Heat pumps in Bicknoller

As a professional engineer of many years standing, I have always had an interest in finding the most cost efficient and effective solution for any problem.

Although my field of expertise was electronics and computer systems, I have been interested in designing houses from the age of about ten. I frequently asked: What should the house look like? How big should it be? How many bedrooms did we need? How many en suites should we have? And of course: How should we heat it?

With my engineering background I knew about heat pumps, and spent many happy hours trying to work out how I could use a heat pump to provide a cost effective central heating system, but try as I might there was no practical solution so we fitted a gas boiler. We moved into that house in 1970 and had 30 very happy years living there.

So why didn’t I fit a heat pump. The answer is simple £.s.d. The heat pump market was in its infancy and there were very few companies making them. In consequence the price was very high. The technology had been around for years in fridges and freezers which are simply heat pumps which move the warm out to the black grill on the back of the machine, and leave the cold inside the box.

A heat pump for a building does exactly the opposite it moves the heat into the building and discharges the cold outside. But the technology was only delivering efficiency gains in the region of two kilowatts of heat out for every kilowatt of electricity which you put in.

In 1999 I had retired and we bought a beautiful plot on the junction of Trendle Lane and Church Lane. On looking at the technology we found that heat pumps were available which could deliver up to four kilowatts of heat for every kilowatt of electricity which you put in. After some research I bought a Calorex heat pump which was designed for heating swimming pools, and this unit kept the house comfortably warm throughout the winter of 2001/02 with the cold simply being discharged into the outside air.

Unfortunately the unit had reliability problems, and those of you who may have lived in Trendle Lane at the time might have noticed your lights going dim from time to time. That was because when our pump switched itself on, it took about 100 Amps of electricity. That is about the same as eight three kilowatt electric fires all being switched on together.

When the time came to sell the house, I knew that this problem was unacceptable, so we took that unit out and replaced it with a Nu Heat unit which was supplied by their UK subsidiary in Honiton. The new unit is quite amazing, it still discharges the cold into the outside air, but the new unit can discharge the cold into air which might itself be at -6°.

When we bought Rowan Cottage, the choice of heating system loomed large once again, but this time the choice was not gas or oil. It was which heat pump do we buy, and do we go for air or ground discharge?

Having had two air discharge systems we decided to install a ground heat recovery system in Rowan Cottage. This involved digging two meter deep trenches and laying in the region of 500 metres of water pipes through them. Cold water pumped out from a British made Kensa heat pump gives up its coldness to the earth, and returns to the heat pump slightly warmed.

This system has worked extremely well through this last winter although we do light a wood burner to supplement the system on the coldest days. We could increase the output temperature of the heat pump, but efficiency reduces as the output temperature increases, and in any case we like coming home to a lovely warm hall.

Our house is substantially reliant on electricity. We have no gas and no oil. We believe that the total cost of electricity for this year will be around £1,300.

Another advantage of the system is that heat pumps need no annual inspection or maintenance.

We are delighted with the system and would recommend it to anybody who is building a new property or upgrading the heating system in an older property. We have four bedrooms, lounge, dining room, kitchen and utility. Total area is about 2,200 sq ft.

Should you wish to have more information from the writer of this Case Study please e-mail:jim.laflin@talktalk.net

Information on the environmental risks of heat pumps from the Environment Agency

 After the highly successful evening on Heat Pumps held by QE in Bicknoller on Nov. 4th 2011 it was agreed to display the following notes from the Environment Agency submitted by Ian Myers. 

Introduction

Overall the Environment Agency (EA) supports the use of renewable energy and recognises the role that heat pump technology can play. There are some environmental risks and legal requirements however. Installers and householders can face the risk of legal action both statutory and civil if problems occur.

The Risks

For any below ground system:
1)      Temperature changes can impact on adjacent water courses where there is direct connectivity, most watercourses are ground water fed to some extent but highly permeable ground is more risky.
2)     Drilling and ground excavations can connect aquifers and impact on both quality and quantity of ground water resources.
3)     Thermal transfer fluids are pollutants.

For open systems there are additional risks:
4)     Groundwater levels can be decreased.
5)     Impact on other abstractions and watercourses.  

With open systems amd borehole drilling there is a need to obtain permission from the EA.

For all projects do a risk assessment:

1)     Establish whether there are any private or public abstractions both groundwater or surface water that might be potentially impacted.
2)     Is the site likely to be contaminated from past activities.
3)     Is the site near a SSSI or sensitive wetland.
4)     Is the site near a river, watercourse or land drain.
5)     Are there any services in the area, these often act as conduits for groundwater flow.
6)     Is the site near any other ground source heat pumps.
7)     Is the site near a septic tank, cess pit or soakaway system.

Good practice includes:

1)     Ensure you install a good quality system with a competent company, the right materials, pipework and pressure, take a long term view.
2)     Pressure test before backfilling any excavations.
3)     Minimise or avoid pipe joints especially below ground, don’t use mechanical joints.
4)     Fit an isolation system.
5)     Fit an auto shut off that activiates on pressure or temperature drops.
6)     Overlay pipework with marker tape.
7)     Label the type of thermal transfer fluid that is used
          a.   Monoethylene glycol is toxic, polypylene gycol is better;
          b.   Corrosion inhibitor is also toxic and may contain biocides;
          c.   Think about how these chemicals are stored during installation and disposed of, don’t dispose to ground or sewer;
8)     Think about what you will do if you have a problem
          a.   Talk to the EA immediately 0800 807060
          b.   Advice can also be obtained from Local Authority Environmental Health Officers
          c.   Have a plan, know the risks and your neighbours
          d.   Look after and check the system regularly.

More information available from:

1)     Ground Source Heat Pump Association
2)     EA
3)     QE website
4)     Local Authority, Environmental Health or Building Control

EA website:     http://www.environmental-agency.gov.uk/business/topics/128133.aspx
EA Good Practice Guide:     http://publications.environment-agency.gov.uk/pdf/GEHO0311BTPA-E-E.pdf

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