Carrier TP-NHP - Manual (Page 47)

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Temperature Offset After Power Cycle
To compensate for internal heat build−up from the electronics in the thermostat,
the thermostat will add an offset to the actual temperature that it measures. If the
thermostat power is cycled quickly, one can witness an immediate increase in the
actual temperature displayed due to this added offset. The thermostat display will
return to the actual room temperature after several minutes of operation.
TROUBLESHOOTING
If the display module doesn’t power up after power is applied, check the Rc/Rh
and C terminals for 24VAC. If 24VAC is present, check the voltage between Vg
and V+. This voltage will be approximately 12−20VDC. If voltage is present,
check the polarity to make sure it is wired correctly. The display will not power
up if polarity is reversed.
If dashes appear for Option 01 in config and during reboot, the problem could be
the red pigtail being wired to Rc or Rh and the black pigtail being wired to C. If
so, remove the two−wire pigtail and connect to the V+ and Vg terminals.
Error Codes
“−−” − If AC/HP Control cannot properly read room temperature, display will
indicate “−−” and all outputs (except fan, if on) will turn off. In the case where
the installer has selected to average the local sensor and the remote room sensor,
the AC/HP display will alternate between “−−” for the failed sensor and the
temperature sensed by the working sensor every 10 seconds. The control will
operate from the temperature sensed by the working sensor.
E1 − If the Display Module and the Equipment Control Module cannot
communicate via two−wire connection, an E1 will be displayed.
E2 − There is no E2 error message.