Frequently Asked Questions
Heat Pumps
- Best rated heat pumps
- Heat pump diagram
- How does a heat pump work?
- Heat pump prices
- Heat pump reviews
Buffer Vessels
- What is a buffer vessel?
- What are the advantages of a buffer vessel?
- Can I have zone control without a buffer vessel?
- Can I install a heat pump without a bugger vessel?
Heat Pumps
Best Rated Heat pumps
The energy efficiency for heat pumps (ground & air source) is rated by the term C.O.P (Coefficient of Performance/Potential): please refer to the examples given below. Generally, heat pumps use the gas refrigerant R407c; although the earlier refrigerant R22 was more efficient, it posed potential issues to the ozone layer. Some heat pump manufacturers are now developing CO2 as a alternative refrigerant, as is the case with Mitsubishi.
Stiebel Eltron WPL 10 Air source
0°C heat source temp output 35°C gives a C.O.P of 3.0
0°C heat source temp output 50°C gives a C.O.P of 2.4
Hoval Belaria 10 Air Source
0°C heat source temp output 35°C gives a C.O.P of 3.1
0°C heat source temp output 55°C gives a C.O.P of 2.0
Daiken
0°C heat source temp output 35°C gives a C.O.P of 3.0
0°C heat source temp output 50°C gives a C.O.P of 2.4
Mitsubishi 8.5Kw Ecodan Air source
°C heat source temp output 35°C gives a C.O.P of 3.0
0°C heat source temp output 55°C gives a C.O.P of 2.4
An important issue regarding efficiency (C.O.P) is how big a role the outside source temperature plays. When it comes to ground source heat pumps, the temperatures in the winter time remain relatively high (8 - 10°C) which greatly improves C.O.P but it comes at the additional cost of groundworks/boreholes etc. Ground Source is the best solution from an energy effectiveness perspective and we would always recommend ground source as your best option for that reason.
Heat pump Diagram
How does a heat Pump Work?
The Physicist, Robert Boyle is attributed with publishing the original gas law in 1662, a liquid refrigerant with a low boiling point absorbs through a evaporator the source energy provided by the air or through the ground via collectors or boreholes, the higher the source energy the more efficient the heat pump will be (COP). The refrigerant containing the free energy is drawn by an electric scroll compressor which further increases the pressure which turns the refrigerant from a liquid into a gaseous state; this energy is extracted via another heat exchanger (condenser) to produce the energy for your heating requirements. The refrigerant continues on its way via the expansion valve and returns back to a liquid for the process to continue.
Heat pump Prices
Heat pump prices vary dramatically, particularly now with competition from the Far East. Generally though, a cheap price comes at the detriment of quality of components. Subheat do supply heat pumps from various manufacturers and we are always happy to supply various makes and prices and to offer advice on other makes you may be interested in. We are always content to quote on a like for like basis and happy to give our view on the heat pump market. Grants may be available and we are happy to advise on these, but they are not always the best option as some larger suppliers and installers use these as part of their marketing strategy and inflate the price at the other end. Our advice is simply compare the final price of the project quoted, the quality of the products they have quoted for and be very clear as to what work they are agreeing to carry out. We prefer to supply and install quality products from a reputable company such as Stiebel Eltron who have a strong reputation in heat pump manufacture.
Heat Pump Reviews
There are at present no heat pump comparison on-line sites; however it is our intention in the near future to add this feature to our developing website and run it in conjunction with our e-commerce site.
Buffer Vessels
What is a buffer vessel?
The aim of a buffer vessel is to remove the possibility of any short cycling of the heating appliance; it acts as a system separator for extending the heat pump operating time and for partially bridging power OFF periods as well as the hydraulic separation of the flow from the heat pump and the heating circuit.
What are the advantages of a buffer vessel?
A buffer vessel can also be used for multiple take-offs for additional heat sources such as solar and fossil fuel boilers and a buffer vessel is generally required for the defrost cycle of Air Water heat pumps, a buffer vessel also allows for complete zone control of the heating circuits.
Can I have zone control without a buffer vessel?
You can install heat pumps without buffer vessels but a constant heat pump flow rate is required so you would need at 20 to 25% of your heating circuits to be open and not be controlled by individual thermostatic actuators to allow flow from the heat pump and prevent short-cycling occurring.
Can I install a heat pump without a buffer vessel?
Failure for not allowing this nominal flow rate may result in the heat pump experiencing a high pressure shut down. A buffer vessel may not be necessary if the heating circuits have no requirements for zone control such as large area heating systems.
