Lennox EL296UH090XV36C - Page 57

Page 57
TABLE 20
7501 - 10000’
Unit Set Point Low Heat Set Point High Heat
-045 0.35 0.50
-070-1 through -6 0.41 0.74
-070-7 & later 0.40 .070
-090 0.45 0.81
-110 0.41 0.74
-135 0.41 0.74
Pressure Switch Check
To check pressure switch di󰀨erential, refer to FIGURE 18
and use the provided ttings and tubing to follow the steps
below.
1 - Remove thermostat demand and allow unit to cycle
o󰀨.
2 - Remove the tubing from the negative side (red
and black or red) and positive side (black) of the
pressure switch (leave both connected to cold end
header box).
3 - Take the 2” length square tubing and connect to the
positive (+) side of the pressure switch. Take the 10”
length square tubing and tee into the tubing from
the positive side of the cold end header box and
the other side of the 2” square tubing. Connect the
other end of the 10” square tubing the positive (+)
side of the measuring device.
4 - Take a second piece the 2” length square tubing and
connect to the negative (-) side of the pressure
switch. Take a second piece of 10” length square
tubing and tee into the tubing from the negative
(-) side of the cold end header box and the other
side of the 2” square tubing. Connect the other end
of the 10” square tubing to the negative (-) side of
the measuring device. Operate unit and observe
manometer reading. Readings will change as heat
exchanger warms.
a. Take one reading immediately after start-up.
b. Take a second reading after unit has reached steady
state (approximately 5 minutes). This will be the pressure
di󰀨erential.
The pressure dierential should be at least 0.15”
greater than those listed in the tables 18, 19 and 20.
Readings in table are the set points or “break points”.
5 - Remove thermostat demand and allow to cycle o󰀨.
6 - Replace original pressure switch tubing.
NOTE - Pressure dierential values (set point)
in table are the ”break”, or ”open” specications.
”Make”, or ”close” pressure dierentials are 0.15”
greater than the set points listed in table.
PRESSURE SWITCH CHECK
Black Tubing
(positive +)
Red and Black
or Red Tubing
(negative −)
Tee
2” long Square
Tubing
Measuring Device
10” Long Square Tubing
FIGURE 18