Is my home suitable?
Yes, there are hundreds of models available, and there is pretty much
something for everyone. You need to work out which is the best type of
system for you though.
How much experience does The Green Company have with Heat Pumps?
Our design and installation team have experience of installing around 500 systems since 1996.
Is this an established and standard technology?
Yes – it is relatively new to the UK, but is industry standard in
Sweden where 97% of new houses have heat pumps for heating and hot
water. They are common in the USA and mainland Europe where there are
over 550,000 in operation. The first ground source heat pump was
invented more than 50 years ago, and continuous development has greatly
improved their efficiency and reliability. They are proven, cost
effective, reliable and safe.
What are the benefits of a heat pump?
In addition to reducing your domestic carbon emissions by about 50%,
you will see a significant financial saving over the life of the
system. You can also take advantage of a heat pump's unique cooling
ability during the summer. See the case studies below for examples.
How do they work?
Heat pumps work by collecting heat from outside your home and moving it
into your home - essentially a refrigerator working in reverse. The
technology works so well that even when -20°C outside - your home is
still warm and snug. For a detailed technical explanation see below.
What about the costs?
Initial capital costs are higher than a standard boiler, but you will
recoup these with reduced running costs and protection from future
energy price rises. Because you are moving heat, rather than creating
it by burning oil or gas, the system is much more efficient with
average savings of between 50-75% on your annual running costs even
through the heat pump is "always on". VAT on installed heat pumps is
only 5%.
What is the life expectancy of the system?
Our heat pumps come with a standard 10 year warranty. An optional 20
year warranty is available on some models. You should expect a 25 year
life of the system.
How fast do they react to changes in outside temperature?
Since 2002, Building Regulations part L2 has required better insulated
houses. This means that you don't need to turn up the boiler for a
short burst in the morning and evening, and have the heat quickly leak
out. When external temperatures drop quickly (e.g. -10C) the indoor
temperature change will be minimal. If the system is designed
correctly, you shouldn't need to boost the temperature in short bursts.
How noisy are heat pumps?
The table below shows you the range of noise levels from 0 to 140
decibels (dB). In an air source heat pump, there are two boxes – one
inside and one outside. The one that is inside makes the same noise as
a fridge. At maximum output, the noise levels from the air handling
units are 37dB at 5m, 31dB at 10m, and 27dB at 15m. This is usually
masked by background noise.
How do you control the system if the external temperature fluctuates
widely from one day to another, say in the spring or autumn?
The beauty of the heat pump system is that it monitors the outdoor
temperature, as well as the flow and return lines on the heating side
all the time. As the temps change the heat pump accommodates for this
and ensures that the indoor temp doesn't experience the rapid outdoor
change. No additional backup systems are required.
Can I set different temperatures in each room?
Yes. For example you could set the temperature in your bedrooms to be
19°C, the living rooms to be 21°C and the bathroom to be 22°C. This is
achieved by setting the heat pump to the maximum temperature required
and choking back the radiators or underfloor in the other rooms. If you
have a towel rail in the bathroom, we recommend a dual fuel model which
saves turning on the heating cycle during the summer.
Can I use the heat pump to cool my house in summer?
Yes – you can either have an air system which draws hot air from warm
rooms or use your underfloor system to gently cool rooms down.
How do I control my fuel bills?
As with standard boilers thermostats can be set to control the
temperature and leaving doors or windows open will make the system work
harder to replenish the heat that is being lost.
Can I have mains pressure hot water?
Yes. This comes as standard. The heat pump comes with its own specially
designed hot water tanks that will match the mains pressure at the site.
How is the heat pump installed?
Our team of qualified engineers will design and install the system for you.
What about maintenance?
No annual servicing required, 5 yr maintenance checks should be carried out to ensure moving parts do not need attention.
Ok, so how does the technology actually work?
The circuit below shows the heat pump cycle.
For the purposes of this description we will consider a closed loop ground source heat pump with an underfloor heating system.
“Brine” (water/anti-freeze mix) leaves the evaporator at 3°C and is
pumped around the ground loop. The ground warms the brine up by a few
degrees to 7°C .
The brine flows through the evaporator where it gives up the collected energy to the refrigerant within the heat pump.
The liquid refrigerant enters the evaporator (heat exchanger) at around
–20°C . The energy it extracts from the brine causes the refrigerant to
boil and it leaves the evaporator as a gas at 0°C. From here it moves
on to the compressor where it is increased in pressure from around 2
bar to 26 bar. This increase in pressure causes a corresponding
increase in temperature from 0°C to 100°C.
The refrigerant gas leaves the compressor, now at 100° C, and goes
through the condenser where it will give up energy to the domestic
heating circuit.
Water coming from the heating circuit enters the condenser at 40°C .
The water from the heating system extracts energy from the refrigerant
causing an increase in temperature so that it leaves the condenser
(heat exchanger) at 48°C and goes back to the underfloor or radiators
to heat the building.
The refrigerant gas in the meantime drops in temperature to 50°C and
leaves the condenser as a liquid but still at high pressure.
It passes through an expansion valve where it’s pressure and
temperature are reduced back to 2 bar and -20°C respectively. From here
the liquid refrigerant at –20°C goes into the evaporator once more to
pick up more energy from the ground loop.
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