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SERVICE MANUAL
NF97UM Gas Furnace
This is a safety alert symbol and should never be ignored. When you see this symbol on labels or in manuals, be alert to
the potential for personal injury or death.
NF97UM series units are high-efficiency upflow, horizontal
right and left) gas furnaces equipped with variable
capacity gas valve, variable speed combustion air inducer
and variable speed indoor blower motor. All models are
designed only for direct vent (dual pipe) venting system.
NF97UM units are available in heating inputs 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 Technical
Specifications for proper sizing.
Units are factory-equipped for use with natural gas. Kits
are available for conversion to LPG operation. All NF97UM
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
recommendations 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 constitute code.
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.
Table of Contents
Technical Specifications - NF97UM .............................3
Parts Arrangement.......................................................8
Unit Components .........................................................9
Configuring Unit Size Codes .....................................17
LED Diagnostic Codes ..............................................18
Placement and Installation ........................................33
Joint Cementing Procedure .......................................34
Venting Practices .......................................................35
Vent Piping Guidelines ..............................................37
Applications Only .......................................................47
Addendum for All Provinces of Canada .....................47
Condensate Piping ....................................................48
Start-Up .....................................................................53
Heating System Service Checks ...............................54
Typical Operating Characteristics ..............................58
Maintenance ..............................................................59
Wiring and Sequence of Operation ...........................62
Conventional Thermostat ..........................................66
Troubleshooting Flow Chart ......................................69
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.
Page 2
WARNING
31-5000723 Rev. 0
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