Typical Operating Characteristics; High Altitude; Blower Operation And Adjustment; Temperature Rise - Lennox G43UF SERIES Unit Information

I−High Altitude
NOTE − In Canada, certification for installations at eleva-
tions over 4500 feet (1372 m) is the jurisdiction of local au-
thorities.
The manifold pressure may require adjustment to ensure
proper operation at higher altitudes. Refer to table 19 for
proper manifold pressure settings at varying altitudes.
Table 20 lists required pressure switch changes and con-
version kits at varying altitudes.
The combustion air pressure switches are factory−set and
require no adjustment.
Conversion Kit and Pressure Switch Requirements at Varying Altitudes
Model
Input Input
Gas Gas
Si
Size
Nat.
−045 045
−070
LPG
Nat.
−045−7 and later 045 7 and later
LPG
Nat.
−070−7 and later 070 7 and later
LPG
−090 −090 Nat. Nat
−110 110 LPG LPG
Nat.
−135−1, −2, −3 −135−1 −2 −3
LPG
Nat.
−135−4 135 4
and later
LPG
Pressure switch is factory set. No adjustment necessary. All models use the factory installed pressure switch from 0−4500 feet (0−1370 m).
V−TYPICAL OPERATING CHARACTERISTICS
A−Blower Operation and Adjustment
NOTE− The following is a generalized procedure and
does not apply to all thermostat controls.
1 − Blower operation is dependent on thermostat control
system.
2 − Generally, blower operation is set at thermostat sub-
base fan switch. With fan switch in ON position, blower
operates continuously. With fan switch in AUTO position,
blower cycles with demand or runs continuously while
heating or cooling circuit cycles.
3 − In all cases, blower and entire unit will be off when the
system switch is in OFF position.
0 − 4500 ft.
(0 − 1372 m)
Required Pressure
Required Pressure
Conversion Kit Switch
N/A No Change
83M74 No Change
N/A No Change
83M74 No Change
N/A No Change
83M74 No Change
N/A N/A No Change No Change g
83M74 83M74 No Change No Change
N/A No Change
83M74 No Change
N/A No Change
83M74 No Change
Manifold Pressure (Outlet) inches w.c.
Model Model
Fuel Input
Sizes
4500
045,
Nat.
070,
Gas
090,
110
135
135−4
Nat.
and
Gas
later
L.P. All
10.0**
Gas sizes
* Conversion kit required for applications at altitudes above
7501 ft. above sea level.
** Conversion kit required for all applications at all altitudes.
TABLE 20
Altitude
4,501 − 7500 ft.
(1373 − 2286 m)
Required Pressure
Required Pressure
Conversion Kit Switch
N/A No Change
83M74 No Change
N/A No Change
83M74 No Change
N/A 56M05
83M74 No Change
N/A N/A 75M20 75M20
83M74 83M74 75M20 75M20
N/A 56M04
83M74 56M04
N/A 56M04
83M74 56M04
B−Temperature Rise
Temperature rise for G43UF units depends on unit input,
blower speed, blower horsepower, filter resistance and
installed duct system resistance. The blower speed must
be set for unit operation within the range of TEMPERA-
TURE RISE °F" listed on the unit rating plate.
To Measure Temperature Rise:
1− Place plenum thermometers in the supply and return air
plenums. Locate supply air thermometer in the first hori-
zontal run of the plenum where it will not pick up radiant
heat from the heat exchanger.
2 − Set thermostat to highest setting.
3 − After plenum thermometers have reached their high-
est and steadiest readings, subtract the two readings.
The difference should be in the range listed on the unit
rating plate. If the temperature is too low, decrease
blower speed. If temperature is too high, first check the
firing rate. Provided the firing rate is acceptable, in-
crease blower speed to reduce temperature. To
change blower speed taps see the Blower Speed Taps
section in this manual.
Page 36
TABLE 19
Altitude (feet)
0− 4501− 5501− 6501−
5500 6500 7500
3.5 3.5 3.5
3.5 3.3 3.2
3.5 3.5 3.5
10.0** 10.0** 10.0**
7501−10,000 ft.
(2287 − 3048 m)
Required
Required
Conversion Kit
59M16
83M75
N/A
83M75
N/A
83M75
59M16 59M16
83M75 83M75
47M82
83M75
59M16
83M75
7501−
10,000
3.5 3.5*
3.1 3.5*
3.5 3.5*
10.0**
Pressure
Pressure
Switch
56M06
56M06
95M22
56M06
56M06
56M06
56M07 56M07
56M07 56M07
60M35
60M35
60M35
60M35