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3.14.1 GENERAL AIRFLOW OPERATING LIMITS
3.14.2 SELECTING INDOOR BLOWER MOTOR SPEED
The DRAH1T air-handlers must be configured in the field to assure proper air-flow
is delivered for the particular application it is being used in. Refer to the AIR-FLOW
PERFORMANCE DATA in Section 3.14.3 to determine which speed tap is appropriate
for the application.
Important: The pressure drop through the required external filter is not includ
-
ed in the external static pressure shown in the Air-Flow Performance Tables in
Section 3.14.3. The filter pressure drop must be added to the duct system pres
-
sure drop to determine total external static pressure. Filter pressure drop increas-
es as the filter becomes dirty and must be considered when calculating worst
case external static pressure.
3.14.2.1 DRAH1T MODELS (CONSTANT TORQUE ECM MOTOR)
Each DRAH1T model can be matched with 2 different outdoor unit capacities, 1.5 - 2.0
tons, 2.5 - 3.0 tons, 3.5 - 4.0 tons, & 4.0 - 5.0 tons depending on the model. DRAH1T
models have constant torque ECM motors with 5 blower motor speed taps, labeled T1
through T5. Speed selections are made on the low voltage terminal block located on
the motor housing. Speed tap T1 is always dedicated to continuous fan operation and
delivers approximately 50% of the speed tap T4 air-flow. Speed taps T2 & T4 are for
applications with an external static pressure up to 0.5” W.C. (speed tap T2 for lower ton-
nage & speed tap T4 for higher tonnage). Speed taps T3 & T5 are for applications with
an external static pressure above 0.5” W.C. (speed tap T3 for lower tonnage & speed
tap T5 for higher tonnage). All models are shipped from the factory with speed tap T5
selected. For optimum performance, efficiency, dehumidification, and the lowest possi-
ble noise level, select the appropriate speed tap for the specific application at the time
of installation.
Note:
The external filter pressure drop must be included in the external
static pressure when selecting a blower motor speed.
To change the indoor blower speed on DRAH1T air-handlers, move the BLUE wire con-
nected to terminal T5 located on the motor housing to the appropriate terminal (T2 – T5)
on the same terminal block.
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*CFM [L/s] per ton requirements are
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