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Air Source Heat Pumps

The Green Lodge Air Source Heat Pumps

The house was built by a developer in 2013/14 and designed to be heated by two Samsung series 3
twin fan RC160MHX Air to Water Heat Source Pumps (ASHPs), which would also provide 600 litres of
domestic hot water. The house is entirely reliant on electricity for everything.
To get the best results from this type of system the house (EPC rating C) has been heavily insulated
and has underfloor heating on all three floors. Domestic hot water is stored in two 300 litre hot
water tanks, which are also heavily insulated, losing less than 1/3 rd C per hour.


Does the system work?

Yes, the house maintains a very consistent pleasant temperature even
during the coldest weather but in order to achieve ease of use and consistency we have had to
replace all 22 of the original Polypipe room thermostats with Heatmisers. This was expensive but
had an immediate effect, reducing energy consumption. The biggest benefit, however, is a system
which can be minutely controlled, if required, using a smart phone or tablet. It has to be
remembered that unlike fossil fuelled systems the results of any change can take time to materialise
eg more than an hour to increase room temperature in winter by 1 C. Thinking ahead or taking this
into account when setting up the thermostats is essential.


Hot water is adequate: the air source pumps only heat water up to 48 C (latest versions apparently
achieve 55 C) which is fine for showers but baths require diligent addition of cold water.
Is the system reliable? The system is complex and relies on many ancillary parts, which have
suffered a number of failures over the last seven years. Apart from replacing the thermostats, three
of the six motorised valves controlling flow to the heating zones have had to be replaced; one of the
two remote pump control panels failed, as did one of the five zone wiring centres and one of the five
zone circulating pumps. Whilst this has been frustrating and expensive I hope that the system as a
whole might now run reliably for the next few years.


Is the system efficient and cost effective?

We are currently consuming about 52,000 kWh per
annum, reduced from 62,000 kWh three years ago by dint of controlling temperatures better. This
still seems excessive but does now include heating and dehumidifying an indoor pool, which was
added to the house in 2016. The split is approximately 60% house 40% pool. Unfortunately, I don’t
have a direct comparison but as originally installed I do not believe that the system was particularly
efficient or cost effective. However, since it seems that heat pumps, either air or ground, are likely
to become the only option in this area, I am glad that the system structure, which is the most
expensive part, is in place. Furthermore, Samsung are continuing to develop their pumps and my
understanding is that the latest series is noticeably more efficient. With the rapidly increasing cost of
electricity, it won’t be too long before it will be cost effective to upgrade our original air source heat
pumps.

In complete contrast to Green Lodge we are currently extending my son’s house in Denham Terrace
and taking the opportunity to remove the oil combi boiler, pipework and radiators and install an
ASHP plus underfloor heating on the ground floor. The cost of the heat pump including all the pipe
work is approximately £16,500, part of which is recoverable through government grant, subject to
certain criteria such as meeting a minimum EPC rating of C. This will add further cost and, if the
work had not been part of a larger project, we would probably have installed a new oil fired boiler
and waited until forced to change, since government appears to have ignored the full cost of
installing heat pumps. For many homes this is likely to exceed the cost of the pump itself by a
considerable margin, if it is to work effectively.