Yes. Our radiators work with all central heating systems. All our connections are BSP and will accept manual or thermostatic valves.

Yes, but if you have a system that has a central heating system expansion tank (usually in the loft), then there should be a 1 metre clearance between the top of the radiator and the bottom of the header tank.

Some of the design radiators have baffles inside the water-carrying tubes to divert the water flow around the whole radiator to maximize efficiency.

Yes, as long as an inhibitor for mixed metal systems is used.  In reality, most systems are mixed metal, as many already have aluminium heat exchangers in the boiler, plus copper pipes and steel radiators.

There is no problem with integrating individual radiators into an existing system.  When new or additional radiators are being installed, the system should be drained, cleaned and flushed in accordance with BS7593 and a good quality inhibitor, suitable for mixed metal systems, used to protect the system.

It is important did the salt does not get into the central heating system.  In an open or unvented system, if there is a leak, the water in the top-up tank for the central heating system will automatically be topped up with softened water, which will get into the radiators.  This must be avoided.  If the central heating system or a radiator has been drained and is to be refilled, the controls to the water softener must be switched over so that unsoftened water is fed into the header tank.

Inhibitor is a chemical mix that should be added to the central heating system water to prevent corrosion and prolong the life of the system.

The size will depend on the heat required for the room.  This can be established by your plumber/installer.

However, as a guide:

• Calculate the volume of the room by multiplying the height, width and length to get the volume in cubic metres.
• For bedrooms, hallways and kitchens allow 40 Watts per cubic metre, and multiply the total by 40; for bathrooms, living and dining rooms, multiply the total by 50. This will give the output required in watts.
• Example: A bedroom 3.6m long x 3m wide x 2.4m high has a volume of 25.92 cubic metres. Multiply this by 40 to get 1036 Watts.
• If the room has large windows or exposed walls, increase the total by 10%.
• Always choose the next radiator size up if the exact output is not available and allow more length and less height for radiators under a window.
• To convert watts to Btu’s, multiply by 3.412.

These are a calculation between Flow, Return and room temperatures. All Zehnder radiators are tested to EN442 which has a flow temperature of 75°C, a return temperature of 65°C and a room temperature of 20°C. Our outputs are published to ΔT50°C and also at ΔT60°C for those who may have older boilers that may be running at temperatures above 75°C.

Unless the installer/heating engineer has taken it into consideration when calculating the heat loss requirements of the room, the radiator will be oversized by up to 25%.

The temperature can be moderated by the use of a thermostatic valve, and in the future, when the boiler is replaced with a condensing type the radiators will be of the correct size.

Unless the installer/heating engineer has taken it into consideration when calculating the heat loss requirements of the room, the radiators will be undersized by approximately 25%, and the room will not be sufficiently heated.

The installer must know the flow and return temperatures of the boiler in question, and select the appropriate ΔT output data for the room.

If you can hear water cascading, dripping or falling inside your radiator it’s because it not full and there are air pockets trapped inside the radiator. Venting alone will not move these. Please download the instructions on the right to help solve this problem.

When calculating the heat output, there are many factors that need to be considered. We do not advise an estimated calculation. We recommend calculation by a specialist dealer.

Flow balancing is the limiting of the water volume flows to values that correspond to the heat requirement of the plant. By means of a 'hydraulic regulation', which generates the same resistances for all the radiators in a heat distribution network, flow noises, overheated rooms and rooms with a shortfall of heat supply are avoided. In addition, the energy consumption for heat generation and heat distribution are optimized. Your specialist dealer is the correct contact person for a radiator that works at a comfortable and economical level.

One frequent cause of 'knocking sounds' at the thermostat valve is interchanging of the flow and return. As a result, the flow in the valve is in the wrong direction. Please contact your technical specialist.

There could be several reasons for this: Is the setting of the thermostat sensor correct? Is the radiator correctly deaerated? Is the flow temperature sufficient? Is the circulation pump working correctly? Has the heating plant been flow balanced? Please contact your specialist dealer.

There are sounds that could be heard as rushing sounds constantly over an extended period of time. These are generally flowing noises. Generally, these are due to excessively high flow rates (because of excessively high differential pressures) in certain sections of the heat distribution, for example in valves. Flow balancing (see the notice "Flow balancing") by a specialist dealer can help.

In the case of electrical heating cartridges with a controlling device, this device must be installed in the same room as the radiator, as far as possible, such that there is a visual contact to the heating cartridge. Radiators with electrical heating cartridges in central heating systems must always be completely filled with water and de-aerated. For rectifying a fault, you can briefly (for about 30 sec.) interrupt the mains supply (mains plug, safety cutout, fault current switch) and if required, replace the batteries in the control device. You can test the working of the socket easily with any other load (e.g. a hair dryer).
Please see our instructions in the operating manual. If, after the tests, the electrical heating cartridge does not work, please contact your specialist dealer.

To make expansion of the heating fluid possible upon heating, the radiator is not completely filled with heat conducting medium. The air collects in the upper elements. It is therefore completely normal that the radiator does not become quite so hot in the upper area. The radiator and the rating of the immersion heater are exactly matched to one another. The heat output is thus always ensured.

In most cases, no, as the product is filled with heat conducting liquid at the factory. However, if the product is fitted with an airvent, it can be vented from time to time to ensure all air is removed. Never attempt to add or remove liquid to the towel rail or radiator.

Never. Should there be any suspicion of missing fluid, please contact your specialist dealer immediately.

Yes. Zehnder has several models for the so-called mixed operation or dual energy. Your specialist dealer will be happy to provide you with further information.

Zehnder uses only the best quality for surface treatment. Finish-painted radiators have a two-layer paint, consisting of a primer and a surface coating. The surface coating is a stove enamel powder coating. The high quality Zehnder powder coating is a particularly smooth and hard-wearing surface. We recommend to gently clean our high-quality surface with our special lambskin brush or with a soft, fiber-free cloth. Please do not use any scouring or aggressive cleaners.

We recommend gentle cleaning of the high-quality chromium surface with our special lambskin brush or with a soft, fiber-free cloth. You can use agents specially suitable for chromium, according to the manufacturer's data of the supplier.