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Published on April 10th, 2017 | by Martin Clancy

Heat Pump vs Boilers

When it comes to space heating and your domestic hot water, heat pumps are an ever-increasing solution to cater for both. The electrically powered pump uses a compressor and coolant similar to that used in your standard domestic fridge. Renewable solar gain stored in the earth, air or water bodies is transformed to energy via a heat exchanger. This solar gain differs slightly to that of thermal energy associated with solar panel collectors. Essentially, all types operate on the same basis inside your home, they vary in the method of collecting the heat.

  • For each unit of electricity used for the pump, 3-4 units of thermal energy (kWh) should be returned, on average. In reality, this may be 2-2.5 in cold weather with an air source heat pump.
  • The most energy efficient option is the vertical geothermal married to UFH and while it has very low running costs it is the most expensive technology considering the initial capital outlay.
  • Air to water heat pumps won’t touch your landscaping and are the least-costly retrofit excluding the upgrades to insulation and air tightness.
  • Using heating controls, they will monitor indoor temperature and accordingly send heat to the floor and/or radiators to adjust temperatures up or down in line with those set on your thermostat.
  • When comparing systems, the best performance in statistics featuring heat pumps (COPs) are generally taken from new builds where multiple factors are contributing. Takin top-of-the-line vertical geothermal bores, fully optimised building design, extensive UFH and top of the range insulation is all included. It is important that people are wary of inflated claims of the performance of a retrofit system.
  • When it comes to grants, there is currently no government grant support for heat pump technology itself. The Better Energy Homes Scheme does have grants for heating controls of up to €600 and running the system on night-rate electricity will also save you money.
  • You have to get an energy survey for your house and site but it’s important to note that if you have efficient natural gas heating, a heat pump is more than likely not going to be cost-effective to retrofit.
  • Just like other electrical appliances, the efficiency of heat pumps varies. And in similar fashion, the EU has introduced energy labelling of pumps this past year.
  • After making sure that an energy survey is in place before changing your system, if your radiators are of suitable size, a retrofit of an air-to-water heat pump will involve about two days of work by two fitters working on plumbing and electrical upgrades, so these costs must also be considered when looking to upgrade.

What is a heat pump?

Using electrically powered compressor technology, heat pumps are able to recover the solar gain from the earth, from the air or bodies of water. Then using a heat exchanger, they bring this thermal energy to a useful temperature for central heating.

For every unit of electricity used, the heat pump can multiply it into four units of heating energy. When you apply this to a larger home with sufficient insulation, it can be highly economical once it us and running.

The heat pump system can be effectively separated into three parts:

  1. The Collector
  2. The Heat Pump (Where the heat exchanger executes)
  3. Distribution System

The resulting output is refined by heating controls. In the colder winter months, the heating tends to be on fairly constantly, something familiar to anyone with under-floor-heating (UFH) – or on night-rate electricity. Radiators when used are larger, cooler but heat slowly and longer than regular radiators.

Geothermal heating is process of collecting heat from the stable temperatures within the earth itself. This is done through a horizontal collector made up of plastic pipes in a closed loop set over a garden in shallow trenches one to two times the square footage of the house. Water is sent through the pipes before returning a higher, warmer temperature after taking the heat from the earth (The temperature beneath the earth’s surface here in Ireland is generally maintained between 11°C and 13°C according to the SEAI).

When it comes to vertical geothermal collectors, bored deep into the ground like a well in a space saving spike (often in pairs). Water based open loop collectors can use lakes, rivers and wells – but this technology is more commonly applied to commercial premises due to increased maintenance obligations than horizontal ground-source or air setups.

The last heat pump solution, the air-to-water system, takes heat directly from the air to the heat pump, kicking up its temperature through compression, similar to the technology used in a refrigerator, but cycling warmth to a water distribution setup (in UFH), or even air-to-air in a fanned air central heating system.

Air-to-water systems are the most popular system of choice when replacing a traditional central heating boiler with a heat pump. A lot of this is down to the fact that there is no ground work or costly civil work needed like a geothermal collector. In fitting one, you’ll most likely have a large metal appliance like a large air conditioner attached to an external wall outside directly feeding into a heat pump the size of a fridge-freezer on the inside. Heat pumps do create some outdoor noise but this is generally lower than the noise levels of a standard boiler (Between 45-55db).

As I mentioned earlier, stories of disappointment with actual performance on poor installs or DIY retrofits are all too common. The importance of all factors being considered within your home and its design is crucial when considering the installation of a heat pump in your home. The payback is typically about 8-10 years on an efficient installation and system. The life expectancy of the system is around 20 years. Once installed a heat pump requires very little maintenance and anyone installing a heat pump should speak with their installer regarding a maintenance agreement. As mentioned, they do not work like boilers as boilers aren’t as dependent upon as many other factors as a heat pump.

In certain circumstances, it can be a highly economical solution for your home. It is important that appropriate consultation with energy and heating professionals is undertaken before a heat pump is considered for installation.


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