tekmar 665 Snow Detector & Melting Control Installation - Manual (Page 14)

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tekmarNet ® (tN2) Device
A Remote Display Module (RDM) 040 or Remote Start / Stop Module 039 can be
connected to the tekmarNet
® (tN2) input. Connect the Com terminal from the
appropriate tN2 device to the Com terminal (7) on the 665. Connect the tN2 terminal from
the appropriate tN2 device to the tN2 terminal (8) on the 665.
Note: The wires from the RDM and Remote Start / Stop Module are polarity sensitive.
The tN2 device does not operate correctly if the wires are reversed.
7 8
7
Com
6
Out
STEP SIX TESTING THE WIRING
Each terminal block must be unplugged from its header on the control before power is applied for testing. To remove the terminal
block, pull straight down from the control.
The following tests are to be performed using standard testing practices and procedures and should only be carried out by properly
trained and experienced persons.
A good quality electrical test meter, capable of reading from at least 0 – 300 V (ac) and at least 0 – 2,000,000 Ω, is essential to
properly test the wiring and sensors.
Test the Sensors
In order to test the sensors, the actual temperature at each sensor
location must be measured. A good quality digital thermometer with
a surface temperature probe is recommended for ease of use and
accuracy. Where a digital thermometer is not available, a spare
sensor can be strapped alongside the one to be tested and the
readings compared.
Temperature Resistance Temperature Resistance Temperature Resistance Temperature Resistance
°F °C °F °C °F °C °F °C
-50 -46 490,813 20 -7 46,218 90 32 7,334 160 71 1,689
-45 -43 405,710 25 -4 39,913 95 35 6,532 165 74 1,538
-40 -40 336,606 30 -1 34,558 100 38 5,828 170 77 1,403
-35 -37 280,279 35 2 29,996 105 41 5,210 175 79 1,281
-30 -34 234,196 40 4 26,099 110 43 4,665 180 82 1,172
-25 -32 196,358 45 7 22,763 115 46 4,184 185 85 1,073
-20 -29 165,180 50 10 19,900 120 49 3,760 190 88 983
-15 -26 139,403 55 13 17,436 125 52 3,383 195 91 903
-10 -23 118,018 60 16 15,311 130 54 3,050 200 93 829
-5 -21 100,221 65 18 13,474 135 57 2,754 205 96 763
0 -18 85,362 70 21 11,883 140 60 2,490 210 99 703
5 -15 72,918 75 24 10,501 145 63 2,255 215 102 648
10 -12 62,465 80 27 9,299 150 66 2,045 220 104 598
15 -9 53,658 85 29 8,250 155 68 1,857 225 107 553
A good quality test meter capable of measuring up to 5,000 kΩ (1 kΩ = 1000 Ω) is required to measure the sensor resistance. In
addition to this, the actual temperature must be measured with either a good quality digital thermometer, or if a thermometer is
not available, a second sensor can be placed alongside the one to be tested and the readings compared.
First measure the temperature using the thermometer and then measure the resistance of the sensor at the control. The wires
from the sensor must not be connected to the control while the test is performed. Using the chart below, estimate the temperature
measured by the sensor. The sensor and thermometer readings should be close. If the test meter reads a very high resistance,
there may be a broken wire, a poor wiring connection or a defective sensor. If the resistance is very low, the wiring may be
shorted, there may be moisture in the sensor or the sensor may be defective. To test for a defective sensor, measure the
resistance directly at the sensor location.
Do not apply voltage to a sensor at any time as damage to the sensor may result.
Test the Sensor Wiring