Multi-pipe units, also known as 4-pipe units or polyvalent units, are different from heat pumps.

Did you know that the efficiency of multi-pipe units is expressed in Total Efficiency Ratio (TER)?

A multi-pipe unit provides cooling and heating to two separate water loops. The unit can provide cooling only, heating only or simultaneously cooling and heating. One water loop always provides cooling, and the other loop provides heating.

They use renewable and recovered energy to produce hot water and can replace the existing fossil-fuel boiler and chiller system to deliver both chilled water and hot water for the entire building with no direct greenhouse gas emissions. This contributes to decarbonization of buildings and creating better air quality in and around the building.

Multi-pipe units are particularly used in the HVAC systems of multifunctional facilities like office buildings, hospitals, theatres, and hotels which require simultaneously heating and cooling in different parts of the building, seasonal or all year round.

So because multi-pipe units operate differently from heat pumps, the way to calculate their coefficient of performance is different from the well-known EER/SEER for efficiency in cooling mode or COP/SCOP for efficiency in pure heating mode, commonly used for chiller and heat pump technologies.

EER and COP are not sufficient for assessing the energy performance of multi-pipe or polyvalent units when they provide simultaneous cooling and heating.

Therefore, Total Efficiency Ratio (TER) is the industry standard and the most accurate indicator to calculate performance of a multi-pipe or 4-pipe or polyvalent unit. TER is recognized in the Eurovent Certification program.

How do you calculate TER?
The formula is TER = (Cooling capacity + Heating capacity) / Total power input.

A high TER means that the cooling and heating demands of a building are completely balanced. For example, the Trane Sintesis™ Balance CMAF offers Total Efficiency Ratio (TER) of up to 8.4, one of the highest levels of all air-sourced scroll multi-pipe units available on the European market.

The ratio also expresses the substantial energy savings when the unit operates in its simultaneous cooling and heating mode because the building is benefitting from renewable and recovered energy, energy that would otherwise have been wasted.
The building owner will also benefit from lower annual operating costs, bringing significant savings to the building owners’ bottom lines.

For more information about Total Efficiency Ratio (TER), watch this explainer video.