What is this?

[infinity]

This is an out of the box 1Ø, 480 volt, 200 amp fused disconnect. Any idea what the #1/0 jumper is for?

 

[don_resqcapt19]

I have seen that where the disconnect is used for DC. You need more contact interruption distance for DC than you do for AC and one way to get that is to series two contacts. I have seen instructions that called for that so you could use an AC disconnect for DC.

 

[infinity]

That makes sense but why a #1/0 jumper for 200 amps, wouldn't the terminals be rated for only 75° C?

Also for AC would you remove the jumper?

 

[don_resqcapt19]

That makes sense but why a #1/0 jumper for 200 amps, wouldn't the terminals be rated for only 75° C?

Also for AC would you remove the jumper?

It is a factory installed jumper so the NEC ampacities do not apply. Even if the NEC did apply I think you could use Table 310.15(B)(17).
Being that is a factory jumper, that disconnect may not be listed for AC use. If it is listed, I see no reason to remove the jumper.

 

[infinity]

Yes it's listed AC or DC.

 

[Dennis Alwon]

It is a factory installed jumper so the NEC ampacities do not apply. Even if the NEC did apply I think you could use Table 310.15(B)(17).
Being that is a factory jumper, that disconnect may not be listed for AC use. If it is listed, I see no reason to remove the jumper.

You never cease to amaze me. :thumbsup:

 

[iwire]

Sometimes the instructions call for doing this in the field when dealing with DC. I have run into it with solar.

And yeah, Don is pretty amazing.

 

[infinity]

You never cease to amaze me. :thumbsup:

And yeah, Don is pretty amazing.

I agree, does anyone have a document that shows this? I've been poking around but am coming up empty and I know that people will be asking.

 

[kwired]

It is a factory installed jumper so the NEC ampacities do not apply. Even if the NEC did apply I think you could use Table 310.15(B)(17).
Being that is a factory jumper, that disconnect may not be listed for AC use. If it is listed, I see no reason to remove the jumper.

I see that kind of thing in pump panels, panelboards, etc. all the time. Factory installed (or even factory supplied but field installed) leads between components that are otherwise smaller then what you would have to use if assembling same components that are not part of a listed assembly.

In pump panels I often see as little as 2 AWG conductor between the disconnect and the motor starter yet the minimum NEC required conductor for the motor being supplied is as much as 2/0. Also seen many short pre formed conductor links as part of a main breaker kit to install in a panelboard that are not the same size as I would have to install if NEC applied to them.

 

[Little Bill]

I agree, does anyone have a document that shows this? I've been poking around but am coming up empty and I know that people will be asking.

Are you asking for a document showing that Don is amazing or a document showing that what Don said is true?
If the former, I think his Mom wrote one up!

 

[don_resqcapt19]

The following is from a Eaton document for their solar DC disconnects.

Switching devices primarily designed for DC service require design features to increase the total arcing voltage. This can be achieved by designing larger single air gaps and multiple gaps in series, or by using magnetic fields to force arc movement.

You watch a demo of a knife switch open a 2600 watt load at 220 AC and at 220 DC in this youtube video.
https://www.youtube.com/watch?v=Zez2r1RPpWY

 

[brantmacga]

I bought some 1-phase heavy duty Eaton disconnects awhile back that came like this. Was also curious ..... Now I know


Sent from my iPhone using Tapatalk

 

[JFletcher]

The following is from a Eaton document for their solar DC disconnects.

You watch a demo of a knife switch open a 2600 watt load at 220 AC and at 220 DC in this youtube video.
https://www.youtube.com/watch?v=Zez2r1RPpWY

Why does 220VDC arc like that? Is that really 220VDC? Looks like a LOT more.

 

[FionaZuppa]

Why does 220VDC arc like that? Is that really 220VDC? Looks like a LOT more.

its 220ac(rms) and its 220dc(rms). no filtering thus a bunch of dc humps at 120hz. the zero crossing of ac is a good quenching process.
if its US resi then its really 240v

 

[jumper]

Are you asking for a document showing that Don is amazing or a document showing that what Don said is true?
If the former, I think his Mom wrote one up!

I want a document that verifies Don's mom stated that what he said is truly amazing. Preferably notarized and such if possible.

 

[roger]

I want a document that verifies Don's mom stated that what he said is truly amazing. Preferably notarized and such if possible.

Well, there is this


Roger

 

[winnie]

Yes it's listed AC or DC.

From the label, it looks like it is listed for DC or _single phase_ AC. I don't see it listed for 3 phase use.

IMHO the jumper has to stay for any of the uses listed on the label.

It wouldn't surprise me if the assembly sans jumper with a different label is listed for 3 phase use. I also would not be surprised if the 'matching' 3 phase device had a lower voltage rating or different short circuit ratings.

-Jon

 

[iwire]

Well, there is this


Roger

:thumbsup:

 

[Smart $]

Why does 220VDC arc like that? Is that really 220VDC? Looks like a LOT more.

DC has no zero volt crossing like AC to "assist" with extinguishing the arc.

 

[FionaZuppa]

DC has no zero volt crossing like AC to "assist" with extinguishing the arc.

this particular DC does have a zero "crossing" @ 120Hz :thumbsup:

that same video using full bridge rectifier at say 30Hz or 200Hz (AC) will show way different results.

a 240 battery, even more different results.