Pre Start; Test Modes; Verifying Proper Air Flow (Units With Belt Drive Indoor Fan) - Trane TH 150-300 Series Installation, Operation And Maintenance Manual

Pre Start

Test Modes

There are three methods in which the "Test" mode can be
cycled at LTB-Test 1 and LTB-Test 2.
1. 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 8. Service test guide for component operation
TEST
STEP MODE Fan Econ
Minimum
Position
Fan On
Setpoint
1
0%
Minimum Select-
On
Ventilation able
Economizer
2 On Open
Test Open
Cool Stage Minimum
3 On
1 Position
Cool Stage Minimum
(c)
4 On
2 Position
(c)
5 Reheat On Minimum
Heat Stage
(c)
6 On Minimum
1
Heat Stage
(c)
7 On Minimum
2
(a) The exhaust fan will turn on anytime the economizer damper position is
equal
(b) The condenser fans will operate any time a compressor is "On."
(c) Steps for optional accessories and non-applicable modes in unit will be
skipped.
34
Table 8.
Comp Comp Heat Heat
(a)
1 2 1 2
Off Off Off Off
Off Off Off Off
Off Off Off Off
(b)
On Off Off Off
(b) (b)
On On Off Off
On On Off Off
Off Off On Off
Off Off On On
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
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):
1. 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:
Actual Motor Amps
Motor Nameplate Amps
b. Using the fan performance tables in the unit Service
Facts, plot the actual rpm
Ohm
2a) to obtain the operating cfm.
3. If the required cfm is too low, (external static pressure
2.2K
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
3.3K
Step 2.
4. To increase fan rpm, loosen the pulley adjustment set
4.7K
screw and turn sheave clockwise.
6.8K
5. To decrease fan rpm, loosen the pulley adjustment set
screw and turn sheave counterclockwise.
33K
6. If the required cfm is too high, (external static pressure
10K
is low causing motor horsepower output to be above
table value), change indoor fan speed and repeat
15K
1 and Step 2.
7. 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 8, momentarily jump
X Motor HP
(Step 1) and the bhp (Step
Step 1 and
Step
RT-SVX25J-EN