Automation system of the residential complex «Blizhnyaya Dacha».
Author: Zakharov N.S. Leading specialist in air conditioning systems, Moscow representative office of Mitsubishi Electric
In the spring of 2006, the residential complex «Blizhnyaya Dacha» will be put into operation in Moscow, where multi-zone air conditioning systems «City Multi» manufactured by Mitsubishi Electric are installed. The general contractor for this project was the Austrian construction company Strabag, the design, delivery and installation of air conditioners were carried out by ZAO «Hikoniks».
According to the technical assignment formulated by the customer, the following requirements were imposed on the air conditioning system:
— energy efficiency (the total electrical power of the air conditioning equipment must not exceed a certain value);
— installation of system units and assemblies on the roof of buildings (installation of devices on facades is excluded);
— phased commissioning (as the finishing of residential premises is completed);
— construction of a unified air conditioning equipment dispatching system for the entire complex of buildings;
— differentiated metering of electricity consumption within the central system.
The best energy efficiency indicator among central solutions today is provided by multi-zone direct expansion systems, the so-called VRF systems.
Their fundamental difference from chiller-fan coil systems is the absence of an intermediate coolant circuit, and, therefore, losses on intermediate heat exchangers.
Only VRF systems made it possible to fit into the existing restriction on the installation capacity of climate control equipment at the facility.
Modern VRF systems using R410A refrigerant are characterized by a significant length of freon pipelines (300-400 m) and allow placing outdoor units out of sight on the roof of buildings.
The need for a phased commissioning of the system, namely the gradual connection of indoor units, is due to the extended, possibly several years, occupancy of the facility. And the first residents must be provided with a working air conditioning system.
This requirement was the second reason for choosing a direct expansion system, rather than a «chiller-fan coil» scheme.
How will the phased commissioning of the system take place?
By the time the building was handed over, the contractor had installed the outdoor units and refrigerant lines (before entering the apartments).
The ends of the liquid and gas pipes were closed with ball valves. In addition, a single signal line was connected to each apartment from the outdoor unit.
Next, during the finishing of the premises, the installation of the internal units and the connection of the refrigerant lines to the shut-off valves is carried out.
On the side of the internal units relative to the shut-off valves, Schroeder valves are soldered into the gas and liquid lines. The signal line is brought to the junction box and is not connected yet.
Commissioning work on connecting a new apartment to the system is very simple and comes down to several operations, which take a maximum of two days to complete, and the functioning of the existing part of the system is not disrupted. It should be noted that the City Multi direct expansion multi-zone systems do not require adjustment and configuration during the step-by-step introduction.
Control algorithms based on the principles of fuzzy logic, embedded in the external and internal devices, allow the system to automatically adjust to the new configuration.
The construction of the climate control system was implemented using a hardware and software complex manufactured by Mitsubishi Electric, since the technical specifications did not require the integration of air conditioners into a single control system for a residential complex.
It consists of the following components.
— Universal central controller GB-50A (at the rate of one GB-50A for every 50 indoor units).
This universal device is designed to perform all the main dispatching tasks: central control and monitoring, differentiated metering of electricity consumption, limiting the peak power of the system, connecting to BACnet networks and many others.
This feature of the GB-50A allows for further expansion of the capabilities of the dispatching system without both hardware and software upgrades to the device.
Each GB-50A controller already has all possible software modules, and they are activated using a special code when implementing (activating) a particular function.
The full list of built-in software models is given in Table 1. For communication with the computer and scaling of the control system, the controller is equipped with an Ethernet interface. Data exchange between system components is carried out in XML format.
— The TG-2000A software visualizes control and management.
The program allows you to place icons of indoor units on floor plans, store information on power consumption, and configure universal GB-50A controllers to perform special functions.
For example, to limit peak power, organize standby heating or configure energy saving mode parameters. The program is based on interaction with the MS SQL database management system (DBMS).
All information about program settings, air conditioner status, and power consumption data are stored in the database, which ensures high-speed access to information and reliable storage. TG-2000A allows you to connect up to 40 universal GB-50A controllers, i.e. provides interaction with two thousand indoor units.
— The design process of the control system began with determining the required number of GB-50A controllers.
For this, taking into account the maximum possible number of indoor units, fixed for any apartment, we formed associations of outdoor units with a total number of indoor units of no more than 50.
A GB-50A is connected to each such association. As a result of the calculation, it turned out that, depending on the number of floors, 3-4 universal controllers are required for each building of the residential complex.
All controllers, as well as the dispatcher's computer, are connected via a local Ethernet network. For the GB-50A controllers to interact with the TG-2000A dispatching program, at least the «web-control» software module must be activated in them.
Separate metering of electricity consumption within the central system is necessary in each apartment building.
At the same time, accounting for the power consumption of indoor units is not difficult — their circuit is powered through the input circuit breaker of the apartment, and the corresponding costs are recorded by the apartment meter.
It is more difficult to differentiate the power of an outdoor unit common to several apartments. To solve this problem, you can do it simply and, for example, divide the energy consumed proportionally to the area of the apartments or take into account the operating time of the indoor units per apartment.
Unfortunately, simple solutions do not ensure a fair division of costs and, most likely, will not be understood by users.
How to implement fair accounting? The only parameter that can be taken as a basis for calculation is the flow rate of refrigerant through the internal units. For this purpose, the universal controller has a software module «electricity consumption accounting».
After its activation, GB-50A informs the dispatching program which indoor unit is loaded with the outdoor unit. This parameter is calculated by the controller based on the degree of opening of the indoor unit expansion valve. This approach solves the task as accurately as possible if the operation service is satisfied with manual input of data on electricity consumed by the outdoor unit during the billing period for each indoor unit.
If fully automated accounting is required, including printing of payment receipts, it is necessary to additionally organize a data collection channel from electricity meters and connect it to the dispatcher's computer.
Mitsubishi Electric offers a complete solution based on the freely programmable controller (PLC) MELSEC series «Q», which can be implemented by any climate control company.
The controller specification is given in Table 2.
Up to 32 meters with a relay telemetry output can be connected to the PLC input modules. The number of meters corresponds to the number of GB-50A controllers.
They are included in the power supply circuit of the outdoor units, combined by GB-50A. According to the specification of the QX40 input module, an additional power source of 24 V DC is used.
The specially developed software of the PAC-YG11CDA controller calculates pulses from the meters and transmits data to the TG-2000A dispatching program via the Ethernet module QJ71E71-100.
It is necessary to note an important feature of the presented accounting scheme: the dispatcher's computer is used only for visualization of control, performing final calculations and storing information on electricity consumption for past months.
Operational information on the outdoor unit load factors and data from the meters are processed and buffered via channels that do not depend on the stability of the Windows operating system.
The corresponding data will be autonomously collected by the controllers (GB-50A and PLC) of the electricity metering system for 61 days in the event of a malfunction of the dispatcher's computer.
Unfortunately, it was not possible to use all the capabilities of the Mitsubishi Electric scheme at this facility due to the impossibility of installing meters with a relay telemetry output.
Instead, they used Mercury 230AM meters with an open collector pulse output designed for a nominal voltage of 12 V DC.
Theoretically, it was possible to replace the PLC input module with an analog that works with the same output circuits — QX70.
However, since a full-scale test at the manufacturer's plant was required to confirm the system's operability, this opportunity could not be used.
A combined solution was adopted: the channel for information on the loading of the outdoor unit by indoor units was organized on the basis of GB-50A controllers, and the collection of meter readings was carried out for them by the provided network solutions.
As a result, the following system of differentiated electricity consumption accounting was implemented. GB-50A controllers transmit data on the consumption of refrigerant by indoor units of each apartment to the TG-2000A program.
The program calculates the outdoor unit utilization factors per apartment. The sum of the factors for all apartments within the coverage area of one GB-50A controller (or all controllers) is equal to one.
The program saves the table «apartment number — outdoor unit utilization factor» in a text file in csv format (data separated by commas).
The pulse output of each meter is connected to the CAN interface converter to combine the meters into a network and transmit data to the control room of the residential complex.
The control room computer is equipped with a CAN converter and specialized software that supports data exchange with meters and saves them in text format.
At the end of the reporting period, the dispatcher is provided with two text files, the first with the outdoor unit load factors, the second with the meter readings.
Software that produces formatted information output — printing payment receipts — was developed specifically for this project.
The use of a combined solution eliminated one of the advantages of the original scheme. The channel for collecting data from the counters turned out to be unbuffered.
Indeed, excluding the PLC, there are no devices with memory left in this chain, and the pulse counting is performed by a program under the Windows operating system, which is not usually trusted with real-time tasks.
However, if the computer freezes and misses several pulses from the meters, then, having detected a discrepancy between the meter readings and the program data, the dispatcher will only need to manually restore the correspondence.
Thus, the customer received a completely ready-made solution that meets all the points of the technical specifications: compact energy-efficient equipment that allows for the phased commissioning of indoor units, centralized control and monitoring (including remotely).
A unique solution from Mitsubishi Electric, among other things, allows for a fair distribution of energy costs between users.
It should be noted that another factor is often of decisive importance when choosing a system such as «City Multi» from Mitsubishi Electric — its cost for the investor.
By paying only for the outdoor units and pipelines, the investor receives a building with the most modern air conditioning system, and the upgrade of the housing class and the corresponding cost per square meter will more than pay for the investment in air conditioning.
At the same time, the buyer gets the opportunity to choose the type and location of indoor units in apartment, purchasing them as needed.