AIR TO WATER HEAT PUMPS IN VICARAGES

AIR TO WATER HEAT PUMPS IN VICARAGES

Air-water heating

An air-water heat pump can be a good solution for many vicarages, located outside areas with district heating.

The efficiency of an air-water heat pump is slightly lower than for a well dimensioned ground source heat pump. If there isn’t space for burying water pipes of sufficient length, an air-water heat pump is a better solution.

If connecting the vicarage to district heating is possible, this is normally recommended rather than installing a heat pump.

Which buildings are suitable?

The building should be reasonably well insulated and have normal density for it to make sense to install a ground source heat pump. To keep costs down, it is very important to keep the flow temperature as low as possible. Underfloor heating in most of the building is preferable, but not a requirement.

If there are radiators, it is important that they are sufficiently dimensioned. This will normally be the case in an older building, which is renovated and reinsulated by newer standards and where the old radiators are preserved.

It is fairly easy to test whether the radiators are large enough compared to the insulation-related condition of the vicarage. The test is best performed in winter in cold weather over a period of 7-14 days. Turn the flow temperature to 60° C (or lower: down to 45 - 50° C, if the boiler can handle it. If necessary, contact a plumber). If the temperature stays at a comfortable level, it is likely that the heat pump can be installed without problems. The “test" is more reliable, the lower the outdoor temperature is.

If the vicarage gets too cold in the test period, it will either require more insulation, better sealing of the building, or larger radiators. It might even be necessary to do all of the above, in which case it is worth considering whether a ground source heat pump is the right solution at all.

Placing the outdoor unit

Outdoor unit placement must be carefully considered, as there are both aesthetic considerations and noise limits to comply with. Regarding neighbours, the Danish Environmental Protection Agency has noise limits, but the municipality may choose to impose other limits. Regarding the cemetery, there may be locations that are undesirable due to noise.

It is important that the outdoor unit is placed in the open air, to ensure a good supply of fresh air. Attics or similar places are generally not recommended. If a foreclosure is built for the outdoor unit, it must be very open. If sufficient ventilation isn’t ensured, energy consumption will be unnecessarily large.

Inspection

An annual inspection is mandatory because the plant contains more than 1 kg refrigerant.

Economy

Cost savings are typically 50 - 60% if oil heating is replaced with a heat pump. If there is pellet heating or district heating, there are normally no cost savings.

The investment is of course dependent on the heat pump's size. A small air-water heat pump in "single family-size" typically costs about 100,000 kr. In large, old vicarages investments may be more than 200,000 kr.

Example

A vicarage built in 1953 in central Jutland has the Energy Label "D". The heated area is a total of 475 m2, distributed on ground floor, 1st floor, and a basement with confirmation classrooms. The building is heated using oil. The boiler and tank are from 1974 but the burner is newer. The heating bill amounts to 36,000 kr. annually.

The parish council has decided to replace the old boiler to achieve energy savings and better reliability. There are two solutions possible:

New oil-fired boiler:
The oil-fired boiler can be replaced with a new condensing boiler with higher efficiency. At the same time the old oil tank must be replaced according to rules regarding oil tanks. The total investment will be approximately 80,000 kr. A cost saving of about 8,000 kr. annually will be achieved with a payback time of approximately 10 years.

Air-water heat pump:
The old boiler is scrapped and the oil tank blocked or removed. Installing an air-water heat pump costs about 150,000 kr. The heating bill will now be in the order of 16,000 kr. Thus, there is a saving of about 20,000 kr. annually. The payback time is 7-8 years.The investment for the air-water heat pump is almost twice as large as the new oil boiler and tank. But already after about 7 years, the investment pays for itself with the heat pump.



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