3 vs Single Phase


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Old 08-02-06, 12:10 PM
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3 vs Single Phase

At work i manage a Server room which needs to be cooled 24/7. Right now we currently have a Single Phase 5-ton unit, that runs 24/7 unless the power goes out, so i'm looking to bring in a new unit to help with our cooling needs. Our building has both 3 and single phase coming into it, so my question is which one would be cheaper to operate in the long run. thanks for your help
 
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Old 08-02-06, 12:15 PM
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Neither.
Single or three phase; a watt is a watt, A Kw is a Kw, A ton is a ton.

Three phase equipment requires smaller wires and circuits than equivalent single phase. That's all.
 
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Old 08-02-06, 12:18 PM
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three phase power can be cheaper to purchase, especially if you have to make the single phase with a transformer. Three phase motors and compressors can be more efficient to run.
 
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Old 08-02-06, 01:13 PM
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3 phase choice

If you have it there it would be more economical in the long run (after amortizing the rewiring costs, etc.) The surges of power in 3ph motors are closer together than in single phase motors. Therefore, they are more efficient power sources. From what I recall, 3ph motors are available from 1/2hp up.
 
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Old 08-02-06, 03:24 PM
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I think you will be way better off with Single Phase units cost wise up to that 5 ton. From the 71/2 ton on up they have the units in 3 phase . Have put a lot of 10 ton set ups in with 2- 5 ton units.Do a 10 ton duct lay out tie the blowers together and put the high sides on 2 stage stat with a time delay.Works like a dream.

ED
 
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Old 08-03-06, 08:29 AM
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A 3-phase motor is superior to a single-phase motor because a single-phase motor essentialy has to be wired as a 2-phase motor with a "Starting" phase winding and a "Running" phase winding.This requires capacitors and relays connected in the Starting phase winding to cause a time-displacement between the currents in the Starting and Running windings.

By "Phase", we mean a definite time-interval between the the peak, or maximum values of the currents in the Starting winding and the Running winding.At ANY given instant, the current values in the two windings are never equal because of the phase/time displacement.

A 3-phase motor has an "inherent" time-diplacement between 3 coils, and does not require time-reponsive components-- capacitors--- and current-detection relay connections in the Starting winding.

The compelling reason for a 3-phase motor- "If it's not there, it can't fail."
 
 

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