overcurrent protection
- Thread starter snjeza
- Start date
- Status
- Location
- Mission Viejo, CA
- Occupation
- Professional Electrical Engineer
Re: overcurrent protection
If it applies, you may want to review Article 240, Part VIII, Supervised Industrial Installations (Sections 240.90 and 92). If it does not directly apply, you may try to use it along with some of the tap rules in 240.21 as the basis for requesting a 90.4 "special permission."
Personally, I would avoid it, except in supervised installations. Not because it would result in an inherently unsafe installation but it definitely results in substandard reliability performance which may have a consequent safety impact.
If it applies, you may want to review Article 240, Part VIII, Supervised Industrial Installations (Sections 240.90 and 92). If it does not directly apply, you may try to use it along with some of the tap rules in 240.21 as the basis for requesting a 90.4 "special permission."
Personally, I would avoid it, except in supervised installations. Not because it would result in an inherently unsafe installation but it definitely results in substandard reliability performance which may have a consequent safety impact.
brian john
Senior Member
- Location
- Leesburg, VA
Re: overcurrent protection
Maybe I am missing something, but what differentiates this from a riser situation, with multiple panels on the same feeder?
Maybe I am missing something, but what differentiates this from a riser situation, with multiple panels on the same feeder?
fc
Senior Member
- Location
- New Jersey
Re: overcurrent protection
If your installing parallel runs then you would have to land all cables at one location and then if you can install a tap to the next panel.
If your installing parallel runs then you would have to land all cables at one location and then if you can install a tap to the next panel.
Re: overcurrent protection
I don't think we all understand your question.
Would you run 2 sets of 600KCM to each panel, or just one set to each panel?
I think you are saying 2 sets to each panel. In that case, I don't see any problem. Each set would be protected at its ampacity. But it seems like a real waste. 840 amps worth of wire to each panel, but only half of 800 available at the source.
Still, I can imagine some cases where this would be a good idea.
Steve
I don't think we all understand your question.
Would you run 2 sets of 600KCM to each panel, or just one set to each panel?
I think you are saying 2 sets to each panel. In that case, I don't see any problem. Each set would be protected at its ampacity. But it seems like a real waste. 840 amps worth of wire to each panel, but only half of 800 available at the source.
Still, I can imagine some cases where this would be a good idea.
Steve
- Location
- Mission Viejo, CA
- Occupation
- Professional Electrical Engineer
Re: overcurrent protection
This is a quick sketch of what I believe was being described.
This is a quick sketch of what I believe was being described.
Re: overcurrent protection
Steve was correct. That's what client wanted. But they understood that's waste of money, so they decided to run 2 runs of 3 #600MCM to one panel and continue with same (2)runs to the second panel and tap 3#300MCM into feeder to feed that second panel. Tap will be close to the panel (less than 25'). But still is the continuation of (2)of 600MCM considered as tap or I can consider reducing part of the end feed as the tap.
Distance from first panel to second panel is about 50'. If I confused you please let me know.
Thank you.
Steve was correct. That's what client wanted. But they understood that's waste of money, so they decided to run 2 runs of 3 #600MCM to one panel and continue with same (2)runs to the second panel and tap 3#300MCM into feeder to feed that second panel. Tap will be close to the panel (less than 25'). But still is the continuation of (2)of 600MCM considered as tap or I can consider reducing part of the end feed as the tap.
Distance from first panel to second panel is about 50'. If I confused you please let me know.
Thank you.
fc
Senior Member
- Location
- New Jersey
Re: overcurrent protection
when you install the 300mcm that would be a tap.
when you install the 300mcm that would be a tap.
fc
Senior Member
- Location
- New Jersey
Re: overcurrent protection
( It's a transformer tap ) I lost you on that one.
You can't tap a tap. A transformer is a tap so you can't tap from the wires of the transformer.
( It's a transformer tap ) I lost you on that one.
You can't tap a tap. A transformer is a tap so you can't tap from the wires of the transformer.
Re: overcurrent protection
I feed transformer with continuation of the (2) 600MCM feeder. But transformer is only 150kVA and does not need so big cable. Also transformer is protected on the primary side with fused disconnect. 400A fused disconnect can not take (2) 600MCM feeder, so I had to downsize feeder, and I consider that downsized cable as tap.
Is that clear now? If not please let me know. I will try again.
I feed transformer with continuation of the (2) 600MCM feeder. But transformer is only 150kVA and does not need so big cable. Also transformer is protected on the primary side with fused disconnect. 400A fused disconnect can not take (2) 600MCM feeder, so I had to downsize feeder, and I consider that downsized cable as tap.
Is that clear now? If not please let me know. I will try again.
fc
Senior Member
- Location
- New Jersey
Re: overcurrent protection
Got it now.
Got it now.
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