In our articles we have already considered options for connecting heaters by connection type (star, delta) and by connection sequence (parallel, series). This article is a conclusion in this chain. In the article we have tried to combine the knowledge already acquired to connect electric heating elements.
It is an established fact that the use of electric heating elements is a key point to ensure the efficiency of the entire heating system. The method of connection determines the productivity of the use of the heaters.
When several different types of heaters are introduced into one system, one should know how to connect them so that the heating processes provide the right mode. It is suggested to review the methods of connection of heating elements and understand what to choose and in which case.
In the world of industrial heating systems, it is common to use multiple heating elements together. This raises the question of how to connect these heaters together to achieve the desired result.
Сalculation of multiple heating elements!
Two rules of thumb:
– for resistive wire the pole is not important;
– the resistance of the heating element is stable and is calculated as follows:
Resistance Value = Rated Voltage * Rated Voltage / Rated Power
R = U * U / P
Since the rated voltage and power are known, the resistance value can be determined. The actual power produced by the heating element can be calculated using the formula:
Actual Power = Operating Voltage * Operating Voltage / Resistance Value.
P = V * V / R
Resistance cannot be varied. What is the purpose of “referencing” to the nominal voltage value? If the real value exceeds the nominal value, the output power will change. And this is fraught with problems concerning overheating of the heating elements and violation of the calculated power values.
Heater connection types
As early as at school they study electrical circuits and the two main options for connecting the components: parallel and series. Also heaters can activate the scheme “triangle”, “star”, apply a multi-circuit type of connection.
- Parallel connection is selected when high operating currents must be distributed.
- Series circuit is used in low voltage networks to reduce the current load.
- Combination (“delta”, “star”) allows optimal load distribution.
- Multi-circuit configurations are used in complex industrial installations.
The correct selection and professional installation of the wiring diagram are the most important factors for a safe electric heating system.
Parallel connection of heating elements
The heaters are placed parallel to each other to create a closed circuit. This allows an even distribution of the load between the elements, ensures system reliability and flexibility when replacing individual heaters. However, parallel connection requires a high supply voltage. It is used when something powerful is in operation, where the heaters are separately connected to a common circuit.
The method with a single power source is convenient because it is able not to interrupt the operation of the other heaters if one of the heating elements fails.
Parallel connected elements are activated and deactivated independently of the other components. This is useful for controlling thermal processes, especially when constant and precise temperature control is required. For example, in the production of plastic products, where a lack or excess of degrees Celsius can adversely affect the physical state of the heated mass.
But there are some peculiarities. In order for the power to be uniform, the heaters must have equal resistance. Otherwise, components with lower values will use more energy, and thus overheat. And this already leads to rapid failure (not only of the heating element, but also of the larger power supply unit).
In large plants and large production lines, the parallel connection of heaters is the only justified model that will prevent a complete shutdown of production. The ability to change and maintain precise temperature values helps to produce products with rigid manufacturing parameters.
How to calculate the total power of identical heaters in a parallel electrical circuit
Calculation is easy when the power value of one heating element is known, provided that they are all identical in performance. The voltage is evenly distributed over the number of heating participants, so each unit receives equal current and power. Therefore, the calculation is reduced to one formula:
P = n * P1
where n is the number of heating elements in the electric circuit, P1 is the power of one heater, P is the total power of all heating elements.
When heating elements are connected in parallel, their resistances add up according to a special law. In contrast to the series connection, where the resistances are simply summed up, in this case a formula is used:
R total = 1 / (1/R1 + 1/R2 + … +1/Rn)
Here R total is the resultant resistance of the whole circuit, and R1, R2, etc. – are the values of each individual heating element. When all heating elements have equal resistance, the formula looks like this:
R total = R / n
where n – is the number of parallel connected heating elements.
Connecting heaters in series
The series connection of heating elements, e.g. heating elements, means that they are connected in a chain in such a way that the electric current flows first through one heating element, then through the next and so on. In such a circuit, the same current flows through all heaters and the voltage across each element is proportional to its resistance according to Ohm’s law.
The following formulas can be used to calculate the resistance and power of a heating element system when connected in series:
R = R1 + R2 + … + Rn
where R1, R2, … Rn – resistances of individual heating elements.
The total resistance of the system is equal to the sum of the resistances of all heating elements. The formula is simplified when all elements are of the same type, with equal values:
R = R1* n,
where R1 – resistance of one heating element, n – their number.
The power of the system as a whole is equal to the power of one heating element, since the current through all elements is the same.
Therefore, knowing the resistance and power of one heater and the total number of heaters in the system, it is easy to calculate the total resistance and power of the entire chain of heating elements in series connection.
Triangle connection of heaters
The delta arrangement of heating elements, e.g. heating elements, is used in three-phase AC networks.
The idea is that the heaters are connected at the ends to form a closed triangle. The current is divided at each connection, passing through each heating element. An important feature is that the voltage across all heating elements is the same.
Let’s consider how to calculate the resistance and power of the heating element system in a delta connection.
The total system resistance is determined by the formula:
R = R1 / √n
The total resistance of the circuit is the result of dividing the resistance value of one element and the square root of the number of heating elements used.
As can be seen from the formulas, unlike in series connection, in delta connection the total resistance and power depend on the number of heating elements. Knowing the parameters of one heater and their total number, you can easily calculate the resulting resistance and power of the entire chain of heating elements connected by a delta. This variant of connection of heating components is often used when connecting powerful loads to three-phase networks.
This scheme allows a higher power output compared to series connection at the same mains voltage. This is because the voltage at each heating element is higher than in series connection. The even loading of the mains phases improves the load balance. The circuit has increased reliability, because if one of the heating elements fails, the others continue to function.
The total resistance and power are not constant and depend on the number of heating elements in the circuit.
Star connection of heaters
This type of heater connection is also used in industrial three-phase networks.
The idea is that one lead of each heater is connected to a common point and the other leads are connected to different phases. This configuration resembles a star, hence the name.The voltage across each heating element is not the same and depends on its resistance.
The formula is used to calculate the total resistance of the system:
R = n * R1,
where n is the number of heating elements and R1 is the resistance of one of them.
The total power in the “star” circuit is determined by the following formula:
P = P1 / n,
where P1 is the power of one element.
The star circuit is often used when many heating elements need to be connected to a low voltage source. It provides a more even distribution of the load over the phases.
Combined heaters connection scheme
It involves the use of different configurations – series, parallel and mixed connection of heating elements. Several heating elements are connected in series and then the groups are connected in parallel. This approach allows flexible customization of the operating parameters of the system.
When designing a combined circuit, it is important to calculate all the parameters for each part of the system using the appropriate formulas. This will allow you to select the optimal configuration and avoid errors.
The main advantage of combination circuits is flexibility and the ability to fine-tune the heating element system to meet specific power, voltage and other requirements.
Which connection method to choose
Before leaving the connection diagram of the heating elements, pay attention to 5 parameters:
– what should be the current and voltage (according to the type of production and requirements);
– the length of the heating elements
– the calculated number of heating components
– the level of permissible operating temperature;
– the necessary requirements regarding the thermal management of the heating elements.
Do not forget to consider the voltage rating of the heater. For example, in three-phase 380V industrial networks, heaters are aggregated into a single delta circuit.
Conclusions
The quality of performance of the heating elements depends on how they are connected. Choosing the correct type plays an important role in maximizing the performance of the heating element. From the article you learned about the types of connections of heating elements in the electric circuit and the expediency of using each scheme. Images have been added so that you understand what the connection options look like in the manufacturers’ supplied instructions. It also indicates what you should consider when determining the correct way to connect the heaters together.
Using the above tips, you will be able to make the correct electrical chain of heating elements and check its operation in practice. If additional information is required, do not hesitate to check with Intmax by filling in the electronic form on the website or by calling back during working hours on the contact numbers.