Monobloc Air to Water
The monobloc air to water heat pump contains it’s refrigerant entirely in the outdoor unit. Your heating system goes outside to be heated by the monobloc.
These systems require freeze protection to prevent the heat exchanger from cracking if power is cut below freezing outside. Visit here to read more about freeze protection.
A true monobloc contains all components necessary for the system to operate, such as water circulation pump, expansion vessel and sensors.
The most common system in the UK due to its cost and ease of installation.
Pros
Only one box to install
Lower cost
Easier installation
No F-gas requirement
Wide range of choice
Less space taken up inside
Cons
Larger outdoor unit
Requires freeze prevention
More common to see bodge installations
Water connections restrict distance from property
Hydro-Split Air to Water
The hydro-split is the same as the monobloc except there is a box inside the building for wiring, circulation pump, sensors and expansion vessel.
Refrigerant is still housed entirely in the outdoor unit. The heat exchanger is the only hydraulic (water) component in the outdoor unit.
Hydro-split is more of a spectrum. Some systems such as the Daikin Altherma 3 HHT, have a ‘gas boiler sized’ indoor unit whereas the Mitsubishi Electric Ecodan range only has an ‘FTC wiring centre’ and all hydraulic components have to be plumbed in by the installer.
Also very common in the UK.
Pros
Outdoor unit smaller than the monobloc
No F-gas requirement
Wide range of choice
Integrated DHW tank systems available which are tidy
Cons
Outdoor unit still larger than other options
Requires freeze protection
Water connections restrict distance from property
More installation time compared to monobloc
