Carrier 48/50AJ specifications

compressor is brought on and 5 seconds afterwards. The rate of suction pressure change from 5 seconds before the compressor is brought on to when the compressor is brought on is calculat- ed. Then the rate of suction pressure change from when the compressor is brought on to 5 seconds afterwards is calculated.

With the above information, the test for reverse rotation is made. If the suction pressure change 5 seconds after compres- sion is greater than the suction pressure change 5 seconds be- fore compression – 1.25, then there is a reverse rotation error.

This alarm will disable mechanical cooling and will require a manual reset. This alarm may be disabled once the reverse rotation check has been verified by setting Configuration→ COOL→REV.R = Yes.

A150 (Unit is in Emergency Stop) — If the fire safety input condition occurs to indicate a fire or smoke condition, then Alarm code 150 will occur and the unit will be immediately stopped. Through separate inputs the unit can be put into purge, evacuation, and pressurization. This requires a manual reset.

If the CCN point name “EMSTOP” in the System table is set to emergency stop, the unit will shut down immediately and broadcast an alarm back to the CCN indicating that the unit is down. This alarm will clear when the variable is set back to “enable.”

T153 (Real Time Clock Hardware Failure) — A problem has been detected with the real timeclock on the MBB. Try reset- ting the power and check the indicator lights. If the alert contin- ues, the board should be replaced.

A154 (Serial EEPROM Hardware Failure) — A problem has been detected with the EEPROM on the MBB. Try resetting the power and check the indicator lights. If the alarm continues, the board should be replaced.

T155 (Serial EEPROM Storage Failure Error) — A problem has been detected with the EEPROM storage on the MBB. Try resetting the power and check the indicator lights. If the alert continues, the board should be replaced.

A156 (Critical Serial EEPROM Storage Failure Error) — A problem has been detected with the EEPROM storage on the MBB. Try resetting the power and check the indicator lights. If the alarm continues, the board should be replaced.

A157 (A/D Hardware Failure) — A problem has been detected with A/D conversion on the boards. Try resetting the power and check the indicator lights. If the alarm continues, the board should be replaced.

A171 (Staged Gas Control Board Comm Failure) — This alarm indicates that there are communications problems with the staged gas heat control board, which is located in the gas section on units equipped with staged gas heat. If this alarm occurs, the staged gas heat will be disabled. The alarm will automatically reset.

A172 (Controls Expansion Module Comm Failure) — This alarm indicates that there are communications problems with the controls expansion board. All functions performed by the CEM will stop, which can include demand limit, reset, fire control modes, and the fan status switch. The alarm will auto- matically reset.

A173 (ECB1 Board Communication Failure) — This alarm indicates that there are communications problems with the economizer control board. This will result in the economizer and the power exhaust not working and the dampers to be fully closed. The exhaust fans will stop. The alarm will automati- cally reset.

A174 (ECB2 Board Communication Failure) — This alarm indicates that there are communications problems with the ECB2 which controls the VAV unit indoor fan inverter speed and hot gas bypass on CV and VAV units. Because the control of the fan is critical to unit operation, the unit will be stopped. The alarm will automatically reset.

T177 (4-20 mA Demand Limit Failure) — This alert indi- cates a problem with the optional remote 4 to 20 mA demand limit signal (Inputs→4-20→DLM.M) that is connected to the CEM module (if the signal reads less than 2 mA). If this occurs, then demand limiting will be disabled. The unit must be configured for 4 to 20 mA Demand Limiting using the

Demand Limit Select (Configuration→DMD.L→DM.L.S).

T178 (4-20 mA Static Pressure Reset/VFD Failure) — If this transducer fails (if the signal reads less than 2 mA on the input of the CEM module), and the unit is configured to perform static pressure reset or remote control of the supply fan VFD with this transducer, no static pressure reset or VFD control will be performed and an alert will be generated. Recovery is automatic. Reason for error is either a faulty sensor, wiring error, or damaged input on the CEM control board.

A200 (Linkage Timeout Error — Comm Failure) — If link- age is established via the CCN with ComfortID™ terminals, a 5-minute timeout on loss of communication will be monitored. If 5 minutes expires since the last communication from a VAV Linkage Master, the unit will remove the link and flag the alert. When the rooftop looses its link, the temperature and set points are derived locally. Recovery is automatic on re-establishment of communications. Reason for failure may be wiring error, too much bus activity, or damaged 485 drivers.

T210 (Building Pressure Transducer Failure) — The building pressure transducer (Pressures→AIR.P→BP) fails if the signal from the 4 to 20 mA building pressure transducer (used to control the power exhaust fans and the building pressure) is below 2 mA. If the alert occurs, then the economizer will be closed and the power exhaust fans turned off. This alert will automatically reset. Check the building pressure transducer and sensor tubing. The sensor is located in the auxiliary control box. The alert will automatically reset.

T211 (Static Pressure Transducer Failure) — The static pres- sure transducer (Pressures→AIR.P→SP) fails if the signal from the 4 to 20 mA static pressure transducer (used to control the VFD speed) is below 2 mA. This failure will cause the unit to stop due to the potential damage that could occur due to over-pressurization. Check the pressure transducer and sensor tubing. The sensor is located in the auxiliary control box. The alert will automatically reset.

T220 (Indoor Air Quality Sensor Failure) — The indoor air quality sensor (Inputs→AIR.Q→IAQ) fails if the signal from the 4 to 20 mA sensor is below 2 mA. If the indoor air quality sensor fails, demand control ventilation is not possible. The control defaults to the maximum vent position. Recovery is au- tomatic. Reason for error is either a faulty sensor, wiring error, or damaged input on the MBB control board.

T221 (Outdoor Air Quality Sensor Failure) — The indoor air quality sensor (Inputs→AIR.Q→OAQ) fails if the signal from the 4 to 20 mA sensor is below 2 mA. If the outdoor air quality sensor fails, OAQ defaults to 400 ppm and demand control ventilation will continue. Recovery is automatic. Reason for error is either a faulty sensor, wiring error, or damaged input on the CEM control board.

T229 (Economizer Minimum Position Override Input Fail- ure) — If the unit is configured to use the remote position override for the economizer and the input Econo Min. Pos. Override (Configuration→IAQ→AQ.SP→IQ.O.P) input 4 to 20 mA reading is less than 2 mA then an alert will occur and the default software minimum position will be used for the economizer. The alert will automatically reset.

T300 (Space Temperature Below Limit) — If the space tem- perature is below the configurable SPT Low Alert Limits (occupied [Configuration→ALLM→SP.L.O] for 5 minutes or unoccupied [Configuration→ALLM→SP.L.U] for 10 minutes), then an alert will be broadcast. The alert will automatically reset.

98