The detached property in rural Northamptonshire comprised a four-bedroom house approximately 200 m2 with underfloor heating installed.
The water-heating source was a Worcester Bosch Greenstar 18/22 condensing oil boiler. After only two years following the installation, oil prices increased rapidly, and the homeowner contacted ACS Renewable Solutions for advice. After a free survey, they recommended a complete replacement of the boiler using an Air Source Heat Pump.
Initially reluctant to dispense with the oil-fired boiler the customer became convinced after seeing the projected savings on fuel cost.
The government are also very keen for consumers to switch their heating systems to “greener” forms of energy whilst reducing energy consumption. A grant is available from your local authority when you switch over to an Air Source Heat Pump Boiler, which in 2009 was £900. The VAT rate for domestic installations is only 5% and a final immediate boost to cash flow came after cancelling the annual winter fuel contract. You may even find there are still people who will be happy to buy your old oiled-fired boiler as happened in this particular case study.
The ACS Renewable survey called for the Mitsubishi Ecodan 8.5 kW system, which has a very good reputation for reliability and quality. ACS is a Mitsubishi Business Partner and approved installer for the Ecodan making this a natural recommendation.
Only approved installers are allowed to fit the system making it easier for customers to apply for the full government grant. It may be possible to save some money by reusing the original hot water cylinder together with the radiators however; if they are more than a few years old this can be a false economy and ACS advice customers to upgrade to a more energy efficient water tank and radiators.
How the new hot water system works
The Air Source Heat Pump (ASHP) water boiler works like your fridge. The part of the fridge where food is stored is instead located outside of the house capturing heat from the air. (There is always residual heat in the air even down to -15C)
The black heat exchanger attached to the back of a fridge, usually covered in dust and feeling warm to the touch is instead located outside becoming part of the house heating circuit. Water from radiators or UFH is passed by the heat exchanger, the cooler water heating up very quickly before pumping it round the central heating system.
To heat the house in this study it required a compressor and ancillary circuits – electric pump etc, capable of producing 8.5 kW output of heat energy.
This is not the same as 8.5kW of electricity.
Here’s why: with a coefficient of performance (COP) of 3.6, the compressor and circuitry will only draw 2.36 kW of electricity – clearly a lot less to pay for than 8.5kW of electricity.
The amount of electricity used will fluctuate according to load and ambient temperature; the colder it is outside the harder it will work, using more electricity and the warmer it is the less it will cost you. Radiators are heated to 55 degrees, hot water to 58 degrees. The bottom-line here is that you will usually be using considerably less heat energy than if you had continued burning oil, gas or conventional electric heating system.
The Ecodan has its own controller for setting it up; it has a flow temperature controller for receiving normal 240-volt signal from standard room stats the whole system connects to standard S plan system.
From Customers own report
I had £700 saved for buying oil for the winter as that was about the amount we used last winter for approximately 180 days just for heating and hot water.
My electricity bill for Nov 6th 2008 to Jan 25th 09 was for £348.
Although not a fan of British Gas they were the cheapest. Click energy 6 online tariff, the total units used for this period was 3788 so:-18.784 pence/kWh for 1st 125 units per quarter = £23.48 then 8.665 pence/kWwh the rest. = 3663 x 8.665 = £317.39p + £23.48p = £340.87p – £8 discount = £332 + 5% vat = £348.
Which is for the whole electricity used and roughly £185 of that is for the heating and hot water. I have meter readings captured daily, and the outdoor min / max temps.
To date I have benefited from very efficient heating and hot water even through the coldest of temperatures which fell to -6.7C degrees a few times, and many sub zero days. It has performed very well.
The 8.5kW Ecodan system installed by ACS Renewables replaced an 18/22 oil boiler. This is because you need to calculate the heat load and design the system so that you separate the hot water heating load from the space heating. Central heating 8 kW, hot water 4 – 6 kW but timed before or after heating, rather than the 14 – 16 kW required from conventional heat load calculations of adding heating and hot water together plus 10%.