Connecting 50Hz to a UL Listed 60 Hz device

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whisperinghill

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In Washington State, is it allowed to connect 220/380v 50 Hz source to a UL Listed 277/480v 60 Hz device?

The application is supply voltage passing thru EMI filters. Then to a computers that are being tested for European market.

As long we are not exceeding the Max voltages or the Max frequencies, this really shouldn't be an issue in my book, though the U/L label doesn't say 50/60 Hz.

The end devices are designed for 50Hz 220v.

Can I get some feedback?
Thanks
 
Re: Connecting 50Hz to a UL Listed 60 Hz device

Originally posted by whisperinghill: In Washington State, is it allowed to connect 220/380v 50 Hz source to a UL Listed 277/480v 60 Hz device?
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The short answer is "no."

The voltage and frequency ratings do not represent "maximum" values. Rather, within a narrow band around the rated values, the equipment will operate and will not be subjected to a risk of damage. If you apply too high or too low a voltage, or apply too high or too low a frequency, you may damage the equipment. That is the purpose of NEC articles 110.3(B) and 110.4.

If you believe this is your only option, then you need to check with the manufacturer to see if the equipment will tolerate the voltage and frequency that you intend to apply.
 
Re: Connecting 50Hz to a UL Listed 60 Hz device

the short answer is maybe. testing of this type of equipment is not covered under the NEC as it is not an "installed" item.

in some respects, the answer will depend on just what it is you are testing for. If it is just power on testing, it is quite possible the manufacturer of the stuff may be able to tell you whether the equipment will be damaged in some way or not.

its quite possible the devices will work acceptably at a different frequency than it is labeled for.

OTOH, if you are trying to show that your emi does not exceed the EU limits, than you need to test under the conditions it will actually operate at.
 
Re: Connecting 50Hz to a UL Listed 60 Hz device

If you believe this is your only option, then you need to check with the manufacturer to see if the equipment will tolerate the voltage and frequency that you intend to apply.
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The manufacturer states it is ok for those voltages and frequencies, though they never had it listed for 50Hz.

In reality, these EMI filters have neen connected for 9 years to 220/380v 50Hz and now the customer wants these EMI filters to have a selectable power source using a transfer switch.

The downstream panels 277/480v and the receptacles can handle 250v.

And 110.3
(B) Installation and Use. Listed or labeled equipment shall be installed and used in accordance with any instructions included in the listing or labeling.


This tells me, that it cannot be used on 50Hz unless it has a 50/60 Hz designation?
 
Re: Connecting 50Hz to a UL Listed 60 Hz device

the short answer is maybe. testing of this type of equipment is not covered under the NEC as it is not an "installed" item.
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This is an installed hard mounted/hard-wired equipment to filter EMI at a test chamber.

Anything being tested is designed and to be used on the voltage it is getting tested at.
 
Re: Connecting 50Hz to a UL Listed 60 Hz device

For conductors: the voltage rating is a maximum, anything less is acceptable. I have never seen frequency ratings for power conductors.

For overcurrent protective devices: the voltage rating is a maximum, anything less is acceptable. However the interrupting rating may be different. Some thermal magnetic breakers may have to be derated based on frequency, but not usually for the difference between 50 and 60Hz, in fact Square D breakers are all dual rated (except for GFI, GFP, and Arc-fault).

For magnetic devices like motors and transformers; voltages different than their nominal rating may require excess current to create the proper magnetic field and are usually discouraged. Low frequency can also affect the magnetic field in a similar manner.
 
Re: Connecting 50Hz to a UL Listed 60 Hz device

Our state electrical inspectors spoke with UL regarding the listing. Though listed as a 60 Hz, the manufacturer and UL do not have an issue with using 50 Hz on these units.

I appreciate everyone's input. The code reference's were nice, guess I better refresh on the basics.
 
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