Reading Siemens Series Rating Chart

[Tainted]

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.

There are instances where faults are intermittent sooooo... nice try lol.

FYI the fault in this building is 119500 amps. I think this calculation from Con-Ed is complete BS. I've seen this number thrown around in like 4 buildings already

 

[electrofelon]

FYI the fault in this building is 119500 amps. I think this calculation from Con-Ed is complete BS. I've seen this number thrown around in like 4 buildings already

Yes I'm sure you know but utility fault current values are often not accurate. Not sure why this is, perhaps they're just not willing to put in 10 minutes of work and would rather put in 10 seconds and throw you some BS number, no skin off their back. I had a similar situation on one of my projects in Seattle. City light told me 110 k. I called BS and actually pumped out the transformer vault and went and looked myself, turned out to be about 70k infinite primary, and thus under 65k at the service equipment which made things easier for me and a lot cheaper for my client.

 

[binwork91]

There are instances where faults are intermittent sooooo... nice try lol.

Orderly shut down for everything is expensive. I don't think contractor and owner like to pay extra money for something may not happen, especially when it is not required by code.
Orderly shut down is nice.

FYI the fault in this building is 119500 amps. I think this calculation from Con-Ed is complete BS. I've seen this number thrown around in like 4 buildings already

It is common in Manhattan.. You will see more building with 119500 300+j1000.
And you will see 200kA in some buildings.

 

[Tainted]

Yes I'm sure you know but utility fault current values are often not accurate. Not sure why this is, perhaps they're just not willing to put in 10 minutes of work and would rather put in 10 seconds and throw you some BS number, no skin off their back. I had a similar situation on one of my projects in Seattle. City light told me 110 k. I called BS and actually pumped out the transformer vault and went and looked myself, turned out to be about 70k infinite primary, and thus under 65k at the service equipment which made things easier for me and a lot cheaper for my client.

If I ever I go into Con-Ed's vault I'm going to jail. Wish it was that easy

Orderly shut down for everything is expensive. I don't think contractor and owner like to pay extra money for something may not happen, especially when it is not required by code.
Orderly shut down is nice.


It is common in Manhattan.. You will see more building with 119500 300+j1000.
And you will see 200kA in some buildings.

THIS IS EXACTLY THE IMPEDANCE THEY GAVE ME TOO... ridiculous. They are costing building owners a lot of money cause of their BS calcs

 

[electrofelon]

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.

Granted I haven't looked at the coordination details, but that seems like a small enough possibility to not worry about. Good engineering is not necessarily taking into account every thing that could theoretically happen, it's weighing the likelihood, frequency, and ramifications of something happening and deciding if the costs justify it.

 

[Tainted]

Granted I haven't looked at the coordination details, but that seems like a small enough possibility to not worry about. Good engineering is not necessarily taking into account every thing that could theoretically happen, it's weighing the likelihood, frequency, and ramifications of something happening and deciding if the costs justify it.

Your comment actually makes me feel a little better.

I let perfectionism get the best of me

 

[electrofelon]

If I ever I go into Con-Ed's vault I'm going to jail. Wish it was that easy

Yeah I wasn't proposing that you should, just an example and yes usually we are just at the mercy of what the POCO gives us with no way to verify. One other time was talking to the Poco field planner and I asked if they had the transformer. He said yes it's in the yard, I said can you take me a picture of the data plateq and he said yes! That doesn't happen often (in that case the infinite primary fault current was about half of what they told me).

 

[Tainted]

Yeah I wasn't proposing that you should, just an example and yes usually we are just at the mercy of what the POCO gives us. One other time was talking to the Poco field planner and I asked if they had the transformer. He said yes it's in the yard, I said can you take me a picture of the data plateq and he said yes! That doesn't happen often (in that case the infinite primary fault current was about half of what they told me).

I know, don't take it literally lol.

Dealing with Con-Ed is like talking to a wall. They will not do anything like that if you ask.

 

[electrofelon]

But back to your comment in post #3, I have noticed some rather annoying "gaps" in Siemens' series ratings.
1. They seem to have very few triple ratings
2. No series rating for a 10k Q/B Branch with a 200A R fuse (I mean come on how common is that set up)
3. No series rating for a 10k Q/B with an upstream frame larger than 250 amps, gotta go up to 22k branches.

 

[Tainted]

But back to your comment in post #3, I have noticed some rather annoying "gaps" in Siemens' series ratings.
1. They seem to have very few triple ratings
2. No series rating for a 10k Q/B Branch with a 200A R fuse (I mean come on how common is that set up)
3. No series rating for a 10k Q/B with an upstream frame larger than 250 amps, gotta go up to 22k branches.

Are you using this chart attached?

 

[electrofelon]

Are you using this chart attached?

Oh nice thanks! I guess they put the three breaker combinations in a different publication. I actually haven't needed a three-tier so I never really dug much for it.

 

[Tainted]

Oh nice thanks! I guess they put the three breaker combinations in a different publication. I actually haven't needed a three-tier so I never really dug much for it.

A siemens rep gave it to make, I never found this one online