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issue: June 2009 APPLIANCE Magazine

European Heating International Report
Successfully Downsizing a Heat Pump/Boiler Combi

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Paul Roggema, Europe correspondent

Through clever engineering, Dutch OEM Daalderop achieves significant efficiency improvements with minimal extra cost and installation effort.

Daalderop’s Combinair air-to-water heat pump with gas combi-boiler.

Through clever engineering, Dutch OEM Daalderop achieves significant efficiency improvements with minimal extra cost and installation effort.

It may not seem like rocket science: combining an air-to-water (exhaust air) heat pump with a traditional gas combi-boiler. Still, by clever dimensioning the Dutch manufacturer Daalderop (www.daalderop.nl) was able to engineer the Combinair to achieve significant efficiency improvements with little in the way of added cost or increased installation effort.

The heat pump uses exhaust air from the ventilation system and combines it with outside air. The heat from the condenser is combined in the boiler and used in the space heating water circuit.

Until recently, it was widely assumed that you needed low-temperature floor heating and a low-energy house when using a heat pump, which made installation in existing houses unattractive. The modest capacity of a heat pump was also seen as an obstacle.

But the engineers at Daalderop decided to perform lengthy field tests in an existing, average house. They found that the required average heating power was quite low (in a mild climate, that is), contrary to popular belief. They also found that the room-heating capacity of the gas-fueled boiler will be needed only a few months per year, for an estimated 10% of the total heating power. The low temperature of the water was less of a problem than expected; it works well in newer, well-insulated houses. But they also found that many older houses have large-surface radiators whose capacity was not fully used because of later insulation.

The heat pump uses about 150 m3 of ventilation air per hour, resulting in 1 kWh, and 300 m3 of outside air.

Heat pump output is 2.5–3 kW, using 600 kW electric power. In a well-insulated house in a mild climate, energy savings up to 50% can be achieved, and a renovated house will see savings of 30–40%. Research showed that at an outside temperature of 9°C, savings can go up to 70%.

Daalderop is especially proud of the easy installation: you only need a larger air inlet and outlet, and no extra ventilation channels or floor heating. Installation is not error-prone and, in fact, not much different from existing methods, so installers will feel confident to use the Combinair. The boiler has a dual heat output, for separate heating of a study or a bathroom.

Why did other manufacturers not come up with this solution? That’s unknown—and now it’s too late, thanks to Daalderop’s new patent. “We all made the mistake of focusing on traditional ideas of heating, and looking at maximum capacity in cold winters,” Peter van Waarde, export manager, tells APPLIANCE magazine. “But a heating capacity of 20–30 kW is seldom used. Instead, we focused on testing at moderate temperatures and found that the heat pump capacity is sufficient for most of spring and autumn. And because of minimal installation efforts, you have a payback period of only three to five years, which is much better than other solutions.”

Waarde notes that there is another alternative: the air-to-air heat exchanger, which warms incoming air with exhaust air. “This solution never really caught on because of general complexity and installation efforts, and it is not integrated with the heating/domestic hot water boiler,” he says. “We are proud that our solution tackled exactly these problems.”



APPLIANCE Europe Correspondent Paul Roggema is based in Amsterdam and travels extensively to report on the appliance industry throughout Western and Eastern Europe. Read more of his Europe Reports at:



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