FAQ's
What is a Heat Pump and how does it work?
A heat pump is an electrical device that extracts heat from one place and transfers it to another. The heat pump is not a new technology; it has been around the world for decades. Refrigerators and air conditioners are both common examples of heat pumps.
Heat pumps transfer heat by circulating a substance called a refrigerant through a cycle of alternating evaporation and condensation. A compressor pumps the refrigerant between two heat exchangers. In one heat exchanger, the evaporator, the refrigerant is evaporated at low pressure and absorbs heat from its surroundings. The refrigerant is then compressed en route to the heat exchanger, the condenser, where it condenses at high pressure. At this point, it releases the heat it absorbed earlier in the cycle.
Will we have a big electricity bill with a heat pump?
Yes, you will have a bigger electricity bill because the heat pump uses power to gather in the free heat energy from the source, but your overall expenditure on energy will be considerably less than traditional fuels such as oil etc.
How much cheaper is it than oil for instance?
SEAI's domestic fuel cost comparison sheets for April 2011 show oil burnt at 80% efficiency costing 11.83 cent per kW Hr. A heat pump (with a seasonal average C.O.P. of 4) running on electricity costing .16 cent per kW would cost just 4c per kW hr to run.
If talking about an average Irish home using 30,000 kW hrs of energy per year, that's €3549.00 for oil, and just €1200.00 for the heat pump.
What is a C.O.P.?
A C.O.P. means the Coefficient of Operating Performance - the relationship between the power required by the compressor process and the energy delivered by the heatpump. E.G. a heat pump using 2.6 kW of power for its compressor and delivering 12 kW of heat energy to the system would have a COP of 4.6 (12 / 2.6)
Is Heat Pump technology classified as Renewable Energy?
Yes, heat pumps are officially classed as providers of renewable energy by the EU and the International Energy Agency.
What's the payback time of a heat pump?
A heat pump that is retrofitted into an existing house or building can save large amounts of money over many years. It is not uncommon for the payback time to be as little as four or five years, that is dependent on the cost of the fuel you are currently using.
The annual running cost plus the cost of financing the work usually come to less than the annual purchase cost of oil or LPG gas, so the benefits are immediately felt.
In a new house there may be little or no difference over choosing a heat pump over say a condensing oil fired boiler and solar panels. A heat pump will cost a lot less to run and can deliver energy to the building when the solar apnels can not.
Do we have to have Underfloor Heating or do we need to upgrade all our radiators?
A heat pump will work more efficiently supplying heat to a floor heating system because of its lower operating temperature requirements, but it is not true to say that you cannot have radiators!
If installing a new system with radiators they may be dimensioned slightly larger to run at lower temperatures. Where retrofitting, the existing house radiators may also be fine, as they are generally oversized in any case, and when used with heatpumps are left running at a lower temperature for longer periods. Market experience has shown that in most cases the radiators did not need to be changed but this would need to be looked at on a job to job basis.
Do we need Three Phase electricity?
Most manufacturers have single phase machines designed for the Irish climate that can provide coverage up to around 400Sq. M of floor area. Bigger buildings will usually need a three phase supply or else several heat pumps. Alternatively peak loads may be catered for by docking a heat pump with another back-up source of heat such as oil, gas or electricity.
What are the service requirements for a heat pump?
A heat pump itself, like a fridge usually needs very little servicing as such, but the overall system should be checked by the installer or manufacturers personnel annually.
Can a heat pump be linked to Solar Panels?
Yes, a heat pump can be combined with solar thermal panels for hot water and heating support too. Heat pumps that have water heating systems already built in can be fed a pre-heated water supply from a solar system too.
What's involved in a Borehole or Energy-well?
A borehole is drilled usually when there is not enough room for a horizontal collector or space is at a premium, and also in bigger installations where there may be several drills. The drill holes are done with large rigs similar to those used for water wells, but the holes are often much deeper - from 90 to 200M deep. Inside the borehole are usually two 'u-bend' continuous joint-free pipes (also called probes) which collect the heat from the rock. They are filled with an antifreeze mixture, usually ethylene glycol or ethyl alcohol and commonly referred to as brine.
The bore-hole is full of water right up to the level of the ground water table - the active borehole depth is from the top of the water to the u-bend. The surrounding water conducts the heat from the rock into the pipes and also neutralises the pressure (grout or Bentonite is only injected into a borehole if its devoid of water -highly unusual in Ireland!). Multiple boreholes need to be placed 12 to 15 metres apart to minimise their influence on each other
The ground operates as a gigantic battery where water conducts new heat into your bore hole.
What's the lifespan of a heat pump?
Like fridges and freezers, market experience has shown that life-cycles of fifteen years as a minimum are not unrealistic.
Which kind of heat pump works best?
Lowest annual running costs are usually from ground source heat pumps as their heat source is warmer in colder weather than that of air to water, but in milder weather when temperatures climb above around 8°C, and heating is still required, air to water heatpumps can overtake the GSHP's efficiency. In practice it will depend on each individual application and the ease of installation for air to water for retrofits for instance would usually weigh the decision in that direction. It is also quite common for air to water heat pumps to need an additional source of heat to cover peak loads in severe weather. Which is 'best' is better answered perhaps by which is best for your particular needs.
Can anyone have rock-/ground-/lake source heating?
It completely depends on the circumstances. If you have a rock shelf not too far beneath the surface of the ground it is no problem. If you have a large plot or fields around the house, ground source is a very good alternative because it is many times cheaper to install. If your house is near a lake and you have a lake plot with permission to use water source heating this is also a good alternative.
How deep must the collector be between the bore hole and the house?
The collector should be laid about 1 m deep and act as a ground collector on the way to the house. Incoming and outgoing pipes should be separated or insulated from each other.
Will the heat in my bore hole run out?
The heat that is taken from the ground comes from the sun’s rays and as long as the sun shines the ground is recharged during the summer months provided that the installation is correctly dimensioned. The ground operates as a gigantic battery where water conducts new heat into your bore hole.
We are a family of four, is the integrated water heater of 180 litres enough?
That completely depends on what your hot water consumption is as a family. In normal use 160 litres is fine for a family. If one has a jacuzzi that is used frequently one should perhaps consider either supplementing with an external hot water heater (Compact 200 type) or select an 11-model with external accumulator tank.
I have a pool, wood boiler and solar panels. Can I use these together with the heat pump?
NIBE’s heat pumps and other products, such as boilers and hot water heaters, are designed to be compatible with lots of different products and operating conditions. NIBE recommends different solutions for dockings between different systems. These can be found in “Installation and Maintenance Instructions” which can be downloaded from the website. For special cases contact NIBE and we will help find the best solution.
How should one isolate the collector at the house?
The collector must be insulated for the last few metres (at least 2 m) to the house. This is to avoid freezing around the collector with frost ruptures as a result.
Why dimension with an immersion heater as back-up, isn’t it better to have a more powerful compressor and therefore use less expensive electricity?
A heat pump is dimensioned for best operation and that is obtained if it is too little for the coldest days of the year (which is when the immersion heater kicks in) and just right for the rest of the year.
How many starts of the compressor is normal per day/year?
That varies quite a lot, it depends on how many hours the compressor runs in a year. Normal number of compressor hours is anything from 3000 to 4500 hours/year. As a result of this there are more starts if the hours are fewer. Likewise if the starts are fewer the hours are more. Normal number of starts is anything from 4000 to 16000 starts/year. There may be even more in special circumstances.
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