Problem:
Nuisance Alarms for Loss of Charge Detected or Lockout
Issue:
The Loss of Charge Detection function should help detect excessive refrigerant leakage. A key method to diagnose loss of charge is to recognize the loss of the normally expected mass flow rate through the EXV.
| Diagnostic | Target | Severity | Persistence | Condition/Response | Reset Level |
|
Loss of Charge Detected CktX where X is “1” or “2” |
Circuit | Warning | Non-Latching |
Loss of Charge is detected on circuit X, severe enough to warn a technician, but not severe enough to shut down the circuit. No unit response. |
Local |
|
Loss of Charge Lockout CktX where X is “1” or “2” |
Circuit |
Immediate Shutdown |
Latching |
Loss of Charge is detected on circuit X severe enough to shut down the circuit. Circuit X is inhibited. |
Local |
Possible scenarios that can cause a perceived loss of mass flow through the EXV:
- Running in an area of the operating map where the coil cannot provide enough subcooling.
- Loss of refrigerant charge.
- Excessive liquid line pressure drop. The main cause of this would be a plugged filter/drier cartridge.
- Incorrect EXV installed (only Applicable with IPAK: RAUK's are still TXV) in the unit (smaller EXV than expected by the configuration data). See below...confirm that the physical valve matches the Configuration. See the Service Alert Link below:
Symbio 800 Intellipak 1 & 3 Shipped with Incorrect EXV Selection
- EXV has lost steps and is operating at a smaller opening than it reports to the unit controller (only Applicable with IPAK: RAUK's are still TXV).
- EXV installed and/or bound to incorrect refrigeration circuit (only Applicable with IPAK: RAUK's are still TXV).
- Suction Line Fast Acting temperature sensors installed and/or bound incorrectly to incorrect refrigeration circuit suction line.
- Mixed Air Temperature sensor reading inaccurate (only Applicable with IPAK: RAUK's are just condensing units).
- Outdoor Air Temperature sensor reading inaccurate.
The detection method attempts to limit the likelihood of nuisance trips while detecting a significant number of actual charge loss events (or other scenarios that require intervention by a service technician).
Solution:
1. Verify proper charge at full compressor capacity and all condenser fans on that the unit is operating per performance charts located in the IOM.
2. Install the latest firmware for IntelliPak and RAUK with Symbio controls, version 4.10.002. IntelliPak Symbio 800 - Replacing controller and updating Firmware
Symbio 800TM Version 4:10.002 - Loss of Charge Diagnostic Changes – 10/12/2024
- Enhanced Loss of Charge algorithm calculation.
- Loss of Charge Warning diagnostic no longer triggers when in active Reheat or Hot Gas Bypass.
- Loss of Charge Detection diagnostic modified to warning, non-latching. Loss of Charge detection time has been extended from 300 to 1800 seconds.
- Loss of Charge Lockout diagnostic time interval has been extended from 300 to 900 seconds.
3. Stroke EXV in Manual Operating Mode and with the aid of an inspection mirror, verify that the EXV is stroking open and close per your command.
4. Verify the following temperature and pressure transducers are reading accurately with field gauges and temperature probes.
- Discharge Pressure Transducer (s)
- Suction Pressure Transducer (s)
- Suction Temperature Sensor(s)
- Mixed Air Temperature Sensor
- Outdoor Air Temperature Sensor
5. Verify Pressure Transducer(s), EXV(s) and Suction Line Temperature(s) sensors are bound to correct locations utilizing Component Layout Schematic. See example below EXV and Suction Line Temperature sensors.
Note: In some applications that operate with higher return air temperatures such as a data centers, this feature may need to be disabled. The Loss of Charge function can be Disabled in Settings >> Feature Settings >> Loss of Charge Detection. This should only be done as last resort and after steps 1 - 5 have been COMPLETELY checked and verified.
WARNING:
Information in this article is intended for use by individuals possessing adequate backgrounds of electrical and mechanical experience and who comply with all federal, state, and local laws, rules, orders, or regulations related to the installation, service, or repair of a heating or central air conditioning product. Any attempt to install, service, or repair a heating or central air conditioning product may result in personal injury and/or property damage. The manufacturer or seller cannot be responsible for the interpretation of the information contained herein, nor can it assume any liability in connection with its use.