Honeywell T775A/B/M Series 2000 Electronic Stand-Alone Controllers

Product Description

The T775 electronic stand-alone controllers are designed for commercial and agricultural applications, offering remote temperature sensing and switched or proportional outputs for various loads. Five models feature analog (modulating) outputs for actuator and motor control, with NEMA-4 weatherproof enclosures available for demanding environments.

IMPORTANT: Each T775A/B/M controller functions as an operating control, not a limit or safety control. A separate safety or limit control device is required for applications necessitating such functions.

Controller Configurations

Table 1 details the T775A/B/M controller configurations, including model numbers, descriptions, replacements, relay outputs (SPDT, Modulating, Floating), sensor inputs, and enclosure types.

^a All models include a digital input for use with the disable or setback option.
^b The modulating (analog) outputs are 4-20 mA, 0-10 Vdc, 2-10 Vdc, or Series 90 selectable.
^c Each floating output eliminates two SPDT relays.
^d These models can support a high/low modulating limit at Sensor B for temperature control at Sensor A.

Temperature Sensors

The controller accepts 1,097 Ohms PTC at 77°F (25°C) sensors. Available sensors include:

• 50021579-001 – Standard sensor (included with all models except NEMA 4X)
• T775-SENS-STRAP – Strap-on sensor with wiring box
• T775-SENS-WR – Water-resistant with 5-foot leads (included with NEMA 4X models)
• T775-SENS-WT – Watertight with 6-foot lead
• T775-SENS-OAT – Outdoor air temperature sensor
• C7031B2005 – 6-inch duct mount with wiring box
• C7031D2003 – 5-inch immersion sensor with wiring box (requires immersion well P/N 50001774-001)
• C7031J2009 – 12-foot duct averaging sensor with wiring box
• C7046D1008 – 8-inch duct probe with mounting flange
• C7100D1001 – 12-inch fast response, duct averaging sensor with flange
• C7130B1009 – Room mount sensor

Refer to form 62-0265 for detailed information on T775 Series 2000 Stand-alone Controller Temperature Sensors.

Accessories

• 107324A – Bulb Holder, duct insertion
• 107408 – Heat Conductive Compound, 4 ounce
• 50001774-001 – Immersion Well, stainless steel 304, 1/2 in. threading

Product Changes

Changes introduced in Series 3 (March 2009) include:

• Modulating high and low limits now function in both heat and cool modes.
• MIN ON feature added.
• SYNC feature added.
• Differential and throttling range increased to 300°F.
• Setpoint and Enable options added to DI options.
• HIDE option added to MOD1 and MOD2 for home screen display.

Controller Dimensions

Diagrams show the controller dimensions in inches (mm) for Top, Bottom, Left, Right, and Front views.

Before Installation

Review the "SPECIFICATIONS" on page 35 before installation. Follow these instructions carefully to prevent product damage or hazardous conditions. Ensure the product's ratings are suitable for the application. Installation should be performed by a trained service technician. Verify product operation after installation.

Installation and Setup Overview

The installation process typically involves the following steps:

1. Mounting the controller and temperature sensor(s).
2. Wiring the controller.
3. Performing checkout procedures.
4. Programming the controller.
5. Setting up scheduling (optional).

Additional topics include temperature sensor calibration, interface overview, advanced setup options, summary menu, and troubleshooting.

Mounting

Controller Mounting

The controller can be mounted in any orientation. Mounting as shown in Fig. 1 (page 2) allows for optimal LCD display and keypad visibility.

NEMA 4 Enclosure Mounting

For NEMA 4 enclosures, use waterproof wire/conduit fittings at knockouts. Ensure all unused knockouts are sealed.

Temperature Sensor Mounting and Location

Sensors can be located up to 1,000 feet (304 m) from the controller. Mounting options include wall/panel sensing, pipe strapping, or immersion wells for water sensing. For duct sensing, sensors can be taped to a cap or bulb holder. Mount sensors with lead wires exiting downwards to prevent moisture ingress.

IMPORTANT: Avoid mounting in areas with corrosive fumes or explosive vapors. Ensure adequate clearance for wiring, servicing, and removal.

Use a screwdriver to remove knockouts as needed. For DIN rail mounting, remove knockouts first. Mount the controller using the four provided mounting holes with #6 or #8 screws.

Wiring

All wiring must comply with applicable electrical codes. Controller wiring connects to internal screw terminal blocks.

Wiring Connections Access

Access wiring connections by removing two screws on the left side of the enclosure and gently opening the top. Be careful not to stress ribbon cables.

Temperature Sensor Wiring

CAUTION: Prevent short circuits. Ensure sensor metal tubes do not contact terminals.

IMPORTANT: Avoid routing sensor wiring near power wiring, contactors, electrical motors, or welding equipment. Ensure good mechanical connections. Do not mount sensors with lead wire ends pointing upwards where condensation may occur. Use shielded cable if these conditions cannot be avoided.

NOTE: While each controller requires its own sensor(s), the T775 offers accuracy with minimal differential (±2°F / ±7°C) between controllers.

Multiple Parallel Sensors

For sensing average temperatures in large spaces, multiple sensors can be wired in parallel-series. The number of sensors must follow an n² pattern (e.g., 4, 9, 16) for optimal accuracy. Refer to Fig. 3 for wiring details.

Temperature Sensor Wire Type and Size

Use standard AWG 18/2 unshielded wire for sensors. Shielded cable is recommended for runs over 25 feet or in areas with electrical interference. Refer to page 11 for wire size selection based on cable length.

Controller Wiring

WARNING: Disconnect power before wiring to prevent electrical shock or equipment damage.

CAUTION: Do not use 24 Vac power for external loads if 120 Vac or 240 Vac powers the controller. Ensure a separate earth ground connection.

CAUTION: Handle the unit carefully to prevent electrostatic discharge damage.

Wiring methods involve connecting sensors and outputs first, then power. Terminals accommodate 14-22 AWG wire. For 24, 120, or 240 Vac power, use 14-18 AWG wire. Wire preparation involves stripping insulation, twisting multiple wires if necessary, and ensuring secure connections.

Figure 5 illustrates proper earth ground connection. Figure 6 details attaching multiple wires to terminal blocks.

Controller Wiring Details

Figure 7 shows terminal and feature locations. Table 2 describes wiring terminal connections for sensors, inputs, power, and outputs. Wiring applications are illustrated in Figures 8-22, covering various control scenarios such as two-stage, four-stage, modulating outputs (ML7984, Modutrol motors), and digital inputs.

Checkout

Inspect all wiring connections and verify compliance with wiring diagrams. After installation and wiring, apply power. Pay close attention to power connections (24, 120, or 240 Vac).

Power Loss

Date and time settings are retained for 24 hours after a power outage. Settings beyond 24 hours may require re-entry. All other settings are permanent.

Temperature Sensor Calibration

Wire length affects resistance and temperature readings. Calibration can be done by adjusting the value to compensate for wire loss. Table 3 provides temperature offsets based on wire gauge and length. If the required calibration offset exceeds the controller's limits (±10°F / ±6°C), use heavier gauge wire. Refer to page 18 for calibration instructions.

Figure 23 illustrates the relationship between sensor resistance and temperature.

Interface Overview

The controller features an LCD panel and a 6-button keypad for status display and user input. The interface includes a Menu Area, Data Area, and Lock Icon. Navigation is done via the keypad buttons (HOME, MENU, Left/Right Arrows, Up/Down Arrows).

Home Screen: Displays current temperatures, modulating output status, active relays, and error codes. Active relays are indicated by a black square. Pressing arrow buttons cycles through related information.

Menu Navigation: MENU button accesses Program menu. Holding MENU for five seconds accesses Setup menu. Arrow buttons navigate menus and adjust values.

Programming

The controller requires programming before service. Programming uses a hierarchical menu structure. Key parameters include Setpoint, Differential/Throttling Range, Sensor selection, Heat/Cool mode, and Setback temperature.

Setpoint and Differential

Heating Mode: Differential is below the setpoint. Relay de-energizes when temperature rises to setpoint; energizes when it drops to setpoint minus differential.

Cooling Mode: Differential is above the setpoint. Relay de-energizes when temperature falls to setpoint; energizes when it rises to setpoint plus differential.

Setpoint High Limit

A single, irreversible maximum setpoint value can be set for all outputs by simultaneously pressing HOME, , and for five seconds. This action cannot be undone.

Programming Procedure

Enter Program mode via the MENU button, then select PROGRAM. Configure outputs by selecting parameters like SETPOINT, DIFFRNTL (or THROT RNG for modulating outputs), SENSOR, HEAT/COOL, and SETBACK.

Setup (Advanced Options)

The Setup menu allows modification of factory defaults for sensors, outputs, reset control, and scheduling. Navigation follows a hierarchical menu structure similar to programming.

Entering Setup Mode

Press and hold the MENU button for five seconds.

Setting up the Sensors

Configure the number of sensors (1 or 2), units (°F or °C), calibration values, and labels for Sensor A and Sensor B (if applicable). Sensor B settings may include LIMIT and THROTTLING RANGE for modulating models.

Setting up the Outputs

Configure Modulating Outputs (TYPE, MIN OUT %, INTEGRAL, DERIVATIVE, SCHEDULE, HIDE) and Relay Outputs (TYPE, SCHEDULE, RESET RT). Floating relay options are available for specific models.

Scheduling

Scheduling enables setting daily temperature settings for up to two events per day (daytime setpoint and nighttime setback). Scheduling must be enabled in Setup (USE SCHED = YES).

Creating a Schedule

Enable scheduling in Setup, enter Schedule mode, set Schedule Options (SET TIME, SET DATE, DAYLIGHT), and then set Individual Schedules for different time periods (e.g., Mon-Fri, Sat-Sun).

The Summary menu allows viewing the configured schedule times and temperatures for each day.

Troubleshooting

Power Loss

Date and time settings are retained for 24 hours. Longer power outages may require re-entry of these settings.

Errors and Diagnostics

Error Message: EEPROM Failure indicates a hardware issue and requires device replacement.

Diagnostic Messages:

• Sensor Open or Shorted (--) indicates a sensor issue (open circuit >1570 ohms, short circuit <770 ohms) or a disconnected sensor. Control stages cease operation.
• Temperature Out of Range (-60° or 270°F / -51° or 132°C Blinking) indicates the sensed temperature is outside the displayable range but control continues within limits.

Blinking Relay Status: A blinking relay indicator () signifies that the Minimum Off Time is active for that relay.

Specifications

Power: 24, 120, or 240 Vac; 50/60 Hz. Requires separate earth ground.

Power Consumption: 8 VA max (60 Hz), 10 VA max (50 Hz).

Temperature/Humidity: Operating range -40° to 140°F (-40° to 60°C). Humidity 5% to 95% non-condensing.

Relay Contact Output Ratings: Various ratings for N.O. and N.C. contacts, including horsepower, VA pilot duty, and amperage ratings.

Modulating Outputs: Support 0-10 Vdc, 2-10 Vdc, 4-20 mA, Electronic Series 90, and Floating outputs.

Emissions Compliance: EN 55022, CISPR 22, VCCI, ICES-003, FCC Part 15 Subpart B Class B.

Immunity Compliance: EN 61000-6-1 standards.

Safety Compliance: UL 60730-1 for US and Canada.

FCC Compliance Statement: Complies with Part 15 of FCC rules for Class B digital devices, designed to provide reasonable interference protection.

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