13 July 2023
By Alberto Ferrandi
A traditional two-pipe system for heating and cooling may not be an optimal solution for buildings with mixed usage that combines, for instance, retails, offices and hotels. Besides, the southward side of the building facing the sun might require cooling at the same time that the northward side, in the shadow, might require heating. This demands a highly flexible heating and cooling solution.
Many, if not all, buildings over time require both heating and cooling. A traditional two-pipe system provides one supply line and one return line to be used by both the heating and the cooling units. In effect, the entire building can be either heated or cooled, as chosen by the user. The system works, but it’s not very flexible. For example, in modern buildings with large glass areas, the southward side facing the sun might require cooling at the same time that the northward side, in the shadow, might require heating.
A four-pipe system, on the other hand, consists of separate supply and return lines for the heating units, and separate supply and return lines for the cooling units. This means that one part of the building can be heated while another can be chilled. This flexibility increases the comfort considerably.
Combine your 4-pipe system and with a polyvalent unit
A four-pipe system works even better if combined with a polyvalent unit. A polyvalent unit can provide both heating and cooling simultaneously, depending on demand. The combination of polyvalent units and four-pipe systems is especially potent when it comes to energy efficiency. Instead of simply transferring energy to or from the outside, like traditional heat pumps, the polyvalent unit can transfer energy between different parts of the building. The system might, if we return to the example modern glass building briefly, transfer heat from the sunny south side to the shadowy north side, killing two birds with one stone. With advanced algorithms controlling the system, it will at all times provide correct and precise amounts of energy to all parts of the building.
It consumes less energy
In short, the combined system is much more energy-efficient than traditional systems with separate heating and cooling. It consumes less energy, lowers emissions and saves money. The initial cost for a four-pipe system might naturally be higher than for a two-pipe system, but a polyvalent unit needs less investment than separate heat pumps and chillers. And the lower energy consumption and higher efficiency lower the operating costs significantly.
Increased demand for simultaneous cooling and heating
The four-pipe and polyvalent unit combination has become increasingly popular over the last few years, as more buildings benefit from requested simultaneous and asynchronous cooling and heating. Many modern buildings are for example designed for mixed use, with some parts being used for retail or offices, while other parts being dedicated to residential use, with largely differing load requests over the day or the week.
But the benefits are not limited to modern buildings – more and more older buildings are being retrofitted with four-pipe systems and polyvalent units as well. The increased energy efficiency alone makes the investment economical, not to mention he gradually stricter emission regulations.
If you have a four-pipe system in place, Swegon can provide a polyvalent unit, complete with HVAC, controllers and pumps for water circulation in a primary circuit.