Honeywell RA889A - User Manual

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PRODUCT DATA

68- 0216- 2

® U.S. Registered Trademark

RA889A

Switching Relay

APPLICATION

The RA889A Switching Relay provides intermediate switching

of line- and low-voltage devices from a line- or low-voltage

controller and is typically applied in hydronic heating systems.

FEATURES

• High load switching capability.

• Troubleshooting LED.

• Push-to-test button.

• Replaceable transformer fuse.

• Long-life DC relay drive control technology.

• Relay for use with external 24 Vac or 24 Vdc supply,

with line-voltage control, or with internal 24V

transformer supply.

• One model replaces many Honeywell models. (See

Table 1 Replacement Cross Reference.)

Contents

Application ........................................................................ 1

Features ........................................................................... 1

Specifications ................................................................... 2

Ordering Information ........................................................ 2

Installation ........................................................................ 3

Mounting ........................................................................... 3

Wiring ............................................................................... 4

Operation .......................................................................... 4

Checkout .......................................................................... 4

Troubleshooting ............................................................... 4

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Summary

Troubleshooting

Test Button

This connection is the same as a call for heat connection between the R(T) and W(T) terminals.

Relay LED

This LED lights whenever there is 120 Vac (L1) on the N.O. terminal (when COM/N.O. relay contacts are closed).

Summary

Troubleshooting

Test Button

This connection is the same as a call for heat connection between the R(T) and W(T) terminals.

Relay LED

This LED lights whenever there is 120 Vac (L1) on the N.O. terminal (when COM/N.O. relay contacts are closed).

The RA889A Switching Relay is an essential component designed for hydronic heating systems, providing intermediate switching capabilities for both line- and low-voltage devices. It acts as a bridge between a line- or low-voltage controller and the controlled equipment, ensuring reliable operation of your heating system.

Function Description

At its core, the RA889A integrates a transformer, an Spdt (Single-Pole Double-Throw) line-voltage relay, an Spst (Single-Pole Single-Throw) low-voltage relay, and a set of wiring terminals. This comprehensive design allows it to manage various control scenarios. When line-voltage is supplied to the transformer, the relay is powered upon thermostat contact closure. This means that when your thermostat signals a need for heat, the RA889A activates, allowing the heating system to respond.

Beyond simple activation, the RA889A can also provide electrical isolation in low-voltage circuits. This is particularly useful when the relay is powered by an external 24 Vac or 24 Vdc source connected to its W(T) and C terminals. Fiber barriers are incorporated into the design to maintain clear separation between line- and low-voltage connections, enhancing safety and preventing interference.

The relay's primary function is to switch high loads, making it suitable for demanding applications within hydronic systems. This capability ensures that it can reliably handle the electrical requirements of various heating components.

Usage Features

The RA889A is designed with several features to enhance its usability and simplify installation and troubleshooting:

High Load Switching Capability: This relay is built to handle substantial electrical loads, making it a robust choice for controlling various components in your heating system.
Troubleshooting LED: A built-in LED provides immediate visual feedback. This LED illuminates whenever 120 Vac (L1) is present on the N.O. (Normally Open) terminal, which occurs when the COM/N.O. relay contacts are closed. This feature is invaluable for quickly diagnosing operational status and identifying potential issues.
Push-to-Test Button: For quick and easy testing, the RA889A includes a push-to-test button. This button simulates a call for heat, effectively mimicking a connection between the R(T) and W(T) terminals. This allows installers and service technicians to verify the relay's functionality without needing to manipulate the thermostat.
Replaceable Transformer Fuse: The secondary side of the transformer is protected by a replaceable 1A automotive fuse. This design choice simplifies maintenance, as a blown fuse can be easily replaced, minimizing downtime and protecting the transformer from overcurrent conditions.
Long-Life DC Relay Drive Control Technology: The RA889A incorporates advanced DC relay drive control technology, which contributes to the longevity and reliability of the relay. This technology ensures consistent performance over an extended operational life.
Versatile Power Supply Options: The relay can be used with various power configurations. It can operate with an external 24 Vac or 24 Vdc supply, with line-voltage control, or utilizing its internal 24V transformer supply. This flexibility makes it adaptable to different system designs and requirements.
Broad Compatibility: The RA889A is designed to replace many older Honeywell models, streamlining inventory and simplifying replacements. This "one model replaces many" approach reduces complexity for distributors and technicians.
Thermostat Compatibility: It is compatible with all Honeywell electromechanical and most other electromechanical 2- or 3-wire thermostats. For optimal performance, thermostats should be selected with a 0.12A heating anticipator setting to match the electrical rating of the switching relay.
Captivated Wire Clamp Screw Terminals: The electrical connections are made using No. 8 captivated wire clamp screw terminals. These terminals are designed to securely hold copper wires, ensuring reliable electrical connections and simplifying the wiring process.
Zinc Plated Steel Finish: The relay features a durable zinc-plated steel finish, providing protection against corrosion and contributing to the unit's overall longevity.
Conduit Knockouts: The case includes knockouts for conduit connections: three 1/2 inch (13 mm) knockouts on the bottom for conduit boxes and one 7/8 inch (22 mm) knockout on the top for wiring. These provisions facilitate neat and compliant wiring installations.

Maintenance Features

The RA889A is designed for minimal maintenance, focusing on reliability and ease of service:

Self-Cleaning Contacts: The relay contacts are engineered to close with a wiping action, making them self-cleaning. This design helps prevent the buildup of deposits that could impair performance. While the contacts may discolor over time, this is a normal occurrence and does not impede proper operation. Consequently, the contacts do not require manual cleaning.
Easy Fuse Replacement: The replaceable 1A automotive fuse for the transformer secondary simplifies troubleshooting and repair. If the transformer secondary circuit experiences an overcurrent, only the fuse needs to be replaced, rather than the entire unit or a more complex component.
Troubleshooting LED: As mentioned, the LED serves as a diagnostic tool, indicating when the N.O. terminal has 120 Vac. This allows for quick verification of the relay's switching action without needing to open the unit or use external testing equipment.
Accessible for Service: The design encourages installation in locations that are easily accessible for both installation and service. This consideration helps reduce the time and effort required for any future maintenance or inspection.
Cover for Protection: The relay cover should remain on during normal operation and only be removed for service and checkout. This protects the internal components from dust, debris, and accidental contact.

In summary, the RA889A Switching Relay is a robust, versatile, and user-friendly device engineered to provide reliable control in hydronic heating systems. Its thoughtful design, incorporating features for easy installation, troubleshooting, and minimal maintenance, makes it a valuable component for both new installations and system modernizations.

Honeywell RA889A Specifications

General

Voltage Rating	120 VAC
Frequency	60 Hz
Current Rating	10 A
Contact Configuration	SPDT
Contact Ratings	10 A at 120 VAC
Operating Temperature	-40 to 150°F (-40 to 66°C)