Jason Cox, product and technical manager at Ferroli, looks at the increasing influx of air source heat pumps in light of environment-led government directives
With the advent of stringent environmental legislation, reducing the carbon footprint of homes will soon not just be desirable but imperative. A thorough understanding of the benefits of installing renewable heating and hot-water systems will become increasingly crucial for installers and contractors.
Technologies such as heat pumps and solar are genuine growth markets with unprecedented interest from today's increasingly eco-conscious customers.
There is a massive business opportunity for those proactive enough to capitalise on this trend and develop appropriate product and service offerings.
The well documented Code for Sustainable Homes has been introduced to help arrest the UK's contribution to global environmental decline. Under the Code, properties will be more energy and water-efficient and the government has targeted 2016 as the year by which all new homes should be zero-carbon rated.
The first milestone on the timeline for this target is indeed 2008. Already, publicly funded developments must reach level three on the code's star-rated system which dictates a minimum improvement of 25% on the Dwelling Emissions Rate (DER) set out in the 2006 Building Regulations.
Furthermore, by 2010, all refurbishment and new-build projects must also reach this level 3 status.
Energy saving
The incorporation of energy-saving features is one of the easiest ways to improve a dwelling's total score and consequently achieve the target rating. As such, the installation of renewable technologies can help developers and housing associations comply, by reducing the carbon footprint of new and existing housing.
As an added incentive, they can also enable tenants to benefit from lower fuel bills in the battle against fuel poverty.
The case for air source pumps as the ideal solution is strong. They offer a cost-efficient and environmentally sound heating solution because they tap into an infinite supply of pollution-free heat from the surrounding air.
They can be located discreetly outside a house or building, negating the need for expensive groundworks and reducing the payback period. With minimal maintenance required, the only external energy required is electrical power to drive a small pump and compressor. The leading air source heat pumps boast an impressive coefficient of performance of 3.5 (350% efficiency).
Once the decision has been made to use an air source heat pump, the design of an effective system follows a similar pattern to conventional central-heating specification.
In terms of suitable applications and potential locations, they can be installed in virtually any home, from low-level houses to high-rise construction flats.
The key consideration is the type of unit to be selected and this is governed by the intended role. Will the unit be used solely for room heating, or for both heating and hot water purposes?
It is important that the system is designed so the heat pump is used only when it can perform at its most efficient levels. Not only are they far more effective when functioning at a constant, consistent rate, the life of the compressor is prolonged.
One way of creating this ideal scenario for heating the property and generating hot water is by using the system in conjunction with a thermal store or hot-water cylinder. By heating a large volume of water directly, the heat pump is activated for longer periods rather than cycling on and off.
Generally, air source heat pumps are available as base units, where the contractors must provide the circulating pump. The alternatives are units with pumps included.
Either could be used for heating and hot-water in conjunction with the thermal store or cylinder as described above.
For applications where only the heating function is required, most manufacturers would use the unit without the store but with a buffer vessel. For installations of this nature, Ferroli has taken design a stage further with its VA storage versions which include a circulating pump and tank as part of a complete system.
Simple sizing
Once the type of configuration has been decided, sizing is relatively simple. Typical heat loss and flow and return calculations can be made using the same methods and software as conventional system designs but using slightly different parameters to take into account the external location of the unit and the lower water temperatures produced. Typical flow and return values are in the region of 50˚C and 39˚C respectively, with a minimum outside temperature set to -5˚C.
With insulation and house construction techniques improving, a well-designed system will only require major input from a boiler at the coldest times of the year.
Designed for domestic applications, Ferroli's RVL range of air source heat pumps is available in four sizes with outputs ranging from 6.1kW to 11.1kW. Producing hot water up to 45˚C, they are ideal for the direct heating of low-surface-temperature radiators, thermal stores or underfloor heating systems.
Ferroli has been manufacturing its own air source heat pumps for nearly 20 years and offers training, servicing and a bespoke design service.