Maxium control voltage

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khjones235

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I am using a 230vac coil contactor to control 230vac power distribution in an in:-? dustrial control panel. The concern is the NEC code states a maxium 120vac control voltage is to be used except for certain conditions.

Do I need to lower the control voltage or can I continue with 230vac? The NEC code requirements are very confusing.

Thanks
 
If you buy a 575 volt combination starter, you are going to get a 575 volt coil. (unless you specify a different voltage). Same with 460, 240, 120. These devises are designed to use line voltage to control them. Keep in mind these are stand alone units and if required to be integrated into the existing control scheme, order the correct coil and xfmr if included.
As far as I know you are limited to voltages under 600 VAC. I prefer 120 as it is easier to troubleshoot. But 24 volt DC is very common, and as said above, much safer.
 
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the NFPA 79 (Electrical Standard for Industrial Machinery) states that the control voltages shall be at or below 120 volts.

for existing equipment with nothing but 220 volt coils for example, that rule should not apply. when you rework these controls, or design a new machine, you would then have to apply this rule.

regards,
james
 
khj, I find your question very interesting from an inspectors point of view.
As far as I know, the NEC (NFPA70) has no such limitation.
As you pointed out in a message and as James noted, NFPA79 has that requirement.
I find it interesting as that sheds more light as to why, in this State, we look for NRTL (U.L.etc) listings on assembled equipment.
Until it was brought to my attention here, I did not know such a restriction existed, but as an inspector, I don't enforce NFPA 79.
Had we not required NRTL listings, that would have slipped by.
 
If someone gets hurt, then OSHA and lawyers are involved.. OSHA states that the employers SHALL provide a SAFE workplace, and that CONSENSUS Standards SHALL be applied.

So, NFPA79 is not a CODE, but Standard. IMO, NFPA79 would be considered a "Consensus Standard" and followed closely when making new additions to the systems. The standard is NOT intended to be applied retroactively, but new additions should adhere to current standards.
 
IMM_Doctor said:
If someone gets hurt, then OSHA and lawyers are involved.. OSHA states that the employers SHALL provide a SAFE workplace, and that CONSENSUS Standards SHALL be applied.

So, NFPA79 is not a CODE, but Standard. IMO, NFPA79 would be considered a "Consensus Standard" and followed closely when making new additions to the systems. The standard is NOT intended to be applied retroactively, but new additions should adhere to current standards.
Click to expand...

UL508A is an accepted standard, it does allow control voltages above 120V.
 
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