTION.
SEE NOTE 4
SEE NOTE 5
ISOLATION RELAY
(FIELD SUPPLIED)
SEE NOTE 4
ISOLATION RELAY
SEE NOTE 4
OUTDOOR UNIT
(NO TRANSFORMER)
OUTDOOR UNIT
(WITH TRANSFORMER)
RC
ISOLATION RELAY
(FIELD SUPPLIED)
SEE NOTE 3
B/C
B/C
B/C
From Dwg. 21B341423 Rev. 2
NOTE:
Maximum pressure to the gas valve for natural gas is
13.8" W.C. Minimum pressure is 5.0" W.C. Maximum
pressure to the gas valve for propane is 13.8" W.C.
Minimum pressure is 11.0" W.C.
All gas fittings must be checked for leaks using a
soapy solution before lighting the furnace.
DO NOT
CHECK WITH AN OPEN FLAME!
The upflow/ horizontal furnace is shipped standard for
left side installation of gas piping. A knockout is pro-
vided on the right side for an alternate gas piping ar-
rangement. See Figure 37.
The installation of piping shall be in accordance with
piping codes and the regulations of the local gas com-
pany. Pipe joint compound must be resistant to the
chemical reaction with liquefied petroleum gases.
Refer to piping Table 10, for delivery sizes. Connect gas
supply to the unit, using a ground joint union and a
manual shut-off valve as shown in Figures 37-39.
National codes require a condensation drip leg to be in-
stalled ahead of the controls as shown in Figures 37-39.
The furnace and its individual shut-off valve must be
disconnected from the gas supply piping system during
any pressure testing of that system at test pressures in
excess of 1/2 psig (3.5 kPa).
The furnace must be isolated from the gas supply piping
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 (3.5 kPa).
GAS PIPING