Automation design solutions for an individual heat substation

Based on the design results, working documentation for the automation of an individual heat substation in a hotel has been developed.

Heat substation automation design solutions

Individual Heat Substation Automation Solutions

Individual Heat Substation Automation Project

Main Automation Solutions

To solve automation and control tasks, the project uses a complex of technical equipment from a US-based manufacturer. The complex includes:

  • Primary transducers with a unified analog output signal: pressure sensors, immersion temperature sensors;
  • Automation panels with built-in processor modules, distributed input/output modules, mounting modules, and communication bus modules.
  • An automation panel with built-in distributed input/output modules, mounting modules, and communication bus modules.

The main automation panel also includes modules for connecting signals from other systems (see the relevant project documentation). The automation panels with the controller provide:

  • Management of main and backup pump motors based on an operating time schedule (adjustable resource utilization) - alternating every 48 hours;
  • Activation of the backup pump if the main one fails, based on a signal from a differential pressure sensor;

Regulation and control of water temperature for heating and ventilation systems, with the setpoint determined by the outdoor air temperature according to a heating curve:

  • When the outdoor air temperature rises, the water temperature setpoint decreases, the control valve on the heat carrier pipeline to the main heater closes proportionally, and vice versa. The control law is Proportional-Integral (PI);
  • Regulation and control of water temperature for the Domestic Hot Water (DHW) system:
  • If the water temperature decreases, the control valve on the heat carrier pipeline for the DHW heater opens; if the temperature increases, it closes.

Heat substation automation system project

PI Regulation

Regulation and control of water pressure in the heating system make-up lines via a pressure sensor:

  • If the pressure in the return pipeline of the Heating System, Zone II drops, the make-up valve opens fully and the make-up pump activates;
  • If the pressure increases, the make-up pump deactivates and the valve closes completely. If the pressure in the return pipeline of the Heating System, Zone I drops, the make-up valve opens fully;
  • If the pressure increases, the valve closes.
Positional Control

Regulation and control of water pressure in the ventilation system make-up lines via a pressure sensor:

  • If the pressure in the return pipeline of the Ventilation System, Zone II drops, the make-up valve opens fully and the make-up pump activates;
  • If the pressure increases, the make-up pump deactivates and the valve closes completely.
  • If the pressure in the return pipeline of the Ventilation System, Zone I drops, the make-up valve opens fully;
  • If the pressure increases, the valve closes. Measurement of current process parameters;
  • Monitoring of equipment status (local/automatic control, on, off, fault, normal operation);
  • Transmission of alarm, warning, and statistical information about the technological process to the dispatch center.

Pump Operation Algorithm

DHW and Make-up Pumps. Control of Domestic Hot Water (DHW) and make-up pumps must provide 2 modes:

  • Local control (testing) of pump motors from the control panel installed in the heat substation room;
  • Automatic control.

Automatic control is carried out according to a specified program from the controller. Automatic mode can be started by an operator command (at the location of the automation panel). The operator can set the pump operation mode:

  • Start and Stop - activation/deactivation regardless of the time schedule;
  • Auto - activation/deactivation according to a specified time program (in summer mode, make-up pumps are switched off by a timer).

Auto mode is the preferred mode as it does not require intervention from maintenance personnel. To turn pumps on and off outside the programmed schedule, their startup must be reprogrammed or switched to Start/Stop mode. Local control mode is used only for debugging pump motors. DHW pumps operate year-round, except during scheduled maintenance.

Ventilation and Heating Pumps

The pumps are operated using a variable speed drive system, which provides smooth power regulation based on a frequency converter in accordance with the changing pressure differential. The control system ensures:

  • Maintaining a constant pressure differential;
  • Automatic alternating pump operation based on load and time, as well as in case of malfunctions;
  • Smooth regulation of pump motor speed depending on the required setpoint for pressure differential;
  • Signaling of pump operational and fault status via dry contacts.

Organization of Control and Management

The main automation panel with built-in controller modules is located in the primary heat substation room. A second automation panel is located in a secondary substation room. A third panel with input/output modules is located in a third substation room. Information collected by the modules is transmitted via a communication bus to the controller in the main automation panel. A portable operator panel is provided for data access and display.

Monitoring of Process Parameters

The project provides for the measurement of the following process parameters:

  • Outdoor air temperature;
  • Temperature and pressure of the supply and return network water;
  • Temperature and pressure of water for DHW, heating, and ventilation (supply and return);
  • Mains water pressure.
System Operation Alarming

The following information is displayed on the heat substation automation panels and in the dispatch center:

Pump Status:

  • On/Off - based on the status of the pump magnetic starter contact;
  • Normal/Fault - based on the status of the thermal protection relay or a signal from a differential pressure sensor;
  • Position of the "Local/Auto" switch;
  • Water temperature after heaters (above/below normal).
  • Water pressure in the return pipelines of heating and ventilation systems (below normal).

[Section on wiring standards and installation notes has been condensed as it contains highly specific local regulations and standards.]

Automation and Control Equipment.

The instrumentation and automation equipment ensures the heat substation operates in automatic mode, without constant maintenance personnel.

The automation project provides for:

  • Regulation of heat carrier temperature in the heating networks depending on the outdoor air temperature;
  • Regulation of heat consumption in heating and limitation of the maximum network water flow at the consumer;
  • Maintaining the set temperature of water in the domestic hot water system;
  • Maintaining the set pressure in the return pipeline or the required pressure differential in the supply and return pipelines of the heating networks;
  • Protection of the heat consumption system from excessive pressure or temperature;
  • Maintaining static pressure in the heat consumption systems;
  • Protection of the heating system from draining;
  • Activation of a backup pump upon failure of the main one;
  • Protection of pumps from dry running;
  • Visual indication of operational or fault status.

The heat substation includes commercial metering of heat and coolant. This system is intended for commercial accounting of the building's thermal energy consumption. Heat metering for heating, ventilation, and DHW is performed separately from the heating system make-up metering.

Parameter and archive data transmission from heat calculators is performed to an automated dispatch system. The control panels are custom-made. The automation system is a local installation capable of operating both autonomously and as part of an integrated system.

[Detailed descriptions of winter/summer operational algorithms for heating and DHW circuits, including control logic for valves, pumps, and heaters, have been condensed for brevity, preserving the core functional principles.]

The control panel generates signals for the dispatch system regarding temperatures, pressures, pump status, valve positions, and alarms. It also receives commands from dispatch for start/stop and seasonal mode switching.

Communication cables with low fire hazard, flame-retardant, low smoke and gas emission, and low toxicity characteristics are used for the dispatch system connection. Cables are laid in solid metal trays and corrugated conduits as specified.