What happens if I reverse the thermostat wires?
What happens if I reverse the wires of the boiler thermostat ? A question that is often asked by those who, not being professional installers, want to replace the old thermostat or are preparing for a new installation.
Introduction: How many wires do we connect to the thermostat?
In this article we will only deal with the connection of consent cables of the boiler (usually indicated with TA), and not of any external probes.
Therefore in the case of a battery thermostat we will have two wires to be connected, while in the one to 230V there will be four : those supplying the thermostat and those enabling the boiler.
▲ The installation and electrical connection of the device must be carried out by qualified personnel and in compliance with current laws.
▲ Before making any connections, make sure that the electricity supply is disconnected.
How to connect the boiler consent cables (TA)
To understand the operating logic of the thermostat connection you need to imagine it as a switch which turns the boiler on and off. I two consent cables of the boiler must therefore be communicated with each other.
The thermostat terminal block where they are connected usually has these three inputs : Common (C), Normally Open (NO), Normally Closed (NC). One of the two consent cables always goes to contact C, the other goes to NO or NC depending on the boiler model. In the vast majority of cases it is NO.
However, we recommend that you always refer to wiring diagram connection supplied with the thermostat. See below for an example of our Freetime Evo .
It is possible to invert NO with C, or NC with C, without any consequences for the correct functioning of the thermostat and boiler. However, NO and NC cannot be interchanged with each other, otherwise the thermostat will malfunction.
How to connect the power cables and how to distinguish them from those of the boiler
In the case of a thermostat powered by 230V we must be careful not to confuse the consensus cables with those of voltage . Usually the voltage cables are brown (Phase) and blue (Neutral) and must be connected to the contacts marked with the letters L (Phase) and N (Neutral).
Also in this case, inverting L and N has no consequences (we refer to Seitron products such as Wi-Time hygge which require a 230V power supply).
If you want to learn more about thermostat installation then read this article: How to connect a two wire thermostat .
What happens if we reverse the consent cables with the power cables?
If by mistake we exchange the boiler consent cables (TA) with the power ones we can irreparably damage the thermostat.
Extreme attention must therefore be paid to this point and in case of doubt it is necessary to contact a professional.
We can therefore conclude the following:
- Do not confuse consent cables boiler (TA) with those of power supply
- Reversing the contacts C-NC or C-NO does not cause problems
- Reversing the contacts L-N for the power cables does not cause problems (we are referring to Seitron products)
- Reverse sensing cables with power cables damage the thermostat
How do I check if the thermostat works and is properly connected?
A quick test to verify the correct connection of the thermostat is as follows:
- Activate manual mode (usually hand key)
- Set the temperatura di set point greater than that detected in the room
- Check that a appears on the thermostat display. little flame and that you can feel the typical click metallic which signals the tripping of the relay
- Check that the boiler is turn on .
If step 3 is passed successfully, but the boiler does not turn on , there are two options:
- The thermostat is connected so incorrect
- The boiler has a problem .
In case of incorrect connection of the thermostat it is necessary to check that you have chosen the right contact between NO and NC or that you have not carelessly connected the consent cables to a wrong terminal, such as the one reserved for the external probe.