Buildings and industry

Integration of air conditioning units, Sacre Coeur II

Residence Sacre Coeur 2 is part of a polyfunctional block of houses in Holečkova and Grafická streets in Prague. The building contains apartements, garages and shops. It is controlled by a building management system which monitors and controls gas boilers, heating, and air conditioning units including split air condition units in the apartments

In the control room there is a management station equipped by a PC running SCADA software. To provide garages, boiler room, and sales areas with fresh air, and to exhaust the apartements, there is 8 AHUs in the building. The heating supplies four circuit: three for the apartments, one is a supply pump for the air handling units.

Up to this point, the technology is not different from those in usual polyfunctional buildings. The main difference in the building control system (BMS) against most projects is in the apartments. They are air-conditioned by LG split units which are integrated into a central controller in each apartment, together with floor heating and – in some rooms – convector heating.

The apartments contain, according to number of rooms, up to 12 floor heating circuits, up to 10 convectors with thermoelectric actuators, up to 6 VRV units, up to 5 communicative room units Domat UI010 or UI012 (according to required outputs for thermoelectric actuators) and one or two heat meters. As the functional variability is high, every apartment has its own freely programmable controller Domat mark320. Total number of controllers in the building is 84.

The programmable controller mark320 provides 4 serial ports (2× RS232 and 2×RS485). One RS485 line is occupied by triac output modules M312 for control of thermic actuators and communicative room units UI012 to control the convectors, or room units UI010 with no outputs. All components are talking Modbus RTU. The second RS485 port integrates the air condition units using LGAP protocol (formerly called PI485). This communication is able to set the VRV unit status, operating mode, air flow direction, temperature and fan speed setpoint, and monitor room temperature and other parameters. The PI485 protocol was available in the previous Domat MiniPLC controllers range, however, in the Domat mark320 controllers it is implemented as open structured text (ST) and freely available as an example of a customer-editable communication protocol. The mark… process stations may be programmed either in structured text, which brings more flexibility, or in the functions block language (FBD), which is easier to understand for most of the BMS engineers. Both ways of programming may be combined in one controller, and users are free to create customized function blocks as structured text or function blocks programs.

In this project, the aim was to coordinate the function of air conditioning and heating so that no concurrent heating and cooling by the VRV may occur. Unified room operation by room units UI010 or UI012 makes user intervention easy, the control commands for the air conditioning unit are communicated over the bus to the outdoor unit (common for all the indoor units of one apartment) and the outdoor unit sends them to the indoor units. The room units UI012 control the thermic actuators in the respective rooms, which saves cabling costs. The actuators located in the floor heating manifold box are controlled by a common M312 triac output module with 8 triac outputs.
Data from the process stations are communicated to a central SCADA. The users may conect to the control system over the Internet and monitor or control their apartment from their mobile devices.

There are other systems integrated on the apartment level (KNX for lighting control, Wago process stations) and on the SCADA level (Sauter primary controls). Sacre Coeur 2 is a project where close cooperation of air conditioning, hrating, and BMS designers proved to be fruitful. This was the only way to give birth to a building with integrated solution saving both investment and operational costs.