Gas Pressure Adjustment; High Altitude Information; Other Unit Adjustments; Electronic Ignition - Lennox G21Q Series Installation Instructions Manual

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Gas Flow
To check proper gas flow to the combustion chamber,
determine Btu (kW) input from the appliance rating
plate. Divide this input rating by the Btu per cubic foot
(cubic meter) of available gas. Result is the number of
cubic feet (cubic meter) per hour required. Determine
the flow of gas through gas meter for 2 minutes and
multiply by 30 to get the hourly flow of gas to burner.
Gas Pressure
1 - - Check gas line pressure with unit firing at maxi-
mum rate. Normal natural gas inlet line pressure
should be 7.0 in. w.c. (1.74 kPa). Normal line pres-
sure for propane/LP gas is 11.0 in. w.c. (2.75 kPa).
NOTE - - Minimum gas supply pressure is listed on
unit rating plate for normal input. Operation below
minimum pressure may cause nuisance lockouts.
2 - - After the line pressure has been checked and ad-
justed, check the regulator pressure. The correct
manifold pressure (unit running) is specified on
the unit nameplate. To measure, connect gauge to
the pressure tap in the elbow below the expansion
tank.
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The G21Q unit is approved for altitudes of 0 to 4,500 ft. (0
to 1,372 m) above sea level in both the U.S.A. and Cana-
da. No adjustment is necessary. Due to the self- -adjust-
ing characteristics of Pulse combustion, a high altitude
kit should NOT be necessary at any altitude.
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Heat Anticipation Settings
Units with White Rodgers gas valves - -- - 0.6
Units with Robertshaw gas valves - -- - 0.6
Propane/LP Gas Conversion
NOTE - - G21Q series units are NOT shipped with the
components required for field conversion to propane/
LP gas. A separate kit must be ordered. Follow the
directions supplied with the conversion kit.
Limit Control
Limit Control - -- - Factory set. No adjustment necessary.
Fan Control
Fan- -On Delay - -- - Factory set at 45 seconds and adjust-
able from 30 to 60 seconds.
Fan- -Off Delay - -- - Factory set at 180 seconds and adjust-
able from 120 to 240 seconds.
Temperature Rise and External Static Pressure
Check the temperature rise and the external static pres-
sure. If necessary, adjust the blower speed to maintain
a temperature rise and external static pressure within
the range shown on the unit rating plate.
Electrical
1 - - Check all wiring for loose connections.
2 - - Check the fuse located on the unit control box. The
fuse should be a 2 amp AGC fast blow.
3 - - Check for correct voltage at the unit (unit operating).
4 - - Check amp- -draw on blower motor.
Motor Nameplate __________Actual__________.
NOTE - - Do not secure electrical conduit directly to
ducting or structure.
Blower Speeds
Refer to the blower speed selection chart on the unit
wiring diagram.
NOTE - - CFM readings are taken external to unit with a
dry evaporator coil and without accessories.
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The ignition control has an internal watchguard control.
The watchguard automatically resets the ignition control
if it has been locked out because the burner has failed to
light. This type of nuisance lockout is usually attributed
to low gas line pressure. After one hour of continuous
thermostat demand for heat, the watchguard will break
and remake thermostat demand to the furnace and auto-
matically reset the electronic ignition control to relight
the furnace.
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