Heating up a 6-star
Hydronic heating using a heat pump need not be a mystery to install, but for the 6-star homeowner, it is a must-have, writes Deborah Andrich.
Heat pumps for use in hot water systems and hydronic heating still remain a mystery for many plumbers who are more familiar with installing and servicing gas-based or reverse-cycle systems.
Heat pumps has been used extensively overseas as a cost eﬀective method of providing domestic hot water and home heating, particularly in the colder climates of Europe.
In order to help the Australian market come to terms with specifying, installing and commissioning heat pumps for hot water and hydronic heating systems, Stiebel Eltron have brought specialist Oliver Joss from the company’s Switzerland oﬃ ce to Australia.
As head of technology and product management, Oliver was leading the in-house training facility for in-depth industry knowledge on energy, heating and ventilation. With Australia becoming increasingly more aware of renewable solutions, he has recently joined the local team to oﬀer his expertise in heat pump technology and ventilation systems to Australian customers.
According to ﬁgures from the World Energy Council, Australia’s average electricity consumption per household per year is the third highest in the world. With more than 7,000 kWh per year, Australian households use more than double the electricity compared to the global average: 62% of this energy is used for heating, cooling and hot water – it makes sense to start reducing this ﬁgure.
There is a groundswell to move toward more electricity usage instead of gas, particularly as renewables such as solar PV are becoming more cost eﬀective (even with poor feed-in tariﬀs). As a consequence Stiebel Eltron has recognised that products that are smart-grid ready – including heat pumps are a viable option for Australian households.
“In Australia, we have seen consumers wanting more autonomy in what energy source they can use,” says Darren Fletcher national product manager Stiebel Eltron.
“For example, in Victoria, gas was traditionally seen as a cheap, convenient energy source and taken for granted. With energy prices rising, the whole energy sector is becoming a hot topic once more.”
Hydronic heating can be installed in two formats: in-slab or as a radiator.
Darren recommends in-slab as the more eﬃcient method as the heat can be retained in the concrete’s thermal mass. The ﬂow temperature of the water coursing through the pipework can be at, 43–45oC, compared to a radiator at 50oC plus. This demands the surface area of the radiator needs to be larger to heat the room – and many homes simply don’t have the wall sp ace for large hydronic radiators.
The use of hydronic heating tends to be taken up by homeowners who are looking to have a more energy eﬃcient and liveable home where 6-star rating is a minimum.
“Typically, home owners who are building their own home who are looking at this type of heating are well versed on what they want,” says Darren. “They are often on the third or fourth home, and possibly downsizing. The types of speciﬁcations will include double glazing, high level insulation and to their own design – not a cookie-cutter home. Hydronic heating with a heat pump is a natural ﬁ t for them.”
In the early days of heat pumps being introduced to the Australian market, it was seen more as a niche product, but it is becoming a mainstream option. As a result, Stiebel Eltron wants to educate the installers on correct system speciﬁcations, installation and commissioning, hence Oliver’s presence in Australia.
“It is important that speciﬁers and installers understand the size of the heat pump that will be needed and that the heat load required is calculated correctly,’ says Oliver. “It is not like a gas system where you can simply put in a bigger gas unit. If it is wrong, and its in-slab, it is an expensive problem to ﬁ x and can cause a lot of reputation loss for the installer, speciﬁer and Stiebel Eltron.”
As an example, Darren and Oliver have taken an approximation of systems installed thus far in the Australian market to highlight what a ‘typical’ 6-star rated home would require.
An analysis by Sustainability Victoria (2013) estimated that a large house (220m2 built prior to 2005 and 2-star) with a high standard gas hydronic, zoned system would typically cost a Melburnian $4610 per year to operate. For a 6-star home of the same size it is nearer to $1400, however it does not include costs for hot water. The CO2 emissions with a gas-based system would also be higher at around 4900kg/ year.
Oliver’s calculations provide an interesting ﬁgure in the coeﬃcient of performance – namely environmental energy.
In simple terms, air-sourced heat pumps absorb energy from the environment and transfer this energy into the hydronic or domestic hot water systems. Operating in a similar fashion to a refrigeration system, the heat is not rejected, but collected. Power is therefore needed to operate the compressor to move the refrigerant around the system. Buﬀer tanks and domestic hot water heat pumps have the ability to store thermal energy, acting as batteries when solar PV is creating excess energy through the day.
Linking it to a renewable electrical source such as PV, therefore, enables the system to virtually require zero energy supply from the grid.
A smart grid ready heat pump, Oliver says, can be managed by an energy management system. In this way, all appliances, including the hot water and hydronic heating can be staggered to operate throughout the day at a time when solar energy generation is at its greatest, storing the energy for times of low sun.
“We need to help plumbers make the right choices with the equipment that is needed to do a heat pump-based hot water service and hydronic heating system,” says Darren. “It is not as simple as buying a bigger gas unit and an extra couple of metres of pipe. With Oliver here, we can now help plumbers do it right the ﬁrst time, to give the homeowner the best possible solution for their 6-star home.”