38 RT-SVX23F-EN
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 SERVICETEST, 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 ServiceTest Guide in Table 8, p. 38, momentarily
jump across theTest 1 &Test 2 terminals on LTB1 one time
to start the Minimum VentilationTest.
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 PerformanceTables 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.
Table 8. Service test guide for component operation
Test Step Mode Fan Econ
(a)
Comp1 Comp 2 Heat 1 Heat 2 Ohms
Multi-Speed Fan
Output
1
Fan On
Minimum
Position
Setpoint 0%
Off Off Off Off
2.2K Low
Minimum
Ventilation
On Selectable Off Off Off Off
2
Economizer Test
Open
On Open Off Off Off Off 3.3K Low
3 Cool Stage 1 On
Minimum
Position
On
(b)
Off Off Off 4.7K Low
4
(c)
Cool Stage 2 On
Minimum
Position
On
(b)
On Off Off 6.8K
High (2-step cooling)
Low (2-step cooling)
5
(c)
Reheat On Minimum On On Off Off 33K High
6
(c)
Heat Stage 1 On Minimum Off Off On Off 10K High
7
(c)
Heat Stage 2 On Minimum Off Off On On 15K High
(a)The exhaust fan will turn on anytime the economizer damper position is equal to or greater than the exhaust fan setpoint.
(b)The condenser fans will operate any time a compressor is “On” providing the outdoor air temperatures are within the operating values.
(c) Steps for optional accessories and non-applicable modes in unit will be skipped.
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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