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230V control circuit

Chemenger

We've just taken delivery of a control panel that has switches controlling power to two pumps, a 9kW tank heater and an over-temperature trip. The control voltage is all 230V. Our maintenance engineer says that the control voltage, according to EIC 60204, should be stepped down to 24V. Is this mandatory? The panel is fully enclosed with an interlock cutting power when it's opened. There are no complex plc's involved, all very simple controls.

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    Where is the wiring that he thinks should be reduced to 24V installed? - are there unusual risk factors, such as damp or unusually high risk of vandalism, fire  or other damage? 
    Generally the answer is that correctly installed and labelled  230V controls are fine but there may be factors we cannot see, such as it all being in doorbell grade wire or underwater, or maybe open to casual touch during operation  ;-) 
    60204 covers anything from ELV up to about a kilovolt, so we need more info as to the exact objection to comment intelligently.
    Mike.




    Mike

  • +1 in reply to mapj1

    Hi Mike, thanks for answering.

    The wiring is properly installed inside an industrial enclosure rated to IK10 & IP66, with internal hinges and quarter turn locks. The wiring is all very professional looking (although hey, I'm just a chemical engineer so what do I know!), with the power supply coming from an independent isolator through a sealed gland into the enclosure. All terminals within the enclosure are labelled and the door is fitted with an isolator. It will be installed in a secure building inside a factory, with no exposure to rain or vandals!

    The maintenance engineer is quoting Section 9.1.1 of the standard, that "where control circuits are supplied from an AC source, transformers having separate windings shall be used to separate the power supply from the control supply". But then Section 9.1.2 states that "The nominal voltage of AC control circuits should preferably not exceed 230V for circuits with 50Hz nominal frequency". These two statements seem to contradict each other, no?

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  • +1 in reply to mapj1

    Hi Mike, thanks for answering.

    The wiring is properly installed inside an industrial enclosure rated to IK10 & IP66, with internal hinges and quarter turn locks. The wiring is all very professional looking (although hey, I'm just a chemical engineer so what do I know!), with the power supply coming from an independent isolator through a sealed gland into the enclosure. All terminals within the enclosure are labelled and the door is fitted with an isolator. It will be installed in a secure building inside a factory, with no exposure to rain or vandals!

    The maintenance engineer is quoting Section 9.1.1 of the standard, that "where control circuits are supplied from an AC source, transformers having separate windings shall be used to separate the power supply from the control supply". But then Section 9.1.2 states that "The nominal voltage of AC control circuits should preferably not exceed 230V for circuits with 50Hz nominal frequency". These two statements seem to contradict each other, no?

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