8
IM 685-1
Start-up & Operating Procedures
Start-up Responsibility
The start-up organization is responsible for determining that
the furnace, as installed and as applied, will operate within
the limits specified on the furnace rating plate.
1. The furnace must not exceed the specified "Maximum
MBH Input." See "Verify Input Rate."
2. The furnace must not operate at an airflow below the
specified "Minimum Airflow CFM." On variable air vol-
ume systems it must be determined that the furnace will
not be operated if or when system cfm is reduced below
the specified minimum airflow cfm.
3. It must be established that the gas supply is within the
proper pressure range. See "Gas Pressure Requirements."
Start-up Procedure
Only qualified personnel should perform the start-up and
service of this equipment. It is highly recommended that the
initial start-up and future service be performed by McQuay
certified technicians who are familiar with the hazards of
working on live equipment. A representative of the owner or
the operator of the equipment should be present during start-
up to receive instructions in the operation, care and adjust-
ment of the unit.
Before Start-up
1. Notify any inspectors or representatives that may be
required to be present during start-up of gas fuel equip-
ment. These could include the gas utility company, city
gas inspectors, heating inspectors, etc.
2. Review the equipment and service literature and become
familiar with the location and purpose of the burner con-
trols. Determine where the gas and power can be turned
off at the unit, and upstream of the unit.
3. Verify that power is connected to the unit and available.
4. Verify that the gas piping, meter, and service regulator
has been installed, tested, and is ready to go.
5. Verify that proper instruments will be available for the
start-up. A proper start-up requires the following: voltme-
ter, manometer or gauges with ranges for both manifold
pressure and inlet gas pressure, keyboard display module
or a 20K ohm/volt meter for flame safeguard signal
strength measurement, CO
2
indicator, carbon monoxide
indicator, and a stopwatch for timing the gas meter.
About This Burner
Prepurge is Low-High-Low
The burner air control valve will be at the minimum position
during off cycles. Upon a call for heat or any other time that
a prepurge cycle occurs, the air control valve will be reposi-
tioned to the maximum position for the prepurge and then
returned to the minimum position for low fire start.
Low Fire Start
The burner is controlled for proven low fire start. The actua-
tor will position the modulating gas valve and the modulat-
ing air valve to the low fire position each time the burner is
to light off. Switch LS1 proves the air and gas valves are at
the low fire position. If LSl is not "made" at light off, the gas
valves cannot open and the flame safeguard will lock out,
requiring manual reset.
"Pilot" is Main Flame Modulated Down to Pilot Rate
The "pilot" is not a separate flame or burner. The "pilot" is
the main flame operating at its minimum rate. That mini-
mum rate is so low that it qualifies as a pilot burner.
Set Control System to Enable Heating
To allow start-up and check-out of the burner, the control
system must be set to call for heating and must he used to
control the amount of heating. Set the control system to call
for heat so MCB-B011 energizes Relay R20. With MCB-
B011 closed, vary the temperature control set point to
increase, maintain, or reduce the firing rate of the burner as
required for these tests. If MCB-B09 is closed the firing rate
will decrease. If MCB-B010 is closed the firing rate will
increase. If neither are "made" the firing rate will remain
unchanged.
Start-up Preliminary
1. Before energizing the burner verify that the modulating
air and gas valve mechanism moves freely and is not
binding, and check the linkage fasteners for tightness.
This can be accomplished without affecting any adjust-
ments. Remove shoulder screw (12), Figure 16a, that
connects the teflon bushing to the actuator crank arm.
The control rod can now be manually moved back and
forth, it should feel smooth with no binding or scraping.
Always remove shoulder screw (12) and test for binding
after reinstalling the gun assembly on Models HT050-
200.
2. Close the gas line cocks. Install a Keyboard Display
Module, Honeywell Part No. S7800A1001, or connect a
20K ohm/volt meter to the test jack on the flame safe-
guard (see Figure 7).
3. Check the burner fan wheel for binding, rubbing, or loose
set screws.
4. Check power. Position switch S3 on burner control panel
to AUTO. The LED marked POWER on the flame safe-
guard should come on and after a 10 second "Initiate"
period the burner motor should start. Check for (CW)
rotation as viewed through the burner fan housing inlet. If
the motor does not start, press the reset button on the
flame safeguard. If the motor still does not start, consult
the appropriate section of the "Troubleshooting Guide".
Continue on to Item 5 when burner motor will run 10 sec-
onds after the switch is positioned to AUTO.
WARNING
Should overheating occur or the gas supply fail to shut
off, turn off the manual gas valve to the appliance before
shutting off the electrical supply.
Summary of Contents for SuperMod IM-685-1
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