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ASHP System Design & Installation FAQs

Q) Can I have an air source heat pump on an existing microbore (small diameter pipework) system.

A) Yes you can, but considerations must be made to the design. It may have an impact on efficiency. Heat pumps need both a good flow and volume within the system to be able to work efficiently and with high SCOPS. Microbore pipework can reduce both of these with plastic microbore pipework sometime worse due to the inserts used within the pipework for fittings. This however does not mean you need to re-pipe your existing microbore central heating system. If your property is well insulated we can install the system with a volumiser (this helps to reduce your heat pump cycles and provides that needed volume of system fluid to aid in the defrost cycle. Other options can also be designed into the system by our dedicated design team such as providing hydraulic separation or using as an open loop system.

Q) What is an open loop system design when installing an air source heat pump.

A) An open loop system is not technical or complicated. (Our industry sometimes likes to baffle brains). This means operating your heating system so your house is being maintained at roughly the same temperature throughout. This does mean not turning down thermostatic radiator valves in rooms you do not use and in smaller homes where your heating is zoned over the ground and first floors to have these operating at the more or less at the same temperatures (for example 21/22degrees). This will require like most heat pump systems that want to achieve high SCOP values low flow temperature compatible radiators.

These can be of the aluminium design and/or fan assisted radiators. With this design it prevents the need of radiators working harder in some rooms than others which then requires higher flow temperature. Our design engineers can discuss this in greater detail during their site visit.

Q) Do I need to install larger new radiators when installing an air source heat pump.

A) You will need low temperature compatible radiators designed to emit more heat at lower flow temperature. This doesn’t mean they need to be larger in size. Correct fan assisted radiators will work, but these will need a power supply. Remember this is because we want the heat pump to provide lower flow temperatures and be more efficient (achieving a high SCOP).

Q) Is it easier to install a heat pump than a gas boiler?

A)  As with a gas boiler installation there are many things to consider. However with a air source heat pump additional considerations should be included such as system flow rates, flow and return temperature differentials, anti-freeze levels or the demineralisation process of the heating system water. These processes do take a considerable amount of time. If a heating system becomes dirty it is very difficult to remove. This then also produces high electricity consumption and additional compressor ware. To install any heating system correctly with quality and longevity in mind these cannot be rushed. Flooding an install with engineers is not the answer to provide a quality installation. Certain areas of the work may only require one or two engineers but requires the time needed to complete correctly.


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