Ground-to-Water Heat Pumps | HOTJET – Czech Manufacturer

The temperature at a depth of 1.5 metres stays around 8–12 °C all year long. It can be -20 °C or +35 °C on the surface – underground it makes no difference. The heat pump extracts energy from a ground collector (horizontal loop) or a borehole (vertical probe) and transfers it to the water in your heating system.

Why ground instead of air

Stable output – independent of outdoor temperature, heats the same in January and March
Higher COP – constant source temperature = greater efficiency
No outdoor unit – quiet operation, zero noise for neighbours
Passive and active cooling – in summer, coolness from the ground directly, without the compressor
Long lifespan – constant conditions = less wear

What you need

Ground collector: Enough land – roughly 2× the heated floor area. Pipes are laid at a depth of 1.2–1.5 m.

Borehole: Smaller plot, but higher investment. Borehole depth depends on output, typically 80–150 m. You need a hydrogeological survey and a permit.

Both options have one thing in common: once installed, you forget about them – they work reliably for decades.

HOTJET WX – numbers that speak

SCOP up to 5.77 – the highest efficiency in our portfolio
Noise level just 38 dB – quieter than a whisper
Passive cooling with consumption of only 50–100 W
New: 40WXi – inverter model 6–40 kW

Models

Model	Output	Suitable for
7WX	7 kW	Passive and low-energy houses
10WX	10 kW	Standard family houses
15WX	15 kW	Larger houses, older buildings
40WXi	6–40 kW	Apartment buildings, commercial properties

Heat Pump Explorer

HOTJET ZETXe

Air–Water 7 · 10 · 15 kW

Reliable alternative to ZETXp

Same platform as ZETXp, proven by thousands of installations. Inverter, 3 circuits as standard.

HOTJET ZETXp

Air–Water 7 · 10 kW

The coming standard

Natural refrigerant R290, GWP 3

Natural R290 propane refrigerant with minimal climate impact. Ready for EU regulations beyond 2027.

HOTJET 15-20 ZETXp

Air–Water 15 · 20 kW

HOTJET 15-20 ZETXp

R290 propane for larger buildings

Three-phase 400V power, larger housing. For family homes, apartments and commercial buildings with 10–30 kW heat loss.

HOTJET ZETXi

Air–Water 10 · 15 kW

Complete indoor installation

No outdoor unit, no noise for neighbours. Ideal for terraced houses and dense residential areas.

HOTJET Wx ground-to-water

Ground–Water 7 · 10 · 15 kW

Most efficient, longest lifespan

Geothermal source = stable output all year round. SCOP over 5, lifespan 25+ years.

HOTJET Wx water-to-water

Water–Water 7 · 10 · 15 kW

No intermediate exchanger, direct output

Coaxial heat exchanger directly in the borehole. Fewer components, higher efficiency.

HOTJET Mini

Air–Water 5 kW

Smallest air-source heat pump

Minimal dimensions, maximum output per m². Passive houses, low-energy buildings.

HOTJET ONE2

Air–Water 20 · 25 · 35 · 45 · 55 kW

Simple. Robust. Reliable.

Minimal component count, maximum serviceability. Engineered to run trouble-free for years.

HOTJET FW

Accessories 70 kW

Flow-through DHW module

Hygienic hot water without a tank. Plate heat exchanger 70 kW, flow rate 25 l/min.

HOTJET HMD

Hydromodule – wall-mounted hydraulic unit

Complete solution in one cabinet: Siemens control, 7.5 kW electric boiler, circulation pump, 3-way valve and webserver.

HOTJET RZ

Switchboard – control & protection

Electrical cabinet with Siemens control. Manages heating circuits, boiler, pumps and valves.

HOTJET H25/10

Hybrid 10 + 25 kW

Pellet boiler + heat pump in one

Hybrid system: 25 kW pellet boiler + 10 kW heat pump. Siemens controller picks the cheapest source.

We'll be happy to help you choose the right heat pump.