Lennox G43UF SERIES Unit Information

Page 36
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.
TABLE 19
Manifold Pressure (Outlet) inches w.c.
Model
Altitude (feet)
Fuel
Model
Input
Sizes
0−
4500
4501−
5500
5501−
6500
6501−
7500
7501−
10,000
Nat.
Gas
045,
070,
090,
110
3.5 3.5 3.5 3.5 3.5*
135 3.5 3.3 3.2 3.1 3.5*
Nat.
Gas
135−4
and
later
3.5 3.5 3.5 3.5 3.5*
L.P.
Gas
All
sizes
10.0** 10.0** 10.0** 10.0** 10.0**
* Conversion kit required for applications at altitudes above
7501 ft. above sea level.
** Conversion kit required for all applications at all altitudes.
TABLE 20
Conversion Kit and Pressure Switch Requirements at Varying Altitudes
Altitude
Model
Input
Si
Gas
0 − 4500 ft.
(0 − 1372 m)
4,501 − 7500 ft.
(1373 − 2286 m)
7501−10,000 ft.
(2287 − 3048 m)
Input
Size
Gas
Required Pressure Required Pressure Required Pressure
Required
Conversion Kit
Pressure
Switch
Required
Conversion Kit
Pressure
Switch
Required
Conversion Kit
Pressure
Switch
−045
Nat. N/A No Change N/A No Change 59M16 56M06
045
−070
LPG 83M74 No Change 83M74 No Change 83M75 56M06
−045−7 and later
Nat. N/A No Change N/A No Change N/A 95M22
045 7
and
later
LPG 83M74 No Change 83M74 No Change 83M75 56M06
−070−7 and later
Nat. N/A No Change N/A 56M05 N/A 56M06
070 7
and
later
LPG 83M74 No Change 83M74 No Change 83M75 56M06
−
090
Nat
N/A
No Change
N/A
75M20
59M16
56M07
−
090
N
a
t
.
N/A
N
o
Ch
ange
N/A
75M20
59M16
56M07
110
LPG
83M74
g
No Change
83M74
75M20
83M75
56M07
−110 LPG 83M74 No Change 83M74 75M20 83M75 56M07
−135−1 −2 −3
Nat. N/A No Change N/A 56M04 47M82 60M35
−
135
−
1
, −
2
, −
3
LPG 83M74 No Change 83M74 56M04 83M75 60M35
−135−4
Nat. N/A No Change N/A 56M04 59M16 60M35
135 4
and later
LPG 83M74 No Change 83M74 56M04 83M75 60M35
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.
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.

Lennox G43UF SERIES Specifications

General

Brand	Lennox
Model	G43UF SERIES
Category	Furnace
Language	English