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©
2003 Lennox Industries Inc.
Corp. 0304−L4
G50UHi
Service Literature
Revised 10−2005
G50UHi Series Units
G50UHi series units are mid−efficiency gas furnaces used
for upflow or horizontal applications only, manufactured
with Lennox Duralok Plus
®
heat exchangers formed of alu-
minized steel. G50UHi units are available in heating capac-
ities of 66,000 to 154,000 Btuh and cooling applications up
to 5 tons. Refer to Engineering Handbook for proper sizing.
Units are factory equipped for use with natural gas. Kits are
available for conversion to LPG operation. G50UHi model
units are equipped with the Lennox SureLight
®
silicon ni-
tride ignition system and blower control module. The blower
control module allows the G50Ui to maintain a constant
CFM over a wide range of operating static pressure. All units
use a redundant gas valve to assure safety shut−off as re-
quired by C.S.A.
All specifications in this manual are subject to change. Pro-
cedures outlined in this manual are presented as a recom-
mendation only and do not supersede or replace local or
state codes. In the absence of local or state codes, the
guidelines and procedures outlined in this manual (except
where noted) are recommended only and do not constitute
code.
TABLE OF CONTENTS
Introduction
1
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Specifications
2
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
High Altitude
3
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Blower Data
4
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Parts Identification
6
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
I Unit Components
8
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
II Installation
17
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
III Start Up
17
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
IV Heating System Service Checks
17
. . . . . . . . . . . . . .
V Typical Operating Characteristics
20
. . . . . . . . . . . . . .
VI Maintenance
20
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
VII Wiring and Sequence of Operation
22
. . . . . . . . . . . .
VIII Troubleshooting
28
. . . . . . . . . . . . . . . . . . . . . . . . . . .
IMPORTANT
Improper installation, adjustment, alteration, service
or maintenance can cause property damage, person-
al injury or loss of life. Installation and service must
be performed by a qualified installer, service agency
or the gas supplier.
WARNING
Electric shock hazard. Can cause injury
or death. Before attempting to perform
any service or maintenance, turn the
electrical power to unit OFF at discon-
nect switch(es). Unit may have multiple
power supplies.
WARNING
Sharp edges.
Be careful when servicing unit to avoid sharp edges
which may result in personal injury.
Summary of Contents for G50UHi Series
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