-MS/TP @ 19,200 Baud rate
-Limit devices to 40 on a single trunk line.
Control and Safety Feature Details
Emergency Shutdown
The emergency shutdown mode can be activated by a command from a facility management system or a closed contact on BI-2. The default state for the emergency shut- down data point is off. When the emergency shutdown mode is activated, all outputs will be turned off immediate- ly and will remain off until the emergency shutdown mode is de-activated. The first time the compressor starts after the emergency shutdown mode has been de-activated, there will be a random start delay present.
Lockout Mode
Lockout mode can be activated by any of the following fault signals: refrigerant system high pressure, refrigerant system low pressure, water coil low temperature (freeze sensing), and condensate overflow. When any valid fault signal remains continuously active for the length of its rec- ognition delay, the controller will go into fault retry mode, which will turn off the compressor. After the Compressor short cycle delay, the compressor will attempt to operate once again. If three consecutive faults occur in 60 minutes during a single heating or cooling demand, the unit will go into lockout mode, turning off the compressor, enabling the alarm output, and setting the fan back to low speed operation until the controller is reset. If the control faults due to the low pressure input (BI-3) being open during the pre-compressor startup check, the control will go into lockout mode immediately, disabling the compressor from starting and enabling the alarm output (BO-6). The lockout condition can be reset by powering down the controller, by a command from the BAS, or by the holding the ESC and Return keys on the MUI for 5 seconds.
Water Coil Low Temp (Freeze Sensing) Limit (AI-5)
The water coil low temperature (freeze sensing) limit sen- sor will monitor the liquid refrigerant temperature enter- ing the water coil in the heating mode. If the temperature drops below the water coil low temperature (freeze sens- ing) limit trip point for the recognition delay period, the condition will be recognized as a fault. The water coil low temperature (freeze sensing) limit trip point will be factory set for 30°F and will be field selectable for 15°F by remov- ing a jumper wire on BI-5. The water coil low temperature (freeze sensing) limit fault condition will be bypassed 2 minutes at normal compressor startup, to allow the refrig- eration circuit to stabilize. If the water coil low temperature (freeze sensing) limit sensor becomes unreliable at any time compressor operation will immediately be suspended until the problem is corrected. This should be displayed as an alarm on the BAS and the MUI. This alarm will be reported a “Water Low Temp Limit” fault.
High Pressure (BI-11)
The high-pressure switch shall be a normally closed (NC) switch that monitors the systems refrigerant pressure. If the input senses the high-pressure switch is open it must disable the compressor output immediately and count the fault. The compressor minimum on time does not apply if the high-pressure switch opens. The compressor will not restart until the compressor short cycle time delay has been satisfied.
Low Pressure (BI-3)
The low-pressure switch shall be a normally closed (NC) switch that monitors the systems refrigerant pressure. The input shall be checked 15 seconds before compressor start up to be sure the pressure switch is closed and then ignored for the first 2 minutes after the compressor output (BO-2) is enabled. If the switch is open continuously for (30) seconds during compressor operation the compressor output (BO-2) will be disabled. The compressor will not restart until the compressor short cycle time delay has been satisfied.
Condensate Overflow
The condensate overflow sensing circuit will monitor the condensate level as a resistance input to AI-3. If the con- densate water level rises resulting in the input resistance rising above the set point for the recognition delay period, the condition will be recognized as a fault. The condensate will be subjected to a (30) second lockout delay which requires that the fault be sensed for a continuous (30) seconds before suspending unit operation.
Alarm Output (BO-6)
The alarm output will be enabled when the control is in the lockout mode and will be disabled when the lockout is reset.
Test Mode
Raising the zone temperature input (AI-1) reading to 180–220°F or by holding the ESC and down arrow keys on the MUI for 5 seconds will put the control into test mode. In test mode the random start delay and the compressor fixed on delay time will both be shortened to 5 seconds and the reversing valve will be allowed to cycle with out shutting down the compressor. If an MUI is connected to the control LED 8 will flash and the words “Test Mode En- abled” will be shown on the LCD display when the control is in test mode. Test mode will be disabled after a power cycle, 30 minute timeout, or by holding the ESC and Up arrow keys on the MUI.
Sequence of Operation
Power Fail Restart
When the controller is first powered up, the outputs will be disabled for a random start delay. The delay is provided to prevent simultaneous starting of multiple heat pumps. Once the timer expires, the controller will operate normally.
