A tale of 3 swimming pools

Swimming pool heat pump systems installed by John Cantor in the spring of 1982.
Lazonby river sourced system (River Eden)
Greystoke air-sourced system.
Askham air source system (installed 1983).


I had escaped busy London back in 1979 and had moved to a small village called Renwick near Penrith. I was working as a volunteer for an engineer, Rob Hitchins, and helped him to set up his workshop designing simple metal-working machines for developing countries.

We were driving in his van along the River Eden towards Lazonby, when I glanced at the sign ‘Memorial Swimming Pool’. STOP! I exclaimed, and leapt out of the van, much to Rob’s bewilderment. I climbed up to look over the wall and saw a small community-sized swimming pool right next to the river. Rob had guessed that I had more on my mind than simply the desire for a swim. I had recently left my job as a refrigeration engineer at Prestcold in London, and had been reading up about heat pumps. I was already aware of a large pool heated by this method in Dortmund, Germany, and here was an ideal situation for a similar scheme.

Many thoughts passed through my mind as I considered what sort of equipment could be used, but I didn’t think a lot more about it at that time since I didn’t expect that the pool organisation would be as keen as I was on the idea. They would probably think that I was barmy.

However, many months later, I had a visit from a local retired scientist, Dick Whitaker, who had somehow heard of me and who was on the pool committee. He had proposed the idea of a heat pump to the committee previously, but he was probably seen as a bit of a boffin with far-fetched ideas. Dick and I quickly got into some deep discussions, and did some back of an envelope calculations. During the next few weeks I spent many hours pondering over a potential system. At the time, there were very few heat pump installations in the UK, but I did seek out a similar system which was heating the town’s pool at Market Drayton by taking heat from a small river. This system used a big old Prestcold compressor which I was familiar with. Their system had been notoriously unreliable, as was much of the UK’s refrigeration plant at that time. I considered many options of compressor from a variable speed rotary vane type, to the sealed hermetic type. I had some serious decisions to make before a design was finalised.

At that time, I had also been volunteering at The Centre for Alternative Technology in Machynlleth in Wales. They were running a heat pump course and I had been asked to take along a demonstration model to help explain the principles. The course participants were generally those interested in installing a system themselves. One rather quiet member in the class seemed to know quite a bit about the topic. It turned out that he, Peter Boggis, was one of the designers from Eastwood Heat Pumps Ltd. who were the UK’s biggest manufacturer of systems in the early eighties. I had some good chats with Peter, and I think it is credit to him that I chose the Maneurop MT80 hermetic compressor, which is really the heart of the heat pump system and proved to be extremely reliable and long-lived. I called United Thermofrost Ltd. in London about the compressor. My first contact there, Len Fiddler, was very helpful and forthcoming with all the information and graphs that I needed about these particular Maneurop compressors. The design was taking shape. Not that I had much hope that the scheme would actually come to fruition.

The finer details for extracting heat from the river were actually not that straight-forward. The river water was to be pumped up the river bank about 12ft, through some sort of heat-exchanger, then back into the river at about 3 degrees centigrade colder. The heat-exchanger would have to deal with muddy water following floods, and to minimise pump power I had to take advantage of the siphon effect. This meant that the heat-exchanger had to work at a partial vacuum therefore the outer container had to be able to take the negative pressure. We also had to obtain a license, which involved the seemingly pointless task of advertising in the London Gazette.

In general, my policy was to use the best quality parts that I could. I was determined that this installation was going to be reliable, unlike much of the refrigeration equipment that I had worked on in the past. However, good quality parts are expensive and this was in conflict with my frugal nature, so with respect to the river heat-exchanger (the evaporator), it definitely had to be fabricated for the sake of cost. The river pump would be submersible, which seemed a little risky to me since a motor running underwater sounded like a recipe for trouble. However, the engineer at Flygt Ltd. assured me that one of their 3 phase pumps would be no problem.

The next issue was the expansion valve to control the refrigerant flow. I recall my college lecturer describing Sporlan Inc. valves as; ‘the best expansion valves in the world’. I liked and trusted this lecturer, so contacted the UK importers of this USA-made valve. Unfortunately I had a bit of a clash with one of their salesmen. It was actually a misunderstanding of the term ‘balanced port’, Anyhow, I was getting nowhere with Sporlon, so I contacted the only UK manufacturer of expansion valves, and found a very helpful sales rep. I did not really trust the selection they made for the valve type as my working temperatures were way off their graphs, and somehow it didn’t feel right, but I decided to trust the helpful man who was confident it would operate well. So I went for the UK valve, partly swayed by the fact that it was relatively locally manufactured.

Whilst I did not want to compromise on energy efficiency or quality, there was a limit to how much I could spend. The Bitzer shell and tube heat-exchangers for the ‘hot’ side looked very nice, but I decided that I could economise here since this is basically just a metal item – it just had to be big enough; I wanted one as big as I could get. I found a company who imported Italian-made heat-exchangers, and Cupro-nickle ones were available. This type would not corrode with the chlorinated swimming pool water. I gave them my ratings and conditions and they came back with data and temperature differences that were far too high. My working conditions once again, were off their graph, and they struggled to understand why I wanted just 3°C difference between the refrigerant and the pool water. I knew that this was possible since I had seen such systems working in Sweden. Eventually I had to bend the truth and told them that I was increasing the compressor size. This swayed the selection towards my requirements. I was happy and they didn’t think I was being too radical. But I refrained from telling them that I intended to throw away their end plates that had 1 ½” connections, and make my own 3″ straight-through connections so that all the pool water would pass through the heat-exchanger – a few more watts gained.

I was booked to address the swimming pool committee with my proposal. This was now some considerable time since my first sighting of the pool. I knew very little about business practices at that time, so sought advice. Pete Raine, the then director of The Centre for Alternative Technology kindly advised me, and helped me draft out a tender for the project.

My presentation seemed OK, but Dick was a bit disappointed since he thought I had baffled them too much with figures and theory. My lack of sales-pitch was probably confusing. I just told them the facts rather than tell them how wonderful a heat pump would be.

Many weeks passed and the committee pondered their options. Their heating costs were high. £1,700 was spent on oil every year, plus electricity for the circulation pumps. I had predicted that they would save £1,000 per year, and just hoped and trusted that reality would actually match the theory.

Meanwhile, another similar community swimming pool at Greystoke (on the other side of Penrith) approached me. They were not lucky enough to have a river, so an air-source heat pump was the only option.

I probably worked all night, and spent the following day phoning for prices (from a pay-phone phone call box – can you believe it!!). I then presented a proposal to the committee at Greystoke who seemed very interested. They said that they would consider it and meet the following week to make a decision. To me this seemed like such an important decision, like a ‘Y’ fork in the road. If they said YES, it probably meant that Lazonby would also say yes and I would be up to my neck in two very interesting pioneering projects. If NO, then it may be unlikely that I would get any more such projects. Possibly the end of the road for heat pumps – before they had even started.

I was told to ring them at 10pm on the night of the Greystoke meeting, when a decision would have been made. Many of my friends arranged to be in the Melmerby pub to either celebrate, or commiserate the outcome. At 10pm I nervously went to the phone box to get the result “yes we would like you to go ahead” they said . I must have been a little fazed after the call, as one of my friends looked at me and said “oh well never mind. I’ll get you a whisky”. Someone had to directly ask me what the committee had said, since I was obviously in shock. “They said yes”, I replied . Yippee!! And it was drinks all round.

For the next 2 ½ months, the only thing in life was heat pumps. One often hears the phrase; ‘if it hadn’t been for so and so, it would never have happened’. This could not have been more true. I owe a lot to Ian Rogers, a blacksmith and artist who helped a great deal. Not only did he make many of the parts for the heat-exchanger that we fabricated, but he also let me use his workshop at Long-Meg mines where most of the parts were assembled. The first major component was the evaporator this is the heat-exchanger that extracts the heat from the river water. I had worked out that I needed 180m of ½” o.d. copper pipe, split into 12 parallel circuits, and the finer details were all buzzing around my head; how to maintain turbulence around the pipes, how to allow sand and solids to settle out and not block the heat exchanger, and how to ensure oil return in the refrigerant……..

The air-source system at Greystoke was going to have the same compressor and condenser (hot-side heat-exchanger) as the water-source system for Lazonby, but the evaporator (cold side) was to be a finned coil like a car radiator with large fans. I tracked down an air heat-exchanger manufacturer in Kings Lynn. For some reason there are a lot of finned heat-exchangers made in that area. I chanced upon Mr Sen Goupter from ACR Heat Transfer Ltd. who understood what I wanted and made some useful suggestions. I gave him the available foot-print and he sent me back a drawing. I urged him to keep it big. Big means low temperature differences which is good and what I wanted.

Now that the contract had been agreed (I don’t recall any written agreement) and a deposit had been received. I realised that if I was to get the pool heated by May 10th , then I had to get cracking. In fact, the next 3 months was going to be work work work.
Whilst I was fairly certain how things would go, there were various details to sort out – and a lot of them. I had hardly considered the electrics.

It was over the next few months that various friends helped out.

At Lazonby, I had planned a 1m x 1m concrete ring to go in the river bed for the submersible pump. This needed a JCB so a local driver was found. He was rather bemused by my request and suggested that the best way to get to the river edge was not down the 12ft bank, but was by accessing from the opposite side of the river. At that point the river is some 50ft wide, but luckily quite shallow. I approached the land owner and was rather affronted by his negative attitude to helping the community swimming pool. He eventually agreed that the digger could drive across his field to enter the river on the condition that the digger would spend a couple of hours tidying a part of his land. Is this how the landed gentry have got their wealth? It was in contrast to the generosity and help received with the rest of this project.

So dig-day came and I walked in waders across the river to show the driver the best route. The digging was reasonably easy, and ropes were used to lower the ring into position just such that the chamber was always flooded. The height was complete guess work, and since the river varied in level a lot, we were very lucky to have chosen the level and position that we did. It proved to be the perfect place.

Back at Ian’s blacksmith workshop some of the major fabrication was about to take place. Coils of copper had arrived and I had made a steel base, which Ian looked at and shook his head. The next day I arrived and Ian was half way through a much neater version – I was learning. Next I made some calculations for the large fibreglass dome and realised that the forces could be quite high and that the top needed to be an accurate semi-sphere to be strong enough to cope with the pressure. With Ian’s experience from art college, he set-to with plaster of paris and old sponges and a jig that swung around, and within 20 minutes (you have to be quick when using plaster of paris as it sets very quickly) he had made a perfect semi-sphere for the top of the heat-exchanger shell. The pipes were wrapped with corrugated cardboard as a former, the dome on the top and the whole thing was covered in a nice thick layer of fibreglass. When the whole thing was finished it was winched onto Ian’s trailer and looked like a rocket set for the launch pad.

Meanwhile the nice expensive compressors and the shell and tube heat-exchangers had arrived. Things were moving on apace and next we needed some fittings to link into the swimming pool pipework.

I had not previously done any pipe fittings as large as 3″ dia. before, and had not lifted heavy machinery. Another good friend and invaluable assistant to the project was Tom Thwaites. Tom had all the knowledge, experience, equipment and endless energy. He came down to help remove the old boiler. This was the crunch point – the point of no return. With boiler scrapped… I just had to get all these bits in place..and it had to work!!!
Tom and I discussed the heat exchanger fittings .. “no problem” said Tom, as he often does, and off we went to Bowman’s scrap yard in Penrith to search for some old bronze bearings. Back to Ian’s to melt them down in his paraffin blow-lamp/ beer barrel furnace, and pour them into a sand mould. So two blanks were made and off to Tom’s workshop at Moreland. His trusty old Colchester lathe (which is probably still going) had made countless components over the years.

I now had to make up the electrical panels, so a few RS Components Ltd orders for parts, and a few late nights resulted in two posh-looking panels with stick-on letteraset labels. I had decided on using a soft-start for the compressors since this would cause less stress each time they started up. If I had not taken this decision, these expensive compressors may not have lasted as many years as they have.

I had told the committee that it would take 10 days to heat the pool from first starting the system. The calculations were only theory, and I certainly could not guarantee it. Time was moving on and opening day was approaching. I have few memories of the final days of the installation, but I do recall the day when I had nearly finished at Lazonby. By late afternoon the end was in sight and I had the swimming pool water circulating around the system. The river side was all in place and the river pump had been tested but I had a lot of wiring to do. As ever the optimist I thought I might be finished in time for a pint, but I think I was still hard at it at 2 am.

Switch on!! The compressor purred into life and I stared at the pressure gauges and looked at my temperature probes.. river water in at 8C.. going out at 6 ½ C wow.. its working!.. I’m extracting heat from the river, and that heat must be going into the pool, but the refrigerant suction pressure was far to low. No matter what I did I could not get the suction pressure up. I realised that I was working at unusual temperatures for this equipment, the discharge (hot side) pressure was so low that there was insufficient pressure difference the valve. But I had been told that this valve would do the job in these conditions.. albeit off their graph. 30 minutes running and things were not looking encouraging A flash went through my mind; I imagined myself in the future looking back at the time when I use to live in England and took all that money from those village committees for the systems that never worked!! That thought faded, and in desperation I completely bypassed the expansion valve. To my relief the suction pressure came up to a sensible level and the temperature of the water was returning to the pool maybe ½ a degree warmer. It was heating!! I was greatly relieved, but anxiety was lingering from the thought that it may not reach 23°C by opening day! I had no option but to leave the system running with a fixed expansion device and to go and seek a better valve, but sleep was needed first.

I got back onto Sporlan Valves and found the right person to talk to. Their valves were infinitely superior and their graphs almost came down to the working temperatures of the system. They were better all round, and had soldered connections, so the lack of mechanical joints meant a far lower risk of a refrigerant leak. So the vales were ordered and shipped urgently. Fitted a couple of days later and to my relief worked just as I had hoped.

Now that Lazonby was heating, I needed to focus on Greystoke. Luckily for me their opening date was a little later. It was Tom Thwaites to the rescue again, with his experience with big threaded pipework and all hands on deck. The air heat-exchanger was ready for collection from Kings Lynn. I don’t remember if my friend Tony Bell from London had arranged his own holiday up near Penrith, or if I had craftily suggested it, anyhow, I persuaded him to take a detour via Kings Lynn. He arrived with wife and young family on Saturday just as the factory was closing. I think he struggled getting the item on the roof rack of his Vauxhall Viva estate. I cannot even remember if I paid him for his heroic efforts to lift the large heavy heat exchanger into position and bring it up the motorway… Thanks Tony.

The fans that force the air over the heat-exchangers were to be large and slow running so that they would be quiet and energy efficient. I also wanted them to be 3 phase, but the sales rep advised that if I go single phase they could be speed controlled and this would save a bit of energy and make them even quieter. This was a bad decision since they actually needed to be run at full speed for most of the time and they emitted a slight buzz. I wired-out the speed controller to make them quieter.

I cannot remember much about the week Lazonby was heating up, but obviously I was nervous. I was plotting a graph of it climbing, and at first it seemed a bit slow. A few days later it seemed to be rising at a good rate, so I thought that I would easily have a warm pool for opening, however, as the water warmed, the heat loss increased so the rate of increase obviously slowed down, and I am fairly sure that the first day of swimming was a little chilly. I think I kept out of the way since I certainly didn’t want anyone quizzing me or complaining. I think I called early morning and late at night to tweak the refrigerant charge and superheat setting. But as the weather improved, the heat pump easily coped and all were happy…until the wind came !! One thing that I had not considered was what happened when a strong cold wind sprang up. Lazonby can be windy due to the Helm Wind which is unique to that area of the Pennines. At such times the pool cover would blow off and the temperature would plummet. The following days it struggled to bring the temperature back up. On the whole it worked well, but definitely suffered a lack of ‘acceleration’ it was slow to heat up. Mid summer was great, but as September approached, on came some cold weather and so the pool temperature suffered.

It was rather pleasing reading the local newspaper article (Penrith Herald) reporting a better-than-expected saving of £1,100 in the first year, when I had promised a saving of £1,000. I was wondering if any other pools in the area were interested in a system. There are a surprising number of such pools in the Penrith area. Hunsonby and Culgaith had very small unheated pools that ran on a tiny budget and with a lot of voluntary help. Any form of heating would have been a quantum leap for their accounts, so it wasn’t practical. Appleby was certainly a contender. It was right next to the river, and had a well worn boiler, as did Lazonby the year before. At the time I played in the Appleby Brass band, so had contacts in the town. A design was sketched out and a tender presented to the committee. The system would be almost twice as big as Lazonby. The committee also had a quote from the electricity board for an air-source system. I was probably too confident that my river source system was better, and maybe naive about the professional nature of their salesmen. The Committee decided to trust the installation to the larger organisation as opposed to a small outfit like John Cantor Heat Pumps, so I didn’t get the contract. It was a couple of years before I went to see the air source systems; I was not particularly impressed. I am not sure what caused the demise of the open air pool at Appleby, but the pool and heat pump did not last many years. It was eventually replaced by a nice new indoor pool.

Although I was disappointed not to have got the Appleby contract, I was lucky enough to gain a contract at Askham pool, to complete a triangle around Penrith.

The situation at Askham was one of a poverty trap. If they could find £1,000 they could save about that amount in one year. They had a promise of match funding, but their own funds just fell short. A good friend of mine, Frances Carr, though it was a ridiculous situation so went along to the local newspaper, the Penrith Herald, to see if they would cover it as a story/ appeal. Her positive energy got things moving, and within a few weeks the money was raised. So I was full-on again designing and fabricating another system ready for the opening day in May.

I tried to improve on the design, on this, my third installation. The compressors and most components were the same, but the fan arrangement was significantly improved, following experience learnt at Greystoke. There, the air blew down through the heat-exchanger. This is good in some ways, condensed water should be blown down and away with it, but the air flow is less even when you blow, also the fans are more exposed to the surroundings so noise can be a problem. So at Askham, the evaporators went vertically, and the air sucked through. This proved to be better since water ran off better, and air flow was more even. It was certainly quieter.

Since the two systems previously installed were a little under-sized, I had decided to make the one at Askham a bit bigger, with two separate 15kW systems as opposed to single 24kW. The reason for the under sizing was not entirely my fault. I had not allowed for the pool cover being blown off, and the heat demand was based on a pool temperature of 72F, however, the thermometer was actually 2 degrees out. 72F at Lazonby was really 74F. Greystoke, with the air source, seemed to be in a frost pocket, and the Church was notoriously one of the coldest in Cumbria. In addition to that, the small stream that runs beside the pool suggests that moving ground water under the pool could be taking heat away at a greater rate than expected.

Although the first two pool heating systems were a little undersized, the good news was that they saved a lot of money and a lot of energy. Of course when money is saved, the accounts look better, and the obvious question from the committees followed…. “Can we have it hotter”? Well my immediate answer was “no”, not during cold periods. I had never considered that the saving of energy would in part, encourage more energy use. 1983 was a hot summer, and the pools were lovely and hot, but as September approached. The heat dropped again. For the next season I had modified Lazonby by adding another smaller compressor alongside in ‘tandem’. The air source at Greystoke still had its old redundant 72kW off-peak resistance heater which I re-wired to 16kW and reinstated it as an off-peak heater again for use when the pool dropped below 23°C.

Since I knew every detail about these heat pumps, I was best placed to maintain them- which I did for many years. Every year the concrete lid of the ‘sump’ down at the river bank needed to be lifted and the sand that collected during the winter needed to be scooped out. By and large, the reliability was very good. But one or two occasions resulted in me having to drop anything that I happened to be doing to go over to one of the Pools to sort something out before the pool got embarrassingly cold. In one occasion, I came out to Lazonby to find that the River pump (the submersible one in the river) had tripped out. It was clearly jammed up with a leaf or a frog or something. The only problem was that there had been a lot of rain and the river was in flood. This was not a condition that I had allowed for, and the problem needed fixing. The only answer was to put on a wet suit and for me to go in and retrieve the pump which I did, and managed to dislodge a piece of plastic cup from the pump impeller.

I recall being asked the question “how many years will the heat pump last for”? I honestly had little idea, but it was a question that I had considered, and I think I answered that I thought it would last a minimum of 15 years. I find it heartening to know that Lazonby completed 31 seasons, and the only the compressor failure (at Greystoke) was after 29 years!! This technology (unlike boilers) can clearly live-long if carefully installed and adoringly serviced.

There have been no dramatic advances in this technology over 30years , just the gradual development of the compressors. A new replacement would have a rotary scroll instead of a piston type, and maybe have 25% higher energy efficiency. The heat-exchangers and valves would be much the same, but certainly would be more compact in size. However, in a bid to be cost-effective, some modern heat pumps have quite ‘skinmpy’ heat-exchangers, so the resulting energy efficiency may not be a great deal better than the old system.

This technology is probably the best and most practical solution for heating such swimming pools. The CO2 saved over the years is very significant as compared to the oil previously use at Lazonby and Askham. Greystoke originally had off peak electric heating, so the CO2 savings there are even more. I hope these systems keep going for a few more years yet.