Can a heat pump be fitted to an existing heating system?



Can an air source heat pump work in an existing home?
Yes, air-source heat pumps can be integrated into existing, heating and hot water systems with careful consideration and appropriate modifications. These heat pump heating systems work by extracting warm air from the air outside by transferring it inside the building for space heating or domestic hot water.
The air-source heat pumps can work in temperatures as low as -10 degrees Celsius. The integration process involves evaluating the compatibility of the air source unit with your existing system and making necessary adjustments.
The heat pump can work alongside your old system, such as radiators or underfloor heating (UFH), by utilizing the existing distribution system.
However, the efficiency of the heat pump is affected by the design and size of your current system, and it’s recommended to consult with our professional heating engineer to ensure proper integration and optimal performance.
Get a Free Boiler and Heat Pump Installation Quote Today
Ready to upgrade your home’s heating system? Get a free quote today for your boiler installation and enjoy a cosy, energy-efficient winter. Don’t wait—click below to get your fixed prices in minutes!
Why you should choose an air-source heat pump?
Choosing an air-source unit offers numerous options for heating your home.
Alternative choices are available, such as opting for a ground source heat pump as well. To ensure the effective operation of a ground source heat pump, it is necessary to drill deep holes into the ground for the system’s proper installation.
Here are some key reasons why you should consider installing an air-source heat pump:
1. Energy Efficiency: Air-source heat pumps are highly energy-efficient. They extract warm air from the outdoor cold air to provide heating in winter and some areas cooling in summer. Compared to traditional central heating systems that rely on burning a fossil fuel boiler like old gas boilers, heat pumps consume less energy and can significantly reduce your bills.
2. Low Carbon Emissions: Heat pumps produce fewer greenhouse gas emissions compared to conventional systems. By using less fossil fuels for boilers and utilizing renewable energy from the air, they contribute to a greener environment and help combat climate change.
3. Year-Round Comfort: air-source heat pumps in winter take heat from the cold air, providing consistent warmth indoors. In summer, they get enough heat and can reverse the process as much heat to provide you with hot water for the cylinder.
4. Running costs: While the initial investment in an air source unit might be higher than traditional systems, the long-term cost savings are substantial. Reduced energy consumption, higher temperatures, and lower utility bills can lead to a quick return on investment over time.
5. Low Maintenance: Air-source heat pumps have fewer moving parts compared to combustion gas or oil boiler-based heating systems. This translates to lower maintenance requirements and costs. Regular maintenance, such as cleaning filters and checking refrigerant levels, is usually all that’s needed to keep the home heating system running smoothly.
6. Long Lifespan: Heat pumps are designed to last for many years, often exceeding 15-20 years with proper care. This longevity ensures a reliable system for your home.
7. Quiet Operation: Air-source heat pumps operate quietly, at low flow temperatures generating minimal noise both indoors and outdoors. This ensures a comfortable living environment without disruptive sounds.
8. Zoning Flexibility: Heat pumps can be equipped with zoning capabilities, allowing you to zone specific areas of your house and warm your home as needed. This feature enhances comfort and energy efficiency by less energy loss.
10. Future-Proofing: As the world moves toward cleaner energy sources, installing an air source unit positions you ahead of the curve. It ensures that your home is equipped with a technology that aligns with sustainable practices and potential future regulations.
Government Incentives
To encourage people to use energy-efficient devices like heat pumps, many governments offer incentives, rebates, and tax credits. Taking advantage of these benefits can lower the cost of buying and installing hybrid systems even more.
There are currently two government grants available in the UK to help homeowners pay for heat pumps:
- Boiler Upgrade Scheme: This scheme offers grants of £5,000 towards an air source heat pump or £6,000 towards a ground source unit. It is open to homeowners in England and Wales who have an existing fossil fuel system.
- Domestic Renewable Heat Incentive (RHI): This scheme offers payments for seven years to homeowners who install a qualifying heat pump. The amount of payment you receive depends on the type of heat pump you install and the amount of renewable heat it produces. The RHI is open to homeowners in England, Scotland, Wales, and Northern Ireland.
To be eligible for either of these grants, you must meet certain criteria, such as:
- Your home must be a detached, semi-detached, terraced house, or a bungalow.
- Your home must be connected to the mains electricity and gas supply.
- Your existing heating system must be at least 10 years old.
- You must have a valid Energy Performance Certificate (EPC) for your home.
Contact us today!
Do you have any space for the heat pump?
Air-source heat pumps come in various sizes and configurations, making it possible to find an option suitable for most spaces. These units can be installed outdoors, typically on a wall or on a concrete pad, and require sufficient clearance for proper airflow.
It’s important to ensure that there’s enough open space around the unit to facilitate air circulation and efficient operation. If you’re concerned about space limitations, consult with MML Plumbing and our professional installer can assess your property and recommend the best placement for the air source heat pump.



How do heat pumps work with hot water radiators?
Heat pumps can work effectively with hot water radiators and renewable heating systems, but adjustments might be necessary.
Traditional radiators designed for high-temperature systems may need to be replaced or modified to accommodate the low-temperature output of a heat pump. We advise you to increase the size of the radiators in each room the reach maximum performance.
Heat pumps work most efficiently with larger surface area radiators or UFH systems, which can distribute water effectively at low temperatures.
This ensures that the heat pump operates within its optimal efficiency range, providing you with a warm home.
Is the best way to use a heat pump with radiators?
While heat pumps can work with existing radiators too, UFH systems are often considered an ideal match due to their larger surface area and ability to distribute water efficiently at lower temperatures.
UFH provides a more consistent and comfortable indoor environment, as the water is evenly distributed across the floor.
However, if retrofitting the existing boiler for underfloor heating is not feasible, properly sized and designed radiators can still work effectively with a heat pump.
How can I tell if my existing radiators will work with a heat pump?
To determine if your existing radiators are compatible with a heat pump, consult with our professional engineer from MML PLumbing.
We can assess your current radiator setup, considering factors such as size, design, heat pump technology and heat output capacity. If your radiators are oversized for the heat pump’s lower temperature output, they might not provide efficient heating.
In such cases, it’s advisable to consider resizing or replacing the larger radiators to ensure optimal performance.



Minimum size heating pipes for heat pumps
When installing an air source unit, it’s important to consider the sizing of the pipes. Larger diameter pipes are generally recommended to ensure proper flow and distribution of the low-temperature water used by most heat pumps.
The exact pipe size will depend on factors such as the air source unit capacity, the distance to the radiators or underfloor heating, and the overall heat pump and system design.
The minimum pipe we can use is 15mm, which can be found in every home and the unit will work fine, but the best is to upgrade the pipe size to 22mm.
Your existing heating system requirements
Integrating a new heat pump system into your existing heating system may require modifications to ensure compatibility. Your existing radiators or underfloor heating should be evaluated for proper sizing and capacity.
If necessary, adjustments can be made to accommodate the new heat pump system’s low-temperature output.
Additionally, your new heat pump system’s capacity should match your building’s heating load to ensure efficient and effective operation. A professional assessment is recommended to determine the specific requirements for integrating a heat pump into your existing system.
Can a heat pump be too big for a house?
Yes, a heat pump can be too large for a house, and proper sizing is crucial for optimal performance. A heat pump that is too big may turn on and off a lot, which makes it work less well and wear out faster.
It’s important to conduct calculations to determine the requirements of your home. Factors such as insulation, building orientation, and climate play a role in determining the appropriate heat pump size. Our professional installer will help you to choose a heat pump.
Heat pump installation steps:
Informing your District Network Operator (DNO):
It is important to inform your local DNO before installing an air source heat pump. This is to ensure that the electrical infrastructure in your area can support the additional load of the air source unit.
Electrical upgrades:
Upgrades might be needed to accommodate the heat pump system’s additional load. The electrical supplier has to accept your installation that you will need more power from now.
Planning permission:
Check if planning permission is required for the installation of air-source heat pumps. In most cases, air-source heat pumps are considered “permitted development,” but it’s best to confirm with your local authorities.
Upgrading pipework
Evaluate your existing pipework to ensure it can accommodate the flow temperature of the lower-temperature water used by the heat pump. Upgrades might be necessary for optimal flow temperature and performance.
Microbore pipework:
If you have microbore pipework, consider upgrading to larger diameter pipes to generate heat, lower flow temperature and ensure efficient distribution.
The air source unit will not work with the microbore pipework.
Professional installation:
Have a qualified installer assess your property from MML Plumbing and perform the installation, including placing the heat pump and hot water tank, connecting the gas boiler and pipework, and integrating it with your existing heating system.
System commissioning:
Once installed, the system will be commissioned to ensure it operates correctly and efficiently.
Remember that each step is crucial for a successful installation and optimal performance of your heat pump system.
Consulting with professionals throughout the process of installing heat pumps, will ensure a smooth transition from existing systems to this energy-efficient heating solution.
Can you install a heat pump in existing homes?
Yes, air-source heat pumps can be installed in existing properties with relative ease. They are designed to be retrofit-friendly and can work alongside your old systems.
However, the installation may involve certain modifications to accommodate the air source unit and piping.
An assessment of your home heating, loft insulation, energy needs, and existing infrastructure is recommended to ensure a smooth environmentally friendly manner installation process and optimal performance.
Discover the significance of efficient and cosy heating within your household with MML Plumbing. Our heat pump design and installation guarantee you the utmost comfort, even during colder times. Reach out to our gas engineers now to delve into our innovative heating solutions!