6.1.2 Installing Temperature Sensor (Thermistor)
Temperature inside solar collector is monitored by temperature sensor connected via control wire to
Energy Station Controller. Temperature sensor is a thermistor, a metal probe whose resistance changes
with temperature (nominal 10kΩ @ 77°F, 25°C). See Table 6.1.8 for table of resistance vs. temperature.
Thermistor is not pre-installed as only one thermistor is needed per collector array.
Thermistor is installed at upper corner close to roof-penetration.
Thermistor kit is included with appliance and contains:
Thermistor (with high-temperature resistant Teflon wire
insulation), plastic cap with rubber o-ring, two self-drilling hex-
head (¼”) screws (Fig. 6.1.7), and two IDCs (Insulation
Displacement Connectors, not shown).
1. W i t h a m u l t i m e t e r, t e s t t h e r e s i s t a n c e o f
thermistor. Do not hold bare connections between
fingers or you will be measuring resistance through
your body and not through thermistor - alligator clips
work best.
Check associated temperature from table of
resistance vs. temperature (Table 6.1.8). If
resistance is not as expected, check meter and
connections, and test again.
2. Locate thermistor hole approximately 12”
(305 mm) from top of one collector
(stagnation-control device is at top) on
connection side (label side).
3. Remove rubber cap and carefully cut or
punch out foil-covered foam insulation. Be
careful not to damage absorber or tube
inside collector.
4. With flattened portion of thermistor in-line
with collector edge, insert thermistor such that
flattened portion seats between absorber
plate and internal tube (Fig. 6.1.9).
Thermistor will have to be directed towards
glass to contact back of absorber plate.
Continue to insert until thermistor is seated
firmly between absorber plate and internal
tube.
Table 6.1.8 – Thermistor resistance vs. temperature.
Fig. 6.1.7 – Thermistor kit.
Solar Collector
Installation Manual
20
Module 4
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