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3. Unit Component Operation
3.1.
Compressor Protection and Delays
3.1.1.
Compressor Minimum Run Time (3 Phase Units Only)
Each compressor stage has a minimum run time of four minutes (ECTO 1.11, 4.13).
3.1.2.
Compressor Off Delay (Single phase units only
Compressors have a five minute (default) compressor off delay. (ECTO 1.10, 4.12).
3.1.3.
Blower On Delay
On gas units, the blower is delayed 40 seconds (default) after the gas valve is energized. There is no blower delay on cooling and
heat pump units (ECTO 1.02, 2.02, 3.02, 4.02).
3.1.4.
Freezestats (S49, S50, S53, S59)
Normally closed freezestats open when evaporator coil temperature drops to de−energize the corresponding compressor.
Once coil temperature rises the switch automatically resets to allow compressor operation. The corresponding compressor
is locked out after three occurrences. (ECTO 4.04).
3.1.5.
High Pressure Switches (S4, S7, S28, S96)
High pressure switches open on a pressure rise to de−energize the corresponding compressor for five minutes (ECTO
5.02). Switches automatically reset when pressure drops. The corresponding compressor is locked out after three occur-
rences. (ECTO 4.14).
3.1.6.
High Temperature Switches (compressor internal)
High temperature switches open on a temperature rise to de?energize the corresponding compressor. Switches automati-
cally reset when temperature drops.
On certain compressors, these switches are in series with the high pressure switches, and will cause a five minute (ECTO
5.02) off period, and an alarm code. The corresponding compressor is locked out after three occurrences of either high
pressure or high temperature conditions during a demand cycle (ECTO 4.14).
3.2.
Gas Units Burner Protection And Delays
3.2.1.
Primary or Secondary Limits (S10, S21, S99, S100, S130, S131)
If primary or secondary limits open during heating, the M2 will de−energize the gas valve and energize the blower. If primary
or secondary limits open three times during a thermostat cycle, the heat section operation will be locked−out for one hour.
3.2.2.
Roll−Out Switch (S47, S69)
If roll−out switch opens, the gas valve will be de−energized and a manual reset is required to restart.
3.2.3.
Combustion Air Switch (S18, S45)
If the combustion air switch opens during heating the gas valve is de−energized. If the combustion air switch opens 3 (de-
fault) times, the service alarm output will turn on.
3.2.4.
Gas Valve Sensor
If the gas valve is not energized 2 minutes after a heating demand, the M2 will display and store error code 58 for gas valve 1
and 68 for gas valve 2.
If the gas valve is energized and de−energized 3 (default) times during a single heating demand, the M2 will display and store
error code 59 for gas valve 1 and 69 for gas valve 2. The service relay will be activated.
The M2 will also de−energize all outputs and turn on the service output if the gas valve is energized without a heating de-
mand.
3.2.5.
Gas Valve Delays
The M2 has a 30 second (default) delay between first and second stages. A timed off delay (100 seconds default) will pre-
vent gas heat operation until 100 seconds has passed from the previous cycle. (ECTO 3.05, 3.06).
3.3.
Miscellaneous Components
3.3.1.
Unoccupied Or Night Setback Mode
During the unoccupied time period dampers do not operate at minimum position (no minimum ventilation requirements dur-
ing unoccupied period).
3.3.2.
Local Thermostat Mode
The unoccupied time period occurs when there is no input at A55_P297−8.
506457−01 05/10
Page 12
3.
Unit Component Operation
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