Reznor JT4BD Unit Installation Manual - Manual (Page 9)

9
Short Cycle Protection
1. Set the thermostat system mode to COOL. Observe the
temperature setting of the thermostat and gradually raise
the set-point temperature until the unit de-energizes.
2. Immediately lower the set point temperature of the
thermostat to its original setting and verify that the
indoor blower is energized and outdoor unit remains
de-energized.
3. After approximately 5 minutes, verify the outdoor unit
energizes and the temperature of the discharge air is
cooler than the room temperature.
System Cooling
1. Set the thermostat’s system mode to COOL and the
fan mode to AUTO. Gradually lower the thermostat
temperature setpoint below room temperature and
verify the outdoor unit and indoor blower energize.
2. Verify blower wheel is spinning in direction indicated by
arrow. Feel the air being circulated by the indoor blower
and verify that it is cooler than ambient temperature.
Listen for any unusual noises. If unusual sounds occur,
determine the source of the noise and correct as
necessary.
3. Verify HI and LO refrigerant pressures.
notE: If refrigerant pressures are abnormal and the
compressor is rotating backwards, shut off main power to
the unit and switch any two field wires at the disconnect.
Do not alter unit wiring.
4. Allow the system to operate for several minutes and then
set the temperature selector above room temperature.
Verify the fan and compressor cycle off with the
thermostat. notE: The blower should also stop unless
fan switch is set to the ON position.
System Heating
1. Set the thermostat's system mode to HEAT and the
temperature mode to below room temperature.
2. Verify the outdoor unit and indoor fan stop running. After
5 minutes, increase the temperature on the thermostat
to it's maximum setting.
3. Verify the outdoor unit and indoor blower energize. Feel
the air being circulated by the indoor blower and verify
that it is warmer than ambient temperature. Listen for
any unusual noises. If unusual sounds occur, determine
the source of the noise and correct as necessary.
Defrost cycle timer
The defrost cycle timer controls the time interval of the hot
gas defrost after the defrost sensor closes. It is located in
the lower left corner of the defrost control board on the of
the control panel. Three interval settings are available: 30,
60, and 90 minutes. Time setting selection is dependent
on the climate where the unit is being installed.
• Example 1: Dry climate of Southern Arizona - A 90
minute setting is recommended.
• Example 2: Moist climate of Seattle, Washington - A
30 minute setting is recommended.
To set the cycle timer, place the timing pin on the defrost
control board to the desired time interval post.
notE: All units are shipped from the factory with the
default time setting of 30 minutes. Longer settings are
recommended for drier climate areas and shorter time
intervals are recommended for moist climate areas.
Maximum heating performance can be acheived by setting
the time to 90 minutes.
Defrost control Board
Operational Information
• Terminals r - rc must have 24±V present between
them in order for the time delay and defrost sequences
to be operational.
• Jumpering the t2-DFt test pins will communicate to the
board that the defrost T-stat is closed (if compressor is
running). The defrost thermostat tells the board whether
a defrost cycle needs to be started or terminated.
notE: The defrost T-stat is closed at 32° F or below
and is open at 68° F or above, but it’s state is unknown
if the temperature is between 32° F & 68° F.
• With the DFT closed, the unit will run for 30/60/90
minutes in heat mode and then defrost the outdoor
coil. The defrost will turn off the outdoor fan, turn on the
compressor and raise the coil temperature to 68° F. This
will open the DFT and terminate the defrost. If the DFT
does not open the defrost will end after 10 minutes.
• To over-ride the defrost boarrd and initiate a faster defrost
test in 5, 10 or 15 seconds as determined by the 30, 60
or 90 minute defrost pin settings (factory setting is 30
minutes), jumper the tESt terminal to the c (common)
terminal while the compressor is in heat mode.
– This will bypass the compressor off delay when the
unit goes into defrost test and if left in defrost test, the
delay will be bypassed when the test is terminated
by the processor. notE: If the jumper is removed
before the test is over, the processor will perform the
remainder of a normal defrost. See bullet 2 above.
• To switch from no-delay to delay, remove the pin from
the no - delay pin location and shift it to the delay pin
location. The delay/no-delay pin concerns compressor
operation during defrosts. The default setting is delay.
– Reciprocating compressors should only use this
setting in conjunction with an approved hard start
kit.
– Scroll compressors that have noise issues while
going into or coming out of defrost should use this
30 second delay to reduce the defrost noise.
– Manually initiating a defrost will cause the compressor
to run continually when entering defrost.
Normal defrost operation
To test normal defrost operation when the temperature is
above 35° F, jumper r to DFt on the board and allow the
unit to run for 30 minutes. Defrost will continue until the
r to DFt jumper is removed or for 10 minutes. Remove
the jumper.