OPERATING INSTRUCTIONS
06/01/2008
Detailed Operation
•Heater Voltage is regulated by a Solid State Relay (SSR), which is turned ON and OFF rapidly according to the temperature controller DC OUT signal. A “zero cross” type SSR is used to minimize electrical noise.
•Heater Element is protected with a resistive photo detector and a thermal resistor (thermistor) mounted at the heater inlet. These sensors are connected in parallel with the DC input signal going to the SSR.
o If the element overheats (bright orange color) the photo detector resistance decreases which reduces the control signal which, in turn, limits power to the heater.
o If the air temperature in the housing reaches an unsafe level, the thermistor resistance decreases which reduces the control signal, which in turn, limits power to the heater.
o A small fixed resistor in series with the control signal sets element and air temperature limits.
•The large black dots on the wiring diagram represent connections that are made on the internal terminal strip. The terminal strip allows the customer easy access to remove and replace the heater element and blower if necessary.
OSRAM SYLVANIA
131 Portsmouth Avenue
Exeter, NH 03833 USA
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