Reading Siemens Series Rating Chart

Tainted

Tainted

Senior Member
Location
New York
Occupation
Engineer (PE)
How do I read this Siemens series rating chart? I need to find series rating for HQP breaker fed by a fuse. Is the chart below saying that the HQP breaker is series rated with class J fuse? Or is it only saying that it's series rated with a Class T fuse (300V)? Or is it series rated with both?

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The excerpt you provided does not show any series rating with Class J fuses. Every line with HQP in column 4 has Class T in column 2.

Cheers, Wayne
 
wwhitney said:
The excerpt you provided does not show any series rating with Class J fuses. Every line with HQP in column 4 has Class T in column 2.

Cheers, Wayne
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HQP breakers are a pain, they have virtually no fuse series rating except for class T...
 
Do you need 100k? There are more options at 65k, where you can rate with a class L, R or J in addition to T

Can you go to a breaker upstream? With upstream breaker your choices expand dramatically with up to a 1200 amp device at 100k or even 400 amp device at 200k
 
electrofelon said:
Do you need 100k? There are more options at 65k, where you can rate with a class L, R or J in addition to T

Can you go to a breaker upstream? With upstream breaker your choices expand dramatically with up to a 1200 amp device at 100k or even 400 amp device at 200k
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Yea I need 100K series rating. I might have to amend my plans to make series ratings.

My circuit right now goes like this:

2000A class L -> 600A class J -> feeds 600A meter bank with 65KAIC HQP & HQS breakers

HQS is series rated with class L T J and R
HQP is series rated with only class T fuses

Downstream of 600A class J needs to have 35 feet of wire to get it down to 65KAIC unless I replace class J fuse with class T fuses because HQP breakers are not series rated with class J or class L fuse. I'm trying to avoid running 35 feet of wire...

To get the 100KAIC series rating my new circuit needs to look like this (notice I switch J to T):

2000A class L -> 600A class T -> feeds 600A meter bank with 65KAIC HQP & HQS breakers
 
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binwork91 said:
WS3600CU is your solution.
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Thanks but why is this a solution? I already have a switchboard feeding the meter bank shown on the drawing. A vacubreak switch is feeding the meter bank. The vacubreak switch can hold class T fuses
 
Tainted said:
Thanks but why is this a solution? I already have a switchboard feeding the meter bank shown on the drawing. A vacubreak switch is feeding the meter bank. The vacubreak switch can hold class T fuses
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I see, You have 600A in the switchboard.
Then if you can have class T in your vacubreak switch, you already have solution.

I don't know how often you see class T fuse in vacubreak switch?
At least meter bank with fuse switch is a type of solution i have seen many time.

Maybe you can try it.
 
binwork91 said:
I see, You have 600A in the switchboard.
Then if you can have class T in your vacubreak switch, you already have solution.

I don't know how often you see class T fuse in vacubreak switch?
At least meter bank with fuse switch is a type of solution i have seen many time.

Maybe you can try it.
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I've seen a lot of those siemens meter banks in NYC and I have a feeling people don't do any short circuit calculations or series ratings. People simply don't care or don't know how to do it.

The only issue I have with using class T fuses is that they might not coordinate well with HQS and HQP breakers. So if there is a short circuit downstream of the HQS or HQP breaker, the main 600 amp class T fuse might trip.
 
Tainted said:
I've seen a lot of those siemens meter banks in NYC and I have a feeling people don't do any short circuit calculations or series ratings. People simply don't care or don't know how to do it.
Click to expand...

If nobody check it, then they don't care.

But if there is a EOR, then they know what to do.

Tainted said:
The only issue I have with using class T fuses is that they might not coordinate well with HQS and HQP breakers. So if there is a short circuit downstream of the HQS or HQP breaker, the main 600 amp class T fuse might trip.
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That is one reason you need to conduct the coordination study, isn't it?

To ensure that equipment is installed correctly, a power system study is important.
 
binwork91 said:
If nobody check it, then they don't care.

But if there is a EOR, then they know what to do.


That is one reason you need to conduct the coordination study, isn't it?

To ensure that equipment is installed correctly, a power system study is important.
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Coordination is not required in some circumstances, but it is highly sought out.
 
binwork91 said:
I mean in your case, If it is not required, then why do you worry if class T does not coordinate with HQS and HQP.
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Cause the 600 amp class T fuse feeds 15 apartments. If there is a short circuit in one of the apartments and the class T fuse blows, good luck to the contractor finding out where the fault came from.
 
Tainted said:
Cause the 600 amp class T fuse feeds 15 apartments. If there is a short circuit in one of the apartments and the class T fuse blows, good luck to the contractor finding out where the fault came from.
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I don't think they care much about this.

However, I am not a contractor. Let's wait for the contractor's response.
 
binwork91 said:
I don't think they care much about this.

However, I am not a contractor. Let's wait for the contractor's response.
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The contractor might not care cause it's $$$ for them. But think about the power downtime for the 15 apartments figuring out where the fault came from.
 
Tainted said:
The contractor might not care cause it's $$$ for them. But think about the power downtime for the 15 apartments figuring out where the fault came from.
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I don't think it is hard to find out.
I am not a electrician. But I will open all apartment breaker in the meterbank. close the 600A upstream. then close apartment breaker in the meterbank one by one until class T fuse blow again.
 
electrofelon said:
It's too bad they don't give you that option. Then why not go with just all qs tenant breakers?
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Cause I am refeeding apartments that are fed by 60 amp breakers. New meter bank will be installed with 60 amp breakers, apartments can upgrade if they want for future.
 
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