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120V from 250V 3 phase?

Subject: 120V from 250V 3 phase?
From: Brian Kemp <>
Date: Wed, 01 Oct 2003 17:25:24 -0700
I have a power problem in the office I'm going to be moving into 
shortly. I have a rack of computer equipment that needs a dedicated 120V 
20A circuit that doesn't exist in the new location. What I do have is a 
twist lock 250V 20A 3 phase outlet 4 wire outlet. According to, it is a NEMA L15-20 outlet.

I'd like to make a cord to plug into this outlet and get a standard 120V 
receptacle that I can plug the computer rack into. I expect that this is 
possible, but hope someone out there can confirm that it is safe for the 

I'd try and use an electrician to put on the proper outlet, but the 
building is less than helpful and it will take more than a month to 
coordinate funding transfers, insurance requirements, and approval. 
Management told me I'm moving Monday.

The outlet has 4 slots:
1. prong like a bent "L"
2. narrow slot
3 and 4. wider slots

Thinking a 3 phase system needs 3 "hot" lines leads me to believe I 
either have a neutral or ground as the 4th wire. While I know neutral 
and ground are probably connected at the breaker box, I'm not going to 
chance a bunch of expensive computer equipment on a poor power supply. 
So as it is now, I don't think this will work.

I've done enough electrical work to understand what I'm doing, but would 
like confirmation from one of the smarter people about this idea. I 
looked for a UPS to go into the outlet, but didn't find any with a 3 
phase input.


Brian Kemp

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