Thermal unit. Thermal energy measuring unit. Thermal circuits

Thermal unit is a set of devices and devices that take into account the energy, volume (mass) of the coolant, as well as the registration and monitoring of its parameters. The accounting unit constructively represents a set of modules (elements) connected to the pipeline system.

Appointment

The heat energy metering unit is organized for the following purposes:

• Controlling the rational use of heat carrier and heat energy.
• Control of thermal and hydraulic modes of heat consumption and heat supply systems.
• Documenting the parameters of the coolant: pressure, temperature and volume (mass).
• Implementation of mutual financial accounting between the consumer and the organization engaged in the supply of thermal energy.

Essential elements

The thermal unit consists of a set of devices and meters that provide the performance of one or several functions simultaneously: 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 is used as an instrument of account, which includes a thermal resistance converter, a heat calculator and a primary flow converter. In addition, the heat meter can be equipped with filters and pressure sensors (depending on the model of the primary converter). In heat meters, primary converters with the following measurement options can be used: vortex, ultrasonic, electromagnetic and tachometric.

The device of the accounting unit

The heat energy accounting unit consists of the following main elements:

• Stop valves.
• Heat meter.
• Thermocouple.
• Sump.
• Flowmeter.
• Thermal sensor of the return pipeline.
• Optional equipment.

Thermal counter

The heat meter is the main element from which the heat energy unit must consist. It is installed at the input of heat into the heating system in the immediate vicinity of the boundary of the balance belonging to the heat network.

If the meter is remotely mounted from this boundary, the heat network additionally to the meter readings is added to the losses (to account for the heat that is released by the surface of the pipelines from the balance sheet to the heat meter).

Heat meter functions

The device of any type must perform the following tasks:

1. Automatic measurement:

• Duration of work in the error zone.
• Time of operating with the supply voltage applied.
• Excessive pressure of the liquid circulating in the piping system.
• Water temperatures in pipelines of hot, cold water and heat supply systems.
• The flow of coolant in the pipelines of hot water supply and heat supply.

2. Calculation:

• The amount of heat consumed.
• The volume of the coolant flowing through the pipelines.
• Thermal power consumption.
• Differences in the temperature of the circulating fluid in the supply and return pipelines (cold water supply pipes).

Stop valves and sump

Locking devices cut off the heating system at home from the heating network. Mud in this case provides protection of heat meter elements and heat network from dirt, which is present in the coolant.

Thermocouple

This appliance is installed after the sump and shut-off valve in the oil filled sleeve. The sleeve is either fixed to the pipeline by means of a threaded connection, or it is welded into it.

Flowmeter

A flowmeter installed in a thermal unit performs the function of a flow converter. At the measuring site (before and after the flowmeter) it is recommended to install special valves, due to which the maintenance and repair work will be simplified.

After entering the supply pipeline, the coolant goes to the flowmeter, and then goes to the heating system at home. Further, the cooled liquid is returned in the reverse direction through the pipeline.

Thermal sensor

This device is mounted on the return pipeline in conjunction with the shut-off valve and flowmeter. This arrangement allows not only to measure the temperature of the circulating liquid, but also its flow at the inlet and outlet.

Flowmeters and temperature sensors are connected to heat meters, which allow calculating the consumed heat, storing and archiving data, registering parameters, as well as visualizing them.

As a rule, the heat meter is placed in a separate cabinet with free access. In addition, in the cabinet you can install additional elements: an uninterruptible power supply or a modem. Additional devices allow you to process and control data that are transferred by the accounting node remotely.

Basic schemes of heating systems

So, before considering the scheme of thermal nodes, it is necessary to consider what are the schemes of heating systems. Among them, the most popular design is the top wiring, in which the coolant flows along 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 room, from where it branches to the secondary risers and then is distributed over the heating elements. Such a scheme is advisable to use in one-story buildings in order to save free space.

Also there are schemes of heating systems with a lower wiring. In this case, the thermal unit is located in the basement room, from where the main pipeline with warm water leaves. It is worth noting that, regardless of the type of scheme, it is recommended to have an expansion tank in the attic of the building.

Thermal circuits

If we talk about the schemes of thermal points, it should be noted that the most common types are:

• The thermal unit is a circuit with a parallel single-stage hot water connection. 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 heat carrier is fed to the heater from the external network, then the cooled liquid flows in the reverse order directly to the heat pipe. The main disadvantage of such a system, in comparison with other types, is a large consumption of network water, which is used to organize hot water supply.

• Scheme of a heat point with a consecutive two-stage hot water connection. 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 nodes connected with this scheme have is the absence of a special supply of network water, which significantly reduces its consumption. As for the shortcomings - it is the need to install an automatic control system to adjust and adjust the heat distribution. This connection is recommended to be used in the case of the ratio of the maximum heat consumption for heating and hot water supply in the range from 0.2 to 1.

• The thermal unit is a circuit with a mixed two-stage connection of a hot water heater. This is the most universal and flexible in the settings connection scheme. It can be used not only for a normal temperature schedule, but also for increased temperature . The main distinctive feature is the moment that the connection of the heat exchanger to the supply pipe is not carried out in parallel, but in series. The further principle of structure is similar to the second scheme of a heat point. Thermal units, connected according to the third scheme, require additional consumption of network water for the heating element.

The order of accounting node installation

Before installing a heat metering unit, it is important to conduct an object survey and develop project documentation. Specialists who are engaged in the design of heating systems, perform all necessary calculations, select instrumentation, equipment and a suitable heat meter.

After the development of the project documentation, it is necessary to obtain agreement from the organization that is engaged in the supply of thermal energy. This is required by the existing rules for accounting for thermal energy and design standards.

Only after reconciliation, it is possible to establish the thermal units of accounting. Installation consists of tie-in of locking devices, modules in pipelines and electrical installation works. The work on wiring is completed by connecting sensors, flowmeters and the subsequent start of the calculator to the calculation of heat energy.

After that, the heat meter is set up, which consists in checking the system's operability and programming the calculator, and then the object is handed over to the matching parties for commercial accounting, which is carried out by a special commission in the person of the heat supply company. It is worth noting that such an accounting center should function for some time, which varies from 72 hours to 7 days for different organizations.

In order to merge several accounting nodes into a single dispatching network, it will be necessary to organize remote removal and monitoring of accounting of information from heat meters.

Admission to operation

When the thermal unit is allowed to operate, the conformity of the meter's factory number, which is indicated in its passport and the measuring range of the specified parameters of the heat meter to the range of measured readings, as well as the presence of seals and the quality of installation, are checked for operation.

Operation of the thermal unit is prohibited in the following situations:

• Presence of tie-ins in pipelines, which are not provided for in the project documentation.
• The operation of the meter is beyond the limits of accuracy.
• Presence of mechanical damages on the device and its elements.
• Violation of seals on the device.
• Unauthorized intervention in the operation of the thermal unit.