Outdoor Unit Control - Trane 4TXM2318BF300AA Service Manual

6.7 Outdoor unit control

6.6.1 4-way valve control in heating
Multi: Protection when 4-way valve can not reverse in heating: 10 minutes later after compressor startup, if
indoor coil average temp. is below 15degree and keeps for 1 minute, the unit will stop and occur the 4-way
valve protection.
compressor ON
OFF
4-way valve ON
OFF
6.6.2 Electric heater control
If compressor has not run for a long time, the refrigerant will deposit on the bottom of compressor and mix with
the refrigeranr oil. When re-startup, because low pressure reduces, refrigerant will be segregated from the
refrigerant oil and cause soam in the oil, which will make compressor exhaust a lot of oil. Therefore please stop
heating the compressor bottom to ensure the low pressure in startup period should not go down greatly.
• Ambient temp. TA≤27degree, when compressor stops, the electric heater will be electrified.
• When TA≥32degree, or compressor running, the electric heater will be off.
Heater ON
Ambient temp. TA( ℃ )
3.2.5 Control of defrosting in heating
In heating mode, defrosting temp. sensor will check the frosting condition of outdoor heat exchanger and make
defrosting control.
Multi:
a. In heating mode, if the compressor has run for 10 minutes continously and run for 45 minutes in all, the
system will measure the defrosting temperature sensor Te and outdoor ambient temp. sensor TA, if the below
condition can be met for continous 5 minutes, the unit will enter defrosting operation:
Te≤C×TA-α
Herein: C: TA<0 o, C=0.8 TA≥0
According to SW5-2, the setting is as follow: in the place easy to frost, it is H; when out of factory, it is M.
Jumper selection M (out of factory) H
o
α ( C) 8 (E)
b. Defrosting entering condition: -15
c. Stop and Pause condition of compressor running accumulative time in heating mode:
Checking Stop: running operation changes from heating to cooling.
Checking Pause: thermostat OFF, or the unit stops.
Cancel condition:
It will take the max. 10 minutes from beginning defrosting to quit it. Te sensor will measure the condition of
outdoor heat exchanger, if the temp. is over 7
defrosting will be over.
6.6.3 Compulsory defrosting control
Enter condition: in heating mode, after receiving the compulsory defrosting signal from indoor unit, the unit will
perform the compulsory defrosting operation.
o
Cancel condition: Te≥12
15 S（E ）
OFF
o C, C=0.6
6 (E)
o
C≤C×TA-α≤-2
o
C for 60 seconds in all or is up to 12
C and keep for 1 minute or the defrosting time is over 10 minutes. The manual
2 minutes and 55s
27 32
o
C;
118
o
C for 30 seconds in all, the