Charge control
A charge control is an electronic control that uses a temperature sensor (outside sensor) to determine the estimated energy requirement of an electric storage heater in the following hours and specifies a corresponding setpoint for the charge controllers in the individual heat storage tanks.
The charging control is usually only available once in each building (e.g. in the meter cabinet) and is therefore also referred to as a central control device . In terms of terms, a distinction should be made between these charge regulators , which are usually housed in the electrical connection space of each storage heater or, in the case of electrical underfloor heating mats, for example, are arranged in the immediate vicinity of the heating element.
operation area
A charge control is an element of a night storage heating system.
Such a system usually consists of a charge control and several heat accumulators. In the event that only a single storage heater is required, charging controls are also available, which are integrated in the device itself.
In order to take into account the different heat requirements in different parts of the building, so-called group control devices can be connected between the central control and the heating stoves , which adapt the control signal to the local conditions and the needs of the user. They are mostly installed in the distribution of the usage unit. The use of group control devices increases the number of heating devices that can be controlled by a charging controller with an ED control signal.
The purpose of a charge control is to not always charge the heat storage up to its maximum capacity, but only with the amount of energy that is likely to be required for the next delivery phase, and to control the charging phases so that they are in the periods with the lowest electricity price. The charging should also be controlled in such a way that the heat release takes place as evenly as possible or the room temperature can be adapted to the respective use during the day.
economics
With the use of a correctly set charging control, the efficiency of the heating increases, since only as much is heated as is necessary depending on the season or outside temperature.
Components of a charge control
A charge control always includes an outside temperature sensor, also known as an outside sensor, which is usually installed on the north side of the building at a height of at least two meters above the ground. Some providers point out the corresponding DIN, according to which the sensor is to be embedded in the plaster in the outermost layer of the building's exterior wall .
The ripple control receivers provided by the energy supply company (EVU) or network operator are used to enable the charging phases for the storage heaters and to switch the two- tariff meter between low (NT) and high-tariff electricity (HT). The ripple control receiver usually controls the power circuit of the storage devices via a contactor , while the signal from the ripple control receiver is only processed by more complex, programmable charging controls that have a microprocessor and are able to execute control processes such as reverse control .
Instead of the ripple control receiver, the contactor of the power circuit is also switched by the charge control in some cases.
Both the charge control and the group control (and the discharge controller) can be coupled with time switches in order to implement night or weekend reductions.
Some basic details of the interconnection of the electrical heating system are specified in the technical connection requirements of the electricity supply company.
Loading models
The charging model shows the charging process over time. Forward, reverse and spread control are common. The responsible EVU specifies which control system is to be selected.
With forward control (priority) the power circuit is released at the beginning of the charging time, with reverse control (subordinate) it is released so late that the heat accumulators can only be charged at the end of the charging time and with spread control either in the middle of the charging time, or in two blocks at the beginning and at the end. We always try to avoid load surges in the network and to distribute the load.
loading time
The release time is often between 10 p.m. and 6 a.m. and is therefore eight hours. However, the release times can even vary within streets in order to distribute the load. With some EVUs, an additional release of up to two hours during the day is possible.
Working principle
The charging control determines the estimated amount of heat required for the next delivery phase (day) from the temperature profile of the outside temperature before the next charging phase (night). This is transmitted to the individual heat storage tanks in the form of a setpoint. Each heat storage tank has a charge regulator that can interrupt the power circuit of the individual storage tank. The temperature of the storage medium, such as the fireclay bricks , is determined as the actual value via a sensor. If the stored amount of heat (i.e. temperature) has reached the target value, the charging process is ended.
Setpoint transfer
Two types of setpoint transmission have become established:
DC control
A DC voltage between 0.91 and 1.43 V is used for the transmission, 0.91 V means full charge and 1.43 V charge suppression, i.e. full charge in the event of failure of the charge control.
AC control system
The so-called ED signal was the standard in older systems. The 80% ED signal is common. In this case, the charge controllers of the heating devices prevent charging (charge suppression) if an AC voltage of 230 volts is present 80% of the time. If there is no signal, as is also the case if the charge control fails, the devices charge up to their maximum capacity (pre-charge). In the past there were also systems in which the charge suppression was caused by a 37%, 40 &, 68% or 76% signal.
In night storage heaters, the signal is usually switched on and off with a very low frequency of up to 0.1 Hz, i.e. a period of around 10 seconds. Many central control units have a signal light marked with "ED", which flashes in time with the ED control signal, i.e. slowly flashes accordingly. This form of transmission is quite robust, so that "single-wire control" is possible. The neutral conductor , which is carried in the usual 7-pole control line to the individual distributions anyway, is used as a return line, so that only one additional "wire" is required.
This control system is also referred to by the manufacturers as thermomechanical charge regulation, since the ED signal immediately heats up a control resistor, which in turn switches a thermal relay triggered by a bimetal through its heat emission . Since the power consumption of the control resistors cannot be neglected, a control device can only control a limited number of approx. 20-40 storage stoves directly. In order to connect a larger number of heating stoves, group control devices are interposed which reproduce the signal. In summer, either the control line should be disconnected or the central control unit should be switched off at the backup fuse in order not to unnecessarily heat up the control resistors in the warm season. The power consumption in multi-family houses can be well over 100 W. In the case of electronic control units, the set values should be noted beforehand, as the control unit may forget them if there is no mains voltage.
This type of signal transmission is also referred to as vibration packet control ( vibration packet controlled alternating voltage according to DIN 44574 ) or pulse width modulation . The latter means that the size of the transmitted signal is determined by the ratio between the switch-on and switch-off times.
Charge regulator
There is a charge controller in each heat storage tank, which ends charging depending on the setpoint of the determined heat energy requirement (specified by the central charge control) and the actual value of the heat energy still stored (temperature measured by the residual heat sensor in the storage core).
Commercially available heat accumulators usually have an additional actuation element (e.g. in the form of a rotary control) with which the charge of the accumulator can be reduced. This is useful, for example, in rooms that are temporarily unused or in bedrooms with lower heat requirements.
In addition to fully electronic charge controllers, there are also electromechanical charge controllers when using the ED signal. These use temperature-sensitive, mechanical devices to switch off the charge. There are two mechanical temperature sensors, one is located in the storage stones, the second together with a heating resistor in an insulation. The heating resistor is controlled directly by the ED signal and thus transmits the setpoint to the thermo-mechanical controller (e.g. thermal relay ). Due to the power consumed by the heating resistor, group controls must be used as intermediate amplifiers in larger systems, as otherwise the control output of the charge control could be overloaded.
The setpoint for the charge controller is set to charge suppression by a modern charge controller at the beginning of the charging time, and is only set to the actual setpoint signal after the release for the power circuit. Due to the inertia and statistical phenomena , this means that the heat accumulators never start charging at the same time, but rather at different times, which in turn reduces load surges in the network .
Setting the charge control
The setting should be left to a specialist, as there are specifications from the responsible power supply company that are not readily available to private individuals.
However, there are a few sizes that may need to be adjusted individually.
- The temperature threshold below which the storage devices are fully charged (e.g. −15 ° C); usually referred to as E1 ("full charge").
- The temperature threshold, above which charging is prevented (e.g. 15 ° C), usually referred to as E2 ("start of charging").
- The base charge, i.e. the value to which at least one is charged when falling below E2 (e.g. 20%), sometimes referred to as S, SOL or E2 jump.
Setting the night storage heating system
If the charge control is set by a specialist, there are usually three points at which the system can be set: The group control, the charge controller on each storage tank and the room thermostat .
The room thermostat is completely decoupled from the charge control. It should be set to the desired room temperature. It only determines the heat energy output.
The group control is best set during the transition period when the temperature does not drop below 10 ° C at night. To do this, all charge controllers ("rotary controls" on each heat storage tank) are set to the highest value. If the heat storage tank is empty in the evening, i.e. if only cold air is emitted even when the room thermostat is set high, the rotary control on the group control must be adjusted to higher values. If the storage tanks are still hot, the value on the group control must be reduced. Once the optimum point has been found, the charge can be further reduced step by step on the individual charge controllers (e.g. in the bedroom).
Individual evidence
- ↑ Dimplex: "Assembly and operating instructions for charging control" (PDF; 775 kB)
- ↑ DRT: "Installation of the weather sensor" (PDF; 62 kB)
- ↑ SABI: "Operating Instructions Universal Charging Machine" ( Memento of the original from November 27, 2015 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 1.8 MB)
- ↑ Frensch: "Operating and assembly instructions" ( Memento from March 23, 2013 in the Internet Archive ) (PDF; 159 kB)
