Honeywell ML7421A User Manual

PRODUCT DATA
® U.S. Registered Trademark
Copyright © 1996 Honeywell Inc. • All Rights Reserved
X-XX UL 63-2517-1
ML7421A,B
Electric Linear Valve Actuator
APPLICATION
The ML7421A,B Electric Linear Valve Actuators are
modulating control motors for use with low-voltage controls
that provide an analog output of 0 to 10 Vdc or 2 to 10 Vdc.
These actuators operate standard Honeywell valves in
heating, ventilating, and air conditioning (HVAC) applications.
FEATURES
• Quick and easy installation.
• No separate linkage required.
• 3/4 in. (20 mm) stroke on ML7421A;
1-1/2 in. (38 mm) stroke on ML7421B.
• No adjustments required.
• Accurate valve positioning.
• Low power consumption.
• High close-off ratings.
• Force-limiting end switches.
• Manual operator.
• Synchronous motor.
• Corrosion-resistant design.
• Maintenance free.
• Conduit connector knockout.
Contents
Application .......................................................................... 1
Features .............................................................................. 1
Specifications ...................................................................... 2
Ordering Information ........................................................... 2
Installation ........................................................................... 3
Operation ............................................................................ 6
Checkout ............................................................................. 7

Honeywell ML7421A Specifications

General

Type	Electric Actuator
Control Signal	2-10 VDC or 4-20 mA
Fail-Safe Mode	Spring Return
Number of Outputs	1
Mounting Type	Direct Mounting
Input Voltage	24 VAC/VDC
Operating Temperature Range	-20°C to +60°C
Input Signal	Voltage
Stroke	90 degrees

Summary

Application

Features

Specifications

Ordering Information

Installation

Location

Specifies the recommended placement of the actuator for optimal installation and servicing.

Mounting

Details the procedure for physically attaching the actuator to the valve collar using set screws.

Wiring

Provides instructions and diagrams for connecting power and control signals to the actuator terminals.

Operation

General

Explains the basic mechanical principle of converting motor rotation to linear stem motion using a worm gear.

Manual Operation

Describes how to operate the valve manually using the built-in knob, including safety precautions.

Signal Input Failure

Outlines how to configure the actuator's behavior during control signal loss using coding switches.

Actuator Override

Explains how to force the actuator to a specific position, bypassing the normal control signal, for applications like freeze protection.

Direction of Action

Details how to change the actuator's response to the control signal (extend/retract) using a selector switch or signal reversal.

Checkout

Direct Checkout

Describes how to test the actuator's functionality directly without a controller, verifying valve position and signal application.

Controller Checkout

Explains how to verify actuator operation when connected to a controller, checking setpoint response and wiring.