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  1. #1
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    cheaper to operate

    is it cheaper to operate a 13 seer 3 phase ac unit compared to a 13 seer single phase ac unit considering all things are equal such as run time, voltage, etc. i am not looking to count pennies by factoring in startup draw, but on the whole, is there much difference. thanks, john

  2. #2
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    both units will cost the same to run. The 3 phase unit will cost more up front, but will generally be more reliable (contactors last longer and there is no compressor capacitor or start relay)

  3. #3
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    isnt the amp draw on the 3 phase less than the single phase?
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  4. #4
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    yes, 3 phase is 17 rla, 1 phase is 26.3 rla

  5. #5
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    Quote Originally Posted by John E View Post
    yes, 3 phase is 17 rla, 1 phase is 26.3 rla
    so it should be cheaper.... maybe not enough to offset initial costs... but cheaper anyways!
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  6. #6
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    Quote Originally Posted by John E View Post
    is it cheaper to operate a 13 seer 3 phase ac unit compared to a 13 seer single phase ac unit considering all things are equal such as run time, voltage, etc. i am not looking to count pennies by factoring in startup draw, but on the whole, is there much difference. thanks, john
    3 phase will always be cheaper to run than single phase.

    Most residences will not have 3 phase, and to pay to have it installed would be expensive if the power company would even do it.

  7. #7
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    Quote Originally Posted by Bubbleheadski View Post
    so it should be cheaper.... maybe not enough to offset initial costs... but cheaper anyways!
    If it would be cheaper. Then it would be more then 13 SEER.

    3 phase amp to KW is: amps X volts X 1.73


    Unless the cost per KWH, delivery fee, or some other charge is different. A single phase, and a 3 phase of the same SEER, will cost the same to operate.
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  8. #8
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    Quote Originally Posted by bwalley View Post
    3 phase will always be cheaper to run than single phase.

    Most residences will not have 3 phase, and to pay to have it installed would be expensive if the power company would even do it.
    Several areas through out the country. Have residentila neighborhoods, that have 3 phase service.

    Including down in Florida.

    3 phase is NOT cheaper.
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  9. #9
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    Quote Originally Posted by beenthere View Post
    Several areas through out the country. Have residentila neighborhoods, that have 3 phase service.

    Including down in Florida.

    3 phase is NOT cheaper.
    An American Standard TSC060 13 SEER 3 phase 480 v RTU has a max breaker size of 15 amps.

    An American Standard TSC060 13 SEER single phase 240 v RTU has a max breaker size of 40 amps.

    Which one draws more amperage?

    3 phase power is always cheaper to run equipment than single phase.

  10. #10
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    Quote Originally Posted by John E View Post
    yes, 3 phase is 17 rla, 1 phase is 26.3 rla

    Thats because the current draw on a 3 phase unit is divided among 3 wires instead of 2

  11. #11
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    Quote Originally Posted by bwalley View Post
    An American Standard TSC060 13 SEER 3 phase 480 v RTU has a max breaker size of 15 amps.

    An American Standard TSC060 13 SEER single phase 240 v RTU has a max breaker size of 40 amps.

    Which one draws more amperage?

    3 phase power is always cheaper to run equipment than single phase.
    Your not charged by the amp.

    Your charged by the KWH.


    Max breaker size has absolutely nothing to do with what it cost to run a single phase, or a 3 phase unit.

    BUT. In your example, if they did run at max breaker amperage.

    The single phase would use 9.6 KWs per hour.
    And the 3 phase would use 12.456KWs an hour, costing MORE then the single phase.
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  12. #12
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    Quote Originally Posted by bwalley View Post
    3 phase power is always cheaper to run equipment than single phase.

    And a 6 cylinder car ALWAYS gets better milage that the V8 version



    If you have two identical motors but one is 3 phase and one is single, the 3 phase motor will be cheaper to run. However, we are not talking about motors, we are talking about A/C SYSTEMS. A system consists of more than just motors. The single phase unit may have larger coils to lower condensing pressures meaning a smaller compressor can be used in the single phase unit but have an equal capacity to the 3 phase unit. A more efficient refrigeration system is used to make up for a less efficient motor.


    Beenthere said it best "If it was more efficient it would be more than 13 SEER"

  13. #13
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    Quote Originally Posted by bwalley View Post
    An American Standard TSC060 13 SEER 3 phase 480 v RTU has a max breaker size of 15 amps.

    An American Standard TSC060 13 SEER single phase 240 v RTU has a max breaker size of 40 amps.

    Which one draws more amperage?

    3 phase power is always cheaper to run equipment than single phase.

    Like Beenthere said you are charged by KWH.

    If you increase the voltage the amps drop, however Kilowatts are calculated by this formula

    Volts x Amps = KW single phase
    Volts x Amps x 1.73 = KW three phase

    So you figure it out. Double the volts and the amps are half, but 6 is still a half dozen and when you change from single phase the breaker size changes because you are carrying current across more conductors. It's like trying to put 100 cars down a two lane or three lane road. You still have a 100 cars but less per lane.

    In the industry 3 phase motors are cheaper to operate, because they typically have higher efficiencies and are higher torque on startup which will reduce the initial amp draw spike.

    What determines money savings is the utility companies charge per kwh for single phase services versus three phase. Three phase may be cheaper because it's more of a commercial/industrial service in some areas and they expect a higher usage so they reduce cost per kwh.

    Installation cost for higher voltage systems is typically lower because smaller wire can be used. Smaller wire = smaller conduits = easier and cheaper install. The equipment maybe a little higher in cost which means you might not have saved anything.

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