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Heat pumps: field trials reveal good and bad installations
Posted by Cathy Debenham on 13 September 2010 at 9:17 am
The good news is that heat pumps can operate well in the UK, as long as they are well-designed and installed, and the customer understands how to use the controls. The bad news is that the Energy Saving Trust’s (EST) field trial of 83 heat pumps found that isn’t always the case.
System efficiencies for ground source heat pumps in the trial ranged from 1.3 to 3.3, with most in the mid range of 2.3 to 2.5. The system efficiency measures the amount of heat the pump produces for each unit of electricity needed to run the entire heating system (including hot water and supplementary heating such as an immersion). This is different from the COP (coefficient of performance) which just measures the amount of heat produced per unit of electricity used to run the heat pump. Air source heat pump system efficiencies ranged from 1.2 to 3.2, with a mid range near 2.2.
How a heat pump system is designed, commissioned and installed has a significant impact on its performance according to the study. It found that many systems appeared to be installed incorrectly and recommends a thorough review of guidelines and training for installers. It found that the simplest designed systems performed most efficiently. To find out more about what makes a good and bad performing site, EST plans to extend the research to June 2011 and look into individual sites in more detail.
Even when a system is well designed and installed, the customer’s behaviour also determines how well it will function. Many of the householders involved in the study had difficulty understanding the controls for operating their heat pump system, and so weren’t getting the best out of it. Control systems are often too complicated for customers to understand – and installers aren’t giving enough advice and training in how to use them. EST recommends the controls are comprehensively reviewed.
The field trials show that heat pumps have reduced the heating bills for some customers – especially those who live off the gas grid and have used them to replace electricity, oil or LPG. They also found that there was real potential to reduce carbon emissions compared with some other types of heating (such as electric storage heaters).
Generally, the householders in the trial were satisfied with both space heating and hot water provision, with both air source heat pumps and ground source heat pumps.
To summarise, the results of the first year of research suggest that heat pumps can both perform well and save on CO2 emissions in many property types. The second phase, will give a clearer picture of the potential for wider use in actual conditions across the UK housing stock.
Keep an eye on the blog for more findings from the research in the next week or so.
Photo by Bryn Pinzgauer
If you have a question about anything in the above blog, please ask it in the comments section below.
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