McQuay MicroTech 2000

The MicroTech 2000™ Water Source Heat Pump (WSHP) unit controller is a preprogrammed microprocessor designed to monitor and control McQuay and AAF water source heat pumps. It manages the unit's operating mode, monitors water and air temperatures, and indicates fault conditions. The controller is factory programmed, wired, and tested for effective operation.

Function Description:

The controller provides comprehensive control over WSHP units, including heating and cooling operations based on room sensor input. It continuously monitors all equipment protection controls, fan and compressor operation, discharge air temperature, and leaving water temperature. The system also tracks the status of all vital unit functions and offers optional control outputs.

The MicroTech 2000 WSHP controller utilizes LONWORKS® technology, with two application software versions: LONMARK® 3.3 certified application code (current standard for new applications, including standalone units or those integrated into a LONWORKS communication network) and LonTalk® application code (for existing systems with a MicroTech Communications Gateway (MCG) or MCG for Open Protocol (MCGOP) panel). The LONMARK code has a software identification of WHPE2E or higher.

Important Technical Specifications:

Operating Temperature: 32°F to 140°F (0°C to 60°C).
Storage Temperature: 40°F to 176°F (40°C to 80°C).
Relative Humidity: Up to 95% (noncondensing) for both operation and storage.
Analog Inputs: Six standard analog inputs, capable of sensing temperatures from 0°F to 158°F (-18°C to 70°C). These include discharge air temperature, leaving water temperature, condensate overflow, brownout (supply voltage), room air temperature, and tenant override/set point adjust sensors.
Digital Inputs: Four standard digital inputs, sensing the presence or absence of an external 24 VAC ± 20% power source with a minimum of 10 mA AC current. These include refrigerant high pressure (N/C), refrigerant low pressure (N/C), refrigerant low temp (N/C), and remote start/stop (N/O) switches. Digital input conditioning includes RC filtering with a time constant of at least 4.7 milliseconds.
Digital Outputs: All digital outputs, except for the on-board and off-board status LEDs, can control electromechanical or solid-state relays. They switch inductive loads at 24 VAC ± 20%, 0.4 pF, and at steady-state AC RMS currents. Outputs include fan contactor, compressor contactor, reversing valve solenoid, on-board status LED (yellow), off-board status LED (DC-sourced signal, current limited to 10 mA-DC), and multi-purpose (spare) isolated E/M contacts.
Power Supply: Requires a 24 VAC power supply, connected to terminals J41 and J42.
Compressor Short Cycle Protection: Minimum 2 minutes on-time, 5 minutes off-time.
Random Start Delay: 5 to 37 seconds, determined by the Neuron chip ID.
Delayed Reversing Valve De-energization: Approximately 10 seconds delay after compressor re-energization in heating mode.
Brownout Protection: Detects supply voltage below 82% of nameplate value, de-energizes compressor. Resets when voltage is above 90% for 1 second.
High Pressure Refrigerant Alarm: Triggered by high pressure switch opening (395 ± 10 psig), closes at 250 ± 25 psig. Manual reset.
Low Temperature Refrigerant Alarm: Triggered by low temperature switch opening. Manual reset.
Low Pressure Refrigerant Alarm: Triggered by low pressure switch opening (7 ± 3 psig), closes at 22 ± 7 psig. Manual reset.
Condensate Overflow Alarm: Triggered by condensate overflow sensor sensing a grounded signal (conductivity trip point: 2.5 micro ohms). Manual reset.
Change Filter Notification: Network-adjustable set point for fan run time.

Usage Features:

Operating Modes: Supports Occupied, Unoccupied, and Holding modes.
Tenant Override Mode: A wall-mounted switch allows temporary override to occupied mode for a set time (default 60 minutes). Pressing the button for 1.0 to 6.0 seconds activates override. A second press for 1.0 to 6.0 seconds returns to unoccupied mode.
Remote Room Set Point Adjustment: Potentiometer on wall sensor packages allows adjustment of room set point by ±3°F (1.7°C).
Configurable Relay Outputs: One relay output can be configured for:
- Boilerless system/auxiliary heat relay (LONWORKS or LONMARK): Provides output to electric heat or energizes when space temperature reaches heating set point.
- Motorized water valve relay: Shuts off water when compressor is not operating.
- Fresh air damper relay: Opens damper when fan is operating in occupied cycle.
- Timed output relay (LONWORKS only): Controls an auxiliary load based on a specific time schedule.
Network Communication: Allows control sequencing, stop/start, equipment protection monitoring, and fault resets via a network connection. Provides access to various unit parameters like temperatures, compressor/fan status, set points, and run hours.
Optimal Start (LONWORKS only): Calculates optimal time to switch from unoccupied to occupied operation to reach set point by scheduled time.
Load Shed Mode (LONWORKS only): Activates when network load shed level meets threshold, adjusting set points based on network threshold and step value.
Unit Identification (Wink) Command: Allows verification of an individual unit network address by causing the status LED to flash (on 0.5 sec, off 0.5 sec for 15 seconds) and the fan to cycle (off for 5 sec, on for 5 sec, off for 5 sec).
Wall-Mounted Sensor Packages: Optional packages include a remote status LED and tenant override button, with optional set point adjustment and thermometer.

Maintenance Features:

Diagnostic LEDs:
- Yellow Status LED: Indicates operating mode (e.g., Occupied, Unoccupied, Tenant Override) and alarm conditions (e.g., Condensate Overflow, Brownout, Compressor Fault). Flashes constantly during a fault (on 0.1 sec, off 0.1 sec).
- Red Service LED: Indicates Neuron chip status (e.g., Normal, No application/damaged, Unconfigured).
Service Pin: Button to broadcast the Neuron chip's unique 48-bit ID over the LONWORKS network for commissioning.
Fault Monitoring and Control: The controller monitors for specific alarm conditions and executes appropriate control actions. Faults are prioritized, with higher priority faults requiring manual clearing before lower priority faults are indicated.
Clearing Faults: Auto-reset faults clear when conditions disappear. Manual-reset faults require cycling power to the controller. Investigation and elimination of the fault cause are required before returning to service.
Troubleshooting Procedures: Detailed procedures for diagnosing:
- Microprocessor problems (using status LED).
- Power supply problems (checking 24 VAC at transformer secondary).
- Erroneous temperature readings (measuring sensor resistance and comparing to thermistor chart).
- Digital input faults (checking voltage, wiring, and switch contacts).
- Brownout faults (measuring voltage at terminals J41 and J42).
WSHP Controller Replacement: Requires providing full model number, serial number, date code, and software version to the factory for loading unit-specific software onto a replacement controller.