T651A3018 Honeywell Line Voltage Thermostat SPDT – Analog / Mechanical
The T651A3018 Honeywell Line Voltage Thermostat is a precision mechanical, analog thermostat designed for on-off control of heating and cooling systems. Its SPDT switch breaks heating and makes cooling at temperature rise, ensuring accurate control of electric heat elements, duct furnaces, and fan coil units. Built for reliability and high electrical load capacity, this thermostat is ideal for both residential and commercial applications.
✅ Key Features
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✅ SPDT switch – breaks heating and makes cooling on temperature rise
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✅ Vapor-filled dual diaphragm sensor element for high accuracy
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✅ Champagne gold faceplate with beige cover
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✅ Includes vertical scaleplate with thermometer and horizontal scaleplate without thermometer
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✅ Range stops and locking cover screws included for secure setup
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✅ Wall plate included for easy installation
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✅ Voltage compatibility: 120V, 208V, 240V, 277V
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✅ Temperature range: 44°F to 86°F, with 2°F differential
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✅ Mechanical, analog dial for precise temperature adjustment
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✅ On-off control for electric heat elements, duct furnaces, and fan coil units
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✅ High electrical ratings for resistive and motor loads
📋 Electrical Ratings
| Voltage | Resistive Amps | Full Load Amps | Locked Rotor Amps |
|---|
| 120V |
22 A |
9.8 A |
58.8 A |
| 208V |
19 A |
5.6 A |
33.6 A |
| 240V |
22 A |
4.9 A |
29.4 A |
| 277V |
19 A |
4.2 A |
25.2 A |
📋 Specifications
| Specification | Details |
|---|
| Part Number |
T651A3018 |
| Type |
Line Voltage Thermostat |
| Switch Type |
SPDT (Single Pole Double Throw) |
| Sensor |
Vapor-Filled Dual Diaphragm |
| Temperature Range |
44–86°F |
| Differential |
2°F |
| Display |
Analog / Mechanical Dial |
| Color |
Champagne Gold Faceplate with Beige Cover |
| Mounting |
Standard Vertical or Horizontal Junction Box |
| Function |
Heating and Cooling On/Off Control |
| Includes |
Wall Plate, Vertical & Horizontal Scaleplates, Range Stops, Locking Cover Screws |
⚠️ Common Symptoms Indicating Replacement
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Temperature not controlling heating or cooling accurately
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Thermostat fails to activate heating/cooling elements
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Dial or mechanical interface stuck or damaged
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System intermittently switches on/off without cause
❓ Frequently Asked Questions (FAQ)
Q: How does the SPDT switch work?
A: The SPDT switch breaks heating and makes cooling when temperature rises, providing accurate control of your heating/cooling systems.
Q: Can it handle high electrical loads?
A: Yes, it is rated for resistive and motor loads up to 58.8A locked rotor at 120V and other voltage ratings as listed above.
Q: Is this a programmable thermostat?
A: No, this is a mechanical analog thermostat; temperature is set manually with the dial.
Q: Does it include installation hardware?
A: Yes, it includes wall plate, scaleplates, range stops, and locking cover screws for proper mounting.
🛒 Shopping Tips
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Confirm system voltage and load requirements before installation.
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Mount securely on a vertical or horizontal junction box.
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Adjust dial for desired temperature; range stops prevent accidental over-adjustment.
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Inspect sensor and switch functionality if the system shows irregular heating/cooling behavior.
