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NTI · Boiler troubleshooting

Wire a room thermostat

TRX

What is going on

Connecting a room thermostat to the TRX150 is a low voltage job, but it is done inside the control panel, so the power needs to be off and the panel opened the way the manual describes. Use the low voltage terminal table to pick the right terminals, TT1 or TT2, and do not guess from wire colors.

Likely causes

  • Thermostat leads landed on the wrong terminals
  • Loose wire under the terminal screw
  • Wires pinched or strained when the cover is closed

Check in this order

  1. Confirm power to the boiler is off, then access the low voltage connections as described in the manual.
  2. Loosen the cable clamp and feed the thermostat wires in.
  3. Connect the wires to the terminals listed in the low voltage table (TT1 or TT2).
  4. Give each wire a light tug to confirm it is secure.
  5. Make sure the wires are not under stress when the covers are closed.
  6. Power up and confirm the thermostat call starts the boiler.

Applies to: TRX150

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Source: NTI TRX150 manual, p. 55. Written in our own words; check the manual for your exact model.

For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.