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RT-SVX26K-EN

Pre Start

Test Modes

There are three methods in which the “Test” mode can be
cycled at LTB-Test 1 and LTB-Test 2.

Step Test Mode—This method initiates the different
components of the unit, one at a time, by temporarily
shorting across the two test terminals for two to three
seconds.
For the initial start-up of the unit, this method allows
the technician to cycle a component “On” and have up
to one hour to complete the check.

2. Resistance Test Mode—This method can be used for

start-up providing a decade box for variable resistance
outputs is available. This method initiates the different
components of the unit, one at a time, when a specific
resistance value is placed across the two test
terminals. The unit will remain in the specific test mode
for approximately one hour even though the
resistance is left on the test terminals.

3. Auto Test Mode—This method is not recommended

for start-up due to the short timing between individual
component steps. This method initiates the different
components of the unit, one at a time, when a jumper
is installed across the test terminals. The unit will start
the first test step and change to the next step every
30 seconds. At the end of the test mode, control of the
unit will automatically revert to the applied “System”
control method.

For unit test steps, test modes, and step resistance values
to cycle the various components, refer to

Table 12

Verifying Proper Air Flow (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 12

, momentarily

jump across the Test 1 and 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):

Measure 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:

b. Using the fan performance tables in the unit Service

Facts, plot the actual rpm (

Step 1

) and the bhp (

Step

) to obtain the operating cfm.

3. If the required cfm is too low, (external static pressure

is high causing motor horsepower output to be below
table value):

a. Relieve supply and/or return duct static.

b. Change indoor fan speed and repeat

Step 1

and

Step 2

4. To increase fan rpm, loosen the pulley adjustment set

screw and turn sheave clockwise.

5. To decrease fan rpm, loosen the pulley adjustment set

screw and turn sheave counterclockwise.

6. If the required cfm is too high, (external static pressure

is low causing motor horsepower output to be above
table value), change indoor fan speed and repeat

Step

and

Step 2

To stop the SERVICE TEST, turn the main power
disconnect switch to the “Off” position or proceed to
the next component start-up procedure. Remove
electro mechanical test mode connections (if
applicable).

Table 12. Service test guide for component operation

TEST
STEP

MODE

Fan Econ

(a)

(a) The exhaust fan will turn on anytime the economizer damper position is

equal

Comp

Heat

Ohm

Fan

Minimum