Information on climatisation (FAQ)

Here you can find important information and answers to frequently asked questions on the climatisation of control cabinets and the basics regarding thermal processes and special product-specific features.

Control cabinet heater

What is the ideal place for installation in the control cabinet?

Natural convection is the best way to achieve optimum heat distribution. It is therefore recommended to install the heater in the bottom third of the housing. This way, air flows through the heating fins and therefore heats up faster.

With cooling devices, on the other hand, installation in the upper section is recommended so that cold air can escape.

What needs to be considered with regard to convection?

The goal is not to affect the natural convection of the heater negatively by packing the installed devices extremely densely. Installing heaters with fans or blowers or using circulation fans can lead to forced convection. This gives the heating system a higher degree of efficiency and therefore achieves better heat distribution. This results in the whole concept becoming more efficient. Particular attention needs to be paid to the release of the heat output to the air as a matter of principle.

Cooling devices are generally equipped with fans.

What do you need to know about the surface temperatures on PTC heaters?

Due to the lower surface temperature, Lm-therm heaters with built-in thermostats are a safe alternative to PTC heaters. PTC heaters do not have a temperature-triggered shut-off function and their surface temperature is therefore generally high. That’s why it’s important to ensure that a touch guard is in place and that there is enough distance from sensitive components and cables.

Which devices are suitable for big control cabinets?

To achieve better heat distribution it is recommended to install several heating devices, circulation fans or blower fan heating systems with separate temperature controls.

What temperature settings can be preset in Lm-therm heaters?
  • Tropical setting: <35 °C: switch on/70 °C: switch off
  • High tropical setting: <50 °C: switch on/80 °C: switch off
  • Frost protection: <10 °C: switch on/60 °C: switch off

However, if heaters with built-in thermostats and high outputs are used in tropical or cold regions, attention needs to be paid to the heater’s intrinsic temperature!

When does the installation position achieve the maximum degree of efficiency?

Please take note of the information for the specific device in this regard. Generally, however, the natural convection mentioned in point 1 of the FAQ applies.

Is it necessary to install separate controllers?

Heaters with built-in thermostats do not require separate controllers. However, factors like the size of the control cabinet, the number of built-in devices, and other external influences may make it necessary to install a separate controller. For PTC heaters it is generally recommended to insert a controller.

Are Lm-therm heaters electrically fused?

Heaters with a built-in thermostat are linear (ohmic). They can therefore be fused equal to the load current (I=P/U). PTC heaters, on the other hand, are to be protected by a slow-blow fuse with five times the load current (I=P/Ux5) because of the high inrush current (PTC effect).

How are heating devices mounted?

Heating devices can be snapped onto a 35 mm DIN rail or screwed in directly (take note of the device specifications). The electrical connection can be implemented via a connection line or a connection terminal on the device.


What are the most important applications for Peltier technology?

One of the most important applications for Peltier technology is the active cooling or temperature control of switch cabinets with smaller power losses and switch cabinets in difficult ambient conditions. But also the cooling of liquids, the direct cooling of e.g. lasers or hotspot cooling are application areas.

What are the most important indicators for the use of Peltier technology?

Small to medium power to be dissipated, high ambient temperatures, dirt-laden ambient air, mechanical influences such as vibration or shock, precise stabilization of temperatures, tight space conditions.

In which power ranges is Peltier technology useful?

Peltier technology can be used most effectively in a power range from a few watts up to about 800 watts.

How effective are Peltier devices?

The effectiveness of Peltier devices for air-to-air cooling is about COP 0.8..1.1. For direct cooling somewhat higher.

Do Peltier devices need to be serviced?

Depending on the environmental conditions, Peltier units should be serviced between monthly and semi-annually. In most cases, maintenance consists of cleaning the external heat exchanger.

What are the functions of a Peltier device?

Peltier devices are primarily cooling devices. However, all devices with DC supply voltage, except devices with multistage modules (e.g. laboratory devices with deep-freeze function), can also be operated in heating mode. Devices with AC supply voltage, i.e. with integrated power supply unit, can also be operated in heating mode, depending on the model. You will need a special control output for this.

Can Peltier technology be used for cooling/tempering liquids?

Yes. For this you need a liquid heat exchanger on at least one side. But also temperature control or cooling liquid to liquid is possible. For this, liquid heat exchangers are required on both sides of the Peltier device.

Are there Peltier devices that can be mounted directly on a surface to be cooled?

Yes. For this purpose, the Peltier device is equipped with a cooling plate on one side, the shape and mounting holes of which are precisely adapted to the surface to be cooled. In most cases, the cooling plate is also equipped with a flexible, heat-conducting foil to ensure optimum thermal contact.

Is it possible to dehumidify a room using Peltier technology?

Yes. The company Lm-therm offers a standard switching barrier humidifier. But also larger rooms can be dehumidified by means of specially adapted Peltier devices.

Which Peltier device versions are available?

All Peltier devices from Lm-therm are available as semi-recessed devices (cold side dips into the control cabinet) or devices for wall mounting (equipped with a stainless steel mounting frame). In addition, all units are also available in a salt fog proof version.

Are Peltier devices available in other supply voltages?

All Lm-therm Peltier units with AC supply voltage are equipped with a wide voltage input, which allows operation in a voltage range from 90 V-AC to 305 V-AC. The devices with DC supply voltage are operated with 24 V-DC as standard. However, 12 V-DC or 48 V-DC are also available, depending on the device size. Furthermore, special voltages can also be realized.

What temperature differences can be achieved using Peltier technology?

For devices with standard modules, temperature differences of approx. 35-40 K can be achieved. For devices with multistage modules (e.g. laboratory applications) also approx. 70 K and more.

What temperature accuracy can be achieved using Peltier technology?

In standard applications, accuracies of approx. 0.1 K can be realized. With high-precision sensors and controllers, temperature accuracies of approx. 0.01 K can also be achieved.

Is it possible to control the cooling power by means of the supply voltage of the Peltier modules?

Yes, but the cooling power is not linear to the supply voltage or the pickup current.

Is it possible to control Peltier modules using PWM?

Yes, but no “hard” polarity reversals of the supply voltage with a frequency of more than 1 Hz should be performed over a longer period of time.