Why are the Cotherm TSE & TSR thermostat terminals marked A & B?

Both the Cotherm TSE and TSR rod thermostat range are single pole on the regulation. 

Both offer a huge additional benefit of dual pole disconnect on the built in over temperature safety device.

Ensuring the correct polarity means the thermostat switches on the live during normal operation so we need to make sure the LIVE feed is connected to terminal A.

Answer: Terminal A is Live  and B is Neutral.

Answer: YES it really does matter which way round they are wired.

Answer: Not all languages use the same terminology for what we call "LIVE" and "Neutral".

Here's a breakdown of the typical wiring for these terminals: 

Terminal A:

This is the Live terminal (usually a Brown wire) where the incoming power from the mains supply connects to the thermostat.

Terminal B:

This is the Neutral terminal (usually a Blue wire) that carries the power to the heating element once the thermostat closes the circuit.

Cotherm are a true global business, supplying 14 million thermal controls to over 60 countries each year !

Not all of the countries we supply use the Latin Alphabet or refer to the connections as Live or Neutral, so placing L & N or + & - next to the terminals could lead to confusion and incorrect installation. 

A & B continue to be used to indicate that each of the terminals are completely different and which cable is connected needs to be considered.

Cotherm distributes their thermostats globally, and it is important to recognise that terminology related to electrical systems can vary significantly across countries using different languages. 

Wherever ambiguity or uncertainty exists, an additional risk is introduced!

Examples of why L & N may not effectively translate to other countries and their respective languages include:

The German word for "live" is "Phase" or "Außenleiter", which translates to "outer conductor". The term for "neutral" is "Neutralleiter", which directly translates to "neutral conductor". 

In France "live"  is translated as "Phase" or "Fil sous tension" (literally, "wire under voltage") and "Neutral" is "Neutre". 

While in Finland, live and neutral are "Vaihejännite" and "Nollajohdin", respectively. These translate to "phase voltage" and "neutral conductor". 

There is no specific European Directive that dictates the labeling of Live and Neutral; however, there are standards and guidelines that provide guidance and recommendations.

Standardised Terminal Identification (e.g., IEC 60445): 

International standards like IEC 60445 do provide guidance on identifying terminals and conductors using alphanumeric notations.

This is especially relevant in control systems and equipment with specific functions. In some contexts, terminals might be labeled "A" and "B" to indicate distinct connection points for specific functions rather than just power supply (live/neutral).

Specific Applications: 

The use of "A" and "B" for terminals might be seen in particular devices or systems where it makes sense to differentiate between two connection points, for instance, in a thermostat where "A" might be the switch live input and "B" the switch live output.

Colour Codes For Fixed Wiring: 

For standard electrical installations (e.g., in homes and buildings), the primary method for identifying Live, Neutral, and Earth conductors is through colour codes, which are harmonised across Europe.

Live: Brown

Neutral: Blue

Earth: Green and yellow

Safety And Clarity: 

The overarching goal of these standards and practices is to enhance electrical safety and minimise ambiguity during installation, maintenance, and operation. 

Cotherm are here to help our customers!

Products are sold with wiring instructions, but if you are in any doubt, contact Cotherm directly by email, and we will be happy to assist in any way possible.

Click here to contact Cotherm UK.