Lennox International Inc G50UH-48B-090, G50UH-48C-110, G50UH-60D-135 Primary and Secondary Limits

ralgasatallaltitudesis3.5"w.c.Manifoldpressurefor allunitsfueledbyL.R/propanegasat allaltitudesis 10.0"w,c.Seefigures27,28and29forthelocationof themanifoldpressureadjustmentscrews,

NOTE - In Canada, certification for installations at eleva-

tions over 4500 feet (1372 m) is the jurisdiction of local au- thorities.

Manifold pressure for all units fueled by natural gas at all altitudes is 3.5" w,c, Manifold pressure for all units fueled by L,R/propane gas at all altitudes is 10,0" w,c,

NOTE - A natural to L.R propane gas changeover kit is nec- essary to convert this un#. L.R conversion kit 25W20 is used with all units installed at altitudes up to 7,500 feet. L.P. conversion kit 25W21 is used with all units installed at alti- tudes from 7,501 to 10,000 feet above sea level. Refer to the changeover kit installation instruction for the conver- sion procedure.

NOTE - Units fueled by natural gas and installed at alti- tudes of 7501-10,000 feet above sea level require instal- lation of a high altitude orifice kit (59M17).

The combustion air pressure switches are factory-set and require no adjustment, The existing unit pressure switch must be replaced by pressure switch 56L32 for G50UH(X) units installed at altitudes from 7,501 to 10,000 feet above sea level,

Primary and Secondary Limits

The primary limit is located on the heating compartment vestibule panel. The secondary limits (if equipped) are lo- cated in the blower compartment, attached to the back side of the blower. These limits are factory set and require no adjustment.

Flame Rollout Switches (Two)

These manually reset switches are located on (or inside of) the burner box, If tripped, check for adequate combustion air before resetting,

Pressure Switch

The pressure switch is located in the heating compartment adjacent to the combustion air inducer. This switch checks for proper combustion air inducer operation before allow- ing ignition trial, The switch is factory-set and requires no adjustment.

Temperature Rise

Place the unit into operation with a heating demand, After supply and return air temperatures have stabilized, check the temperature rise, If necessary, adjust the blower speed to maintain the temperature rise within the range shown on

the unit nameplate, Increase the blower speed to decrease the temperature, Decrease the blower speed to increase the temperature rise, Failure to do adjust the temperature rise may cause erratic limit operation,

Fan Control

Heating Mode -- The fan on delay of 45 seconds is not ad- justable. The fan offdelay (amount of time that the blower operates after the heat demand has been satisfied) may be adjusted by setting $1 switches 1and 2 located on the SureLight ® control. The unit is shipped with a factory fan off setting of 90 seconds, The fan off delay affects com- fort and is adjustable to satisfy individual applications.

Adjust the fan off delay to achieve a supply air tempera- ture between 90 °and 110°F at the exact moment that the

blower is de-energized. Longer offdelay settings provide lower return air temperatures; shorter settings provide higher return air temperatures. See figure 25.

Cooling Mode --The cooling mode fan off delay (amount of time that the blower operates after the cooling demand has been satisfied) may be adjusted by setting $1 switch 3 located on the SureLight ® control, In the off position, the cooling fan off delay is 2 seconds. In the on position, the cooling fan off delay is 45 seconds, See figure 25,

Thermostat Heat Anticipation

Set the heat anticipator setting (if adjustable) according to the amp draw listed on the wiring diagram that is attached to the unit.

Electrical

1 - Check all wiring for loose connections,

2 - Check for the correct voltage at the furnace (furnace operating).

3 - Check amp-draw on the blower motor.

Motor NameplateActual

NOTE - Do not secure the electrical conduit directly to the air ducts or structure.

Blower Speeds

NOTE - CFM readings are taken external to unit with a dry evaporator coil and without accessories.

1 - Turn off electrical power to furnace,

2 - Remove blower access panel.

3 - Disconnect existing speed tap at control board speed terminal.

NOTE - Termination of any unused motor leads must be insulated.

4 - Refer to blower speed selection chart on unit wiring dia- gram for desired heating or cooling speed.

5- Connect selected speed tap at control board speed terminal.

6 - Resecure blower access panel.

7 - Turn on electrical power to furnace, Electronic Ignition

The SureLight @integrated control has an added feature of an internal Watchguard control, The feature serves as an automatic reset device for ignition control lockout caused by ignition failure, After one hour of continuous thermostat demand for heat, the Watchguard will break and remake thermostat demand to the furnace and automatically reset the control to begin the ignition sequence,

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