440 volt equipment operating at 480 volt

[cae]

My company is starting a design for a renovation project on an old building, which once was a manufacturing facility. I noticed that the main switchboard and several distribution panels are rated 440 volt. Testing the voltage at a distribution panel confirmed my belief that the voltage was 480 volts (it actually ranged from 487 to 493 volts).

The switchboard and distribution panels are quite old and at one time the facility may have had a 440 volt service.

Our scope of work does not include the replacement of 440 volt equipment, but I will be writing a letter to the owner about my concerns.

I feel that the equipment does not comply with article 110.4 regarding voltages and may be a safety concern. The facility engineer feels that they are “grand fathered”. This can’t be the case since they probably had a 440 volt service at one time.

Has anyone had a similar situation?

 

[bphgravity]

Re: 440 volt equipment operating at 480 volt

I feel the equipment rating falls within a nominal range that is acceptable for use. I believe Article 110.4 is for situations like trying to use a 208-volt rated motor on a 240-volt system.

Table 430.150 of the NEC shows an accepted nominal range for typical and standard electrical systems. In this case, 440 to 480 is accepted as being the same. Though your example is not specificaly for a motor installation, I think it can cross over to your particular situation as an example.

 

[rbalex]

Re: 440 volt equipment operating at 480 volt

In all likelihood, the equipment has an actual voltage rating of 600V and the original design utilization voltage was 440V. Most motors in the 440-480 range are actually 460V rated.

NEMA MG-1 generally permits motors to be operated within +- 10% of rated voltage. Other issues such as motor starting may be a consideration, but the slightly higher than "rated" voltage indicated in the original post is usually a benefit.

Personally, I see no problem here

 

[tom baker]

Re: 440 volt equipment operating at 480 volt

It may be ok, but if the voltage goes too much above +10% or 44 volts the motor amperage goes up. 440 and 220 were the older system voltages. It may depend on your actual secondary voltage.