The thermal unit is a set of devices and devices that account for energy, volume (mass) of the coolant, as well as registration and control of its parameters. The metering unit is structurally a set of modules (elements) connected to the pipeline system.
Destination
A thermal energy metering unit is being organized for the following purposes:
- Controlling the rational use of coolant and thermal energy.
- Control of thermal and hydraulic modes of heat consumption and heat supply systems.
- Documentation of coolant parameters: pressure, temperature and volume (mass).
- Implementation of mutual financial settlement between the consumer and the organization involved in the supply of thermal energy.
Basic elements
The thermal unit consists of a set of devices and metering devices that provide the performance of both one and several functions at the same time: storage, accumulation,measurement, display of information about the mass (volume), the amount of thermal energy, pressure, temperature of the circulating liquid, as well as the operating time.
As a rule, a heat meter acts as a metering device, which includes a resistance thermal converter, a heat calculator and a primary flow converter. Additionally, the heat meter can be equipped with filters and pressure sensors (depending on the model of the primary converter). Primary converters with the following measurement options can be used in heat meters: vortex, ultrasonic, electromagnetic and tachometric.
Metering unit device
The heat energy metering unit consists of the following main elements:
- Isolating valves.
- Heat meter.
- Thermal converter.
- Mud.
- Flow meter.
- Return temperature sensor.
- Optional equipment.
Heat meter
Heat meter is the main element of which the thermal energy unit should consist. It is installed at the heat input to the heating system in close proximity to the boundary of the heat network's balance sheet.
When the meter is installed remotely from this border, heat networks add losses in addition to the meter readings (to account for the heat that is released by the surface of the pipelines in the section from the balance separation boundary to the heat meter).
Heat meter functions
Instrumentof any type must perform the following tasks:
1. Automatic measurement:
- Duration of work in the error zone.
- Running time with supply voltage applied.
- Overpressure of fluid circulating in the piping system.
- Water temperatures in pipelines of hot, cold water supply and heat supply systems.
- Coolant flow in hot water and heat supply pipelines.
2. Calculation:
- Amount of heat consumed.
- The volume of coolant flowing through pipelines.
- Thermal power input.
- Differences in the temperature of the circulating liquid in the supply and return pipeline (cold water pipeline).
Stop valves and sump
Locking devices cut off the heating system of the house from the heating network. At the same time, the mud collector protects the elements of the heat meter and the heat network from dirt that is present in the coolant.
Thermal converter
This device is installed after the sump and valves in a sleeve filled with oil. The sleeve is either fixed to the pipeline by means of a threaded connection, or welded into it.
Flow meter
The flow meter installed in the heating unit performs the function of a flow converter. It is recommended to install special gate valves in the measurement section (before and after the flowmeter), which will simplify the service and repairworks.
After entering the supply pipeline, the coolant is sent to the flow meter, and then goes into the heating system of the house. Then the cooled liquid is returned in the opposite direction through the pipeline.
Thermal sensor
This device is mounted on the return pipeline together with shut-off valves and a flow meter. This arrangement allows not only to measure the temperature of the circulating fluid, but also its flow rate at the inlet and outlet.
Flow meters and temperature sensors are connected to heat meters, which allow calculating the consumed heat, storing and archiving data, registering parameters, as well as their visual display.
As a rule, the heat meter is placed in a separate cabinet with free access. In addition, additional elements can be installed in the cabinet: an uninterruptible power supply or a modem. Additional devices allow you to process and control data that is transmitted by the metering unit remotely.
Basic diagrams of heating systems
So, before considering the schemes of thermal units, it is necessary to consider what are the schemes of heating systems. Among them, the most popular is the design of the upper wiring, in which the coolant flows through the main riser and is sent to the main pipeline of the upper wiring. In most cases, the main riser is located in the attic, from where it branches into secondary risers and is then distributed over the heating elements. It is advisable to use a similar scheme in single-storybuildings to save space.
There are also diagrams of heating systems with lower wiring. In this case, the heating unit is located in the basement, from where the main pipeline with warm water comes out. It is worth noting that, regardless of the type of scheme, it is also recommended to have an expansion tank in the attic of the building.
Schemes of thermal units
If we talk about schemes of heat points, it should be noted that the following types are the most common:
Heat unit - a scheme with a parallel single-stage connection of hot water. This scheme is the most common and simple. In this case, the hot water supply is connected in parallel to the same network as the heating system of the building. The coolant is supplied to the heater from the external network, then the cooled liquid flows in the reverse order directly into the heat pipeline. The main disadvantage of such a system, in comparison with other types, is the high consumption of network water, which is used to organize hot water supply
Scheme of a heat point with a two-stage serial connection of hot water. This scheme can be divided into two stages. The first stage is responsible for the return pipeline of the heating system, the second - for the supply pipeline. The main advantage that thermal units connected according to this scheme have is the absence of a special supply of network water, which significantly reduces its consumption. As for the disadvantages,the need to install an automatic control system to adjust and adjust the heat distribution. Such a connection is recommended to be used in case of a ratio of the maximum heat consumption for heating and hot water supply, which is in the range from 0.2 to 1
Heat unit - a scheme with a mixed two-stage connection of a hot water heater. This is the most versatile and flexible connection scheme in settings. It can be used not only for a normal temperature graph, but also for an increased one. The main distinguishing feature is the fact that the connection of the heat exchanger to the supply pipeline is carried out not in parallel, but in series. The further principle of the structure is similar to the second scheme of the heat point. Thermal units connected according to the third scheme require additional consumption of network water for the heating element
Installation order of the metering station
Before installing a thermal energy metering unit, it is important to conduct a survey of the facility and develop project documentation. Specialists who design heating systems make all the necessary calculations, select instrumentation, equipment and a suitable heat meter.
After the development of project documentation, it is necessary to obtain approval from the organization that supplies thermal energy. This is required by current heat metering regulations and design codes.
Only afterapproval, you can safely install thermal metering units. Installation consists of insertion of locking devices, modules into pipelines and electrical work. Electrical installation work is completed by connecting sensors, flow meters to the calculator and then starting the calculator to conduct heat energy metering.
After that, the thermal energy metering device is adjusted, which consists in checking the system's performance and programming the calculator, and then the facility is handed over to the coordinating parties for commercial accounting, which is performed by a special commission represented by the heat supply company. It is worth noting that such an accounting unit should function for some time, which varies from 72 hours to 7 days for different organizations.
To combine several metering units into a single dispatching network, it will be necessary to organize remote removal and monitoring of information from heat meters.
Approval for operation
When a thermal unit is admitted to operation, it is checked that the serial number of the metering device, which is indicated in its passport, and the measurement range of the set parameters of the heat meter correspond to the range of measured readings, as well as the presence of seals and the quality of installation.
The operation of the heating unit is prohibited in the following situations:
- The presence of tie-ins in pipelines that are not provided for by the design documentation.
- The operation of the meter is outside the accuracy standards.
- Presence of mechanical damage on the device and itselements.
- Breaking seals on the device.
- Unauthorized intervention in the operation of the thermal unit.
