T923_O / A923_O or T958_O / A958_O: High Refrigerant Pressure
On the VSODU, this fault will be indicated by the number 29 or L29. The L is when an Alert is finally converted to an Alarm with one hour lockout
The Drive LED's will show 20 flashes of the Yellow LED.
A high pressure event means the high side pressure has exceeded a very high 610 PSIG. This, simply put indicates that there is either too much refrigerant in the system, or the system is failing or struggling to reject heat. In cooling mode heat is rejected outside. In heating mode, heat is rejected from the indoor coil
This can occur because of a failed or poor fan performance. In heating mode this means the indoor blower. It can also mean a dirty condenser coil, which of course is the indoor in coil in heating mode, and the outdoor coil in cooling mode.
For Cooling mode or straight cool units such as (-)A17 or (-)A20 models, this is pretty straight forward.
* Check OD Fan Operation
* Check OD Coil for cleanliness
* Verify Refrigerant Flow
* Check Refrigerant Charge (Do not start here. You must check the first concerns and place the system in high speed to verify refrigerant charge. If at this point it still tripping, remove some refrigerant to allow system to run and stabilize.)
There are instances where this can occur in extremely hot climates. Some places in the desert Southwest can experience outdoor temperatures of over 110 degrees F. Ideally the condenser in this case should be placed in an area where it can remain shaded if possible but most importantly, kept clean.
For heat pumps in heating mode, check the following:
* Check Indoor fan motor operation.
* Check and verify Airflow
* Check indoor coil cleanliness.
* Verify Refrigerant Flow
* Check Refrigerant Charge (Do not start here. You must check the first concerns and place the system in high speed to verify refrigerant charge. If at this point it still tripping, remove some refrigerant to allow system to run and stabilize.)
If the HPC opens three (3) times during the same call for unit operation, the unit will lock out. Clear the fault to return to operation for troubleshooting.
