Monobloc heat pump: what it is and when it makes sense

A monobloc heat pump has the whole refrigerant circuit in a single outdoor unit: compressor, heat exchangers, fan and expansion valve are sealed in the factory inside the same casing. Only two water pipes, the heating flow and return, and the power cable go into the house. All our air-to-water heat pumps are built this way.

What is a monobloc heat pump

Monobloc means the machine is one single block. Inside the outdoor unit the refrigerant takes heat from the air, the compressor raises its temperature and a plate heat exchanger passes it to the water, all inside the same casing. What comes out is hot water, which goes to the underfloor heating, the radiators or the hot water cylinder, just like the water from a boiler. The refrigerant circuit is charged and tested in the factory and is never opened on site.

For the installer it means working as with a boiler: water pipes, valves, expansion vessel and electrical connection. We explain the refrigeration cycle step by step in the article how a heat pump works.

Why propane R290 goes in a monobloc

R290 is propane: a natural refrigerant with GWP 3. It is not a fluorinated gas, so it has no periodic F-Gas checks. It is, however, flammable, class A3. In a monobloc the whole charge stays in the outdoor unit, in the open air, and no refrigerant enters the house; installation follows the safety rules of EN 378.

That is why all our air-to-water units are R290 monoblocs. We describe what is inside a propane heat pump in the article R290 heat pump: how it is built.

Outdoor or indoor monobloc heat pump

Anyone looking for a monobloc will also find indoor models: the machine sits inside the house, in a plant room, and draws and returns outdoor air through two ducts in the wall. There is nothing in the garden or on the facade, but you need space, two large holes in the wall and a room where the noise of compressor and fan will not bother anyone. Our monoblocs are all outdoor units: only the hydraulic part stays inside.

The weak point: water pipes in winter

In a monobloc the heating water leaves the house and runs to the outdoor unit. If the machine stops during a frost, for example during a power cut, that water can freeze in the pipes or in the exchanger. So the outdoor run must be short and insulated, and the installer adds protection: anti-freeze valves that drain the water below a set temperature, or glycol in the circuit.

Where it goes: space and noise

A monobloc stands outdoors on a base, with free space in front of the fan and behind the coil so the air can circulate. Where you put it matters: away from bedroom windows and not in a closed corner where cold air lingers. Sizes, weights and noise of our monoblocs:

Noise values are sound pressure at 1 metre, as given on the product pages.

Installation and cost: what changes with a monobloc

Connecting a monobloc is a job for a plumber and an electrician: water pipes, valves, expansion vessel, hot water cylinder, power cable. The refrigerant circuit arrives sealed and tested from the factory, so on site there is no refrigeration engineer, no evacuation and no gas charging. With propane there is not even the F-Gas logbook with periodic leak checks.

The final cost depends on the heating system in the house: underfloor heating or radiators, hot water cylinder, buffer tank.

Which output: 8, 12 or 20 kW

The next question is the output, and the answer is not in the floor area. As a rough guide, a 150 m² house built to class A needs 4-6 kW on the coldest day; the same house built before 1990 and never insulated needs 12-18 kW. A home usually needs up to 20 kW, up to 30 if it is large and old.

The real figure is calculated from the heat losses of the building, according to EN 12831: we explain how in the article on heat pump sizing. Our monoblocs deliver water up to 70 °C, so they also work with radiators: read heat pump with radiators.

Templari monobloc heat pumps

All Templari air-to-water heat pumps are propane R290 monoblocs, energy class A+++, with domestic hot water up to 70 °C without a backup boiler. Kita SP, MP, LP and LP Plus work with outdoor temperatures below -20 °C.

• Kita XS 7.5 and 9 kW: houses and flats, also with the Armadio Tecnico Mono cabinet;
• Kita SP 8, 10 and 12 kW: detached houses;
• Kita MP 14 to 20 kW: large houses and small offices;
• Kita LP 22 to 35 kW, and the Kita LP Plus at 35 and 40 kW: apartment blocks, commercial buildings, large and old houses.

See the whole air-to-water range