44
RT-SVX22M-EN
Unit Start-Up
Verifying Proper Air Flow
Units with 5-Tap Direct Drive Indoor Fan
Much of the systems performance and reliability is closely
associated with, and dependent upon having the proper
airflow supplied both to the space that is being
conditioned and across the evaporator coil.
The indoor fan motor is factory wired to operate on speed
tap 1 in the cooling and heating mode for electric/electric
units. For Gas/Electric units, the motor is factory wired to
operate on speed tap 1 during cooling. For 3 & 4 ton Gas/
Electric units operating in heat mode, the minimum setting
is Tap 4.
For these units, a separate tap terminal is provided to
change speeds automatically between heating and
cooling. The motor can be rewired for different speed
settings should the application require it. Refer to the
wiring diagram that shipped in the unit and the unit fan
performance tables in the Service Facts.
The indoor fan motors are specifically designed to operate
within the BHP parameters listed in the fan performance
tables of the unit Service Facts.
When verifying direct drive fan performance, the tables
must be used somewhat differently than those of belt
driven fans. Fan performance diagnostics can be easily
recognized when these tables are used correctly.
Before starting the SERVICE TEST, set the minimum
position setpoint for the economizer to 0% using the
setpoint potentiometer located on the Economizer Control
(ECA), if applicable.
ReliaTel™ Control:
Using the Service Test Guide in
Table 9, p. 43
, momentarily jump across the Test 1 & Test
2 terminals on LTB1 one time to start the Minimum
Ventilation Test.
Electro Mechanical Control:
Using the Service Test
Guide perform the proper test mode connections.
With the fan operating properly, determine the total
system external static pressure (inches w.c.) by the
following method (ReliaTel/Electromechanical):
1.
Measure the supply and return duct static pressure and
sum the resulting absolute values,
2. Use the accessory pressure drop table in the Service
Facts, to calculate the total static pressure drop for all
of the accessories installed on the unit; i.e., curb,
economizer, etc.
Note:
Accessory static pressure drop is based on desired
CFM and may not be actual static pressure drop.
3. Add the total accessory static pressure drop (step 2) to
the duct external static pressure (step 1). The sum of
these two values represents the total system external
static pressure.
Using the Fan Performance Tables in the Service Facts,
look up the selected speed tap setting and match the
measured ESP to determine the approximate CFM.
If the required CFM is too low, (external static pressure is
high) do one or both of the following and repeat
procedure:
a. Relieve supply and/or return duct static.
b. Change indoor fan speed tap to a higher value
If the required CFM is too high, (external static pressure is
low), do one or both of the following and repeat
procedure:
c. Increase supply and/or return duct static.
d. Change indoor fan speed tap to a lower value.
Note:
Minimum setting for units with gas or electric heat
is 320 CFM per ton. For 3 & 4 ton gas Heat units
operating in heating mode the heat speed set
cannot be lower than speed Set 4.
4. To stop the SERVICE TEST, turn the main power
disconnect switch to the “Off” position or proceed to
the next component start-up procedure.
Units with Belt Drive Indoor Fan
Much of the systems performance and reliability is closely
associated with, and dependent upon having the proper
airflow supplied both to the space that is being
conditioned and across the evaporator coil.
The indoor fan speed is changed by opening or closing the
adjustable motor sheave.
Before starting the SERVICE TEST, set the minimum
position setpoint for the economizer to 0% using the
setpoint potentiometer located on the Economizer Control
(ECA), if applicable.
ReliaTel Control:
Using the Service Test Guide in
Table 9, p. 43
, momentarily jump across the Test 1 & Test
2 terminals on LTB1 one time to start the Minimum
Ventilation Test.
Electro Mechanical Control:
Using the Service Test
Guide perform the proper test mode connections.
WARNING
Live Electrical Components!
During installation, testing, servicing and
troubleshooting of this product, it may be necessary to
work with live electrical components. Have a qualified
licensed electrician or other individual who has been
properly trained in handling live electrical components
perform these tasks. Failure to follow all electrical safety
precautions when exposed to live electrical components
could result in death or serious injury.
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