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UNIT INFORMATION
UNIT INFORMATION
S e r v i c e L i t e r a t u r e
©2016 Lennox Industries, Inc.
WARNING
Improper installation, adjustment, alteration, service
or maintenance can cause property damage, personal
injury or loss of life. Installation and service must be
performed by a licensed professional HVAC installer or
equivalent, service agency, or the gas supplier.
CAUTION
As with any mechanical equipment, contact with sharp
sheet metal edges can result in personal injury. Take
care while handling this equipment and wear gloves and
protective clothing.
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 disconnect switch(es).
Unit may have multiple power supplies.
SLP99DFV series units are high-efficiency downflow gas
furnaces equipped with variable capacity gas valve, vari-
able speed combustion air inducer and variable speed
indoor blower motor. All models are designed for direct
vent (dual pipe) venting system only. SLP99DFV units are
available in heating capacities from 66,000 to 132,000
Btuh (19.3 to 38.6 kW) and cooling applications from 2 to
5 tons (7.0 kW to 17.5 kW). Refer to Engineering Hand-
book for proper sizing.
Units are factory-equipped for use with natural gas. Kits
are available for conversion to LP operation. SLP99DFV
models include a SureLight
®
variable integrated control
that can be used with a communication thermostat as part
of a communicating comfort system. All SLP99DFV units
meet the California Nitrogen Oxides (NOx) Standards and
California Seasonal Efficiency requirements.
All specifications in this manual are subject to change.
Procedures outlined in this manual are presented as rec-
ommendations 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 recommendations only and do not con-
stitute code.
TABLE OF CONTENTS
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 2
Optional Accessories . . . . . . . . . . . . . . . . . . . . . . Page 3
Blower Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 4
I Unit Components . . . . . . . . . . . . . . . . . . . . . . . Page 10
II Communicating Thermostat . . . . . . . . . . . . . . Page 36
III Placement and Installation . . . . . . . . . . . . . . Page 39
IV Start Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 55
V Heating System Service Checks . . . . . . . . . . Page 56
VI Typical Operating Characteristics . . . . . . . . Page 62
VII Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . Page 62
VIII Wiring and Sequence of Operation . . . . . Page 65
IX Field Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 73
SLP99DFV
100002
10/2021
SLP99DFV SERIES UNITS
