What is the difference between monobloc and split system air source heat pumps?

Size variations between monobloc and split system air source heat pumps

The monobloc air source heat pump is a single unit that is placed on the outside of the residential dwelling as close to the water supply of the dwelling’s heating system as possible. The footprint of the monobloc unit is larger than that of the outdoor unit of a split system air source heat pump. However, a split system also requires internal space to be available for the indoor unit that is placed inside the dwelling.

Flexibility of monobloc and split system air source heat pumps

Although both types of air source heat pump have the same basic components, the split system connects its two units together with pipes that transfer refrigerant between them. The outdoor unit captures heat from the air, and the indoor unit transfers that heat to the heating system of the dwelling. By contrast, the monobloc unit has a closed-circuit system for the refrigerant and it connects in a similar way to a conventional gas boiler to the hot and cold-water supply of the dwelling.

This difference means that monobloc units are better situated as close to the heating system as possible to limit the length of pipe required. As the pipes carry water, they need to be insulated to prevent freezing in the winter and limit heat loss from the warm water generated by the monobloc air source heat pump. Also, as the systems containing water are outside the building, they need to be protected from frost damage by the addition of anti-freeze.

With a split system air source heat pump, freezing is not an issue as all the components that handle water are housed within the indoor unit. The two parts of the split system are connected by refrigerant pipes, rather than water pipes, and the connection can be several metres long if required, leading to greater flexibility when positioning the outdoor unit further away from the dwelling.

The same refrigerants can be used in both monobloc and split system air source heat pumps, however, there are several types that are available for use. Always seek advice from the heat pump manufacturers on any health and safety issues with the refrigerant and check its global warming potential (GWP) for it impact on the environment.

Noise considerations for monobloc and split system air source heat pumps

The overall noise levels of monobloc and split system air source heat pumps are similar, however, the advantage of the split system is the ability to place the fan unit farther away from the dwelling. This distances the source of any potential noise issues from the occupiers and could play a part in projects with a focus on acoustic comfort.

Installation differences for monobloc and split system air source heat pumps

Installation of a monobloc air source heat pump is more straightforward than that of a split system air source heat pump as the connections are to the water supply of the heating system. For split systems, the refrigerant lines running between the two units requires the installer to have F-Gas qualifications and the lines need to be checked for leaks on a yearly basis.

How can you decide if a monobloc or split system air source heat pump is best for your project?

Deciding whether a monobloc or a split system air source heat pump is your best choice will depend upon the heating demand of the dwelling, project limitations on external and internal space, the position of units, acoustic and aesthetic requirements, and the availability of suitably trained installers.

If you would like to learn more about the specification choices that the Dimplex range of monobloc air source heat pumps and split system air source heat pumps can offer to help meet your project requirements, please contact one of our pre-sales team specialists.