Low Pressure Switches (S87, S88, S97 And S98); Loss Of Power Detection (Single-Phase Units Only); Gas Units Burner Protection And Delays; Primary Or Secondary Limits (S10 And S99) - Lennox Prodigy 2.0 Application Manual

3.1.4. Thermal Protector Switches (S5, S8, S31 and S180)
3.1.4.1. Energence Ultra-High Efficiency Units
This model has one pressure switch (S4) that is connected in series with two
temperature switches (S5 and S8) (see figure to right). If pressure switch trips, both
compressors are de-energized. If only one temperature switch is tripped, only the
applicable compressor will be de-energized.
3.1.4.2. All Other Energence Units
High temperature switches open on a temperature rise to de-energize the
corresponding compressor. Switches automatically reset when temperature drops.
The corresponding compressor is locked out after three occurrences (default) of either
high pressure or high temperature conditions during a demand cycle. The number of
occurrences can be changed using for Parameter 98. Adjustable range is 1 to 7
occurrences.
On certain compressors, these switches are in series with the high pressure switches,
and will cause a 300 second delay (default) which is set using Parameter 110). This will
also set off an alarm. Adjustable delay range is 64 to 1800 seconds.
Go to SETTINGS > RTU OPTION > EDIT PARAMETER = 98 (MAX HP OCCURRENCES)
Go to SETTINGS > RTU OPTION > EDIT PARAMETER = 110 (ERR TIME OFF DELAY)
3.1.5.

Low Pressure Switches (S87, S88, S97 and S98)

Standard and High Efficiency units use both the S87 and S88; however, the Ultra­High Efficiency B­Box units use only S87.
See Fig. 4 for Ultra­High B­Box schematic.
Low pressure switches may trip during lower outdoor temperatures, especially with longer time periods between
compressor cycling. Each compressor stage has low pressure switch protection which:
•
Ignores the low pressure switch for a specified period of time after thermostat demand.
•
De‐energizes the compressor for five minutes (default) if the low pressure switch trips (once the ignore time period
which is set using Parameter 100 has elapsed). Default is 120 seconds. Setting range is 0 to 600 seconds.
Go to SETTINGS > RTU OPTION > EDIT PARAMETER = 100 (LP SW IGNORE TIME)
•
Locks out the compressor stage if the low pressure switch trips three times (default) within the same thermostat demand
(once the ignore time period is elapsed).
The default setting change be changed by using Parameter 99. Valid number of occurrence range is 1 through 7. When a
compressor is de-energized due to an open low pressure switch, alarms 22 (S87 switch) or 24 (S88 switch) is issued.
Go to SETTINGS > RTU OPTION > EDIT PARAMETER = 99 (MAX LP OCCURRENCES)
3.1.6.

Loss of Power Detection (Single-Phase Units Only)

The M3 Unit Controller will turn off compressors for five minutes (default) if a loss of power is detected for two consecutive AC
power cycles. This indicates a problem with supply voltage; waiting five minutes allows pressures to equalize ensuring start-up.
This is set using Parameter 110. Adjustable delay range is 64 to 1800 seconds.
Go to SETTINGS > RTU OPTION > EDIT PARAMETER = 110 (ERR TIME OFF DELAY)
3.2.

Gas Units Burner Protection and Delays

3.2.1. Primary or Secondary Limits (S10 and S99)

If primary or secondary limits open during heating, the M3 Unit Controller will de­energize 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
locked­out for one hour.
3.2.2. Flame Roll-Out Switches (S47 and S69)
If the roll-out switch opens, the gas valve will be de-energized and a manual reset of the flame roll-out (ROL) switch is
required to restart.
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