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Heat Pumps
Can't find what your looking for? Our 'Ask the Expert' Q&A archive has hundreds of questions, all answered by our in-house experts, so click here to see if your question has already been answered.
Anybody got any experience of a heat pump? I met a couple of companies at the NEC show recently but to be honest wasn't that impressed. They were mainly salesmen. Any ideas particularly on the situation with hot water? Strikes me that it would struggle to be that efficient getting water up to higher temps.
Hi Henry, we have had a ground source heat pump in our 17th c farmhouse for 5 years now, and i honestly would not be without it. The house is underfloor heated throughout, and maintains a constant temperature of 19 degrees, 24 hours a day, 365 days per year. The hot water is hotter than we would ever need it (hot enough to top your bath up if you stay in it long enough to go cold!)
i can't reccomend them enough. In the UK we are really only just 'catching on'to this 'new' technology, but in Scandinavian countries they are just the norm.
hope this helps. Good luck!
Judy
Hello. I'm also really interested in a heat pump for my project. I'm planning on having underfloor heating throughout the ground floor (covering about 100m2) - although I never really thought about other hot water needs. What I'd really like to know is the kind of cost I should expect to pay? And while I'm interested from a 'green' point of view, I'd also like to know how long it would take to 'make my money back', so to speak. Months, years or decades?! Any thoughts?
Thanks, Babs
Hi Henry,
Any ideas particularly on the situation with hot water?
Heat pumps are designed to operate most efficiently to produce an output water temperature in the region of 35 to 40ºC range which is suitable for under floor heating.
In order to heat hot water to 55ºC or even 65ºC heat pumps have a multiple scroll compressor to reach the higher temperature.
When hot water is required some manufacturers use the control system to switch the full output of the heat pump to heat the hot water cylinder to 55 or 65ºC for approx 20 minutes. This means you are only operating at a slightly lower efficiency for a short time. When the water is hot the heat pump is switched back to under floor heating again.
I have a small plot that probably doesn't have room for a ground source heat pump and is on rock so couldn't do borehole. We are considering air source or utilising the running stream (about metre or so wide and fairly strong flow), that runs along the side of us and never freezes, for water source.
I have heard that air source is not particularly efficient when the temperature drops below 10 degrees.
Any thoughts on the viability/efficiency of either of these two systems?
Tony we are just in the process of installing our heat pump, we are going with an open source loop from the river at the bottom of the plot its a 100ft wide 10ft deep and flow is at its slowest 15m per min and we’ve been advised that its more efficient than ground source.
If we went closed loop in the ground we needed 600m of 40mm pipe, in the river we would need 400m of 40mm pipe. Doing open loop we need to pump 0.6kg/s of water through a tube heat exchanger.
Due to the volume and depth of water we have enables us to use this application, I’m not sure what temperature you would get out of the stream as its thermal store ability would be quite low. The problem I have had is none of the firms I’ve talked to have worked with water source. Best suggestion would be to monitor the winter temperature of your stream, problem is we are 6 months away from that so that’s no help !!
Good luck
Hi Tony,
Open source is slightly more efficient than using ground source as the water is passed directly through the heat pump. However there are some considerations which you need to take into account. Generally you need something like 3 litres per minute per kW flow through the heat pump and this might mean that you will need an extraction license from the Environmental Agency as well as a discharge license. Filtration and treatment (hence additional maintenance) will also be required as will a complete stainless steel welded heat exchanger to avoid corrosion problems.
With regards to the thermal storage ability of the stream as long as there a constant flow (which is large enough) then you have an infinite amount of energy as it is always replenishing itself.
In our experience (Kensa Heat Pumps) although we have sold a number of open loop systems, it is easier to bury/sink closed loop arrays within the stream or water source as this removes the maintenance, stainless steel welded requirement and license from the EA requirements. You will need to get permission from the river owner to do this and how they are installed will depend on other issues such as debris flowing in the stream/river.
Check out our website for further info www.kensaengineering.com
Dear Tony
No problem drilling GSHP boreholes through rock - the Scandinavians and Swiss go down 200m or more. In fact, the drilling can be simpler than through clay or sand. Please feel free to contact me if you would like to discuss without obligation...
I have been an air conditioning and heat pump engineer for the last 15 years. I hope I can give some useful advice in respect to my experience. In the commecial world where heat pumps have been used, the majority have been air to air heat pumps. These are the most efficient form of heat pump on the market you will often see them in shops and offices throughout the country. TOP brands in the industry include DAIKEN, MITSUBISHI,HITATCHI,TOSHIBA,FUJITSU, PANASONIC as you can see most of the major brands you will recognise the name maybe with the exception of Daiken but they are often classed as the best by many air conditioning and heat pump engineers. AIR TO AIR heat pumps will not suit the domestic market in many cases because you always have an airflow in the conditioned space and you cannot heat hot water. They do have the cooling facility though and this makes them an excellent choice for conservatories. All the top brands now use Inverter technology and non ozone depleting refrigerants normally R410A.
The next most efficient systems are air to water. At this moment in time I only no of 3 brands that use the new inverter technology to control the compressor (slows it down and speeds it up with demand rather than just being on and off therefore making it more efficient) to heat the hot water for space heating and domestic hot water. These brands are DAIKEN ALTHERMA, MITSUBISHI ECODAN and HITATCHI. Because of this I assume these 3 brands to be leading the way in air source to water heat pumps which does not surprise me because they have been prestige brands in the air conditioning industry for as long as I have been in the industry. These systems by the above brands have been tested to be effective down to minus 20 degrees celsius ambient temperature. So this leads me to the question Why do we need ground source heatpumps in the UK wich has a mild climate? The Daiken altherma is the only brand at the moment to have a slit system choice which makes it more flexible and it also has a new high temperature range for use with existing radiator systems. Altherma split system must be installed by a qualified air conditioning or refrigeration engineers where the Mitsubishi and Hitachi systems can be installed by a qualified plumber. Daiken Altherma do have a mono bloc system that can be installed by plumbers same as the others. You can add solar technology to heat the tank for the above systems. My company is not tied to any one brand so I hope I have been able to give an unbiased opinion from an air conditioning and heat pump engineer rather than a sales person for any one brand.
cliff@howecool.com
Hi, We are reaching the end of a self build project and all our friends wish we had contacted grand designs, which would have been very interesting, but I have been encouraged to see if there are any competitions out there that we could enter the house in.
I designed the house totally. 80% of house exterior and interior built from reclaimed materials that we have sourced from all over the country, physically taking doors and a staircase out of a house that has been demolished.
Also we have a air source heat pump installed, and having on-going issues with it. Have an independent advisor coming to see us next Tues.
Can you advise me please?
Regards, Jacqui and Cliff Jacques
Hi Henry
The Daiken Altherma has a 55 degree water temp off its normal inverter compressor no need for multiple scroll compressors it also has a high temperature range up to 80 degrees celcius.
cliff@howecool.com
very useful as a guide to other plces to look
Scandinavian specification heat pumps work to much lower outside temperatures.
http://www.slcd.co.uk/index.php?main_page=index&cPath=109 is a good one
Personally I would only use air to air - the disruption and cost of ground source will never be paid back
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