Geothermal Liquid to Water Heat Pumps going into freeze protection mode

Geothermal Liquid to Water Heat Pumps going into freeze protection mode

Scope

This article covers GEO series Hydro Solar Liquid to water heat pumps:
  1. GEO040V1LM
  2. GEO060V1LM
  3. GEO080V1LM

Trigger

Default Heat Pump Parameters setup

GEO series heat pumps with Titanium heat exchanger can be hooked up to both open (Lake, Pond, Artesian Well, etc..) and closed loop (Horizontal, Vertical, etc..) geothermal heat exchangers. When Open loop Heat exchanger is used, leaving fluid temperature from the heat pump in winter shall be less the 0°C (32°F). For this reason, Heat pump has a protection, in order to shutdown compressor when temperature approaches freezing level. This is the default settings of the heat pump.

What causes Freeze Protection Alarm?

When heat pump is hooked up to a closed ground loop heat exchanger (either vertical or horizontal), Heat Transfer Fluid (HTF), usually with anti-freeze protection solution, leaving temperature can go lower than 0°C (32°F) in heating mode. This can trigger a freeze protection alarm. When default settings are unchanged by the user, Heat pump will throw the alarm as soon as incoming HTF temperature is 4°C or less. Alarm is thrown at 4°C and compressor is shut down at 0°C.

Procedure

To prevent having this alarm when HP is hooked up to a closed loop heat exchanger, Antifreeze alarm set points (Level 1 and 2), need to be lowered down to match the operating conditions of the heat pump. Before changing these values, make sure that Heat Transfer fluid on the ground loop side has anti-freeze solution and that an automatic feeder of that solution is installed on the ground loop side piping (without these two conditions, you risk freezing the ground loop heat exchanger, damaging the HP and voiding its warranty).

Please press the Program "Prg" button, and enter the password (please ask your representative for password):
Go to M10 Sub-Menu and press the Enter button
Go to Df02 (Outdoor Loop Pump's Parameters)
Change "Out pump antifreeze 1" and "Out pump antifreeze 2" values to 4°C and 6-8°C below operating ground loop leaving temperature of the Heat Pump.

Example: a Heat Pump installed in Quebec City and hooked up to an 8 feet deep horizontal closed loop geo heat exchanger. In extreme winter conditions, the temperature of the ground will be around 4°C. Heat Transfer Fluid entering the ground loop side of the HP will be at 4°C and leaving temperature will be 4°C minus the temperature drop of the Heat Pump (can be taken from HP Manual). Assuming that temperature drop is 5°C, HTF leaving the ground loop side of the HP will be at (4-5=-1°C).

In this case we should set up "Out pump antifreeze 1" to (-1-4) = -5°C and "Out pump antifreeze 2" to (-1-6) = -7°C or (-1-8) = -9°C