What is a Volt Free Contact?

The name ‘volt free contact’ may suggest that volt free contacts operate without any voltage, but this is not the case.

Volt free contacts are mechanical switches that have no electrical connection to any other part of the equipment. This makes the circuit intrinsically safe. They are sometimes referred to as the secondary sets of contacts of a relay circuit, which does not make or break the primary circuit being controlled by the relay. This allows volt free contacts to provide complete isolation between devices in the circuit. Volt free contacts operate like an ordinary switch. When required, the switch closes, allowing current to flow through to trigger other systems to perform an action, such as lighting a lamp or sounding an alarm.

Volt free contacts are also known as ‘dry contacts’ or ‘potential-free contacts’.

Standard Volt Free Connection sets supplied by Applied Thermal Control allow for the monitoring of alarms, allowing flow, temperature, level and all-OK VFCs to be communicated across 5 wires of D-sub 9pin, at 24V DC. In cases of high flow, temperature within a detectable range, or high levels, the circuit will close, causing a signal to be sent.

Other alarms can be transmitted via VFC when specified and available.

Applied Thermal Control Ltd.
39 Hayhill Industrial Estate, Barrow upon Soar, Leicestershire, LE12 8LD.
Telephone: +44 (0) 1530 83 99 98
E-Mail: sales@app-therm.com
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