Honeywell T451 User Manual

95C-10903-1
T451, T651
Motor-Rated Precision Thermostats
PRODUCT DATA
The T651 thermostat provides direct, accurate line voltage
control of inductively-rated heating, ventilating, or cooling
equipment used in commercial or industrial environments.
The T451 provides precision line voltage control of motor-
rated electric, gas or oil heating equipment.
APPLICATION
FEATURES
• Deluxe styling for commercial buildings.
• Industrial grade MICRO SWITCH™ mechanism
rated 1/2 hp inductive, 5 kW resistive.
• Vertical mounting on 2” x 4” NEMA-standard
single-gang outlet box.
• High-sensitivity, vapor-filled stainless steel dual
diaphragm sensing element.
• Engineering plastic base to isolate sensor from
switch heat and minimize droop.
• CSA Certified, UL Listed.
• Altitude compensation.
• 44°F (7°C) “frost protection” setting for heating
application, independent of calibration or altitude.
• Color-coded leadwire connections.
• Range stops/locking cover security features for
public areas.
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Ordering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Installation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Setting and Adjustment. . . . . . . . . . . . . . . . . . . . . . . . . . 4
Contents
CL 4-01 • © Honeywell Limited/Limitée 2001

Honeywell T451 Specifications

General

Brand	Honeywell
Model	T451
Category	Thermostat
Language	English

Summary

Product Overview and Features

Key Product Features

Details deluxe styling, industrial grade mechanism, NEMA mounting, high-sensitivity sensing element, and frost protection.

Product Application

Describes use for line voltage control of heating, ventilating, or cooling equipment in commercial/industrial settings.

Product Specifications and Ordering

Performance Specifications

Covers control range, differential, droop, barometer sensitivity, and electrical ratings for various voltages.

Physical and Installation Details

Includes finish options, mounting requirements, wiring connections, and product approvals (CSA, UL).

Available Accessories

Lists optional items like range stops, cover locking assembly, wallplates, and thermostat guards.

Ordering Information Guidance

Provides instructions on how to order replacement or modernization products and contact customer support.

Installation Instructions

General Installation Precautions

Emphasizes reading instructions, checking ratings, installer qualifications, and wiring safety (line voltage).

Wiring Connections Diagram

Illustrates wiring configurations for T451A, T451B, and T651A models in heat-only and heat-cool applications.

New Installation Procedure

Details mounting height, placement for accurate sensing, and wire connection steps using approved connectors.

Replacement Installation Steps

Guides on disconnecting power, removing old units, checking wire insulation, and completing installation.

Operational Checks and Adjustments

Thermostat Check Out Procedure

Instructs on verifying heating/cooling operation after installation and thermal stabilization.

Altitude Compensation Guidance

Explains factory calibration at 500 feet and how altitude affects control point, with correction actions.

Recalibration Process

Details steps to recalibrate the thermostat by adjusting the setpoint knob for temperature errors.

Security Features: Range Stops

Explains how to install plastic dowels for limiting the temperature range and checking operation.

Security Features: Locking Cover

Describes installing a Tinnerman Speed Nut and Allen screw to secure the thermostat cover for protection.