Published: 7 November 2014
Category: Q&A
Robin asks this question, which is about the protection requirements for the circuit feeding a 110V socket used within a hazardous area. It has been answered by SELECT (Theme - Fire, Safety & Security):
This Q & A is one of thousands posted in our Technical Expertise area, and answered on a daily basis by our Voltimum Experts.
Question: I’ve been installing a 110V socket located within a hazardous area from a distribution board having a common 3kVA rated transformer. This transformer is centre tapped to earth.
What are the protection requirements for the circuit feeding the socket?
In addition, what are the protection requirements for feeding the transformer?
Answer: As this is a hazardous area, then as the transformer is centre tapped, both live poles should be protected against fault current. This can be provided by using suitable double-pole circuit breakers.
Under some circumstances, it can also be provided by using a suitable thermostat embedded in the primary winding of the transformer. This will cut off the supply to the primary winding and hence isolate the secondary side.
Important – remember that there are hazardous areas where there are risks of explosion because of the presence of flammable substances. In such cases, the above arrangement would be unsuitable.
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