HVACopedia

NTI · Boiler

EMERG Incorrect wiring to BUS connection (emergency mode)

Medium severity TRX

What the control is telling you

The control sensed a short on the BUS connection. The boiler runs CH in emergency mode with a 113 °F target. The emergency setpoint can be changed with parameter 2.10.3.

Applies to: TRX150

Likely causes

  • Short circuit on BUS wiring
  • Wrong polarity on room sensor or zone controller
  • Incorrect daisy-chain wiring in a cascade

Test and repair steps

  1. Disconnect the field wiring from the BUS connection.
  2. If an NTI room sensor or zone controller is connected to BUS, check polarity and look for shorts.
  3. If the boiler is part of a cascade, check the daisy-chain wiring between the BUS connection of each boiler.

Models that show this code

5 models in TRX

TRX085TRX110CTRX150TRX199TRX199C

Other codes on the same units

  • 5 P3 Flame loss during run
  • 5 P6 3rd and 4th ignition failed
  • 06 02 Exhaust temperature above 204 °F (96 °C)
  • 06 03 APS open
  • 06 05 Exhaust NTC circuit open or short circuit
  • 6 12 Insufficient fan speed
  • FILL - 108 Low water pressure lockout
  • NOAVL PCB error: boiler application not set

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Source: NTI TRX150 manual, p. 87. Summarized in our own words; check the original manual for your model.

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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.