Hello, Long time NO POST...Need help trying to find things in my NEC.

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Kyell

Kyell

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Location
Titusville Florida USA
Hello,

I am trying to find the answer to ah, perhaps several questions so please forgive me if I seem verbose.
  • I have been hired at a local industrial plant. Maintenance and install of new equipment.
  • New CNC equipment arrived recently, the owner wants each and every machine to have it own 3 phase 480 to 120/208 transformer. However He does NOT want a disconnect OCPD means on the secondary leading to the machines themselves. He says, "each machine has its' own disconnect means and internal OCPD. Now each transformer is supplied from a 480 3phase panel that is feed from a 225 am buss tap.
  • Now my question...do I have to have OCPD for this install when most of the machine are MORE that 40 feet from its transformer?
  • Each machine, has a 40 amp load ONLY.

Respectfully

Bob M
 
Kyell said:
the owner wants each and every machine to have it own 3 phase 480 to 120/208 transformer. However He does NOT want a disconnect OCPD means on the secondary leading to the machines themselves. He says, "each machine has its' own disconnect means and internal OCPD..
Click to expand...

Still have to comply with 240.21(C).
 
I explained 240.21(c)

I explained 240.21(c)

chris kennedy said:
Still have to comply with 240.21(C).
Click to expand...

Owner is reluctant to abide with the reply, "IT has worked like this for 15 years and passed city and county fire marshall inspection.

I do not feel I need extra disconnect or OCPD" "Do it my way"

my direct supervisor knows I am right in both my calculations and the NEC, but since this a LARGE family run industrial business if I keep complaining I will lose this job and I need it.
 
Kyell said:
Owner is reluctant to abide with the reply, "IT has worked like this for 15 years and passed city and county fire marshall inspection.

I do not feel I need extra disconnect or OCPD" "Do it my way"

my direct supervisor knows I am right in both my calculations and the NEC, but since this a LARGE family run industrial business if I keep complaining I will lose this job and I need it.
Click to expand...
What calculations?

Does the facility qualify for a supervised industrial installation? See Article 240 Part VIII... in particular 240.92(C).
 
Kyell said:
Owner is reluctant to abide with the reply, "IT has worked like this for 15 years and passed city and county fire marshall inspection.

I do not feel I need extra disconnect or OCPD" "Do it my way"

my direct supervisor knows I am right in both my calculations and the NEC, but since this a LARGE family run industrial business if I keep complaining I will lose this job and I need it.
Click to expand...

If previous installs passed inspection, and you have made your objections known, preferably in writing, let it go.

I had a similar job and predicament at one point. I was told by the plant manager "the squeaky wheel gets the grease, but eventually it gets replaced".

Being ordered to do things you think or know are wrong are hard to swallow, but pride and integrity don't pay the bills. Yes, it stinks when you have to do it; picking your battles is part of the game.

ime, the key to getting things like this done are making your supervisor/owner think he came up with the (great) idea. Make him look good. or tell them it will save money in the long run. something that makes them money or shines them on. You know at the end of the day it was your idea; as long as it gets done right, credit is irrelevant.
 
204.92(C)

204.92(C)

Smart $ said:
What calculations?

Does the facility qualify for a supervised industrial installation? See Article 240 Part VIII... in particular 240.92(C).
Click to expand...

NO I do NOT believe so.

My calculations on conductor size for the transformers. That recommendation is being taken into consideration for the install.

However it is more than twenty five feet for most of the installs.

seems the max length is about 60 feet, but is still in the same room as a readily accessible 480 panel that will be supplying the transformers.

I am just trying to do the best I can while still complying with the owner's demands to not install a OCPD on the secondary conductors.

Now here are the stats 480v supplied primary- 45 KVA transformer -secondary 120/208 under twenty feet from transformer,

The next two are 30kva transformer same 480v supply primary -- secondary 120/208 #2 is 20 feet from transformer. #3 is same voltages and 46 feet form transfomers.

Respectfully,
Bob
 
thank you my thoughts exactly.

thank you my thoughts exactly.

Just to be clear the "old installs" passed however I am concerned the new ones I am being asked to do, will not. (sigh)
I must say, ..." you took the words and feeling straight from my heart".
 
Kyell said:
Hello,

I am trying to find the answer to ah, perhaps several questions so please forgive me if I seem verbose.
  • I have been hired at a local industrial plant. Maintenance and install of new equipment.
  • New CNC equipment arrived recently, the owner wants each and every machine to have it own 3 phase 480 to 120/208 transformer. However He does NOT want a disconnect OCPD means on the secondary leading to the machines themselves. He says, "each machine has its' own disconnect means and internal OCPD. Now each transformer is supplied from a 480 3phase panel that is feed from a 225 am buss tap.
  • Now my question...do I have to have OCPD for this install when most of the machine are MORE that 40 feet from its transformer?
  • Each machine, has a 40 amp load ONLY.

Respectfully

Bob M
Click to expand...


Is it a delta-to-delta 3-wire transformer? Because in that application, your primary OCPD can protect the secondary by proxy, provided that when you multiply the primary OCPD by the voltage ratio, you have enough ampacity on the secondary conductors.

The idea is that fault currents in this scenario will line up winding-to-winding, and not distribute over multiple windings to go undetected. It is 2-wire single phase, and 3-wire delta-to-delta, where you can take advantage of this rule. Any WYE or high leg system means that you need secondary OCPD.

Example:
100A primary OCPD at 480V
100A * 480V/208V = 230A

You would need 230A worth of wiring on the secondary, to comply with 240.21(C) without a secondary OCPD.
 
Kyell said:
Just to be clear the "old installs" passed however I am concerned the new ones I am being asked to do, will not. (sigh)
I must say, ..." you took the words and feeling straight from my heart".
Click to expand...
Sounds like it is up the the inspector to me. That said doesn't sound like it should pass but if it does your owner gets his wish and you are just a bump in the road.
 
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