Heat Pumps and Cooling Distribution Systems
All Kensa’s Compact heat pumps can operate in reverse-cycle mode providing chilled water to cool a building and operates in a similar manner to a chiller.
This is a modification that needs to be specified at the order stage as physical changes are required to the heat pump at time of manufacture.
For twin compressor heat pumps, there is an option of having cooling either on one compressor, or on both depending on the cooling load and the effectiveness of the cooling distribution system.
Key considerations for ground source heat pumps and cooling:
At the end of a heating season the ground arrays will normally be operating at around 0°C to 5°C. The amount of time for the array to return to ‘normal’ ground temperatures depends upon the type of array – drilled vertical ground arrays (boreholes) will generally remain cool for a period of time, where as horizontal ground arrays (slinkies) will quickly return to the surrounding ground temperature due to a higher solar gain and especially after a period of rain).
However the ground temperature will generally be cooler than the surrounding air temperature in Summer.
This colder temperature can allow a degree of passive or ‘free’ cooling to occur if the building has passive beams or an underfloor cooling system. This is simply achieved by passing the contents of the cooling system through a plate heat exchanger with the ground array fluid passing through the other side. This system completely bypasses the heat pump and the only energy used is the power required by the water pumps. How effective this cooling is and for how long depends upon the amount of cooling required and again the type of ground array.
A reverse cycle heat pump can also be used to provide ‘active’ cooling where the heat pump is used to generate chilled water (usually at 6 to 12 deg C, although with underfloor distribution systems this might be higher to avoid condensation forming on the floor). For a ground source heat pump to actively cool, modifications need to be made to the unit at the time of manufacture.
- The cooling distribution system will require a level of antifreeze protection along with an inhibitor.
- The cooling water temperature should be managed via an auxiliary control system, not part of the GSHP.
- A buffer tank is required as part of a cooling distribution system, not part of the GSHP
- A flow sensor should also be used as an interlock to stop the heat pumps running if there is no flow around the cooling distribution system.
- Where multiple heat pumps are used and the heating load may be the predominant load; design consideration should be given by the specialist consultant as to the provision of number and types of heat pumps, buffer vessels with control valves to ensure the correct operation of the system to deliver the requirements.
Facts at a glance:
Ground source heat pumps can operate in reverse cycle mode to provide chilled water as well as heating.
How effective the cooling is largely dependent on the cooling distribution system.
Underfloor is not that good at providing cooling as it is slow to react, has poor cooling densities and condensation can occur.
The cooling distribution system will require a level of antifreeze protection along with an inhibitor.
These are required as part as the cooling distribution system.