18
The default setting can be changed by using parameter 99. The valid number of occurrence range is 1 through 7. When a
compressor is de-energized due to an open low pressure switch, alarm 22 (S87 switch) or 24 (S88 switch) is issued.
Go to
SETTINGS > RTU OPTION > EDIT PARAMETER = 99 (MAX LP OCCURRENCES)
NOTE
: Only the displayed alarm(s) will indicate that the applicable compressor has been de-energized. The system
status on the display will only indicates the current demand type in this scenario.
NOTE
: Low pressure switch alarms will not indicate an OFF ON ALARM state (see table 61).
3.1.7.
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.
3.2.3.
Combustion Air Inducer (CAI) Proof Switches (S18 and S45)
3.2.3.1.
Open Proof Sequence of Operations
A
The M3 unit controller will set alarm 166 and/or 167 if either S18 or S45 are not proved open while the combustion air
blower is not energized. If gas heat demand is still present
,
the M3 unit controller will attempt to prove either S18 or
S45 are in a open condition every 60 seconds
.
B
If either S18 or S45 are proven as open, the M3 unit controller will proceed with the gas heat demand (i.e energize the
the combustion air blower).
C
Even while lockout alarm(s) 168 and or 169 are active, the M3 unit controller will continue attempting if either S18 or
S45 are open. Parameter 72 - Max CAI No Open Proof Occurrences default setting is 5 and it adjustable from 1 to 15
occurrences.
D
The M3 unit controller will set alarm(s) 168 and/or 169 (instead of 166/167) if either S18 or S45 are not proved open
while the combustion air blower is not energized, for 5 consecutive times during a single cycle. Even while alarm(s)
168 and/or 169 are active, the M3 unit controller will continue attempting to prove that either S18 and/or S45 are
open. Parameter 72 Max CAI No Open Proof Occurrences default setting is 5 and it adjustable from 1 to 15
occurrences.
To view or change the number of occurrences setting, go to
SETTINGS > RTU OPTION > EDIT PARAMETER =
72 (MAX CAI NO PRF OCC)
3.2.3.2.
Open Proof Alarms
Open proof alarms are 166 through 169.
3.2.3.3.
Closed Proof Sequence of Operations
A
The M3 unit controller will set an alarm(s) (Alarm 56 or 66) if:
If either S18 or S45 switches are not sensed as closed within 30 seconds of energizing the combustion air inducer.
If either S18 or S45 switches are sensed as open for three seconds while gas heat demand is active.
B
The M3 unit controller will set an alarm(s) 57 and/or 67 when three-strikes occur during a single-demand. Parameter
71 default setting is 3 and it adjustable from 1 to 5 occurrences.
To view or change the number of occurrences setting, go to
SETTINGS > RTU OPTION > EDIT PARAMETER =
71 (MAX CAI NO SW OCC)
.
NOTE
: In addition, even if parameter 71 is set to an alternate occurrence number, the alarm itself will aways indicated
three strikes.
3.2.3.4.
Closed Proof Alarms
Closed proof alarms are 56, 57, 66 and 67.
