The Myth of the Room Thermostat: Why It’s Failing Your Heat Pump

Heat pumps are rapidly becoming the go-to solution for low-carbon heating. But even the best heat pump will almost certainly, fall short—not because of the unit itself, but because it’s being controlled by outdated thinking. The heart of that problem?

The humble room thermostat!

It might be smart. It might be wireless. But if your entire heat pump system is being switched on or off based on the temperature in just one room, you're missing the point—and likely missing out on serious efficiency and comfort.

Why Single-Room Control Doesn't Work with Heat Pumps

Most thermostats - smart or not - are designed to monitor just one location. That’s usually the hallway, or sometimes the living room. When that one space hits temperature, the heat pump shuts off. Sounds sensible, right?

Wrong.

Here's what happens:

• That one room may heat up quickly (especially if it gets sun, or has larger radiators versus heat loss compared to other rooms).

• Meanwhile, other rooms remain cold - bedrooms, north-facing rooms, poorly balanced system or those with larger heat losses/smaller radiators (in comparison).

• The system cycles on and off, trying to chase an average that doesn’t exist.

• Homeowners bump up the flow temperature or leave doors open, chasing comfort.

• Efficiency drops. Comfort suffers. Bills go up.

This might have worked with gas boilers that blast heat into a system. But with heat pumps - especially ones designed to run low and slow - it's a recipe for disaster.

What About Multiple Room Thermostats?

Some systems try to fix this by putting thermostats in multiple rooms, each one capable of switching the heat pump on or off when its room is calling for heat.

At first glance, this seems better - but in practice, it often creates chaos.

Here's why it fails:

• Each room acts independently, without awareness of what others are doing.

• The heat pump keeps starting and stopping in short cycles - every time any room drops slightly below its setpoint.

• This constant on/off cycling reduces efficiency and wears out the compressor prematurely.

• The system never achieves a stable flow temperature or operates smoothly in weather compensation mode.

• In colder weather, the flow temperature often gets set too high “just to be safe,” again undermining the whole point of a heat pump.

In short, multi-zone thermostats that each control the heat pump turn a sophisticated system into a chaotic one. You get no coordination, no balance, and no optimisation.

The Problem Isn’t the Thermostat — It’s the Logic

Today’s market is flooded with so-called “smart” thermostats. They offer Wi-Fi control, geofencing, learning schedules... but nearly all of them are either:

• Single-point systems (failing to see the whole picture), or

• Multi-point triggers (failing to coordinate or optimise heat delivery)

Either way, the heat pump is reacting, not thinking. And your comfort, efficiency, and energy bills suffer as a result.

The Better Way: Room-by-Room Intelligence

To make a heat pump work as promised, you need coordinated, dynamic control - the ability to see what’s happening in each room and adjust everything together.

That’s where COP Angel comes in.

Our patented system uses:

·       Motorised radiator valves with built-in room sensors

·       Return water temperature sensors on every radiator (or uf zone)

·       Dynamic control algorithms that constantly adjust the flow temperature

·       Room-by-room data to prioritise underperforming spaces—not just one hallway or rogue thermostat

This allows the system to operate in its sweet spot, avoid short cycling, and keep all rooms comfortable at the lowest possible flow temperature—exactly where heat pumps perform at their best.

Smarter Control = Lower Bills + Greater Comfort

With COP Angel, your system learns how each room behaves and balances heat delivery automatically. The result?

• Better comfort in every room

• Lower energy bills

• Longer life for your heat pump

• Fewer call-backs and complaints for installers

 We are currently developing the solution and have proved concept via digital twin. We hold the UK patent and have international patent pending. If you are interested in investing in this game changing solution get in touch with the inventor here mike.kellett@copangel.com

Why Your Heat Pump Isn’t Delivering the Savings You Were Promised

Heat pumps are often marketed as the ultimate low-carbon, energy-efficient solution to home heating. And on paper, they are. With the ability to provide 3 to 4 units of heat for every unit of electricity.

So why are so many homeowners and housing providers reporting disappointing savings?

The answer lies not in the technology itself, but in how it's controlled, balanced, and commissioned.

The Common Mistakes Undermining Your Heat Pump’s Efficiency

Even the most advanced heat pump will underperform if the distribution system around it isn’t designed or optimised properly. Here are three common culprits:

1. Poor Radiator Balancing

Most UK homes were originally designed for boilers, not low-temperature heat pumps. Boilers run at high flow temperatures—meaning radiators heat up quickly even if they're poorly balanced. Heat pumps, however, work best at lower temperatures to stay efficient.

If your radiators are unbalanced (which they almost always are), some rooms overheat while others never get warm enough. Installers often crank up the flow temperature to compensate, which kills efficiency.

2. Static Weather Compensation

Modern heat pumps often feature weather compensation—adjusting the flow temperature based on outdoor conditions. But here’s the catch: most systems use a static curve, set during commissioning. Once it’s set, it doesn’t respond to how your home actually behaves room to room.

Homes are complex—south-facing rooms get warmer, north colder, room occupancy, cooking, lighting etc all affect the demand. A one-size-fits-all curve just doesn't cut it. Without a dynamic control system, comfort suffers and efficiency drops. See our blog on this here- https://copangel.com/blog/why-weather-compensation-control-in-heat-pumps-must-be-dynamic

3. Generic Smart Thermostats

Most “smart” heating controls are not designed with heat pumps in mind. Many simply switch the system on or off based on a single room temperature—often the hallway. That’s no smarter than an old dial on the wall.

To truly optimise a heat pump, you need intelligent, room-by-room control that works with—not against—your heat pump’s low-temperature strategy.

The Smarter Way Forward: Intelligent, Adaptive Control

This is where COP Angel comes in. Our patented smart controller is designed specifically for heat pumps, with the following key innovations:

·       Motorised radiator valves with built-in room sensors

·       Return water sensors on each radiator to ensure balanced heat distribution

·       Dynamic weather compensation that adjusts in real time based on actual room performance

·       Room-by-room control to reduce flow temperature while maintaining comfort

By constantly analysing how each room heats up and adjusting the system accordingly, COP Angel reduces the average flow temperature—boosting your Coefficient of Performance (COP) and delivering even more savings your installer promised!

Why Radiator Balancing is One of the Most Frustrating Jobs in Heat Pump Commissioning

If you’ve ever commissioned a heat pump system in a property with more than a handful of radiators, you’ll know the feeling: hours spent fiddling with lockshields, endless trips back and forth between rooms, and the growing pressure to wrap things up—but still get it right.

Manual radiator balancing is often seen as a necessary evil. It’s time-consuming, imprecise, and easily undone by things completely outside your control.

Let’s take a closer look at why it’s such a pain—and why so many installers find themselves back on site days or weeks later dealing with the same cold rooms all over again.

It Takes Forever

On paper, radiator balancing seems straightforward. You open or close the lockshield valves to restrict or increase flow to individual radiators until the return temperatures equalise.

In practice? Not so easy.

Every single adjustment you make to a lockshield might take 15 to 20 minutes to show its full effect on the return temperature. And that’s assuming you’re in a stable system with no other variables changing while you work.

If you’re working with ten or more radiators—and you usually are—it’s a long, slow, and repetitive process. Small changes can lead to big swings. Overshooting, retracing your steps, going back and forth—it’s easy to lose an hour or more just tweaking one part of the system.

Balancing a Heat Pump System is a Whole Different Beast

With traditional high-temperature systems—say a gas boiler running at 70°C—you can get away with a lot more. Imbalances still exist, but the sheer heat output tends to mask them. A radiator getting slightly less flow still usually gets hot enough to satisfy the room.

But with a heat pump, running at 35–45°C (and lower), everything changes.

The system is designed to run efficiently at lower flow temperatures. That means there’s less margin for error.
A radiator that’s slightly underperforming on flow or return won’t just be “a bit cooler”—it might not heat the room at all.

So what was a minor issue in a gas boiler system becomes a major comfort complaint in a heat pump system.

In low-temperature systems, every mistake, every imbalance, every underflow is amplified. That’s why getting it right is so critical—and so difficult.

The Return Visit: “This Room’s Still Cold”

You’ve been there: the job’s done, paperwork signed off, customer happy… until they call.

“The small bedroom radiator isn’t heating properly.” “The bathroom’s freezing in the mornings.”

And of course, the installer gets the blame. You return to site, only to find that the flow temperature has been cranked up to 50°C to try and force heat through the cold spot—completely undermining the system’s efficiency.

You go back to adjusting valves. You re-balance. Maybe it works… for now.

But the real issue isn’t the installer—it’s the method.

An Outdated Practice in a Modern Industry

Manual radiator balancing comes from an era of static systems and simple boilers. Today, we’re installing advanced, highly efficient heat pumps that are sensitive to every change in the heating circuit.

Expecting a one-time, manual balancing job to maintain perfect comfort in a dynamic, real-world home is wishful thinking at best.

Installers are working harder than ever to hit performance targets—and being held responsible when systems don’t perform perfectly. But with balancing still done the same way it was two decades ago, we’re asking a lot and giving them very little.

Time for a Rethink?

Radiator balancing is a perfect example of an old method clashing with new technology. The process is manual. The results are temporary. And the pressure on installers to get it “just right” is increasing.

It’s not laziness or lack of skill—it’s the reality of trying to fine-tune a living, breathing system using static tools.

Maybe it’s time the industry looked for smarter, more reliable ways to approach radiator control and system balancing. Oh sorry, yeah- That’s COP Angel!

For more information on how COP Angel will automatically balance your emitters and commission your heat pump system, and then continue to do so dynamically as your loads change, email our inventor directly mike.kellett@copangel.com

Why Weather Compensation Control in Heat Pumps Must Be Dynamic

When installing heat pumps, installers are expected to commission them with efficient weather compensation settings. However, achieving an ideal weather compensation curve is virtually impossible. Here’s why.

Take my own home as an example. My heat pump, now 12 years old, features the original prototype of COP Angel. The house, built in 1842, has solid brick walls, and the radiators are designed to heat the home at the design temperature using a 55°C flow.

Right now, it’s 8:40 PM on Friday, March 14, 2025. The outside temperature is 5°C, and my current flow temperature is just 26°C; an impressive result, even for COP Angel. In January, I would expect this to be 5 to 10°C higher, and with a conventional weather compensation system (with thermostat and not open loop - that’s another story!), it could be another 10 to 15°C higher.

The Impact of Seasonal and Environmental Changes

So why is my flow temperature so low tonight? The answer lies in the dynamic factors affecting my home’s heat demand. By mid-March, we experience, on average, 3¾ more hours of daylight compared to January. Today was particularly sunny, meaning my solid brick walls absorbed and retained heat throughout the day. This residual warmth has carried into the evening, reducing the required flow temperature from the heat pump to just 26°C which is maintaining a comfortable 21°C inside the home.

But sunlight is just one variable. Other factors also impact the required flow temperature:

• Cooking and appliance use - Ovens, stovetops, and other appliances generate residual heat.

• Social activities - More people in the home means additional body heat.

• Alternative heat sources - A wood burner or another heat source can supplement heating needs.

• Wind - The windier the conditions, the more heat loss.

Why Static Weather Compensation Falls Short

A conventional weather compensation system operates on fixed parameters, assuming that a set flow temperature will always be required for a given outdoor temperature. However, this approach fails to account for real-world conditions. Static settings often result in heating systems producing water at 15 to 25°C above what is actually needed, leading to unnecessary energy consumption and reduced efficiency.

A truly smart controller - like COP Angel - must dynamically adjust to all forms of heat gains in real time, ensuring optimal efficiency and comfort. Without this adaptability, traditional weather compensation systems risk overproducing heat, wasting energy, and increasing costs.

Smarter, Room-by-Room Control with COP Angel

And the exciting news doesn’t end there. COP Angel is a patented technology that dynamically regulates the temperature in every room of your home, ensuring each space receives the precise amount of heat needed. By continuously adapting to changes in occupancy, solar gain, and other environmental factors, COP Angel optimizes comfort and efficiency—far beyond what traditional systems can achieve.

Welcome to COP Angel Blog

Welcome to the COP Angel blog – your hub for innovation, efficiency, and the future of heat pump technology. As the world shifts towards cleaner and more sustainable energy solutions, heat pumps are emerging as a key player in the transition. But are they being used to their full potential? At COP Angel, we believe the answer is no—and we’re here to change that. Our groundbreaking control method enhances heat pump efficiency by up to 40%, dramatically reducing energy consumption while maintaining comfort. Through our blog, we’ll share industry insights, technology breakthroughs, case studies, and expert discussions to help you stay ahead in the world of renewable heating. Join us as we redefine efficiency and push the boundaries of what heat pumps can achieve.