Heat pump hydronic cooling

Heat Pump Hydronic Cooling – Advantages

Use reverse-cycle heat pump hydronic cooling in summer as an alternate to air conditioning. 

Consider these advantages:

  1. Heat pumps can operate in reverse cycle for summer cooling whereas gas boilers can heat only.
  2. You only need one outdoor unit for heating and cooling, which is ideal for inner city dwellings with external space constraints.
  3. Heat pumps use water to transfer heat which is 3,300 more effective than air so that small water lines instead of large air ducts can be used. This is ideal for dwellings with cathedral ceilings, multi levels or extensions with minimal room for ducts.
  4. Hydronic water lines have no global warming potential as opposed to air conditioning lines with refrigerant.

Two Types of Cooling

Heat pumps provide cooling in two ways:

  1. Chilled water below the dew point for convector cooling. This absorbs both sensible and latent heat (moisture). Choose hydronic fan coil convectors designed for chilled water.
  2. Cool water above the dew point for underfloor cooling. This absorbs sensible heat only. Therefore, area cooling it is suited to the drier climates of southern and inland Australia.

Consider a mix of these types if you have a two story house. Use a Partage Box to create dual water flow temperatures. 

More information: Case Study

 Heat Pump Hydronic Cooling – Underfloor

Underfloor hydronic systems can provide area cooling also. They do this by running cool hydronic water underfloor in reverse cycle, above the dew point. However, underfloor systems cannot absorb moisture.

Set the floor temperature to around 18 degrees. This feels nice on your bare feet in summer and is well above the dew point. It works best in a dry climate and with ceiling fans.

Heat pump hydronic cooling systems rely on their large underfloor surface area to be effective.

Ensure also that you have good summer shading. Otherwise, the sunshine radiation coming through your windows may overpower your underfloor hydronic system.

Hydrosol image showing a structural slab on ground with 100mm finishing screed laid over PEX hydronic circuits on polystyrene insulation panels and polished for the finished floor.
Structural slab with finishing screed laid over PEX hydronic circuits on polystyrene insulation panels.

Heat Pump Hydronic Cooling – Fan Coil Convectors

Example of an Galletti ART-U fan coil convector, which provides hydronic heating and effective cooling with chilled water below they dew point.
Galletti ART-U fan coil convector for hydronic heating and cooling

Wall Mounted Fan Coil Convectors

Consider wall mounted fan coil convectors if you have hydronic radiator panels with a heat pump. A separate circuit will be installed so that your radiator panels can be automatically shut off in summer. Therefore, only your convectors will receive chilled water for cooling.

Hydrosol recommends the stylish and highly acclaimed Galletti ART-U fan coil convector range. These are most efficient and effective.

A convector has an internal fan that draws air through its coils. This is very important in cooling mode.

Condensation is drained away outside, which gives you both latent cooling as well as sensible temperature cooling.

In winter, hot water from your heat pump is circulated through both your convectors and radiator panels.

Concealed Fan Coil Convectors

Install concealed type fan coil convectors inside walls or above ceilings as another option from wall and ceiling mounted types.

Add ducting to your concealed convectors to distribute cool air to nearby rooms.

Design drop ceilings above robes and cupboards if above ceiling space is limited to mount your concealed convectors.

Image of Briza hydronic fan coil convectors, wall mounted, ceiling mounted, in-wall or in-ceiling types
Jaga Hydronic Fan Coil Convectors, Wall Mounted, Ceiling Mounted, In-wall or Above-ceiling Types
Hydrosol image of trench type hydronic fan coil convector installation.
Trench type hydronic fan coil convector installation.

Trench Convectors

Trench convectors are a good option for buildings with suspended floors where space for radiator panels is limited. This is often the case with Kitchen / Family areas with extensive glass windows and doors.

Choose the optional integrated fan if you plan to operate your heat pump in reverse cycle. In summer, this will provide effective cooling by drawing room heat through the chilled convector coils. 

Install trench fan coil convectors in suspended floors parallel to floor joists. Locate them beside windows or glass doors because they are designed for foot traffic.

Match the grilles to your flooring.

Hydronic Radiator Panels

Radiator panels are not designed for chilled water. Hydrosol recommends adding a fan coil convector with its own circuit if you have radiator panels with a heat pump.

Cycling cool water through radiator panels is only marginally effective for area cooling due to their low surface area for passive heat absorption.

Therefore, add a fan coil convector circuit for effective hydronic cooling with chilled water. The system will switch off the radiator circuit and run chilled water through a second fan coil circuit.

Hydrosol image of hydronic radiator panel
Hydronic Radiator Panel

Heat Transfer Rate

The rate of heat transfer for hydronic cooling in summer depends on the following:

  • Temperature difference between the water in your hydronic coils and the air in your room. For example, in a Melbourne summer, cool hydronic water may be 10-15 degrees lower than room temperature, whilst chilled water could be more than 20 degrees lower and hence more effective.
  • Surface area of the underfloor circuits. The greater the surface area, the greater the rate of heat transfer.
  • Rate of air flow across the surface area of the hydronic coils. Air movement increases the rate of heat transfer from convection.
  • Humidity. The drier the air, the easier it is to cool with underfloor cooling systems.

Humidity & Cooling

  • Consider underfloor area cooling with hydronic heat pumps in southern or inland Australian climates. This is because the air  is dryer with less need to absorb moisture from the air. 
  • Add fan coil convectors if you are concerned about humidity. They will dry the air and provide additional latent cooling using chilled water below the dew point.
  • For a two storey house, consider a combined hydronic system with underfloor cooling on the Ground Floor and fan coil convector cooling on the First Floor. 

Fans & Shading

Turn on a fan and the perceived temperature will drop by around 4 degrees. This will make a room of 28 degrees feel comfortable immediately. Fans create air movement. Therefore, they are ideal with hydronic cooling systems. There are many suitable fans on the market including:

  • Ceiling fans, that also assist your Star Rating
  • Floor and desk portable fans
  • Air conditioning indoor units with air flow mode

Also, make sure you have good summer shading with:

  • Appropriately designed eaves or slatted pergolas for northern windows
  • External awnings for western and eastern windows
  • Deciduous trees or vines shading northern, western and eastern windows

Thermal Mass

Construct your house with plenty of internal thermal mass if it is located in a southern or cold inland Australian climate. Create building mass with concrete floors, internal bricks, concrete walls and/or an over-sized buffer tank.

Also, make sure your house is thermally efficient with a Star Rating of at least 6.

Run your heat pump hydronic cooling system during the day with your solar power for low-cost operation. Turn your system down or off at night and let the cool thermal mass keep your house cool.

Consider enlarging your buffer tank if your home is of lightweight construction. Water is a good store of thermal energy. Read more: Thermal Battery

Contact us to explore heat pump hydronic cooling for your project.