Honeywell Multizone Control System

System Overview

The Honeywell W7080A Multizone Control System is a solid-state system designed for component-for-component field replacement of the Ranco EA3 Lodapt System. It offers control for up to 12 zone dampers, 3 heating stages, 3 cooling stages, an integrated economizer, and modulating valves for hot water and chilled water. Optional units can expand control to 12 additional zones, 5 stages of electric heat, Variable Air Volume (VAV) system fan, and a 4th stage of cooling.

The system is designed to provide precise temperature control and energy efficiency in multizone HVAC applications. Key components include the W7080A Load Analyzer, W7081A Limit Controller, W7082A Load Integrator, W7083A Electric Heat Sequencer, W7084A Zone Adder, and various sensors and thermostats.

Key Components and Features

• W7080A Load Analyzer: Provides SPDT relay switching for heating and cooling stages and a modulating output for economizer and valve motors based on zone demands. It also supplies 24 Vdc power to zone thermostats and sensors.
• W7081A Limit Controller: Manages economizer control and limits for hot and cold decks, as well as mixed air, by supplying modified demand signals to the W7080A.
• W7082A Load Integrator: Controls VAV system fan speed in response to zone demand, reducing fan speed as demand decreases to conserve energy.
• W7083A Electric Heat Sequencer: Sequentially switches up to 5 stages of electric heat, with optional stage turn-on delay.
• W7084A Zone Adder: Allows expansion of the system to control more than 12 zones by monitoring signals from additional zones and supplying the highest and lowest to the W7080A.
• Sensors (e.g., C7100B, C7046B): Provide temperature and enthalpy inputs for accurate system control.
• Thermostats (e.g., T7080A/B): Control individual zone temperature and provide demand signals to the Load Analyzer.
• Motors (e.g., M734J, M745K/L/P): Used for modulating damper and valve control.
• 195325B 4th Stage Cooling Board: Adds a fourth stage of cooling to the system.

Technical Specifications

Electrical Ratings: Voltage and Frequency: 24 Vac, 50/60 Hz. Power consumption varies by component.

Relay Contact Ratings: SPDT pilot duty relays with specific voltage and VA ratings for both inrush and running conditions.

System Input Signals: Various Vdc signals from thermostats and sensors are used to control system operation.

System Output Signals: Vdc signals are provided to control motors, sequencers, and other components.

Temperature Limits: Selectable set points for cold deck low limit (45, 50, 55 F), hot deck high limit (90, 110, 130 F), and economizer mixed air limit (50, 55, 60 F).

Thermostat Deadband: Adjustable from 3 F to 30 F.

Ambient Temperature Range: Operating: -40 F to +150 F; Shipping: -30 F to +150 F.

Installation and Wiring

Installation requires careful attention to wiring diagrams and component connections. Key considerations include:

• Disconnecting power before wiring to prevent electrical shock.
• Ensuring proper wiring between Honeywell and Ranco components, noting terminal designation differences.
• Using appropriate transformers for motor isolation. Never ground transformer secondaries.
• Mounting units securely in locations protected from weather and extreme temperatures.

Wiring diagrams (Fig. 3A and 3B) illustrate typical system configurations, including those with night setback and economizer control.

Operation

The system operates based on signals from zone thermostats and sensors, modulating dampers and controlling heating/cooling stages to maintain desired zone temperatures. The Load Analyzer selects the highest and lowest zone demand signals, which are then processed by the Limit Controller and other components to manage system operation.

Economizer Operation: Initiated on a call for cooling, controlled by mixed air temperature and enthalpy inputs.

Modulating Heat and Cool Outputs: Motors control valves or dampers based on Vdc signals from the system.

Night Setback: Allows for reduced heating or cooling during unoccupied periods, typically controlled by a time clock and resistors.

Checkout Procedures

Detailed checkout procedures are provided for verifying system operation and component functionality. This includes checking system control voltages, thermostat outputs, and the performance of individual components like the Load Analyzer, Limit Controller, and Zone Adder using a simulator (S7080A).

Ranco Cross-Reference

Table 1 provides a cross-reference between Ranco and Honeywell components, facilitating system modernization and replacement.

Safety and Compliance

The system components are recognized by Underwriters Laboratories Inc. (File No. SA481, Guide No. SDFY2D for specific units). Compliance with ASHRAE 90-75 and U.S. Department of Defense guidelines is noted.