Ground Source Units
Ground Source Heat Pumps Troubleshooting
HP / LP Alarm: Commonly referring to an issue with flow; high pressure / low pressure
HP Alarms, in general, indicate a flow issue leaving the heat pump to either the hot water or the heating system. In other words; a restriction of some sort, preventing the intended flow / return, to and from the heat pump.
LP Alarms frequently indicate a flow issue coming into the heat pump from the ground array (outside pipes in the ground). This may signify that either a faulty pump or faulty valve is to blame. Other possible common diagnoses could suggest a restricted filter or glycol (antifreeze fluid) issue.
The initial areas for investigation would be to check whether there is:
– blocked filter
– faulty pump
– faulty valve
– glycol leak
– refrigerant circuit issue
It’s also important to note that there are two main types of ground source systems:
(1) a pressurised – this can be identified as having an expansion cylinder and a pressure gauge to indicate the pressure of the ground array which generally sits between 1-2 Bar.
(2) non-pressurised installation – which will normally have an expansion reservoir (clear container) with glycol inside that should be around halfway full.
Suspected Glycol (antifreeze) Leak: – the fluid running around the system and ground array may become too low for operation.
If either the pressure gauge is reading zero [pressurised system], or there is little or no fluid in the reservoir [non pressurised] this can indicate fluid loss in the system which needs to be investigated by a qualified engineer. Prolonged lack of glycol in the system can be detrimental to the longevity of the system.
You may be able to identify fluid deposits within the plant room or on a heat pump connection fitting – however there is possibility of loss of glycol via pipe connections in the ground array.
Note: A small amount of glycol needing to be added infrequently is quite acceptable due to pressure and temperature fluctuations that occur as part of the system operations.
However, constant pressure loss and need to add a larger volume of glycol may indicate a more fundamental issue with the integrity of the ground array and will require attention.
