T-stat Model 100 & 101 Lead/Lag Controller

Optimize Operation & Reduce Energy Consumption

Controls two single-stage HVAC systems for Fan, Cool and Heat

Power from both HVAC’s 24VAC transformers

Automatic lead change every 24 hours

LCD display for current operating mode and shelter temperature readings


T-Stat Product Matrix in PDF

Quest Controls Model 100 Lead/Lag Controller

The Quest T-stat Lead/Lag Controller Models 100 & 101 are a smart control system designed to replace conventional Lead/Lag controllers that do not offer wide temperature control windows for advanced optimization of HVAC operation.

The T-stat LLC controls two single stage HVAC systems to provide lead/lag operation with automatic switching based upon time. The system has a built in 2 line by 16 character display for status monitoring of the current temperature and operating mode of the HVAC equipment.

Model 100 & 101 Features

Controls two single-stage HVAC systems for Fan, Cool and Heat.

  • Power from both HVAC’s 24VAC transformers.
  • Automatic lead change every 24 hours.
  • LCD display for current operating mode and shelter temperature readings.
  • Comfort mode to allow “Occupied” temperature settings for one hour.
  • Five button keypad for navigation to other status screens.
  • Built in zone temperature.
  • The Model 100 setpoints are factory set to customer’s specifications and are not field changeable.
  • The Model 101 setpoints are factory configured but changeable through password protected menus.

Default Setpoints

The Model 100 setpoints are factory set.
The Model 101 setpoints are field changeable via password.

Setpoint Name
Normal mode - Lead unit cooling on80
Normal mode - Lag unit cooling on84
Normal mode - All cooling off75
Normal mode - Lead unit heating on45
Normal mode - Lag unit heating on
Normal mode - All heating off
Comfort mode - Lead unit cooling on76
Comfort mode - Lag unit cooling on
Comfort mode - All cooling off
Comfort mode - Lead unit heating on
Comfort mode - Lag heating on
Comfort mode - All heating off
Lead Switch time
24 hours
Comfort mode time
1 hour
Lead unit fan operationAutomatic


  • Utilities/Telecommunication/Cable & Broadband – Remote Cabinets & Shelters
  • Data / Switching / Computer Centers / COs / Headends & Hubs


Quest Part number — 150966-2

Outputs — Six solid state digital outputs designed to switch 24VAC

Input — Thermistor temperature sensor ±1°F (0.5°C)

Display — LCD backlit 2 line by 16 alphanumericcharacter display

Keypad — Five button directional arrows plus enter button

Mounting — Wall mount directly or standard single gang electrical box

Power — 24VAC

Enclosure — Two piece thermal molded plastic enclosure. All wiring is done on the mounted base and the controller is pull-off.

Ambient Operating Temp — 23° to 131°F (-5° to 55°C), 0-95% RH Non-condensing

Size — 5.32”W x 3.5”H x 1”D (135 x 89 x 25 mm)

Weight — 0.5 lb. (227 g)

Specifications subject to change without notice