I have a Glow -worm boiler and am replacing the thermostat. The old one just had L, N and E. My new one says I need to remove a wire for Volt Free operation. How do I know if my boiler needs to be volt free?
Volt free thermostat wireing
- Thread starter jmlecterns
- Start date
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I am not sure but I think it just means the thermostat is a switched output and requires no external supply or if it did then it would be isolated from the switched output?
What ever it does it certainly ain't volt free (unless water runs down between insulation and wires???) and is the most ignorant terminology I have ever heard within a trade I am surprised boilers aren't referred to as the 'beasts that breath fire'
What ever it does it certainly ain't volt free (unless water runs down between insulation and wires???) and is the most ignorant terminology I have ever heard within a trade I am surprised boilers aren't referred to as the 'beasts that breath fire'
"Volt free" thermostats are volt free because they operate without any electricity. The contacts will open and closed based on the ambient and setpoint temperatures whether or not you have them wired up. Whatever voltage you apply to them will simply be passed through the contacts (or not) based on the temperature. 240V or line voltage thermostats (or other powered thermostats such as 24V) require an applied voltage in order to operate the contacts. You're probably familiar with the simple bimetallic strip that clicks on and off without any power.
This distinction has become slightly blurred with almost all modern controllers strictly having volt free switching of the thermostat but still requiring a power supply for the electronic functions. Your new boiler thermostat is almost certainly volt free. However the distinction is irrelevant and you simply wire it up based on the wiring supplied from the boiler. The distinction is doubly irrelevant when applied to the boiler since all types can operate happily wired to a volt free thermostat.
If the boiler has a permanent 240V contact and a switched live then you simply connect those to the thermostat and the link inside the thermostat passes the live to also control the electronic functions. There will usually also be a neutral from the boiler that is connected to the thermostat. If you wanted to be perverse you could still remove the link and wire the permanent live and neutral from a separate supply. The boiler switched live may be referred to as live return or LR.
For "volt free" boilers, you still connect a "live" and "switched live" from the boiler to the same thermostat connectors, but you have to wire in a separate power supply to operate the electronics because the "live" isn't necessarily live all the time, or it may carry a voltage other than 240V.
This distinction has become slightly blurred with almost all modern controllers strictly having volt free switching of the thermostat but still requiring a power supply for the electronic functions. Your new boiler thermostat is almost certainly volt free. However the distinction is irrelevant and you simply wire it up based on the wiring supplied from the boiler. The distinction is doubly irrelevant when applied to the boiler since all types can operate happily wired to a volt free thermostat.
If the boiler has a permanent 240V contact and a switched live then you simply connect those to the thermostat and the link inside the thermostat passes the live to also control the electronic functions. There will usually also be a neutral from the boiler that is connected to the thermostat. If you wanted to be perverse you could still remove the link and wire the permanent live and neutral from a separate supply. The boiler switched live may be referred to as live return or LR.
For "volt free" boilers, you still connect a "live" and "switched live" from the boiler to the same thermostat connectors, but you have to wire in a separate power supply to operate the electronics because the "live" isn't necessarily live all the time, or it may carry a voltage other than 240V.
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Which Glowworm boiler?
Make and Model of old stat?
When you say the old stat "just had L, N and E", you presumably mean that it had brown, blue and green/yellow wires (or red, black and earth if its old wiring). Unfortunately heating wiring rarely conforms to any system, so it's better to which terminals are connected.
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