IO-213D 2/04
15
5. Turn on gas supply to valve.
6. Using a leak detection solution or soap suds, check for
leaks at hose connection. Bubbles forming indicate a
leak. SHUT OFF GAS AND FIX ALL LEAKS
IMMEDIATELY BEFORE PROCEEDING TO NEXT
STEP.
7. Read manometer. This reading is the system inlet
pressure.
8. Shut off gas supply upstream of valve.
9. Remove manometer hose from inlet pressure boss.
10. Tighten inlet pressure tap screw to seal pressure port
(clockwise, 13 in-lb minimum).
11. Using a leak detection solution or soap suds, check for
leaks at pressure boss screw. Bubbles forming indicate
a leak. SHUT OFF GAS AND FIX ALL LEAKS
IMMEDIATELY.
12. Turn valve switch to “ON” position.
Outlet Pressure Boss
Inlet Pressure Boss
Valve Switch
SAFETY CONTROL FUNCTIONS AND CHECK-OUT
PROCEDURE
General
In most cases, the safety controls are wired in series with
the “W” leg. It is imperative that these switches remain in
the circuit. Never jumper, relocate (unless as noted on the
furnace) or bypass any control. The safety controls must
be checked for proper operation at the time of start-up of
the furnace.
WARNING
SHOULD ANY SAFETY CONTROL BE ALTERED, JUMPED
OR BYPASSED, A HAZARDOUS CONDITION SUCH AS FIRE
OR THE POSSIBILITY OF CARBON MONOXIDE ENTERING
THE BUILDING MAY OCCUR.
Main Limit Switch
The main limit switch is a 1/2" disc designed to shut off the
burner gas should the outlet temperature exceed the
maximum design outlet air temperature. This switch is not
adjustable. To check the operation, block the return airflow
through the unit temporarily. The limit switch should function
and shut the burner gas off within a few minutes. Remove
the blockage and allow the switch to cool sufficiently before
reestablishing burner flames.
Vent Pressure Switch
This furnace utilizes a vent pressure switch, which prevents
the furnace from operating should any portion of the vent
system become restricted or a venter failure occur. To check
this switch, place the furnace in operation and remove the
hose from the switch. The gas burners will extinguish.
Replacing the hose will allow the furnace to operate normally.
Flame Roll-Out Switch
This furnace is equipped with multiple flame roll-out switches.
These manually resetable switches are 1/2" disc type and
are non-adjustable. They are designed to shut down the
burner gas in the event that flames are detected outside the
heat exchanger. Should a switch function, contact a
qualified service person to determine the cause of
function before resetting. To reset this switch, press the
button on top of the switch after the furnace has cooled. To
test the operation of the switch with the furnace in operation,
place an open flame on the disc portion of the switch. The
switch should function to shut down the burner gas. Wait
until the furnace has cooled sufficiently before resetting
the switch.
Flame Sensor
The ignition is provided by electronic means. The burner
flames should be extinguished if the flame sensor fails to
detect the presence of burner flame. To test, disconnect
the flame sensor wire before placing the furnace in operation.
The electronic ignition should ignite the burners. However,
the burners should shut off after a few seconds of operation.
Disconnect the electrical supply to the furnace, reinstall
the disconnected sensor wire and reset the power supply
to restore the furnace to its normal operation.
Blower Door Interlock Switch
The purpose of the switch is to disconnect electrical power
to the furnace should the blower door become dislodged,
removed, or not properly reinstalled after servicing.
ALLOWING THE FURNACE TO OPERATE WITHOUT THE
BLOWER DOOR BEING SECURELY IN PLACE CAN
CAUSE COMBUSTION PRODUCTS TO BECOME
CIRCULATED THROUGHOUT THE LIVING AREA WHICH
CAN CAUSE SERIOUS ILLNESS OR CARBON MONOXIDE
POISONING. To test the operation of this switch, place the
furnace in operation and remove the blower access door.
The burner flames will extinguish and the venter and
circulating air blowers should both stop. To restore the unit
to normal operation, shut off the electrical power to the unit,
replace the blower access door and restore the electrical
power.
Stack Over-Temperature Switch
Located on the venter blower housing, this switch is
designed to shut down the burners should the circulating
air blower fail or the secondary coil become blocked. To
test this switch, bypass the main limit switch, disconnect
the circulating air blower, and place the furnace in operation.
After a short period of time this switch should function
shutting down the burners.
IT IS VERY IMPORTANT TO REMOVE THE BYPASS FROM THE
MAIN LIMIT SWITCH AND REPLACE THE WIRES, WHICH WERE
DISCONNECTED FOR THIS TEST PRIOR TO RETURNING
THE FURNACE IN NORMAL OPERATION.
Integrated Fan / Ignition Control
This furnace is equipped with a combination ignition module
and fan control. An electronic device ignites the burners
upon a call for heat. It also controls the venter blower and
the various speed selections of the circulating air blower.
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