Volt Free Contact??

F

fandango1

Registered User
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Can anyone enlighten me as to what is meant by a volt free contact?

I was looking through an instruction manual that came with a new central heating boiler, and I came across the following passage:

"If the boiler is to be controlled by a time clock, this must be a VOLT FREE CONTACT time clock only. The volt free contact time clock is to be connected to the control panel by replacing the “external switch link” from the connectors on the board with the cable from the timer. The connection point is shown as “0 volt” on the wiring diagram."

Thanks,

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I'm not an electrician and unless you know about live, neutral and earth don't try and wire up the boiler yourself.

In any event what they are talking about here is this.

Your boiler needs live (brown), neutral (blue) and earth to work.

You feed neutral and earth to the boiler connections but the live (brown) passes through the time clock, which makes or breaks the connection.

So a volt free contact is a live wire going into a device which makes or breaks the wire but does not carry any voltage (as there is no neutral wire).
 
It is a contact that does not switch the live from the mains.

For instance, if you were to have your kettle on a timer so that it is boiled when you get up, the timer switch will supply 220V to the kettle,.e.g. the contact has 220V on one side and will supply it to the other side when on.

In the case of your boiled, you have to use a timer switch that simply control a relay e.g. whatever voltage is required comes from the boiler and it passed through the relay back to the boiler when timer switch is on.
 
First of all the operation of a contact is two metal surfaces being either opened or closed as part of an electrical circuit. The can contact operated mechanically or electrically i.e. a timer could be either but yours is probably electrical. The term 'volt free' applied to this means that the device that the contact is part of applies no voltage to the contact thus the contact is 'volt free' and therefore it can be used to switch an external voltage i.e. in your case the supply (live) to your boiler.

VFC is also commonly know as 'dry' contact
 
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