Heating of rooms and warm water

Electrical heating

An electrical heating system consists fundamentally of electrical resistive elements. They are heated up by the flow of electrical current, and the resulting heat that is generated is given off either directly by the surrounding air or water flow, or indirectly via protective sleeves. Electrical auxiliary heating systems are frequently used in HVAC equipment. The typical auxiliary heating design for a storage water heater is a spiral coil that can also be found in a simplified design in immersion heaters.

Frequent applications that can be found in Europe are the so-called electrical storage heaters. A heat reservoir is heated up at night, and the stored heat is given off during the day. This form of heating is continuously declining at the present time because of the energy costs involved.

With electrical heating of air or water using heating batteries or heating rods the heat energy generated corresponds exactly with the quantity of electrical energy that is applied.

Heat control with Eaton contactors and soft starters

In the simplest case, the control of the delivered heat with slow response heating systems via on-off control is implemented using the contactor (DIL). High contactor operating frequencies result if the mass to be heated is small or the heating power is very large. The control precision demands also play a significant role. In order to guarantee long switchgear service life, it is recommended that a semiconductor contactor (DS7-34x-) be used.
The highest level of accuracy can be achieved using a continuous controller (PID) and a continuous semiconductor control element. This controller and actuator function is already integrated into the larger soft starters (DM4-..) from Moeller.

Heating with heat pumps

Heat pumps extract heat from the environment whether it is from the air, the ground or water. This heat is processed in the unit and transferred to the heating water. The so-called thermodynamic cycle is utilised: A refrigerant with a very low boiling point that vaporises due to environmental heat circulates in a pipe system. This steam is compressed to drive energy using electrical current. Accordingly, the pressure and temperature rise. Thus, the heat from the air, ground or ground water is increased to an exploitable temperature level by a minimal use of energy. In the heat exchanger the core of the heat pump the steam condenses, and the extracted heat energy is transferred directly to the heating circuit. The refrigerant returns to a liquid state and the circuit is thus closed the cycle is then repeated.

A heat pump is a simplified machine, which raises (pumps up) the energy from a lower temperature level to a higher temperature level by utilization of additional drive energy. The heat pump has a compressor driven by an electric motor. This compressor pressurizes a refrigerant (initially in a gaseous state) which heats up as a result. In the subsequent cooling down and liquefaction of the refrigerant, the released heat energy is transferred to a heat exchanger on the heating circuit carrier medium (usually) water or brine. The refrigerant depressurizes and subsequently cools off in an expansion valve. The cooled refrigerant is passed through an evaporator and then reassumes the gaseous state by absorbing ambient heat.

The heat energy exploited in this process is a multiple of the electrical energy of the motor. In total the electrical energy for the compressor drive and the heat extracted from the environment are applied to the heat pump. The relationship between the electrical energy input and useful heat extracted is termed the coefficient of performance (COP). This value is 5 for modern heat pumps.

The most important heat pump types are:
  • Geo-thermal heat pumps
  • Air source heat pumps
  • Ground water source heat pumps.

The initial requirements for the heat pumps are the switching and protection devices (DIL+PKZ) for the electrical drive, and the soft starter (DS) for starting current limitation. For operating and display purposes, the RMQ series is ideal and the easy Relay or easyControl series can be used as control devices.