Radiators are not, in themselves, an obstacle to a heat pump. The key question is whether each radiator can deliver the heat its room needs at the intended water temperature.
A radiator's catalogue output depends on temperature conditions. When the difference between water and room temperatures is smaller, radiator heat output is lower too. Manufacturers, including Zehnder, provide correction factors for specific conditions. S12
It is therefore not enough to say a room already has a large radiator. Its type, dimensions, manufacturer's data and the room's heat demand are needed. Some radiators in a house may be suitable, while others may need enlarging or replacing. Deciding for the whole house from total floor area alone would be an oversimplification.
A heat pump capable of a higher water temperature will not necessarily be most economical at that setting. Permissible temperature and operating efficiency are different measures; check both in the selected model's technical data. S11
Before ordering: photograph the radiators, record their dimensions and gather available information about the current heating. Ask for a separate explanation in the quotation of which emitters will be retained and why.
Information sources
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- S11
- S12
Sources checked on 2026-09-29. If the manufacturer has changed the product or documentation, follow the latest technical information for the specific model.