An ideal partner for heat pumps
Published: 02 November, 2016
The right heat emitter will significantly boost the performance of a heating system based on the use of a heat pump, as Jim Bennett of Smith’s Fan Convectors explains.
As a leading manufacturer of fan convectors, we are watching the growth in the uptake of heat pumps, particularly in rural areas where properties are off grid and not on mains gas, as it continues apace. Understandably, we are keen to educate and inform the industry about the proven benefits of pairing fan convectors with heat pumps.
Critically, we believe that in many cases, the energy savings heat pumps are designed to offer are not always achieved. This is because they are routinely paired with oversized radiators, which will struggle to provide the optimal efficiencies heat pumps are meant to deliver.
In contrast, fan convectors will provide close to the SAP (Standard Assessment Procedure) ratings that underfloor heating does. Using them as a more affordable alternative to UFH, or in tandem with it, is a solution many domestic users will be grateful for. There is also considerable scope for heat pumps and fan convectors to be used in commercial settings, particularly in more rural parts of the UK.
Starting with the technical side, the MCS 021 heat emitter guide*, states, ‘A fan-assisted radiator (fan convector) will have a higher heat output than a standard radiator the same size. You can therefore achieve a higher Temperature Star Rating without the heat emitter becoming too large for a room with a fixed specific heat loss.’
Standard radiators heat up and cool down very slowly. They use more water at significantly higher temperatures, which, combined with a large surface area, takes time to heat a room.
Hydronic fan convectors have only 5% of the water content of an equivalent-output radiator. Forced air convection via a small and energy-efficient electric fan circulates heat almost instantaneously. Significantly, this means fan convectors function very effectively at water temperatures below 45°C, coincidentally the best water temperatures for heat pumps to work at optimal efficiency.
|Heat pumps combined with fan convectors can deliver space heating come close to the efficiency of underfloor heating.|
In comparison, radiators work best at water temperatures of 70°C. They can just about function at a temperature of 45°C, but with the inevitable consequence that the radiator has to be much larger than usual
The SAP calculation is also convincing. A combination of an air-source heat pump and fan convectors in a new build should show at least a 12% reduction in running costs (and carbon usage) when compared with radiators and an air-source heat pump. Using fan convectors achieves close to the efficiencies achieved by installing underfloor heating.
Because fan convectors distribute heat in a highly efficient and cost-effective way, irrespective of the input water temperature, they do not need to be as large to perform economically. They also have considerable siting advantages; they can be positioned high on walls, embedded in ceilings, floor-mounted or under a kitchen base unit —depending on the project and needs of the building.
But what do fan convectors look like in reality?
In Norfolk, many properties do not have access to mains gas and rely on costly oil heating, delivered annually. This has created a receptive consumer market for energy solutions that offer long-term cost savings. Miller Installations specialises in air- and ground-source heat pump installations as one of its renewable solutions and uses Smith’s Eco-Powerad fan convectors in domestic projects for homes with high heat loss.
Business owner Peter Miller had considered other alternatives, such as smart radiators for example, but found them too expensive and with too many unnecessary features, which made the project costs for his customers unrealistic. He had also seen domestic heat pump projects in solid-wall homes where rival firms were recommending standard radiators with huge dimensions (3 x 2 m), which aesthetically would be untenable for any ordinary living room or other domestic space.
Although the SAP ratings for underfloor heating with heat pumps are favourable, it’s not always the most appropriate solution in domestic dwellings, especially in a retrofit project. At the same time, radiators perform poorly when paired with heat pumps, especially in older homes with solid walls because the heat loss is inherently greater than in a new-build property.
His prior knowledge about Smith’s came from regularly installing Space Saver plinth heaters for years.
There are considerable advantages to pairing heat pumps with fan convectors rather than radiators. Using a radiator of any size with a heat pump automatically reduces the heat pump’s efficiency by more than 10%. In fact, the SAP calculations reveal that fan convectors achieve close to the efficiencies achieved by installing underfloor heating.
One project had an old oil-powered boiler and radiators that struggled to successfully keep the solid-wall home sufficiently warm. The occupants were looking for another heating system that would improve the quality of their lives and reduce their heating bills.
Miller Installations recommended an air-source heat pump paired with Eco-Powerads in all downstairs rooms and traditional radiators upstairs in the bedrooms. The lady of the house, Mrs Dereham, liked the aesthetic appeal of the Eco-Powerads, and the couple were keen to choose a renewable energy source.
The solid-wall home already had reasonable insulation and double glazing. Once the heat pump was installed, it was able to operate at the lower water temperatures required to achieve its optimum efficiency because it was paired with fan convectors. The new heating system has created a warm home with lower heating bills.
Peter Miller summarises, ‘We want to give customers the best solution, with products that will deliver the warm, energy-efficient homes they’re looking for. Eco-Powerad fan convectors have been a real hit with all our customers who have had them installed. It means we can offer a true solution, combining an all-round affordable heat emitter on the market, confidently and effectively with the air-source heat pumps we supply.’
Jim Bennett, is sales and marketing director with Smith’s Fan Convectors.