Page 17
Set points vary depending on unit size. See table 13. The
pressure sensed by the switch is negative relative to atmo-
spheric pressure. If the flue becomes obstructed during op-
eration, the switch senses a loss of negative pressure
(pressure becomes more equal with atmospheric pres-
sure) and opens the circuit to the furnace control and gas
valve. A bleed port on the switch allows relatively dry air in
the vestibule to purge switch tubing, to prevent condensate
build up.
The switch is factory set and is not field adjustable. It is a
safety shut-down control in the furnace and must not be by−
passed for any reason. If switch is closed or by−passed, the
control will not initiate ignition at start up.
TABLE 13
G50UHi Unit
Set
Point
High Altitude
Set Point
4501’ − 7500’
High Altitude
Set Point
7500’ − 10,000’
−070
0.47"
0.36"
0.36"
−090
0.51"
0.47"
0.43"
−110
0.58"
0.47"
0.43"
−135
0.51"
0.47"
0.43"
II−PLACEMENT AND INSTALLATION
Make sure unit is installed in accordance with installation
instructions and applicable codes.
III−START-UP
A−Preliminary and Seasonal Checks
1 − Inspect electrical wiring, both field and factory installed
for loose connections. Tighten as required.
2 − Check voltage at disconnect switch. Voltage must be
within range listed on the nameplate. If not, consult the
power company and have voltage condition corrected
before starting unit.
B−Heating Start-Up
WARNING
Shock and burn hazard. G50UHi units are equipped
with a hot surface ignition system. Do not attempt to
light manually.
1 −
STOP
! Read the safety information at the beginning of
this section.
2 − Set thermostat to lowest setting.
3 − Turn off all electrical power to appliance.
4 − This appliance is equipped with an ignition device
which automatically lights the burners. Do
not
try to
light the burners by hand.
5 − Remove top access panel.
6 −
White Rodgers Gas Valve −−
Switch lever to
OFF
.
See figure 16.
Honeywell Gas Valve −−
Turn knob on
gas valve clockwise
to
OFF
. Do not force. See
figure 18.
7 − Wait five (5) minutes to clear out any gas. If you then
smell gas,
STOP
! Immediately call your gas supplier from
a neighbor’s phone. Follow the gas supplier’s instruc-
tions. If you do not smell gas go to next step.
8 −
White Rodgers Gas Valve −−
Switch gas valve lever to
ON
.
Honeywell Gas Valve −−
Turn knob on gas valve coun-
terclockwise
to
ON
. Do not force.
9 − Replace access panel.
10− Turn on all electrical power to unit.
11− Set thermostat to desired setting.
12− If the appliance will not operate, follow the instructions
To Turn Off Gas To Unit" and call your service techni-
cian or gas supplier.
Turning Off Gas To Unit
1 − Set thermostat to lowest setting.
2 − Turn off all electrical power to unit if service is to be per-
formed.
3 − Remove access panel.
4 − Switch lever on White Rodgers gas valve to
OFF
; turn
knob on Honeywell valve clockwise
to
OFF
. Do not
force.
5 − Replace access panel.
C−Safety or Emergency Shutdown
Turn off unit power. Close manual and main gas valves.
D−Extended Period Shutdown
Turn off thermostat or set to UNOCCUPIED" mode. Close
all gas valves (both internal and external to unit) to guaran-
tee no gas leak into combustion chamber. Turn off power to
unit. All access panels and covers must be in place and se-
cured.
IV−HEATING SYSTEM SERVICE CHECKS
A−C.S.A. Certification
All units are C.S.A. (formally A.G.A. and C.G.A. combined)
design certified without modifications. Refer to the G50UHi
Installation Instruction.
B−Gas Piping
CAUTION
If a flexible gas connector is required or allowed by
the authority that has jurisdiction, black iron pipe
shall be installed at the gas valve and extend outside
the furnace cabinet.
WARNING
Do not exceed 600 in−lbs (50 ft−lbs) torque when
attaching the gas piping to the gas valve.
Gas supply piping should not allow more than 0.5"W.C. drop
in pressure between gas meter and unit. Supply gas pipe
must not be smaller than unit gas connection
Compounds used on gas piping threaded joints should be
resistant to action of liquefied petroleum gases.
Summary of Contents for G50UHi Series
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