The local environment that your property is located in is a consideration that is often overlooked by installers outside of Cornwall. The most important factor is proximity to the sea as you will have noticed that in many coastal parts of Cornwall, metal corrodes very fast due to salt mist. This is by no means limited to direct sea spray, but salt in the air that gets into everything, especially metals. The minimum rule of thumb is that if you can see the sea from the heat pump location then protection is needed. Spraying all metal parts inside the outer casing with Blygold is a way of preventing this deterioration and preserving the important working parts of a heat pump. In areas like Camborne and Redruth, Blygold is unnecessary, however as you get closer to both the North and South coast (Portreath or Falmouth) we do recommend Blygold coating on the heat pump along with a regular wash down of the external case of the heat pump with fresh water.
Heat pumps are best sited in the open air away from enclosed spaces. When the heat pump expels cold air the last thing you want is it reflecting back from a retaining wall back into the heat pump, because the colder the air temperature the less efficiently the heat pump will run. In line with manufacturers guidelines for installing a heat pump, the usual criteria is that the outdoor unit needs 300mm clearance both behind and at either side and at least 1.5 meters in front of the fan.
Once recorded, the information is input into specialist software to create a Heat Loss Report. The final report produces a comparison with alternative fuel sources, electricity, LPG, and oil etc. (please see Heat Pump Payback page). This comparison gives our customers the accurate financial information needed to help make a decision.
The Heat Loss Report illustrates heat losses throughout the house and consequently specifies the size of pump and cylinder needed to supply 100% of your central heating and hot water needs at the coldest times of the year (when you need it most). The report also uses software that links your postcode to how exposed that area is. A good comparison would be Truro or Liskeard which are sheltered areas and compared with more coastal areas such as Penzance, St Just or St Ives where the level of exposure must be considered. The average low temperature in exposed locations is often lower than more sheltered areas.
Further to this many properties in Cornwall are stone or granite built with no cavity wall insulation and as a result have thermal bridging, this must also be considered on a detailed report, as it adds to heat loss.
Harvest Cornwall are an MCS accredited company. The MCS governs the methods we use to calculate size of heat pump and cylinder needed. The MCS guide recommends 55 litres per person per day and a further 55 litres to cope with possible excess in demand.
Simply put, a 3-bedroom property would be 55lt x 3 = 165lt + 55lt for excess = 220 litre cylinder. Even though in some cases a 3-bedroom property may only have 2 people living there, the scheme is there to govern future use of the property. Perhaps the customer will not be there in 5 years and the property is bought by a family of four, then the tank would have been undersized for the property’s new occupiers. It is a stipulation of the MCS that this tank is not undersized therefore undersizing will have detrimental effects on receiving your grant (Renewable Heat Incentive).
In Cornwall we often see a different scenario where our customers need a cylinder to be oversized to meet high demand at different times of the year for holiday lets. This accepted and does not have any detrimental effect on receiving the RHI. In this case it is important to bear in mind that there may be a slight cost increase in heating the tank, depending on how much larger the tank is, but if your property does have high levels of occupation at certain times of the year and all the hot water is used in showers and baths, it does only takes 20 minutes to reheat the tank.
The Heat Pump must be sized to meet the space and hot water heating at low temperatures, MCS guidelines stipulate that in Cornwall the average lowest temperatures are -0.2. In order to qualify for the RHI the Heat pump must be sized to fully cope at this temperature. We size all of our heat pumps to cope with -0.2 as a minimum and, more often than not, they are sized to deal with a lot lower temperatures, depending on our customers’ preference. In the unlikely event that the heat pump ever gets to its maximum capabilities due to very cold weather, just like any other heat source (gas boiler, oil boiler, electric heating), a secondary source would be needed to help with the space heating (central heating), the secondary source could be a log burner, heaters etc, anything that you would normally use to cope in extreme cold weather.
Air Source Heat Pumps have two main components, the air source heat pump unit which is situated outside your property and the cylinder which is situated inside the property. The Air source heat pump is connected to the hot water cylinder via 28mm pipework and the cylinder is connected to the central heating and domestic hot water. With this in mind, space is needed in the property for the cylinder. If there is limited space in the house the garage or a small insulated shed is equally as good an option.