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Old 01-20-2018, 02:40 PM   #1
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Default Double tap transformer

Is it legal to have 2 loads come out of the same transformer?
Or is there a sub panel required before branching out?
Both feeds are protected by fusable discos at the machinery.
It doesn't seem right to me but I don't have my code book with me.

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Old 01-20-2018, 02:47 PM   #2
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I think it is rule #2 ? https://m.youtube.com/watch?v=JmA2WYyw-_A
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Old 01-20-2018, 02:57 PM   #3
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There are a lot of variables...but, I think 240.21(C) allows for it.

Transformer Secondary Conductors. A set of conductors feeding a single load, or each set of conductors feeding separate loads, shall be permitted to be connected to a transformer secondary, without overcurrent protection at the secondary, as specified in 240.21(C)(1) through (C)(6). The provisions of 240.4(B) shall not be permitted for transformer secondary conductors.
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Old 01-20-2018, 03:05 PM   #4
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Quote:
Originally Posted by Electrozappo View Post
Is it legal to have 2 loads come out of the same transformer?
Or is there a sub panel required before branching out?
Both feeds are protected by fusable discos at the machinery.
It doesn't seem right to me but I don't have my code book with me.

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Obey the Tap Rules -- and you're good to go.
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Old 01-20-2018, 10:31 PM   #5
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The transformer can power multiple loads, but you must follow tap rules - NEC 240.21. If the machine disconnects are within the permissible tap distances, you are good. If not, you would need to relocate them near the transformer or add redundant disconnects near the transformer.
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Old 01-20-2018, 10:37 PM   #6
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Quote:
Originally Posted by Electrozappo View Post
Is it legal to have 2 loads come out of the same transformer?
Or is there a sub panel required before branching out?
Both feeds are protected by fusable discos at the machinery.
It doesn't seem right to me but I don't have my code book with me.

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It been done like that quite few time with TAP rules.

That is very important to remember it and please look up in NEC 240.21 and I think there is other spot I dont recall there is other one to follow up on that.

but just becarefull with tap rules first two part is most common for taps so please read it carefully on that.

If it dont meet the tap rules then you have no choice but put a OCPD disconnet switch after the transfomer ( yes you can have multi OCPD disconnect switch after the transfomer )
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Old 01-21-2018, 01:31 PM   #7
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Lot of our transformers for shows have multiple sets of camlock connections for this.
Or we just "T" cam adapters until we have what we need.
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Old 01-21-2018, 11:23 PM   #8
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This is awesome to read, and to understand tap rules which so many get wrong so often
Now the next challange: tell my side job foreman we did a wrong install.


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Old 01-22-2018, 09:11 AM   #9
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You treat the conductors coming from transformer terminals as if they were taps... because they are. So the conductors feeding from a transformer to a disconnect must be sized to at least 1/3 of the output capacity of the transformer.

Assuming you meet the minimum requirements of the tap rules and use a the proper lugs, yes, you can come out of a transformer multiple times.
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Old 01-22-2018, 01:24 PM   #10
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You treat the conductors coming from transformer terminals as if they were taps... because they are. So the conductors feeding from a transformer to a disconnect must be sized to at least 1/3 of the output capacity of the transformer.

Assuming you meet the minimum requirements of the tap rules and use a the proper lugs, yes, you can come out of a transformer multiple times.
What he said.

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Old 01-22-2018, 08:41 PM   #11
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Great picture ^
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Old 01-23-2018, 01:27 AM   #12
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What he said.

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I assume based on the phase colors that your pic shows a 480Y/277 V output. If so, was there a reason that the neutral doesn't connect closer to the transformers, saving wire?
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Old 01-23-2018, 05:52 AM   #13
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I assume based on the phase colors that your pic shows a 480Y/277 V output. If so, was there a reason that the neutral doesn't connect closer to the transformers, saving wire?
Maybe this? I honestly don't know. I know they make them up on these busses

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Old 01-23-2018, 05:52 AM   #14
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I know that's a different install but they are similar in design.

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Old 01-23-2018, 08:21 AM   #15
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What he said.

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BUT those could also be parallel feeds.

or utility transformers and secondaries.
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Old 01-23-2018, 02:20 PM   #16
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BUT those could also be parallel feeds.

or utility transformers and secondaries.
Pretty sure they are parallel feeds. I was just wanting to show the lugs and connection to the OP.

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