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© 2001 Lennox Industries Inc.
G40DF(X)
Service Literature
Corp. 0113−L6
Revised 09−2006
G40DF(X) series units are mid−efficiency gas furnaces
used for downflow applications only, manufactured with
Lennox Duralok Plus heat exchangers formed of alumi-
nized steel. G40DF(X) units are available in heating capac-
ities of 44,000 to 135,000 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. G40DF(X) model
units are equipped with a hot surface ignition surface. The
G40DF(X) unit meets the California Nitrogen Oxides (NO
x
)
Standards and California Seasonal 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
Introduction 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Specifications 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Blower Data 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
High Altitude 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Parts Identification 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
I Unit Components 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
II Installation 18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
III Start Up 18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
IV Heating System Service Checks 18. . . . . . . . . . . . . .
V Typical Operating Characteristics 20. . . . . . . . . . . . . .
VI Maintenance 21. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
VII Wiring and Sequence of Operation 23. . . . . . . . . . .
VIII SureLight Troubleshooting Guide 33. . . . . . . . . . . .
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.
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