Siemens Series Rating with Class T Fuses

Tainted

Tainted

Senior Member
Location
New York
Occupation
Engineer (PE)
Siemens series rating chart says that the HQP breaker is series rated with class T (300V) as shown below.

I am wondering if this is saying I must strictly use a 300V class T fuse. What if I use a 600V class T fuse but my applied voltage is 208V? 208V is less than 300V. Would I still be able to achieve the series rating?

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Tainted said:
Siemens series rating chart says that the HQP breaker is series rated with class T (300V) as shown below.

I am wondering if this is saying I must strictly use a 300V class T fuse. What if I use a 600V class T fuse but my applied voltage is 208V? 208V is less than 300V. Would I still be able to achieve the series rating?
Click to expand...
If the chart shows a 300V fuse, that is likely the one it was tested with.
The 600V fuse must have a slightly different performance and therefore is not interchangeable, which is why there are two different sections in the chart.
 
jim dungar said:
If the chart shows a 300V fuse, that is likely the one it was tested with.
The 600V fuse must have a slightly different performance and therefore is not interchangeable, which is why there are two different sections in the chart.
Click to expand...
Got it.

What I am also wondering is why they didn't call out the bottom class T section as "(600V)"
 
Tainted said:
Got it.

What I am also wondering is why they didn't call out the bottom class T section as "(600V)"
Click to expand...
The bottom sections values probably apply to both 300V and 600V fuses.
Look at a QAF2, it can be series rated with a 1200A 600V or a 1600A 300V.
 
jim dungar said:
The bottom sections values probably apply to both 300V and 600V fuses.
Look at a QAF2, it can be series rated with a 1200A 600V or a 1600A 300V.
Click to expand...
Weird though, if that was true then the HQS breaker would be on both top and bottom sections. How come HQS is only on the bottom section?
 
Tainted said:
I was going through my old post because I think we talked about this a long time ago.

The post you made back in March you said they are for 600V only. What made you change your mind?

See below link post #7

https://forums.mikeholt.com/threads/understanding-series-rating-charts.2579598/
Click to expand...
Without going back to my mindset at that time, I don't know. Maybe I didn't look at the chart at all, but it could have been because I didn't notice the limitation in the maximum fuse size at that time.
 
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