SDRA heaters can be easily field if modified to vary the fan speed.
There may be some circumstances where the use of short lengths of
duct may not create sufficient pressure drop to achieve the desired tem-
perature rise. This may also be the case of using the unit without a duct.
This insufficient static pressure drop may result in high air flow, with
the maximum temperature rise below the desired level, (even after the
fan speed has been reduced to the minimum rpm). An accessory AD-
16, adjustable damper, is available and can be attached to the heater to
produce a static load, ranging from .1” to .19” H
2
O which will act to
reduce the amount of air flow.
The “Friction Loss” Graph 4 provides the actual test data on the
friction loss for the AD-16 damper attachment. The losses are stated as
the equivalent length in feet of 20” duct.
The SDRA Dragon includes 2 thermostats. The thermostat on the
air inlet end of the unit is for the minimum air temperature desired. The
thermostat on the discharge end of the heater is for the maximum air
temperature desired. The two thermostats are wired in series with the
heating element contactor coil. The temperature range of both ther-
mostats is 60 - 180˚F.
Adjustable Damper and Duct Adaptor
Rear of
Heater
Front of
Heater
Adjustable
Damper
1/4-20 Wing nut
Provided with
AD-16
Duct
Adapter
