Heat pump technical information

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Do heat pumps work all year round?

Yes, water-source heat pumps will provide comfortable heating, no matter the weather. Water-source heat pumps are more efficient than other heat pump types, as the water source stays at a fairly stable temperature throughout the year. Although the water in streams and lakes feels cold, it is still significantly warmer then the air temperature during the coldest days of the year. These coldest days are responsible for a large proportion of the annual heat demand, so extra efficiency at these times leads to a noticeable reduction in running costs.

It is not possible for a closed-loop water-source heat pump to freeze, as the collector fluid contains a non-toxic antifreeze mixture that inhibits freezing down to -35C.

All heat pump projects up to 45 kW will be certified under MCS ¹ , which provides additional reassurance that the system will heat the house effectively during worst-case conditions.

How efficient are heat pumps?

The average efficiency of the heat pump system is known as the Seasonal Performance Factor (SPF). Water-source heat pumps offer the highest possible SPF, typically providing around 4 units of heat for every unit of electricity used. This effective efficiency of 400% ² is possible because most of the heat is simply transferred from the external environment.

For the best efficiency and financial payback, water-source heat pumps lead the way. Water has a high heat capacity and thermal conductivity, which results in a higher Coefficient of Performance ² than ground- or air-source for a given source temperature. There are also year-round efficiency advantages, as water remains at a stable temperature year-round and does not diminish during the heating season.

What types of heat exchangers are used?

In static or slow-moving water, pond mats are likely to be the best option. These are coils of HDPE pipe mounted onto a frame, weighed down onto the bed.

In faster-moving water, flat plate heat exchangers will be the best option. These can be held in place using ground anchors or mounted to a channel wall. We manufacture our own ‘FireFlo’ heat collectors, specifically designed for water-source heat pump installations. These stainless steel panels are designed to be robust enough to withstand river debris, whilst achieving a high heat transfer rate.

What is the working principle of a water-source heat pump

Cold fluid is circulated through the collector, and is warmed up slightly by the watercourse. This low-grade heat is transferred to a refrigerant circuit in the heat pump, which uses electricity to compress the refrigerant, releasing the heat at a higher temperature. Please see here for further info.

What’s the difference between closed loop and open loop?

In closed-loop systems, a collector is placed within the watercourse, with fluid circulating around a closed circuit. This is generally the best option for smaller projects, as it is cheaper and requires less maintenance.

In open-loop systems, water is abstracted from the watercourse, then filtered and passed through a heat exchanger before being returned to the watercourse some distance downstream. This can allow a larger heat extraction and may also improve efficiency, and is a good option for large-scale projects.

Are heat pumps noisy?

Water-source heat pumps are relatively quiet and much quieter than air-source heat pumps, as they do not require an air circulation fan. Noise levels are similar to a traditional boiler, however it is possible to use noise attenuation features such as anti-vibration pads and flexible hosing, for further improvements.

How do water-source heat pumps compare with air-source or ground-source?

There are a number of benefits to choosing water-source over air- or ground-source heat pumps:

• Efficiency – water-source leads the way in terms of efficiency and performance
• Noise – much quieter than air-source
• Less intrusive – much less excavation and disruption than ground-source
• Long-lasting – water-source heat pump systems have a lifetime of 20-25 years

Can I power my heat pump with solar panels?

Yes, solar PV can be a great way to reduce heat pump running costs, especially during spring and autumn. The heat pump will typically use around 25% of its rated heat output in electricity. So for a 20 kW heat pump, up to 5 kW of electricity would be used. In some cases, battery storage may also be worthwhile, to store electricity for use in the evening and the following morning.

Should a heat pump be sized to match the existing boiler?

Traditional boilers are often oversized, however this can be expensive for heat pump systems. As a result, heat pumps are designed more carefully to avoid unnecessary cost. This includes designing the system to provide a more continuous form of heating, including the use of buffer tanks to smooth out demand. Hot water cylinders are also used to store heat during the night, so that the heat pump can always operate in heating mode during the day. This all means that a lower heat output rating is required to provide the same level of comfort.

How long do heat pumps last?

Water-source heat pumps have a lifetime of 20-25 years, which is significantly longer than most traditional boilers.

A good heat pump manufacturer should offer a warranty of 5 years for the major components.

1. MCS certification for Heat Pumps is provided through an umbrella scheme from Kensa Heat Pumps, where we are their installation contractor and are responsible for the design and efficient operation of the system. We can provide plumbing & electrical contractors or we can utilise your own local contractors.

2. Coefficient of Performance (CoP)  will depend on the source temperature of the collector and the desired supply temperature. Please see the following link from the European Heat Pump Association (EHPA) for their verification of the likely CoP White_Paper_Heat_pumps-1.pdf(page 32).