LENNOX 21Z07 Float Switch Kit Instruction Manual
- June 4, 2024
- Lennox
Table of Contents
LENNOX 21Z07 Float Switch Kit
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.
Shipping and Packing List
Package 1 of 1 contains:
- 1- Overflow (float) switch (S149)
- 3- Mounting brackets
- 1- Wire harness
- 2- Screws #10-32 X 1/2”
- 2- Screws #8-32 X 1/2”
- 10- Wire ties
Application
The overflow switch is used to interrupt cooling operation when excessive
condensate collects in the drain pan.
M2 Unit Controller
The N.C. overflow switch is connected to the Unit Controller (A55) through
DI-3. When the switch opens, the Unit Controller will shut off the unit. After
a five-minute time out, the Unit Controller will verify the overflow switch
position and restart the unit (if the switch has closed). The Unit Controller
has a three-strike counter before the unit locks out. This means the Unit
Controller will allow the overflow switch to open three times per thermostat
demand. If the unit locks out, a reset of the Unit Controller is required
after the switch has closed to restore unit operation.
M3 and M4 Unit Controller
The N.C overflow switch is connected to the M3/M4 Unit Controller through DI-2
or DI-3. If the overflow switch is the only switch installed on the general
purpose programmable input, then M3/M4 Unit Controller will disable compressor
cooling operation when the overflow switch is detected as open. If the
programmable digital input is shared with other protection switches, the M3/M4
Unit Controller will shut down the whole unit operation when the overflow
switch is detected as open. After a five-minute time out, the M3/M4 Unit
Controller will verify the overflow switch position and resume operation
(servicing the demands) if the switch has closed. The M3/M4 Unit Controller
has no 3-strike counter.
Float Assembly
The float switch assembly is shipped for normally closed operation.
Installation
- Disconnect all electrical power to the unit and open the control access door.
- Remove the panel covering the condensate drain pipe.
- LG/LC/LH/LD Units – Secure float switch to bracket. See figure 1. Secure bracket to drain pan. See figure 2 for plastic drain pans and figure 3 for stainless steel drain pans. Use #10 screws to secure assembly. Discard the other two brackets provided in the kit. SC/SC Units – Secure float switch to C-bracket which doesn’t have a square cut-out; secure with locknut. Install the assembly as shown in figure 4. Make sure the square bracket is on the inside of the drain pan and the C-bracket is on the outside. Secure with #8 screws. Discard the bracket with the square cut-out.
IMPORTANT – LG/LC/LH/LD 024-150 UNITS ONLY – When condensate drainage is required through the back of the unit: remove drain pan, install float switch assembly on the left side of the drain pan nipple and install with switch oriented toward the back of the unit. See figure 5. Route wire harness between the drain pan and heat section.
-
Connect wire harness to Unit Controller terminals DI- 2 or 3 and R. See figure 6 for M2 and M3; see figure 7 for M4.
-
Route the other end of the harness to the float switch and secure with wire ties. See figure 8 for LG/LC/LH/LD 072 units, figure 9 for LG/LC/LH/LD 092- 150 units, figure 10 for LG/LC/LH/LD 156-360 & SG/SC 240, figure 11 for SG/SC 036/060 and figure 12 for SG/SC 120 units.
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Connect the wire harness to float switch. Bundle excess wiring using wire ties provided and secure to insulated suction line manifold above drain pan.
-
Replace panel covering condensate drain pan.
-
Restore power to the unit.
Configure Unit Controller
IMPORTANT – Make sure Unit Controller uses V7.05.01 (or later) and the display uses V1.06.05 (or later) software. Use the Unit Controller Installation and Setup Guide to update software.
- Configure the Unit Controller for the Overflow switch as follows:
- Close all access doors.
M2 UNIT CONTROLLER
SETTINGS>INSTALL>FLOAT SW
M3 UNIT CONTROLLER
Go to SETUP / INSTALL and navigage through the various setup questions until
Configuration ID 2 appears. Position three needs to set to 2 when connected to
DI-2 and 3 when connected to DI-3.
M4 UNIT CONTROLLER
Go to RTU MENU > SETUP INSTALL and navigate through the various setup
questions until Configuration ID 2 appears. Position three needs to be set to
2 when connected to DI-2 and 3 when connected to DI-3.
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