Specifications

C) Measurement & Scale
At least one of the sensor wires must be disconnected from the controller before resistance
measurements are taken. A digital multimeter or other low voltage ohmmeter may be used to measure
the sensor resistance.
Important: Units with water/steam coils are equipped with a low limit thermostat.
This thermostat is wired in parallel with the outdoor air temperature sensor, such
that the sensor is shorted when the thermostat closes for low limit conditions.
Nominal Temperature vs. Resistance
°C °F Ohms
-40 -40 10517
-30 -22 10172
-20 -4 9654
-10 14 8933
0 32 8044
10 50 6938
20 68 5798
25 77 5238
30 86 4696
40 104 3707
50 122 2875
60 140 2206
70 158 1685
80 176 1287
90 194 986
100 212 760
110 230 590
120 248 462
D) Sensor Calibration
Out of range sensors must be replaced, as these sensors cannot be calibrated.
E) Sensing Room Temperature - Wall Thermostat vs. Room Air Temp. Sensor
These units are factory configured to use the room air temperature sensor (RAT) as the space
temperature control point. The controller will use one of three inputs as the space temperature value.
The first valid input, ordered as shown below, will be used as the space temperature input.
(1) LON network (nviSpaceTemp) - If the controller is connected to a LON network and this point is
bound to a valid temperature, then this temperature shall be used as the space temperature input.
(2) Room Air Temperature Sensor (RAT) - shall be used as the space temperature input if there is no
network input.
(3) Dual-Mount Thermostat (Wall t'stat) shall be used as the space temperature input, if the room air
sensor input is not valid. The RAT sensor MUST be disconnected to allow the wall t'stat to sense
room temperature.
3) System Diagnostics
A) Sensor Diagnostics with Display Points - Preferred Method
The display on the dual mount thermostat can be used to verify the unit controller is receiving an
accurate temperature signal. This is the preferred method for verifying the operation of the temperature
sensors, since the actual sensor values are displayed. A damaged sensor may provide an input that is
within the allowable range of temperatures, but may be far from the true temperature.
The up and down keys of the thermostat can be used to view four controller points. The four points are
(1) Space Temperature, (2) Discharge Air Temperature, (3) Outdoor Air Temperature, and (4) Outdoor
Air damper position. A display value of "ABn" indicates that the sensor input is out of the allowed range
(ABnormal). See Section 1 for details on the thermostat.
(1) Space Temperature is the default display value. This value is obtained from one of three sources:
LON Network, Room Air Temperature Sensor, and the dual mount thermostat.
(2) The discharge air temperature is the value returned from the discharge air temperature sensor.
(3) The outdoor air temperature is the value returned from the outdoor air temperature sensor.
7/1/03 Part Number 011-200001-003 Page 5