Honeywell W7100 - User Manual

The Honeywell W7100G Discharge Water Temperature Control is a microprocessor-based device designed to maintain an average discharge water temperature for reciprocating chiller applications. It achieves this by staging on and off compressors or unloaders as required. The W7100G can manage up to six stages of cooling independently and can be expanded to control up to ten stages when used with a W7101A Satellite Sequencer.

Function Description:

The W7100G utilizes an advanced proportional-plus-integral (PI) microprocessor control algorithm to minimize temperature droop, ensuring precise and stable temperature control. It employs an integrating control band concept, which matches the required operating capacity to the chiller load and minimizes offset from the control setpoint. This control band is adjustable from 0 to 10°F (0 to 6°C) and is centered on the discharge water setpoint, allowing for stabilization of system operation.

The controller features a soft start function to reduce compressor cycling during system startup. It also offers adjustable minimum on/off timing and time delay between stages, configurable for either 30 or 60 seconds. These timings are crucial for protecting compressors from damage due to short cycling.

The W7100G's setpoint is adjustable from 10 to 110°F (-12 to 43°C). It supports a reset function for the discharge water temperature setpoint, which can be based on either space or outdoor air temperatures. This reset function, adjustable from 5 to 20°F (3 to 11K), helps save energy under lighter loading conditions by adjusting the setpoint upward as average space temperature drops or downward as outdoor air temperature rises. For space reset, multiple sensors (e.g., T7047C1025) can be used to measure average space temperature, with the reset potentiometer set at the lowest desired cooling temperature. Outdoor air reset (using a C7031G1016 sensor) adjusts the setpoint based on outdoor air temperature, with modifications possible using series and parallel resistors to define T-High (no reset) and T-Low (full reset) points.

The number of controlled stages is determined by a fixed resistor value placed across terminals 7 and 8 on the W7100G. This resistor informs the controller of the total number of cooling stages to be managed, influencing its control behavior. LED indicators on the W7100G light up simultaneously with the energization of each stage relay, providing visual feedback on system operation.

Important Technical Specifications:

Input Voltage and Frequency: 20 to 30 Vac at 60 Hz; 20 to 26.4 Vac at 50 Hz.
Power Consumption: Device: 12 VA at 24 Vac and 50 to 60 Hz. On/Off Stages (Cool 1-6) vary from 40 VA to 750 VA inrush and 30 VA to 75 VA running, depending on voltage (24 Vac or 120/240 Vac) and contact type (N.O. or N.C.).
Switching: SPDT relays.
Wiring Terminals: 1/4 inch quick-connect.
Sensor Input Signal: Positive temperature coefficient, 4.8 ohms/°F (2.6 ohms/°C). Resistance: 3484 ohms at 77°F (25°C). The C7170A1010 Discharge Water Sensor is used for water temperature sensing.
Temperature Ratings: Ambient: -40°F to +150°F (-40°C to +66°C). Shipping: -30°F to +150°F (-34°C to +66°C).
Humidity Rating: 5 to 90 percent RH noncondensing.
Mounting: Four mounting holes in base for No. 6 screws.
Approvals: Underwriter's Laboratories Inc. Component Recognized.
Additional System Components: Requires a 24 Vac transformer (sized to system load). Can be expanded with a W7101A Satellite Sequencer for up to 10 stages. Supports T7047C1025 Remote Temperature Sensors, S96381037 Reset Setpoint Potentiometers, and C7031G1016 Outdoor Air Sensors. Immersion wells (121371A Copper or 121371E Stainless Steel) and heat conduction compound (107406) are required for the C7170A sensor.

Usage Features:

Adjustable Setpoint: Allows precise control of discharge water temperature.
Adjustable Reset Differential: Fine-tunes the energy-saving reset function.
Adjustable Control Band: Modifies the controller's response speed and temperature deviation. A narrower band provides faster response and less deviation but risks hunting; a wider band slows response but increases stability.
Fast Response Input: Jumpering terminals 9 and 10 selects 30-second minimum on/off and inter-stage delays; leaving them open selects 60-second delays. This feature is critical for compressor protection.
Number of Stages Configuration: A resistor across terminals 7 and 8 (from the 4074EFV Resistor Kit) configures the W7100G for the total number of cooling stages in the system (1 to 10).
Remote Setpoint Control: Can be used with remote potentiometers (S96381037) for setpoint adjustment.
Reset Options: Supports both space temperature reset (using T7047C1025 sensors) and outdoor air temperature reset (using C7031G1016 sensors) for energy optimization.
LED Indicators: Provide clear visual status of energized cooling stages.

Maintenance Features:

Troubleshooting Guide: A detailed troubleshooting table helps diagnose common issues such as discharge temperature too high, no cooling, and short cycling, providing possible causes and corrective actions.
System Checkout Procedure: A step-by-step guide is provided for field testing the system, requiring specific resistor kits (4074EDJ, 4074EFV), a digital VOM meter, and a test plug (195770A). This procedure ensures proper installation and functionality, covering checks for power, sensor input, stage energization, and setpoint adjustments.
Wiring Practices: Emphasizes keeping wiring at least one foot away from large inductive loads and using shielded cable where necessary to prevent electrical interference.
Component Recognition: Underwriter's Laboratories Inc. Component Recognized status indicates adherence to safety and performance standards.

Honeywell W7100 Specifications

General

Control Algorithm	PID, On/Off
Input Type	Thermocouple, RTD
Output Type	Relay, Voltage, Current
Communication	RS-485
Power Supply	24V AC/DC, 100-240V AC
Operating Temperature	0°C to 50°C (32°F to 122°F)