Diagram for Connecting a Hot Water Heater Tank

Connection Schemes for a Storage Water Heater depend on the thermal and hydraulic regime of the heat source, as well as the requirements for the automation of the heating process.

Diagram with an Integrated Heat Exchanger and One Loading Pump

This diagram is used in boiler rooms when connected to a non-pressure collector or hydraulic distributor. The pump is turned on and off by a temperature sensor installed in the storage water heater. The turn-on and turn-off temperatures are set programmatically on the control controller.

It is recommended to install a check valve on the supply line of the heating circuit, which prevents cooling of the tank through the heating circuit when the pump is stopped.

Diagram with an Integrated Heat Exchanger and Temperature Controller

This diagram is used in water heating systems connected to a heat network or pressure collector of a boiler room that provides heat to several consumers. The temperature regulator can be a two-way regulating valve or a direct-acting temperature regulator. The temperature regulator valve can be installed on both the supply and return pipelines.

The regulator maintains a constant temperature in the middle of the tank by changing the flow rate of the heat transfer fluid through the heat exchanger located at the bottom of the tank.

Diagram with an Integrated Heat Exchanger, One Loading Pump, and a Mixing Valve

This diagram is used when connecting a storage water heater in boiler rooms to a hydraulic distributor or non-pressure collector. The pump can operate continuously, or the signal for turning on and off can come from the control controller.

A three-way regulating valve with an electric actuator, controlled by a controller, or a direct-acting temperature regulator can be used as a mixing valve.

Diagram with an External Heat Exchanger and Two Pumps

This diagram is used when connecting storage water heaters in boiler rooms to a hydraulic distributor or a non-pressure collector with a maximum temperature of the supply line not exceeding 70°C and when the boiler is only used to heat water.

It is also possible to connect to centralized heating networks with an independent scheme supporting a constant heating water temperature not exceeding 70 °C.

The operation of the pumps is controlled by a programmable controller that turns on both pumps and sends a signal to start the boiler (if it is only intended for water heating) based on the temperature sensor in the middle of the tank. A sensor is also located at the bottom of the tank that turns off the boiler and pumps. The water temperature at the outlet of the heat exchanger is maintained by the variable operation of the heating circuit pump. When implementing a similar control scheme, it is important to note that the automatic control of the pumps should be adjusted to prevent cold water from entering the upper part of the tank during boiler heating or heat exchanger heating.

Diagram with an External Heat Exchanger, One Pump, and Temperature Controller

This diagram is used when connecting storage water heaters to centralized heating networks or a pressure collector in a boiler room that provides heat to several consumers. The temperature of the hot water at the outlet of the heat exchanger is maintained at a constant level.

The temperature controller can be implemented using a regulating valve with a controller and temperature sensor or a direct-acting temperature controller. The heating coolant flow rate can be variable, with the option of completely stopping circulation. The flow rate of the heated coolant can be either constant or variable, with pump control based on signals from two temperature sensors located inside and at the bottom of the tank.

Diagram with an External Heat Exchanger and One Pump

This diagram is used when connecting a hot water storage tank to a heating boiler that operates only to provide hot water, while maintaining a constant temperature at the outlet of the boiler for a constant flow rate of the heating fluid. The signal to turn on the loading pump of the heating circuit comes from a temperature sensor in the middle of the tank, while the signal to turn off comes from a temperature sensor at the bottom of the water heater.

It is possible to implement a scheme for turning the boiler on and off with the same signals as the loading pump, but in this case, there is a problem of loading the storage tank with water that is not yet heated from the bottom of the tank during the boiler heating. This problem can be solved by installing a time relay on the secondary circuit pump, which sends a signal to turn on the pump after a certain time after the boiler is turned on.

Diagram with an External Heat Exchanger, Two Pumps, and a Mixing Valve

This diagram is used in boiler rooms that provide heat to several systems and operate according to a heating schedule with a break point that is at least 5-10°C higher than the temperature of the heated water. In this case, the hot water storage tank is connected to a hydraulic arrow or a low-pressure collector.

The water temperature at the outlet of the heat exchanger is maintained by a mixing valve. The second (heating) circuit pump can operate continuously or be turned on by a temperature sensor at the bottom of the tank and turned off by a temperature sensor installed in the middle of the tank. The first (heating) circuit pump can operate continuously or periodically, turning on and off with the same signals as the heating circuit pump. A three-way regulating valve with an electric drive, which is controlled by a controller, or a direct-acting mixing temperature regulator can be used as a mixing valve.

Diagram with an External Heat Exchanger, One Pump, and a Diverter Valve

This diagram is used in boiler rooms that operate on a heating schedule with a breakpoint of no less than 5-10°C higher than the temperature of the heated water, and the water heater is connected to a pressurized manifold. The temperature of the water leaving the heat exchanger is maintained by a three-way valve that separates the flow of the heating coolant.

The pump of the heating circuit can work constantly or be turned on by a temperature sensor signal from the bottom of the tank and turned off by a temperature sensor signal from the middle of the tank. A three-way regulating valve with an electric drive, which is controlled by a controller, or a direct-acting diverter temperature regulator can be used as a diverter valve.

Regardless of the heating control scheme in storage water heaters, it is recommended to choose controllers that allow protection against legionella by briefly raising the water temperature in the tank to 70°C at night.

Parallel and Serial Connection Schemes

A setup of several storage water heaters is used in the following cases:

• Adaptation to specific volume and layout conditions.
• Large size characteristics of one tank complicate transportation and installation.
• The capacity of the largest tank is insufficient to provide the necessary volume of water.
• High reliability of the water heating system is required, with the ability to disconnect one of the tanks without stopping the system.
• A specific water heating scheme is implemented, which allows adapting the heating process to the water consumption and thus selecting the minimum necessary volume of the water heater.
• When connecting storage water heaters in parallel, it is recommended to use a bundle with a concurrent movement of the coolant (the Thielemann scheme). This will allow for even heating of the tanks and even use of hot water from them.

Features of parallel connection of storage water heaters:

• High power of the water heating system.
• Possible disconnection of one of the tanks for maintenance without stopping the water supply system.

Features of sequential connection of storage water heaters:

• Compensation of significant peak water consumption.
• Cooling of the heating circuit coolant is greater compared to parallel connected tanks, which allows connecting tanks to a condensing boiler and achieving maximum efficiency, and with centralized heating, using less coolant flow rate.

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