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Pichler PKOM 4 compact service unit

            Green Home Award Highly Commended  Build It Award 2018 

The PKOM 4 compact service unit provides heat recovery ventilation, with two integral heat pumps, one for space heating and cooling and the other for domestic hot water. This is all in one compact unit - making it the only appliance of its kind.

what is the PKOM 4?

It is a really energy efficient compact service unit providing whole house ventilation with heat recovery, space heating and cooling together with enough domestic hot water for approximately three people.

This impressive list of attributes is all in a foot print of less than 0.75m2 - very convenient if you have limited space in your home or your heat demand is low enough to not warrant a formal heating system. The PKOM 4 is so well regarded, that it won Best Renewable Heating System in the 2018 Build It Awards.


The PKOM 4 is a PassivHaus Certified component and therefore particularly well suited to homes that are to be built to Passiv Haus / EnerPHit standards. However, the PKOM4 may be suitable if your home is very well insulated and airtight with low U-values. 

In Britain, homes with up to four people or between 47m2 and 183m2 in size (at a 2.4m ceiling height) would be considered suitable for the PKOM 4.

Total Home Environment can complete a room-by-room heat loss calculation to establish if this system will be suitable for you and your home. The PKOM 4 can also run up to 20m2 of wet underfloor heating otherwise it can be complimented by electric towel radiators in the bathrooms or a wood burning stove in a living area.

how does the PKOM 4 work?

The PKOM 4 has a heat recovery ventilation matrix with not one, but TWO integral heat pumps for the separate heating of domestic*1 hot water and space heating, with COOLING. This aspect of the PKOM 4 is located above a 212L capacity hot water cylinder.

The mechanical heat recovery ventilation unit has two EC*2 fans in it, one bringing fresh filtered air from outside, whilst the other extracts stale air from wet rooms (kitchens and bathrooms). The two airflows go through a high performance heat exchanger (not mixing) and whilst the stale air (minus it's heat) is exhausted outside, the warmed fresh air is supplied through ceiling terminals, to the habitable rooms of your home (bedrooms, dining/living rooms etc).

It means generally, you will get a whole house air change every couple of hours but remarkably, you will be recycling over 88% of the heat that you would lose through traditional forms of ventilation like extractor fans and trickle vents or other ventilation systems like Passive Stack, PIV or MEV.

However, the PKOM 4 can do more with air! It takes advantage of the ductwork already suppling your home with fresh air, by adding more heat to the air, but in a hugely efficient way. After the heat exchanger has recovered as much heat as it can, the integral heat pumps take even more energy out of the stale air, by compressing a refrigerant which then absorbs heat, releasing it to the supply air and water. (This is rather like when you pump up a tyre and it heats up as you're increasing the pressure inside the tyre. These heat pumps work in reverse to your fridge which takes all the heat energy out of the food and deposits it behind the fridge).This results in energy heating with a COP of 6.8.

On hotter days, when you don't necessarily want to recover heat but still want fresh filtered air coming into the house, there is a fully modulating summer bypass. Of course the heat pump that is dedicated to space heating, can also be reversed on hotter days to provide additional cooling (just like your fridge). You can therefore benefit from energy efficient cooling with a COP of 4.2.

*1 the water that comes out of your taps
*2 electronically commutated to run at optimum energy efficiency

A second heat pump inside the PKOM 4 is dedicated to hot water production, which is again a far more efficient way of heating water than gas or oil. The heat pump is able to produce about 970L of hot water every 24 hours at a temperature of 55oC, so can cater for a family of four comfortably with the 212L water cylinder.


Another advantage of the PKOM 4 is that the water cylinder has an optional secondary heating coil (or heat exchanger) which can either be very conveniently connected to up to 10m2 of wet underfloor heating or it can accept heat from a small solar thermal panel. Of course, it can also accept electricity, from photo voltaic panels on your roof, making the system even more economical to run.

Having two heat pumps integral to the heat recovery ventilation unit, enabling it to heat AND cool air independently to heating water, makes the PKOM 4 the only service unit of its kind in the UK.


Operation of the PKOM 4 is simple and intuitive via the touch screen display panel. Here you can access:

  • temperature required
  • 24/7 programming
  • holiday function
  • the service display for setting air
  • volumes, legionella cycles etc
  • solar panel and additional heater
  • activation
  • intelligent damper control
  • C02 and humidity control
  • heating and cooling.
In addition there is a free smartphone app for iOS and Android, which can easily operate your PKOM 4 whether you're at home or out and about.

certification and specification

The PKOM 4 is a Passivhaus Certified Component and more than covers Part F (Ventilation) and Part L (Energy). A brief specification of the PKOM is below, but for more information see the individual specification sheet in downloads.