The Poldi Pezzoli Museum has chosen Mitsubishi Electric to protect its collections.

State of the art climate control.
The Poldi Pezzoli Museum in Milan has chosen Mitsubishi Electric VRF systems to protect its precious heritage, installing both heat pump and heat recovery facilities. Thanks to these features, not only is it now possible to ensure the preservation of the works and the comfort of visitors, but the installation also met with the architectural constraints of the building without impinging into occupied spaces. The high efficiency of these systems also ensures a complementary and harmonising relationship with the natural environment.

The building and the air conditioning system

Mitsubishi Electric has acquired specialised experience within the museum sector with their VRF systems, which demonstrate their ability to respond to the requirements of the visitor as well as protecting the exhibits. In short, what is essential is to maintain a consistent temperature and relative humidity within precise margins which were imperative to the conservation of the works of art, artefacts and other such items. These specified conditions are maintained, with no compromising of the Mitsubishi Electric VRF systems, as a result of their cutting edge technology, extensive controller functions and precise regulation of both temperature and relative humidity.
One of the major considerations in the design and subsequent installation of the plant systems was to ensure that they did not impinge on the surrounding areas, which were extensively decorated, and did not install disturbing elements, using the small amount of space available to the full. Mitsubishi Electric VRF systems successfully responded to this specific requirement thanks to their modular design, which allowed the installation of outdoor units on the floor and even in cramped service areas. Indoor units housed in vertical casings fitted perfectly in the recesses below the windows and also against the walls, where their presence did not create any disturbance.
Another extremely positive benefit was the minimal passage space required thanks to the small diameter of the two cooling lines; their passage was achieved without any alterations or need for masonry work. Notably, in relation to the VRF heat recovery system, Mitsubishi Electric is currently the only manufacturer on the market to use just two tubes for its cooling lines; this allows the system to be installed when there are architectural and/or aesthetic constraints, resulting in limited available space, as was the case in the Poldi Pezzoli Museum.
The museum building has four floors, a basement, a mezzanine, ground floor and first floor.
The project involved providing air conditioning on the first floor and ground floor, both comprising many rooms with different sized surfaces, some of which were also communicating. The rooms have vaulted ceilings reaching a height of about 4 meters, and are adorned with paintings and ornaments of great artistic value.
The outer walls are built of solid brick, while the windows are constructed of plain glass.
The air-conditioning systems occupy an area of around 235 m2 on the ground floor, and approximately 630 m2 on the first floor.

The project conditions

The internal design conditions for both summer and winter were determined with the dual purpose of protecting the exhibits and providing a comfortable environment for visitors. In this regard, there is a good correlation between the two conditions, as illustrated in the table, and constant environmental conditions are ensured by the high technology of the plant systems; this is crucial in order to constantly maintain the temperature and relative humidity of the air within the specific tolerance thresholds. The winter heating load calculation was carried out in accordance with UNI standards.
The conditions listed in the table, will proficiently ensure the preservation of works and artefacts (paintings, textiles, metals, wood, books, etc..) against the formation of condensation and proliferation of bacterial pathogens during the summer, as well as protecting against possible dehydration during the winter.

The Poldi Pezzoli Museum project conditions:

Air-conditioning systems
As mentioned above, VRF type systems have been installed at the Poldi Pezzoli Museum, with two different installation modes:

• heat recovery outdoor unit model PURY-P250YMF-C and PURY-P200YMF-C
• heat pump outdoor unit model PUMY-P125YMA

Like all installations of this type, the heat pump systems provide non-simultaneous heating and cooling functions and are therefore ideal for use in zones with homogeneous heating loads. Heat recovery systems, on the other hand, provide simultaneous heating and conditioning functions, according to user demands. They therefore represent the perfect solution for use in zones with non-homogeneous heating loads.
The indoor ambient condition control units are flush floor-mounted model PFFY-VLRM, and are installed with flush-mounted air delivery and recovery grilles which remain completely concealed and therefore have no aesthetic impact on the installation zones.
For the two air-conditioned floors, the outdoor units are installed as follows:

• first floor n° 2 PUMY-P125YMA + n° 2 PURY-P200YMF-C + n°1 PURY-P250YMF-C
• ground floor n° 2 PUMY-P125YMA + n° 1 PURY-P200YMF-C

As can be seen, 3 heat recovery systems and 2 heat pumps have been installed on the first floor. Whilst 2 heat pumps and 1 heat recovery systems have been installed on the ground floor. This choice of systems made it possible to achieve simultaneous control over cooling and heating in the relative zones on both floors, whilst in the other zones the air conditioning was achieved using heat pump units. The use of this technology has led to a reduction in overall plant system costs.
To summarise, 8 outdoor units with different capacities were installed, providing a nominal cooling capacity of about 151.2 kW and a heating capacity in winter of 170.5 kW.
It is useful to note that each outdoor motocondensing air cooled heat recovery unit (PURY) can be connected, via specific distributors, to a maximum of 16 indoor units with a total cooling output of from 50% to 150% of the nominal output of the actual unit. The motocondensing heat pump units (PUMY) can be connected, via specific distributor fittings, to a maximum of 8 indoor units with a total cooling output of from 50% to 130% of the nominal output of the actual unit.

The advantages of the Fuzzy Logic

One of the undoubted benchmark features of the Mitsubishi Electric VRF systems is the sophisticated management, supervision and control system that ensures the maintenance of the constant environmental conditions required by the project and the ability to remotely detect, via a personal computer, the operational status of each component and the ambient temperatures. The management system uses Fuzzy Logic, and has the ability to control and streamline the operations of outdoor condensing units with those of the indoor units. This technology is already installed and wired up within the units. Alarm management in the unlikely event of a malfunction is another important advantage of these systems.
The Poldi Pezzoli Museum’s indoor units are controlled independently by means of a single remote control and the centralised controller which has a liquid crystal display. They are hence capable of guaranteeing simultaneous heating and/or cooling for heat recovery systems in response to the demands of all environmental conditions. The outdoor units, distributor, indoor units, remote controls, which all indoor units are equipped with, and the centralised controller, are interfaced by means of a data transmission bus consisting of a non-polarised 1.5 mm2 diameter shielded twisted pair.

Safeguarding the environment

To conclude, it should be highlighted that the Mitsubishi Electric VRF systems carry out all the tasks they have been designed to perform in full respect of the natural environment. Furthermore, they use an eco-friendly coolant (HFC 407C) and generate considerable energy efficiency (with COP in very high summer and winter regimes), which lead to achieving a TEWI factor (Total Equivalent Warming Impact of the atmosphere), which is far lower than that found on most traditional systems.

A small alcove in the wall has been cleverly exploited to house the unit so the Mitsubishi Electric system is practically flush with the wall itself, creating an aesthetically flawless result. This was made possible due to the compact size of the indoor units, and the very small diameter of the connecting cooling lines.

A Mitsubishi Electric VRF heat recovery outdoor unit was installed on a balcony. This heat recovery system is extremely energy-efficient, whilst also ensuring outstanding comfort levels. The energy-efficient systems developed by Mitsubishi Electric highlight their success in instilling a positive relationship with the natural environment.