Specifications

CommStat 4 Lead/Lag Controller Inputs
CommStat 4 PDS 8.2011 rev 43
1. Input Power
The R and C terminals are the input power terminals for each respective air conditioner or heat pump.
2. Modem Connection
The modem connection is used for remote communication and remote programming of the CommStat 4.
It has the capability of providing shelter temperatures, mode of operation, as well as remote diagnosis. All
configuration settings can be viewed and changed remotely.
3. Control Voltage (24 VAC)
The CommStat 4 is powered by 24 VAC or with a user provided 24 VDC or 48 VDC power supply. Should
AC power be lost, the display, user interface and alarm outputs of the CommStat 4 will still be functional.
However,thesystemoutputsoftheCommStat4(Y,G,W,O,andMAR)willnotbefunctionalwhen24
VAC is not present.
4. Line Voltage
The CommStat 4 uses line voltage of 230VAC input from each unit air conditioner to monitor for the
presence of line voltage. If a line voltage loss is not present, the CommStat 4 will energize the High
Voltage Loss Alarm relay. If desired, this alarm can be disabled by the user in Configuration Set Up.
5. Temperature Sensors
 TheCommStat4usesremotetemperaturesensor(s)tomeasurethetemperatureintheshelterand
determine when the system is calling for heating or cooling. Up to three sensors can be connected to each
CommStat 4. There are two options for the sensors. If No(thedefaultsetting)isselectedandmultiple
sensors are being used, the temperatures will be averaged. If Yes is selected and multiple sensors are
being used, the sensor with the highest reading will be used for cooling operation and the one with the
lowest reading will be used for heating. When multiple sensors are being used and there is a temperature
differentialgreaterthanorequalto5°F(4°C)betweenthesensors,theCommStat4lead/lagcontroller
willenergizetheindoorblowers(G)onallconnectedunits.
Screen #20 in the Configuration Mode allows the user to determine how the temperature sensors will be
configured.
6. Smoke Detector
 Thesmokedetectorinputterminalsdeterminewhenthereisasignalfromanexternalsmokedetector.
They can be configured for either a Normally Open(N.O.)orNormally Closed(N.C.)smokesignalin
Configuration screen # 18. During a smoke fault condition, all AC units will be turned off.
The smoke alarm relay reset has two selections -Manual(default)andAuto. If Manual is selected, a
physical reset of the fault is required by holding the Up and Down buttons for 4 seconds. Cycling power
will not reset a smoke fault if Manual is selected.
If Auto is selected the alarm will reset after an adjustable time delay of 3-10 minutes.
Screen #17 in the Configuration Mode allows the user to determine how the smoke alarm relay reset will
be configured.
7. Hydrogen Detector
 Thehydrogendetectorinputterminalswilldeterminewhenthereisa24VACsignalfromanexternal
hydrogendetector.TheCommStat4willswitchtheleadunittoEmergencyVentilationmode(ComPacII
air conditioners or Classic heat pumps with economizers only) when high hydrogen levels are detected. It
will switch back to normal air conditioning mode once the hydrogen levels are acceptable and the 24 VAC
signal is removed from the hydrogen detector input terminals.
8. Generator Relay
The generator input will monitor for a 24 VAC signal which will be used to determine when the CommStat
4 is operating on generator power. When 24 VAC is recognized at the generator relay input, the CommStat
4controllerwillonlyoperatetheunitsselectedbytheuserinscreen#16oftheConfigurationMenu.The
optionsare:
  a.torunonlytheleadunit(default),
b. the lead unit and one lag unit,
c. the lead unit and two lag units, or
d. the lead unit and three lag units.
9. Economizer Mode Status Monitoring
The 2 terminal in the air conditioner is monitored for a 24 VAC signal. When the 2 terminal has 24 VAC
present, mechanical cooling will be energized and the cooling LED will be lit. When 24 VAC is not present
at the 2 terminal, the unit will be in economizer mode and this status will be annunciated on the LCD
display.Economizermodeisdefinedasacallforcooling(24VACoutputatYandO)withno24VACsignal
atthe2terminal.Mechanicalcoolingisdefinedasacallforcooling(24VACoutputatYandO)whilethere
is a 24VAC signal at the 2 terminal.
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