22 Apr Hotel air conditioning systems
In the previous article we illustrated how the Giano Supervisor software allows the facility manager to set, control and manage the thermoregulation of the rooms and common areas, in order to reduce energy waste and increase guest comfort. All this in a transparent manner from the actual device used in the room for air conditioning, with a considerable simplification for the manager.
Let’s now examine the types of existing air conditioning systems (HVAC devices), their peculiarities and how they are managed by Giano.
The radiator is the most common type of heating system in the home and is characterized by high inertia. From the point of view of home automation, the operation of the radiator is activated by opening a solenoid valve (using a relay output).
After that it can be managed in the following ways:
- Activation on / off
Based on the state of check-in, season and room occupancy, an electro-valve is activated which activates the circulation of water in the system. Thermo-regulation is instead delegated to one or more thermostatic valves connected directly to the radiators / decorative radiators concerned. In this mode there is no actual verification of the user settings but only an inhibition upstream of the air conditioning in certain states of the room (which can be set on the supervisor). In this category we also find underfloor heating which shows a considerably higher thermal inertia due to the large mass (the floor) to be heated.
Home automation, through the thermostat probe, carries out a real thermoregulation of the environment. Usually, the strong inertia of the system can cause a natural oscillation of the resulting room temperature (which translates into less comfort for the guest).
The split is the simplest and cheapest choice to equip your own air conditioning rooms, and it is certainly the most common in small systems.
Hotel Automation can manage the split in different ways, gradually more sophisticated:
- Inhibition by power supply disconnection
The split is simply turned off and on by driving its main power supply with a home automation relay. Not all splits are suitable for this type of use or able to return to the previous adjustment state when switched on again.
- Inhibition via standby
If the split is equipped with a standby input (typically provided for connecting the window contact), it can be used to inhibit its operation from home automation (using a relay output).
- Thermo-regulation via standby
It consists in taking advantage of the previous standby input to activate / deactivate the operation of the split as long as the chamber is brought up to temperature. Basically, the home automation thermostat is used as a user interface for selecting the comfort temperature and as a probe, and the split as an actuator for cooling / heating. The set-point setting on the indoor unit is carried out once per season to its maximum value (relative to the season) via an infrared remote control that must be removed from the room.
- Direct split command
It consists in directly controlling the split settings through an adapter (wired or infrared) which simulates the remote control of the unit, but is controlled by home automation. This solution, although refined, requires higher room costs than the previous ones.
The evolution of traditional splits are the VRV / VRF, or centralized air conditioning systems , and represent a significant improvement in terms of installation costs, energy efficiency and system maintenance. This air conditioning solution is characterized by numerous indoor units managed by a single outdoor unit . Each outdoor unit is connected via bus to a centralized control device, called a “touch panel” or “gateway”. It allows you to monitor and intervene on individual units, either with a local panel or software or through an interface dedicated to hotel automation.
The most evident benefit of a centralized air conditioning system is the being able to know and control in detail, remotely, every single status of the units : room temperature, settings, filter cleaning, error codes, etc. … Each of these is shown in the specific windows of the Giano supervision software. There are multiple manufacturers of VRV / VRF systems, each with characteristics, interfaces and peculiarities that we will analyze one by one in the next articles.
The fancoil, or fan coil , is the final part of an air conditioning system that exploits the heat exchange between water and air to thermo-regulate an environment. A hydraulic circuit carries the heated or chilled water, which, through solenoid valves, is circulated in a heat exchange battery (similar to a car radiator) to heat / cool the air in the room. The latter is brought together thanks to a fan.
The fancoil – which is still the most common air conditioning solution in hotels – consists, from the point of view of hotel automation, in two elements to be controlled separately:
- the valve(s) that activate the water circuit in the unit;
- the speed of the fan which regulates the amount of air exchanged.
The simplest and most widespread hydronic system consists of a single circulating heat transfer fluid that enters the unit and that – after the heat exchange – leaves it (hence called “two-pipe”). The liquid temperature determines the mode (heating or cooling) of the system, typically maintained for the entire season. The water circulation is activated by opening an electro-valve, piloted by a home automation relay output (typically by that of the thermostat).
When it is necessary, in the same season, to be able to cool and heat at the same time, it is necessary to transport two heat transfer fluids separately and then control their flow separately in the fan coil through two valves, driven by two home automation relays (typically by those of the thermostat).
Fancoil with on-off engine
The speed of the fan coil fan is determined by the rotation of the motor, controlled through three 230VAC inputs with common (minimum, average or maximum speed). Naturally, the thermo-regulation takes place by adjusting the fan speed according to the actual urgency to bring the chamber up to temperature, that is the distance between the ambient temperature and the set-point.
Fancoil with brushless engine
Some types of motors – called brushless – are controlled by an electronic board whose inputs for the three speeds are electrically different from those connected directly to the motor. The advantage of this type of engine is the low noise and the ability to run slower.
This kind of fancoil requires the use of a specific version of thermostat, called “without RC network” (F-GTR-NRC).
Fancoil with 0-10V engine
Newer brushless motors have linearly controlled fan speed through a 0-10V analog input.
In order to manage them, it is necessary to prepare the GFP-F-GTR thermostats of the GFP-DAC accessory that converts between the 3 on / off speeds and the 0-10V analog signal.
Software user interface
Whatever the thermo-regulation devices used in the structure, the hotel supervisor Giano is able to manage them and exploit their peculiarities to optimize consumption and ensure the best comfort for the guest, as detailed in detail in the previous article.
In the next we will analyze some case studies of interfacing with centralized air conditioning systems (VRV/VRF).