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OPERATING INSTRUCTIONS
6/18/07
4. When turning the heater off the heater power (S2) may be turned off and the blower (S1)
left on to cool the heater housing assembly. This is suggested to prevent burn injury of
personnel around the heater but is not necessary for safety of the heater element.
NOTES:
• 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.
Performance
The maximum air temperature (as displayed on the temperature controller) depends on the exit
configuration, and the position of the inlet air damper. The chart below shows approximately the
maximum air temperature achievable in various heater configurations. Actual performance may
vary slightly, particularly at reduced line voltages. A closed damper (reduced flow rate) will allow
higher operating temperatures until the optical sensor detects the maximum element temperature
is reached. A closed damper (reduced flow rate) will also result in a faster ramp-up time.
MAXIMUM AIR TEMPERATURE vs. HEATER CONFIGURATION
120V 240V
Heater
configuration
Open damper Closed damper Open damper Closed damper
Open ended or
with flare
1000°F (540°C) 1200°F (650°C) 1400°F (760°C) 1400°F (760°C)
With high-flow
nozzle
1300°F (730°C) 1200 °F (650°C) 1400°F (760°C) 1400°F (760°C)
OSRAM SYLVANIA
131 Portsmouth Avenue
Exeter, NH 03833 USA
Tel: 603-772-4331
Fax: 603-772-1072
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