Help with commercial shop calculation

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p051981

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Houston, Texas
I am trying to calculate a service for a commercial message shop. This business is located in a shopping strip and is feed by a 120/240 with a high leg. The store has just basic lighting (parabolic troffers lights). These are the information givin to me:

1500 Sq ft
Air conditioning unit (3 phase) = 60amp
Water Heater 50 gallon = 30amp
Steam Unit = 30amp
Washer
Dryer
Refrigrator
 
p051981 said:
This business ... is feed by a 120/240 with a high leg.

Air conditioning unit (3 phase) = 60amp
Click to expand...
As a side comment, I suggest looking into a small 3ph panel for the A/C, and a 1ph panel for the rest. The high leg can play tricks on you.
 
Your profile indicates you are an apprentice. As such, you should learn how to do the calculating yourself. This is a little different than someone posting a test question, but it is still basically the same.

Show us how you calculate it and we'll tell you whether you are correct or not. The examples in Annex D of the NEC should help you get started.

The main thing you'll have to remember here is that all your 120V (line-to-neutral) loads will be connected to and VA-balanced as best possible on A and C lines. 240V 1? (line-to-line) loads can be put on A-B and B-C to help balance the overall 3? loading... but this will somewhat depend on whether the poco is providing full-current delta 3?, or a reduced power open-delta high leg. If unknown at present, figure for full delta but be prepared to shuffle your loads if otherwise.
 
p051981

Just for reference, here is the equation for Neutral currents.

*:) EL_IneutralCurrent_equation.txt
Ineutral =
SQRT (
I?A + I?B + I?C
- (IA x IB) - (IB x IC) - (IC x IA)
)

Welcome to the forum.
 
glene77is said:
p051981

Just for reference, here is the equation for Neutral currents.

*:) EL_IneutralCurrent_equation.txt
Ineutral =
SQRT (
I?A + I?B + I?C
- (IA x IB) - (IB x IC) - (IC x IA)
)

Welcome to the forum.
Click to expand...
Very thoughtful of you... but it don't apply to a 240/120 3? 4W system.
 
glene77is said:
I am curious
why this would not apply to any 3 phase system?
Click to expand...
Probably because the only loads that use the neutral are A- and C-phase loads. The A-N-C section of a high-leg Delta behave exactly like a 120/240v 1ph system. Only 3-ph, A-B, and B-C line-to-line loads use the high leg.
 
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