Lennox Pressure Switch Replacement Kit -- SLP98UHV & SLP98DFV Units Installation guide

Lennox
Brand
Lennox
Model
Pressure Switch Replacement Kit -- SLP98UHV & SLP98DFV Units
Type
Installation guide
Page 1
INSTALLATION INSTRUCTIONS FOR COMBUSTION AIR PRESSURE SWITCH KITS
(74W36, 74W37, 93W75 and 93W76) USED WITH 90% EFFICIENCY VARIABLE CAPACITY
AND MODULATING GAS FURNACES
Litho U.S.A.
506620-01
04/2015
Supersedes 06/2012
PRESSURE SWITCH
REPLACEMENT KIT
GAS KITS & ACCESSORIES
E 2015
Shipping & Packing List
Package 1 of 1 contains:
1 - Pressure switch
Application
Pressure switch replacement kits (74W36, 74W37, 93W75
and 93W76) are used with variable capacity and
modulating furnaces. See table 1 for usage and elevation.
WARNING
This kit is to be installed by a licensed professional
service technician (or equivalent) or other qualified
agency in accordance with the manufacturer's in
structions, all codes and requirements of the author
ity having jurisdiction in the USA, and the require
ments of the CSA-B149 installation codes in Canada.
If the information in these instructions is not fol
lowed exactly, personal injury or loss of life may oc
cur. The qualified agency performing this work as
sumes responsibility for this conversion.
TABLE 1
Kit Number and Elevation
Kit Elevation (ft.)
74W36, 93W76 0 - 7500
74W37, 93W75 7501 - 10,000
Installation
1 - Turn off the electrical power and gas supply to the unit.
2 - Remove the heating compartment access panel.
3 - Remove the tubing and disconnect wires from the
existing pressure switch. Label wires and tubing
making note of tubing color and negative and positive
pressure switch ports.
NOTE - Black tubing is used for the positive port. Red
tubing or red and black tubing is used for the negative port.
4 - Remove the existing pressure switch by carefully
pressing the tab which secures the switch assembly to
the cold end header box. See figure 1.
5 - Reconnect existing wires to replacement pressure
switch.
6 - Install replacement pressure switch. Reconnect
pressure switch tubing as shown in figures 2 and 3.
7 - Replace access panel and restore the electrical power
and gas supply to the unit.
8 - Follow lighting instructions on unit nameplate.
REMOVING PRESSURE SWITCH
FIGURE 1
Tab
Pressure Switch
Assembly
Gas
Valve
Cold End
Header Box
Negative
Port
Positive
Port
Low Fire
High Fire
Page 2
UPFLOW/HORIZONTAL FURNACE
(shown in upflow position)
FIGURE 2
Gas Valve
Cold End Header Box
High-Fire Pressure
Switch
Low-Fire Pressure
Switch
1
2
3
4
1 - Black hose from front port on low-fire pressure switch to
positive port on the gas valve.
2 - Red and black or red hose from rear port on low-fire pres
sure switch to the negative port on the gas valve.
3 - Red and black or red hose from front port on high-fire pres
sure switch to negative port on cold end header box.
4 - Black hose from rear port on high-fire pressure switch to
positive port on cold end header box.
DOWNFLOW FURNACE
FIGURE 3
1
2
3
4
Gas Valve
Cold End
Header Box
High-Fire
Pressure
Switch
Low-Fire
Pressure
Switch
1 - Black hose from front port on low-fire pressure switch to
positive port on the gas valve.
2 - Red and black or red hose from rear port on low-fire pres
sure switch to the negative port on the gas valve.
3 - Red and black or red hose from front port on high-fire pres
sure switch to negative port on cold end header box.
4 - Black hose from rear port on high-fire pressure switch to
positive port on cold end header box.
PRESSURE SWITCH WIRING FOR UPFLOW/
HORIZONTAL AND DOWNFLOW FURNACES
FIGURE 4
NO
C
NO
C
PRESSURE SWITCHES
LOW
FIRE
HIGH
FIRE
PINK
PURPLE
PINK
VIOLET/PURPLE
To P58 12 pin
connector on the
integrated control
To P58 12 pin
connector on the
integrated control
To P58 12 pin
connector on the
integrated control
  • Page 1 1
  • Page 2 2

Lennox Pressure Switch Replacement Kit -- SLP98UHV & SLP98DFV Units Installation guide

Lennox
Brand
Lennox
Model
Pressure Switch Replacement Kit -- SLP98UHV & SLP98DFV Units
Type
Installation guide
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