Frequently asked questions

Kermi ABC – specialist terminology explained

Frequently asked questions

Preliminary notes

Here you can find answers to frequently asked questions. We consistently strive to give you access to all the information available on our products.

However, please understand that it is not possible to answer any technical questions about your heating system. To give you these answers, it is essential to perform an analysis of the problem on site. In such cases, please contact a qualified specialist installer.

Dimensions, radiators

You can find this information in the technical documents of the product in question or in the downloads area of this website.

Connection situation

For more information on this, see the technical documents for the product on this website.

Swapped connections, BASIC-50 centre connection

The feed and return pipe connection is not important in the case of the BASIC-50 designer radiator, as there is a stopper (partition) between the two connections.

Replacement radiators

Kermi also offers many different solutions for conversion, renovation, and modernisations. You can find more information on this subject in the sections of this website dealing with renovations.

Operating manual / installation instructions

For more information on this, see the technical documents for the product on this website.


For more information on this, see the technical documents for the product on this website.


As an end customer, you can only get our products from your qualified specialist installer. They will be glad to draw up a quotation for you. You will find spare parts and accessories for radiators in our online shop. Find the right filters for your controlled residential ventilation system.

Blanking plugs

Blanking plugs are included in the delivery of our radiators.

Window box / window sill

Special fixings for window boxes are available for use on steel panel radiators, convectors, and Kermi Decor. For details of the fixings, see the technical documents for the respective product. We do not supply the actual window boxes or similar covers.

One-pipe heating systems

Installing one-pipe heating systems and radiators with a 50 mm centre connection
All radiators with a centre connection can also be operated in single-pipe systems. Depending on the design, you will need either a one-pipe radiator valve or a one-pipe radiator valve with a thermostatic valve (from the eccolution system, for example).

One-pipe system with thermowell valve

One-pipe system with thermowell valve, connecting Kermi radiators
Kermi compact radiators can be connected with the aid of a special separating plug, even where a thermowell valve (lance valve) is present.
The corresponding separating plug for Kermi steel panel radiators is available in our accessories. Additional products available on request.

Electrical operation of Kermi designer and bathroom radiators

Designer and bathroom radiators from Kermi are set up for all popular heat sources – whether they use oil or gas – at the factory. If you want to be completely independent from the hot water central heating system, choose one of the Kermi models for electric operation. Delivered complete with electronically controlled heating rod, heat transfer fluid, and controller. Simply connect to the power supply and feel the benefits. A cost-cutting and time-saving solution primarily for old buildings.

Air vent plug

Air vent plugs are included in the scope of delivery of our radiators.

Spare parts

Spare parts for indoor climate and shower design solutions can be obtained in our Kermi online shop for spare parts. There, you can find indoor climate spare parts for steel panel radiators, Verteo, heating panels, convectors, bathroom radiators, and controlled residential ventilation.

Colour repairs

The accessories include a touch-up pen (item number ZK00100001 RAL 9016) as well as a 150 ml spray can (item number ZK00160001 RAL 9016) and a 500 g can of paint (item number ZK00090001 RAL 9016) which you can use to touch up minor damage to the paintwork. You can also buy these items in our online shop for spare parts, from your qualified specialist installer, or from specialist wholesalers.

Colour, standard colour steel panel radiator

Since October 1997, our steel panel radiators have been painted in Traffic White according to RAL 9016. RAL 9010 was used prior to this, and RAL 9001 until April 1996.

Window recesses

Window recesses for radiators used to be standard in most houses as a means of installing very deep radiators. However, this is an unfavourable solution because it impedes convection, i.e. the circulation of warm air. The wall recesses also weaken the insulating effect that the wall provides. An additional heat shield on the radiator can be useful.

Towel rail

You can find available accessories in the information for the product in question on this website.

Radiator is only half warm

If the required room temperature is still being reached, then don’t worry about this. The thermostat controls the water supply in a way that means the radiator may contain partial quantities of water, causing it to give this impression. A remedy can be provided by using a radiator with x2 technology, in which the flow passes through the front panel first. The front panel becomes uniformly warm and the rear panel serves as a shield against the cold outer wall during partial load mode (90 % of the heating period).
For more detailed information, please contact your heating engineer.

Heat cost allocator

Most Kermi designer radiators are suitable for heating cost recording using a heating costs allocator. As the positioning of the acquisition devices differ from one manufacturer to another, please contact the manufacturer in question for the details.

Radiator type

On the back of the radiator, you will find a sticker with the date of manufacture and the type.

Hydraulic balancing

To ensure that the heating system works without any problems, the volume flow of the heating water needs to be adjusted to the heat demand of every individual radiator. Kermi valve radiators are preset at the factory according to the standard heat output of the radiator. This saves energy costs and ensures optimal thermal comfort.

Product prices

As a consumer, you can only get our products from your qualified specialist installer. They will be glad to draw up a quotation for you. It is not possible to purchase products directly from the factory.


You can find all information for the product in question on this website.

Cleaning pipes or ribbed radiators

These radiators can be easily cleaned with special brushes, which you can buy from your qualified specialist installer or specialist wholesalers.

Cleaning steel panel radiators

Lift the plastic clip of the side cover and unscrew anticlockwise. From BL 1000 onwards with Plan-HK or BL 1400 with Profile-HK, remove the retaining bar from the top cover.

Cleaning, detergent

According to DIN 55900, paint finishes must be cleaned using suitable aqueous household cleaning products. Suitable cleaning agents for paint surfaces are not abrasive and not strongly alkaline or acidic (chemically aggressive).

Dust formation

Dust formation inside the radiators is a natural process that depends on the circulation of the warmed air. This cannot be prevented with technical measures. Accessible locations should be cleaned periodically.

Radiation shield

The purpose of a radiation shield is to reduce heat radiation to the facade. The material plays only a minor role here.
The important thing is to create an additional air shaft between the radiator and facade, and to allow the heat from the radiator to enter the room unimpeded.

Technical information

You can find all the technical information you need for the product in question.

Valve does not function

In the case of radiators that have not been used for a long time, the valve tappet may have become stuck due to deposits or the annular gap in the cross section aperture may have been shifted by particles. After very long downtimes, significant incrustation can be formed due to the precipitation from substances in the water. It often helps to remove the thermostatic sensor head and move the tappet several times with an object which is not too hard (such as the handle of a hammer). To install the thermostatic sensor head, move it to position 5.
In many cases, the problems can be avoided by turning the radiator thermostats to position 3 in empty homes. The valve is then kept continuously in motion and deposits are unable to form.
In some cases (heavy incrustation), the only alternative that remains is to replace the valve insert. Once again, care should be taken to avoid periods of valve inactivity.

Valve tapping

Tapping sounds from the valve suggest that the feed and return valve on the radiator have been mixed up. You can check this by allowing the radiator to cool down. If everything has been connected correctly, the pipe pointing to the middle should get warm afterwards when the valve is left open.
If this is not the case, then a reverse manifold needs to be installed.

Please consult a qualified specialist installer.

Valve inserts

You can find out everything you need to know about factory-preset Kermi valves in our practical, pocket-sized valve guide.

Changing a valve insert

Please contact your qualified specialist installer about this. Relevant spare valves are also available from them.

Flow and return mixed up

Please contact your specialist installer. We cannot provide answers concerning system engineering.

Which side is right for the flow?

See the technical document for the product in question.

Wall spacing during radiator installation

Refer to the technical documents for the product in question on this website.

Heat output/standard heat output

You can find the heat output of our radiators in the technical information for the product in question. When determining the heat output, make sure you select the temperature pairing correctly. The standard heat output according to EN 442 is determined on the basis of temperature pairing 75/65/20 °C. In practice, lower temperatures are commonly used nowadays. Please contact your specialist installer for the final calculation.