Good evening dear forum members,
The construction as well as the deep drilling project have now progressed further and we need to decide how (deep) to drill.
Basic information:
Living area based on the living area calculation according to the Living Space Ordinance: 126.45m²
Living area based on the execution drawings:
Upper floor: 65.05m²
Ground floor: 67.05m²
Basement: 69.62m² (with underfloor heating: 23.17m², underfloor heating + radiators: 59.94m²)
Totals: 201.72m², 155.27m², 192.04m²
The question now is – which heat pump. Since we have not yet received the thermal insulation certificate, we talked to the heating engineer and he said – they definitely need a 10kW heat pump.
So the choice falls on a Viessmann Vitocal 300-G (BWC 301.B10):
Nominal heating capacity: 10.36kW
Cooling capacity: 8.43kW
Electrical power consumption: 2.07kW
Coefficient of performance (COP) in heating mode: 5.01
Maximum flow temperature: 65°C
Our first offer from the deep drilling company included a down-the-hole hammer drilling for 125m², a geothermal probe Raugeo PE-RC 32 x 3.0 mm as well as grouting of the borehole with GeoSolid 235 – probably sufficient for a “normal” single-family house.
With the requirement of a 10kW heat pump, we have now requested a concrete offer and received an offer for 2 down-the-hole hammer drillings of 90m each (otherwise same conditions). Since the price of a probe distribution shaft is added here, we also asked for an offer for a single borehole.
With the adjustment of the probe to 40 x 37 mm, a depth of 152m was offered. This could just be sufficient with the larger probe...
Our own estimation with formulas from the internet leads to the following values:
Heating capacity (50W/m²): 9.602kW (192.04m²)
Extraction capacity: 7.685kW
Borehole depth (1800h with 55W/m): 139.7m
Borehole depth (2400h with 50W/m): 153.7m
Since only the 155.27m² from the area calculation is heated continuously, the 152m should easily suffice.
Nevertheless, we are totally uncertain how many meters are necessary and whether it would be better in the long run to have one or two boreholes?! Do you perhaps have any advice?