277/480V panels used on 120/208V System

[sparkyrick]

I saw another thread on 120/208 panels on 277/480 systems and I didn't want to hijack the thread, so I'm starting this one.

When I was an apprentice, I went to install a 400A service on the church project I was working and discovered that I was sent 277/480V panels, but it was only a 120/208V system. I called my boss and I was told to go ahead and install them. That was almost twenty years ago, but it still pops into my mind as something I shouldn't have done.

To help me sleep at night )) will 277/480V breakers work properly on a 120/208 system?

 

[GoldDigger]

I saw another thread on 120/208 panels on 277/480 systems and I didn't want to hijack the thread, so I'm starting this one.

When I was an apprentice, I went to install a 400A service on the church project I was working and discovered that I was sent 277/480V panels, but it was only a 120/208V system. I called my boss and I was told to go ahead and install them. That was almost twenty years ago, but it still pops into my mind as something I shouldn't have done.

To help me sleep at night )) will 277/480V breakers work properly on a 120/208 system?

Absolutely. With the very remotely possible caveat that some breakers with built-in electronics, like GFCI or AFCI, may not work properly at the lower system voltage. There is still not a solid consensus on that one.
Simple things like the basic breakers, including both magnetic and thermal elements, will work just fine. Same for shunt trips, although they might be just a fraction slower than at higher voltage?

The higher voltage panel and the breakers to go in it will take up more space and cost more, but once you have them in hand and the job is underway there is no good reason not to use them.

 

[kwired]

I saw another thread on 120/208 panels on 277/480 systems and I didn't want to hijack the thread, so I'm starting this one.

When I was an apprentice, I went to install a 400A service on the church project I was working and discovered that I was sent 277/480V panels, but it was only a 120/208V system. I called my boss and I was told to go ahead and install them. That was almost twenty years ago, but it still pops into my mind as something I shouldn't have done.

To help me sleep at night )) will 277/480V breakers work properly on a 120/208 system?

I installed a couple I-Line panels recently on a 208/120 system. IIRC all the breakers installed were rated for 600 volts. There are some breakers for this line that are for other voltages, but most standard inverse time types of units are rated 600 volts. They generally do have different interrupting ratings for specific voltages though.

I-Line is rated 600 volts, comes with three buses, that is only way they make it. If you have 120/240 single phase but need large capacity breakers (that are not generally available in smaller frame series panelboards), this is one of few panel series out there that will have what is needed, but you still get it with a 600 volt three phase bus, you just don't use one of the buses. And single and double pole breakers must specify when ordering which particular bus you will need to connect to.

 

[infinity]

This is also done when the 208Y/120 volt equipment needs a higher AIC rating. We've installed 480Y/277 volt panels for 208Y/120 loads when the engineer specified 65KAIC. You can see the 65KA/120 volt rating in the photo.

 

[xformer]

I saw another thread on 120/208 panels on 277/480 systems and I didn't want to hijack the thread, so I'm starting this one.

When I was an apprentice, I went to install a 400A service on the church project I was working and discovered that I was sent 277/480V panels, but it was only a 120/208V system. I called my boss and I was told to go ahead and install them. That was almost twenty years ago, but it still pops into my mind as something I shouldn't have done.

To help me sleep at night )) will 277/480V breakers work properly on a 120/208 system?

I have a tendency to think of Voltage (electromagnetic force) as analogous to PSI.... Can a hose rated for 480 PSI handle 120 PSI? Sure....

 

[kwired]

I have a tendency to think of Voltage (electromagnetic force) as analogous to PSI.... Can a hose rated for 480 PSI handle 120 PSI? Sure....

But that is only part of what needs to be looked at. The other question is whether or not the device will still provide sufficient protection at the lower voltages? Standard thermal magnetic breakers should, others may need to be applied at specific voltages. Then you have to throw in interrupt ratings. There is a lot more energy in a 10kA fault at 480 volts then there is at 208 volts, and the device must be able to handle that energy long enough for fault to be cleared without suffering catastrophic damages. At same time a power supply of a certain kVA rating will generally have higher available fault current at lower voltages than one of the same kVA rating at a higher voltage so even though the voltage of the breaker is not exceeded, you must still make sure that you are ok on interrupt rating.