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©
2000 Lennox Industries Inc.
Corp. 0005−L3
G50UH(X)
Service Literature
Revised 09−2006
G50UH(X) series units are mid−efficiency gas furnaces
used for upflow or horizontal applications only, manufac-
tured with Lennox Duralok Plus heat exchangers formed of
aluminized steel. G50UH(X) units are available in heating
capacities of 44,000 to 154,000 Btuh and cooling applica-
tions up to 5 tons. Refer to Engineering Handbook for prop-
er sizing.
Units are factory equipped for use with natural gas. Kits are
available for conversion to LPG operation. G50UH(X) mod-
el units are equipped with the Lennox SureLight silicon ni-
tride ignition system. The G50UH(X) unit meets the Califor-
nia Nitrogen Oxides (NO
x
) Standards and California Sea-
sonal Efficiency requirements. All units use a redundant gas
valve to assure safety shut−off as required 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
Specifications
Page 2
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Blower Data
Page 6
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High Altitude
Page 15
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Parts Identification
Page 16
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I Unit Components
Page 18
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II Installation
Page 27
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III Start Up
Page 27
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IV Heating System Service Checks
Page 27
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V Typical Operating Characteristics
Page 29
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VI Maintenance
Page 30
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VII Wiring and Sequence of Operation
Page 32
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VIII SureLight Troubleshooting Guide
Page 38
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IMPORTANT
Improper installation, adjustment, alteration, ser-
vice or maintenance can cause property damage,
personal 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.
