Heat Pumps Are Not New | Nathan Gambling

Heat Pumps Are Not New | Nathan Gambling

In this episode of Energy Unwrapped, I’m joined by Nathan Gambling, lecturer in plumbing and heating and host of the BetaTalk podcast, for a trip through the history of heating in Britain.

We go right back to the days before central heating, through town gas, natural gas, oil heating and the rise of the combi boiler. But the main theme running through the conversation is something Nathan has said for years: heat pumps are not new technology.

We look at Graeme Haldane experimenting with heat pumps in Scotland in the 1920s, John Sumner’s remarkable water-source heat pump in Norwich in the 1940s and the long history of refrigeration, air-to-air heat pumps and commercial heating and cooling. Nathan also brings a unique family connection to much of this history, with generations of his family working across combustion, oil heating, refrigeration and some of the UK’s earliest commercial heat pump systems.

It turns into a much wider conversation about how we heat our homes, why some of today’s heating practices are a legacy of technologies we no longer use, and what previous energy transitions can teach us about the move from fossil-fuel heating to heat pumps.

What we cover in this episode

• why heat pumps really aren’t new
• Nathan Gambling and the BetaTalk podcast
• peer-to-peer learning in the heating industry
• Nathan’s family history in heating and engineering
• heating homes before central heating
• the rise of central heating in Britain
• town gas and manufactured gas
• the transition from town gas to natural gas
• the Canvey Island natural gas trials
• the development of the UK gas grid
• Graeme Haldane’s heat pump experiments in the 1920s
• John Sumner’s Norwich water-source heat pump
• why early heat pumps didn’t become mainstream
• storage heaters and off-peak electricity
• oil heating in Britain
• the rise of the combi boiler
• why radiators traditionally ran hot
• weather compensation and variable flow temperatures
• why heat loss changes with outside temperature
• air-to-air heat pumps and comfort cooling
• early VRV and VRF systems
• how heating industry training has changed
• why poor practice can be passed between generations
• what previous heating transitions can teach us today

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Full Transcript

Below is the full transcript for this episode, lightly edited for readability.

Nathan Gambling, BetaTalk and Peer-to-Peer Learning

Nathan is a lecturer in plumbing and heating and will be familiar to many people as the host of the BetaTalk podcast.

We start by talking about something Nathan championed particularly strongly during the early days of energy social media: peer-to-peer learning. Engineers sharing what they know, questioning each other and continuing to learn rather than treating a qualification as the end of their education.

Nathan explains that this type of learning has always existed. What social media did was give engineers a much larger community in which to do it. The discussion also touches on Heat Geek, the Guild of Master Heat Engineers and the importance of people actively working in an industry sharing current practice with each other.

Nathan Gambling’s Family History in Heating

Nathan’s connection with the heating industry stretches back generations.

His grandfather became a leading oil combustion specialist and spent time in Sweden working with oil burner technology before bringing that knowledge back to Britain. Other members of the family worked with industrial refrigeration, comfort heating and cooling and commercial heat pump systems.

Nathan’s own route eventually took him into teaching plumbing and heating, giving him an unusual mix of practical, historical and educational experience.

That family history gives us a useful route through several of the major changes in British heating over the last century.

How Did We Heat Homes Before Central Heating?

Central heating feels completely normal today, but its widespread adoption is relatively recent.

For many households, heating historically meant keeping one main living space warm. Bedrooms and other rooms could remain extremely cold. Gas fires, electric fires, portable heaters and solid-fuel appliances were common.

Nathan describes the move towards whole-house central heating as a long transition rather than something that happened overnight. Even into the 1980s, plenty of British homes were only just gaining the radiator systems we now take for granted.

How Central Heating Changed British Homes

The attraction of central heating isn’t difficult to understand.

If you’ve grown up heating one or two rooms and someone offers a system capable of keeping every room warm, the improvement in comfort is enormous.

Installation could be highly disruptive, with floors lifted and pipework installed throughout an existing house, but the benefit on the other side was obvious: warm bedrooms and much more consistent comfort throughout the home.

What Was Town Gas?

Before Britain’s natural gas network, much of the gas used around the country was manufactured gas, commonly known as town gas.

Rather than extracting it from underground gas fields, it was produced from materials including coal, coke and oil. Different areas had their own production and distribution infrastructure.

At the time, gas wasn’t primarily about the central heating systems we associate with it today. Cookers, water heaters and individual gas fires represented a large proportion of domestic gas appliances.

From Town Gas to Natural Gas

The discovery and availability of large natural gas reserves changed everything.

Natural gas burns differently from manufactured gas, which meant existing appliances couldn’t simply continue operating unchanged. Burners and other components had to be converted or, where conversion wasn’t possible, appliances replaced.

Nathan describes thousands of different appliance types and conversion kits being involved.

The transition eventually required millions of appliances across Britain to be altered as the country moved onto natural gas.

Canvey Island and Britain’s Natural Gas Experiment

Canvey Island plays an important role in the story.

It became a terminal for imported liquefied natural gas and was subsequently used to test natural gas in domestic properties before the wider conversion of the country.

From there, Britain began building the infrastructure that would ultimately become the natural gas network we know today.

The scale of what followed is worth remembering when comparing that transition with today’s attempt to decarbonise heating. Nathan describes the gas conversion as a highly organised programme operating in a very different industry structure from the fragmented heating sector we have today.

The Rise of Gas Central Heating

Natural gas arrived at roughly the same time as British households increasingly wanted central heating.

Over the following decades, gas boilers became dominant, but this wasn’t an immediate switch. Oil remained an important heating fuel, particularly outside the gas network, and Nathan recalls oil boilers still being a major part of the market when he entered the industry.

Central heating itself was therefore another gradual transition involving several competing technologies.

How the Combi Boiler Changed Home Heating

Another major change came with the combination boiler.

Changes to water regulations, technological development and a growing self-employed installer market helped the combi become enormously successful in Britain.

For homeowners, it offered central heating and effectively continuous hot water without needing a traditional hot water cylinder.

That convenience eventually became the normal expectation for millions of households, but it also influenced how heating systems were designed and installed.

Why Heat Pumps Are Not New

This brings us to the central argument of the episode.

Heat pumps aren’t new.

They can feel new because Britain is now discussing them as a replacement for domestic gas boilers. But the technology itself has a history stretching back well over a century.

Nathan points out that heat pumps are already everywhere. Refrigerators, chilled display cabinets, vending machines and comfort cooling systems all rely on the same fundamental refrigeration cycle.

Moving energy from one place to another isn’t experimental technology. We’ve been doing it for generations.

Graeme Haldane and Heat Pumps in the 1920s

One of the most interesting names in the episode is Graeme Haldane.

Haldane was experimenting with heat pump technology in Scotland in the late 1920s, including systems extracting energy from the ground and water.

He also played a role in the development of Britain’s early electricity grid, making him a particularly interesting figure in the history of British energy.

The important point is the date. We were experimenting with heat pumps in British buildings decades before natural gas became the dominant way of heating our homes.

John Sumner’s Norwich Heat Pump

Then there’s John Sumner.

Working for the Norwich Corporation Electricity Department, Sumner developed a water-source heat pump in the 1940s that extracted energy from the River Wensum.

The system was built in the mid-1940s and commissioned in 1948.

Even more remarkably, Nathan explains that the system continued operating into the 2000s and achieved seasonal performance of around 3.4.

This wasn’t a laboratory experiment that disappeared after a few months. It was a working heat pump system demonstrating the technology many decades ago.

Why Didn’t Heat Pumps Take Over in the 1950s?

This raises an obvious question.

If heat pumps already worked, why didn’t Britain adopt them?

One part of the answer lies in the electricity system of the time. Britain had invested heavily in coal-fired electricity generation and wanted to create demand for electricity overnight when consumption was low.

Storage heaters provided a straightforward way of doing that.

Nathan discusses Sumner’s frustration that heat pumps weren’t given greater support while the electricity industry pushed technologies such as storage heating instead.

Heat Pumps Have Been Hiding in Plain Sight

Even while domestic wet heating became dominated by gas boilers, heat pump technology never disappeared.

Walk into a petrol station, supermarket, office or commercial building and you’ll probably be surrounded by refrigeration and heat pump equipment.

A fridge is a heat pump.

A chilled drinks cabinet is a heat pump.

The refrigeration keeping food cold is using the same basic principle.

And the systems commonly described as air conditioning can usually move energy in both directions, providing heating as well as cooling.

Air-to-Air Heat Pumps Aren’t New Either

Britain also has a long-established commercial market for air-to-air heat pumps.

Nathan’s own family worked with early variable refrigerant systems, including some of the first installations of their type in Europe.

He recalls systems being installed for Paul McCartney’s offices and Classic FM around 1990.

Again, this matters because it challenges the idea that heat pumps suddenly appeared when governments began talking about replacing domestic gas boilers.

Why Do We Think Radiators Need to Be Hot?

The history also helps explain some of the habits we’ve inherited.

Traditional boilers often needed to operate at relatively high temperatures to protect the boiler itself. That meant radiators were supplied with hotter water than the house necessarily required throughout much of the heating season.

Over time, homeowners and installers began associating a hot radiator with a heating system working properly.

But the radiator doesn’t need to feel hot. It needs to transfer enough energy into the room to replace what the building is losing.

Those aren’t the same thing.

Heat Loss Changes With Outside Temperature

This leads into one of the most useful technical parts of the conversation.

We often describe a house as having an 8 kW or 10 kW heat loss, but heat loss isn’t a fixed number.

As the outside temperature changes, the rate at which energy leaves the building changes too.

A heating system therefore makes engineering sense when it adjusts its output to match that changing demand.

That’s exactly what weather compensation and low-temperature continuous heating are trying to achieve.

Low and Slow Heating Versus On and Off

This is also why Nathan questions the way many boilers are still controlled.

Modern boilers are capable of modulation and variable flow temperatures, yet many systems are effectively controlled as simple on/off appliances.

The heating overshoots, switches off, the house cools and the boiler starts again.

A properly controlled heat pump provides a very different experience. Instead of repeatedly heating and cooling the house, it can continuously adjust the amount of energy being supplied to maintain a stable indoor temperature.

Why Heat Pump Heating Can Feel More Comfortable

We discuss my own experience of this.

With weather compensation adjusting the radiator temperature, the house simply stays around the target indoor temperature regardless of whether it’s relatively mild or freezing outside.

The radiators might only feel warm or even tepid, but the house remains comfortable.

Nathan explains some of the science behind why this steady-state approach can feel different from the temperature swings created by traditional on/off heating.

The Heating Industry’s Knowledge Problem

The conversation inevitably moves into training.

Britain has highly skilled gas engineers capable of diagnosing and repairing an enormous range of equipment. But being excellent at maintaining gas appliances doesn’t automatically mean someone has been taught about heat pumps, weather compensation or low-temperature heating.

That creates a difficult transition for the industry.

When Peer-to-Peer Learning Goes Wrong

Peer-to-peer learning can spread good practice incredibly quickly.

Unfortunately, it can spread bad practice just as effectively.

We discuss the example of a young apprentice who had already learned that heat pumps “don’t work” while not knowing what weather compensation was.

The problem isn’t necessarily the apprentice. If the person teaching them doesn’t know something, the same knowledge gap can simply be passed to the next generation.

What Previous Heating Transitions Can Teach Us

Looking backwards gives today’s heat pump transition some useful context.

Britain didn’t move from individual fires to central heating overnight.

We didn’t move from town gas to natural gas without an enormous coordinated programme.

Combi boilers didn’t suddenly appear in every home.

Every major change in heating has involved new infrastructure, new skills, new business models and changes in what homeowners expect from their heating.

The transition to heat pumps will be no different.

Heat Pumps Were Here Before Natural Gas

By the end of the conversation, the historical point is difficult to ignore.

Heat pumps were being installed in British buildings before the country had converted to natural gas.

John Sumner was heating a building from a river in Norwich in the 1940s. Graeme Haldane was experimenting with the technology even earlier. Refrigeration and commercial heat pump systems have subsequently become part of everyday life.

So when someone describes a heat pump as unproven new technology, the history tells a very different story.

About the Energy Unwrapped Podcast

Energy Unwrapped is my podcast about renewables, home electrification and how energy technology works in the real world. You can browse all episodes, platform links and future updates on the main Energy Unwrapped Podcast page.

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