Question 1

What is a Heat Pump and how does it work?

Accepted Answer

A heat pump is a machine 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 free heat it absorbed earlier in the cycle.

Question 2

Will we have a big electricity bill with a heat pump?

Accepted Answer

Yes, you will have a bigger electricity bill (but no oil or gas 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.

Question 3

How much less does it cost to run a heat pump than oil or gas ?

Accepted Answer

in 2017 heat pumps are running at around half the cost* of oil and ( natural ) gas.... for many years they were more like one third of the cost of oil, but oil had come down in price to its present level.... Historically though, it has always been that the use of a heat pump has offered very significant savings and greater comfort due to the more sophisticated controls normally associated with the technology.
 
*SEAI's domestic fuel cost comparison sheets are published bi-monthly and show up to date prices for different energy sources including heat pumps, oil gas etc. There you can see the price differences per kilowatt hour of the different fuels....note that  for comparison you should normally average the heat pumps running between rates 'DD' and night rate at 50/50.

Question 4

What is a C.O.P.?

Accepted Answer

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 kW of power for its compressor and delivering 8 kW of heat energy to the system would have a COP of 4 .

Question 5

Is Heat Pump technology classified as Renewable Energy?

Accepted Answer

Yes, heat pumps are officially classed as providers of renewable energy by the EU and the International Energy Agency. Using a heat pump will therefore be an easy way usually of complying with your needs for renewables in a new build for Part L regulations.​

Question 6

​What's the payback time of a heat pump?

Accepted Answer

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, and in fact it even cost less! over choosing a heat pump over say a 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 panels can not.​

Question 7

Do we have to have Underfloor Heating or do we need to upgrade all our radiators?

Accepted Answer

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 heat pumps 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.​

Question 8

Do we need Three Phase electricity?

Accepted Answer

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.

Question 9

What are the service requirements for a heat pump?

Accepted Answer

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.​

Question 10

Can a heat pump be linked to Solar Panels?

Accepted Answer

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.​

Question 11

What's involved in  a Borehole or Energy-well?

Accepted Answer

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.

Question 12

What's the lifespan of a heat pump?

Accepted Answer

Like fridges and freezers, market experience has shown that life-cycles of fifteen years as a minimum, and a  twenty-year life expectancy is not unrealistic.

Question 13

Which kind of heat pump works best?

Accepted Answer

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 heat pumps 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. 
 
If you are building a very highly insulated air tight house, perhaps an exhaust - air heat pump may be the best choice, or consider the fact that you can get passive cooling with a ground source heat pump to free-cool such a well-insulated home in the summer!
 
Which is 'best' is better answered perhaps by which is best for your particular needs and any of our members will be pleased to show you the benefits available with their products.