Switchboard Applied at Wrong Voltage

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JerryHonolulu

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In conducting an audit of installed electrical apparatus at a commercial office building, I recently encountered something I had never seen before.

The secondary switchboard is connected to the 480Y/277V secondary of a 750 Kva oil-filled transformer through a 1000A main breaker. This is an old FPE system, consisting of a dual-feed primary, metering, fuses, the transformer, the secondary main (air circuit breaker), and the secondary switchboard. The date of installation, as far as I can determine, was 1957.

At the bottom of the secondary switchboard is a manufacturer's ID tag, riveted to the sheet metal panel. This tag states that this switchboard is for use on a 208Y/120 volt system!! This has been in service for an estimated 56 years.

Your comments and observations, please.
 
JerryHonolulu said:
In conducting an audit of installed electrical apparatus at a commercial office building, I recently encountered something I had never seen before.

The secondary switchboard is connected to the 480Y/277V secondary of a 750 Kva oil-filled transformer through a 1000A main breaker. This is an old FPE system, consisting of a dual-feed primary, metering, fuses, the transformer, the secondary main (air circuit breaker), and the secondary switchboard. The date of installation, as far as I can determine, was 1957.

At the bottom of the secondary switchboard is a manufacturer's ID tag, riveted to the sheet metal panel. This tag states that this switchboard is for use on a 208Y/120 volt system!! This has been in service for an estimated 56 years.

Your comments and observations, please.
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Two things,
1) If you were to remove all of the breaker and had a panel board chassis left you should be concerned about if that chassis was insulated for 480v phase to phase and 277v phase to ground. The panel is labeled 208 v/120 and as such it should be applied at a maximum of 208v ph-ph and 120v ph-grd. However the panel may have originally been designed for 480v or even 600v but it still must be applied at 208Y/120 and as such you have a code violation.
2) Then consider the breaker ratings. If they are not rated 480/277v or 480v minimum that would be you second issue.
 
Some of these old systems used the same stuff for different voltages and the only difference was what the nameplate said.

A system that old is close to being ready for replacement anyway.

I would not get real excited about what the nameplate says without looking a lot closer.

It has worked for 56 years.
 
In the building code of NYS - the administrative section - used equipment is only permitted if it meets the current standards. I would bet that equipment (1957) does not. I am sure, but not positive that most if not all building codes have the same requirement in their administrative codes.
 
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