Automated Home 2.0 – #33 Our Air Source Heat Pump
I previously covered our MVHR system and now it’s time to look at the rest of our mechanical setup.
Electrification of Heating
Heating, just like transportation, will be increasingly electrified over the coming years. Indeed the ‘Sixth Carbon Budget’ recently published by the Climate Change Committee (December 2020) points to a future where there will be millions of heat pumps installed across the UK, predicting…
…a total of 5.5 million heat pumps installed in homes by 2030, of which 2.2 million are in new homes
Climate Change Committee
Hitachi Yutaki Heat Pump
There seemed little point in fitting another oil or gas fired boiler, in fact we decided not to burn anything anymore.
So the new Automated Home is heated using this 11kW Hitachi Yutaki M Monobloc Air Source Heat Pump. This air to water unit supplies the Roth underfloor heating system on both floors as well as the 300 litre Joule Cyclone DHW tank.
There is plenty of FUD circulating on forums and Facebook Groups about heat pumps. Lots of ‘expert’ opinions from people that have never owned one or lived in a house with one. While there are undoubtedly horror stories out there (as with every trade), a properly spec’d heat pump, designed and installed by a real expert company like Daly Renewables, in a well insulated airtight house is an efficient solution.
The heat pump is controlled by our Loxone Smart Home system which is also collecting energy usage information as we go through our first winter (more on that in a future post).
So while we’re still gathering the data to compare the running costs with our last similar-sized house and its oil-fired boiler, for now we can say that comfort levels are a huge improvement. The house feels so much warmer than the old place (and we’ve been down to -6° so far this winter) and the big tank is always full of hot water.
Time to turn to Ryan Daly once more for an explanation of heat pumps and more on the system that keeps the Automated Home warm in the winter.
Heat Pumps Explained
Air Source Heat Pumps work using similar technology as ground source heat pumps, but instead of having pipe work buried in the ground they use the outside air as its energy source.
In the UK and Ireland, the outside air temperature rarely goes below -3°C. The heat or energy moves from hot to cold (the 2nd law of thermodynamics) and the refrigerant in the heat pump boils at very low temperatures of -30°C, so the difference between the outside air and refrigerant creates the energy that flows into the heat pump. An Air Source Heat Pump uses a fan to draw the outside air across the evaporator.
An Air Source Heat Pump will have an efficiency rating of approximately 350% to 470% depending on system design and installation. In simple terms, this means that for every 1kW of electricity that the heat pump uses to power the compressor, which is the main component in the heat pump, it will get the remaining 2.5kW to 3.7kW of energy from the air outside.
In comparison a fossil fuel gas or oil boiler will only ever be 70% to 95% efficient. The lower the heating system operating temperature the more efficient the heat pump will be and therefore this will result in lower running costs.
Heat Pumps are an ideal fit for New Build Homes which have an Underfloor Heating System installed as the water running through the UF Heating Pipe work is less than 35oC. The system is designed to be left running and will maintain a constant temperature in the home and will always have the hot water tank heated ensuring ample hot water for showering and bathing. In the Summer when the heating is not required the heat pump can heat hot water separately.
At Daly we advise all our clients to work closely with their architect in order that they specify low U-values and come up with an air tightness brief to make the house a low energy dwelling from the outset. In our experience, our systems work really well in timber frame houses as they are well insulated and air tight but they can also perform as well in masonry houses as long as the air tightness measures are applied correctly on site.
In terms of capital cost an air source heat pump will cost approximately £2,000 to £3,000 more to install over a conventional oil or gas boiler system. Depending on fossil fuel prices, the payback compared to an oil boiler system will be between 3 to 6 years. The main difference in an oil boiler and a heat pump is the fact that a heat pump has an inverter compressor which means it can match the exact heat load of the house. It does this by varying the frequency of the inverter. The smallest oil boiler available is 15kW and has a high temperature heat output which is not designed for an UF Heating System.
If using UF Heating with oil, mixing valves have to be fitted at manifolds which reduce the temperature of the water in the system from 80oC to 35oC. This results in the boiler cycling more often which results in higher running costs. Having mixing valves at the manifolds pushes up the cost of the UF Heating System and also adds to the maintenance requirements for the system. These are not required when using a heat pump to heat the UF Heating as the heat pump can match the exact temperature the UF Heating needs by using a process called weather compensation.
Weather compensation uses an outdoor sensor which is pre-wired to the heat pump unit. This automatically adjusts the flow temperature going through to the house via the UF Heating according to the temperature outside. This intelligent operation helps to reduce running costs even further as it will enable the heat pump to run at a lower temperature on milder days and step it up when it gets colder outside. By doing this it also helps to maintain the indoor temperature at a comfortable level on a continuous basis.
In houses where we have heat pumps installed (going back 10 years now), we have found that the typical annual heating and hot water cost associated with having an air source heat pump will be in the region of £350.00 – £700.00 per annum for an average 3,000 square foot house. This is the
electrical cost to operate the compressor in the heat pump. Compared to an oil boiler system, this usually works out at between 50-70% cheaper depending on the energy load of the house and the fuel prices. Electricity prices tend to remain more stable than oil prices and to know that your bill will be more or less the same every month allows clients to pre-plan that all important family budget. Some clients get an Economy 7 tariff installed where you get electricity for less than half price for 7 hours at night which can be a very cost-effective way of operating a heat pump system.
The other main benefits a heat pump has
over a gas or oil boiler apart from the lower running costs is that it has no
harmful emissions, it does not require regular maintenance, it does not require
fuel top ups every few months as it is using electricity to operate it and this
also means the home owner only has one utility bill for the home. With more
energy than ever coming from renewable sources, we see heat pumps here in Ireland
and the UK as being part and parcel of future energy efficient heating options.
One only needs to look to Sweden where
80% of all domestic houses are already heated by heat pumps.
At Daly we have been supplying and installing the Hitachi Yutaki range of air source heat pumps for the last 7 years. Having installed hundreds in that period we have become the biggest heat pump installer in Northern Ireland and have built up a vast knowledge of the product in that period. The units come with a 7 year parts warranty which is one of the best warranties in the industry and we have undertaken the product training courses to provide a complete after sales support service.
Contact Dalyrenewables.com for more information.
In a future part 2 post we’ll look at controlling the heat pump from our Loxone system and the running costs of our heating. In the meantime remember to check out our Instagram to follow the project, read the rest of the Automated Home 2.0 blog posts and find the links to all the products we’ve used in our self-build.