Safety Switch Input (A42-Optional); Air Flow Proving Switch (S52 - Optional); Dirty Filter Switch (S27- Optional); Blower Overload Relay Switch (S42 - Optional) - Lennox Prodigy 2.0 Application Manual

3.3.4.

Safety Switch Input (A42-Optional)

The M3 Unit Controller has 24VAC optional inputs (D1-2 or DI-3) which may be used for additional safety switches (such as a
blower overload, loss of phase protector, or supply duct high pressure limit switch). Wire the safety switch in series with the
input.
When the normally open Safety Switch A42 is open, the M3 Unit Controller will turn off all outputs and display alarm 20. The
unit will be locked out if the Safety switch is activated 'Max Phase Monitor (A42) Occurrences' times in single demand cycle.
based on Parameter 116 setting. The factory default for this parameter is three occurrences. The adjustable occurrence
range is 1 to 15. Once the switch has been physically installed, perform the following procedure to enable safety switch
monitoring:
Go to SETUP > INSTALL. Configuration ID 2, position 5 will need to be set to either 2 or 3 depending whether A42
is wired on DI-2 or DI-3.
Using parameter 115 is only applicable if Safety switch A42 is enabled via Configuration ID 2.
Go to SETTINGS > RTU OPTION > EDIT PARAMETER = 116 (MAX PHASE MON OCC)
3.3.5.

Air Flow Proving Switch (S52 - Optional)

The air flow switch closes during normal unit operation. If air flow is not established (S52 closed) within 16 seconds of blower
start or if the S52 opens at any time after that, the M3 Unit Controller de-energizes the compressor, gas valves, electric heat,
and closes economizer damper. The service alarm output will turn on.
Go to SETUP > INSTALL. Configuration ID 2, position 1 and set to C to enabled the air flow proving switch monitoring
via the M3 Unit controller.
If S52 is physically connected to DDC controller, Configuration ID 2 position 1 is set to D. The M3 Unit Controller will
not monitor S52 using this configuration.
3.3.6.

Dirty Filter Switch (S27- Optional)

The dirty filter switch is open during normal unit operation. A dirty filter will close S27 and the M3 Unit Controller will display
and store the error code and turn on the service alarm output (if configured).
Go to SETUP > INSTALL. Configuration ID 2, position 2 will need to be set to C. This will enable the dirty filter switch when
installed.
3.3.7.

Blower Overload Relay Switch (S42 - Optional)

S42 is a three-phase thermal overload relay. This switch is connected in line with the blower motor to monitor the current flow
to the motor. When the relay senses current that exceeds the operating limits of the motor, a set of normally closed contacts
open to de-energize the blower.
Go to SETUP > INSTALL. Configuration ID 2, position 4 has to be set to either 2 or 3 to enable the blower overlay
relay switch if installed.
NOTE - The N setting option will disable S42 monitoring of 2 (DI-2) or 3 (DI-3).
3.3.8. Overflow Switches (S149 / S179 - Optional)
The N.C. overflow switch or switches are connected to the M3 Unit Controller (A55) in series (when applicable) through
either D1-2 or DI­3. When the switch opens, the Unit Controller will shut off the compressor. After a five­minute time out, the
Unit Controller will verify the overflow switch position and restart the compressor(s) as long as a cooling demand is present
(if the switch has closed).
Go to SETUP > INSTALL. Configuration ID 2, position 3 has to be set to either 2 or 3 to enable the overflow switch
if installed.
NOTE - The N setting option will disable S149 / S179 monitoring of 2 (DI-2) or 3 (DI-3).
3.3.9.

Blower On-Delay

•
For electric heat units, the Blower On-Delay is disabled (i.e. set to zero).
•
For gas units, the blower is delayed 40 seconds (default) which is set using Parameter 66, after the gas valve is energized.
Adjustable range is 8 to 60 seconds.
Go to SETTINGS > RTU OPTION > EDIT PARAMETER = 66 (HG GAS BLR ON DELAY)
•
For gas units (A Box only), the blower on is delayed 20 seconds (default) after the gas valve is energized. This value is
fixed and cannot be changed.
•
For cooling units, the blower is delayed zero seconds (default) which is set using Parameter 79. Adjustable range is 0 to
60 seconds.
Go to SETTINGS > RTU OPTION > EDIT PARAMETER = 79 (COOL BLR ON DELAY)
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