Heat Pump for Radiators
ECO-TEC · technical guide for renovation and existing heating systems
Already have radiators and want a heat pump? That does not automatically mean the entire heating system must be replaced. Compatibility depends on required flow temperature, actual radiator output and building heat loss.
Yes, a heat pump can work with radiators
The key question is not simply whether radiators are installed. What matters is the water temperature at which the existing radiators can cover the building heat loss under the coldest design conditions.
If the building can remain comfortable at moderate flow temperatures, conditions are favourable. If very high water temperatures are permanently required, the cause should be identified.
The four checks that matter
1. Building heat loss
Capacity should not be selected from floor area alone. Insulation, glazing, air leakage, geometry and local design temperature all matter.
2. Required flow temperature
We determine whether the radiators cover the load at 45°C, 50°C, 55°C or 60°C, or whether higher temperatures are required.
3. Radiator output
Radiator output decreases as water temperature falls, so available output must be checked for the actual operating conditions.
4. Winter heat-pump output
Nominal capacity alone is not enough. Available output must be checked at the relevant outdoor and water temperatures.
Typical flow temperatures
| Heat distribution | Typical flow temperature | Comment |
|---|---|---|
| Underfloor heating | 30–40°C | Very favourable conditions for heat-pump operation. |
| Fan coils | 35–50°C | Depends on coil selection and airflow. |
| Well-sized radiators | 45–55°C | Can be an excellent range for a modernised system. |
| Existing radiators requiring more output | 55–65°C | Efficiency and available capacity require careful verification. |
| Old systems with undersized radiators | 65°C and above | Larger radiators or building improvements may be beneficial. |
When can existing radiators be retained?
- The building has reasonable insulation and moderate heat loss.
- The radiators have sufficient surface area or were originally oversized.
- The building remains comfortable with approximately 45–55°C water during much of the heating season.
- The hydraulic system provides sufficient flow.
- The selected heat pump has enough output at the design outdoor temperature.
Older cast-iron radiators are not automatically unsuitable. Their large surface area can make some existing systems surprisingly compatible with lower water temperatures.
When should the system be adapted?
If only a few rooms have undersized radiators, replacing the entire heating system is often unnecessary. Increasing radiator capacity in the critical rooms can allow the whole system to operate at a lower flow temperature.
Improving insulation can also reduce both required heat-pump capacity and future electricity consumption.
Why R290 is relevant to radiator systems
The ECO-TEC range includes R290 air-to-water heat pumps designed for high-temperature applications, including selected models specified for water temperatures up to 80°C.
This temperature reserve is useful in refurbishment projects, but the design objective remains the same: use the lowest flow temperature that can reliably heat the building.
A simple test before detailed sizing
If your existing boiler allows flow-temperature adjustment, reduce the temperature gradually during cold weather and observe whether the building remains comfortable.
If the house maintains indoor temperature at approximately 50–55°C, this is a useful positive indication. Critical rooms can then be checked individually.
This practical test does not replace a heat-loss calculation.
How we size an ECO-TEC radiator system
Step 1
Calculate building heat loss at the local design outdoor temperature.
Step 2
Determine the flow temperature required by the existing radiators.
Step 3
Check heat-pump performance at the relevant outdoor and water temperatures.
Step 4
Define hydraulics, domestic hot water preparation and system controls.
What determines electricity consumption?
Annual consumption cannot be predicted from rated heat-pump capacity alone. It depends on building energy demand, flow temperatures, climate, domestic hot water use, operating profile and seasonal efficiency.
Two houses with the same floor area can therefore have very different consumption.
Frequently asked questions
Can a heat pump work with existing radiators?
Yes, in many installations it can. Required flow temperature, radiator output at that temperature, building heat loss and heat-pump capacity at the design outdoor temperature must all be checked.
Do all radiators have to be replaced?
Not necessarily. Oversized radiators and radiators in well-insulated buildings may perform very well at lower water temperatures. Sometimes only a few critical radiators need to be enlarged.
Why is flow temperature important?
The lower the flow temperature that can still heat the building correctly, the better the operating efficiency of a heat pump will generally be.
Can ECO-TEC heat pumps operate at high temperature?
The ECO-TEC range includes R290 high-temperature models, including models specified for water temperatures up to 80°C. The actual required temperature must be determined from the building and heating system.
How can I make a quick compatibility check?
If the building remains comfortable during cold weather with approximately 45–55°C flow temperature, conditions are generally more favourable for a heat pump. Final selection still requires a heat-loss calculation.
How should a heat pump be sized?
Sizing should start with the building heat loss at the local design outdoor temperature rather than floor area alone. Required flow temperature and radiator capacity must then be verified.
Want to know whether your existing radiators can be retained?
Use our sizing calculator for a first estimate, then provide the building location, area, construction details and information about the existing heating system.
