RT-SVX23G-EN
39
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 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 percent using the
setpoint potentiometer located on the Economizer Control
(ECA), if applicable.
ReliaTel™ Control.
Using the Service Test Guide in
Table 8, p. 38
, momentarily jump across the Test 1 & Test
2 terminals on LTB1 one time to start the Minimum
Ventilation Test.
With the fan operating properly, determine the total
system external static pressure (inches w.c.) by the
following method:
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:
•
Relieve supply and/or return duct static.
•
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:
•
Increase supply and/or return duct static.
•
Change indoor fan speed tap to a lower value.
Note:
Minimum setting for units with Electric Heat is 320
CFM per Ton.
To stop the SERVICETEST, 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 percent using the
setpoint potentiometer located on the Economizer Control
(ECA), if applicable.
ReliaTel™ Control.
Using the Service Test Guide in
Table 8, p. 38
, momentarily jump across the Test 1 & Test
2 terminals on LTB1 one time to start the Minimum
Ventilation Test.
Once the supply fan has started, check for proper rotation.
The direction of rotation is indicated by an arrow on the fan
housing.
With the fan operating properly, determine the total
system airflow (CFM) by;
1.
Measuring the actual RPM,
2. Measure the amperage at the supply fan contactor and
compare it with the full load amp (FLA) rating stamped
on the motor nameplate.
a. Calculate the theoretical BHP using (Actual Motor
Amps/Motor Nameplate Amps) X Motor HP.
b. Using the fan performance table in the unit Service
Fact, plot the actual RPM (
Step 1
) and the BHP (step
2a) to obtain the operating CFM.
3. If the required CFM is too low, (external static pressure
is high causing motor HP output to be below table
value),
a. Relieve supply and/or return duct static.
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.
