cheaper to operate

[John E]

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

[craig1]

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)

[Bubbleheadski]

isnt the amp draw on the 3 phase less than the single phase?

[John E]

yes, 3 phase is 17 rla, 1 phase is 26.3 rla

[Bubbleheadski]

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!

[bwalley]

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.

[beenthere]

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.

[beenthere]

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.

[bwalley]

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.

[craig1]

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

[beenthere]

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.

[craig1]

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"

[jdblack]

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.

[beenthere]

Single phase, is amps times volts equals watts.

3 phase is amp times volts times 1.73 equals watts.

[jdblack]

Single phase, is amps times volts equals watts.

3 phase is amp times volts times 1.73 equals watts.

Yeah I edited after reading through it again to specify the difference between single phase and three phase

[beenthere]

Thats where a lot of people make the mistake of thinking 3 phase A/C is cheaper to operate.

[John E]

i just thought that 13 seer would cost the same to operate using the same kw/hr rate regardless if single or 3 phase. i'm inclined to go with beenthere but would like to know for sure

[beenthere]

SEER=Seasonal Energy Effificeny Ratio.

Basically, a 13 SEER removes 13 BUs per watt of electric it consumes.
(Not 100% true, but close enough for this explanation)

So, if you have a sinle phase 13 SEER, and a 3 phase 13 SEER.
They are both removing 13 BTUs per watt of electric they consume.
So if they are both 2 tons/24,000BTUs.

The 2 ton single phase would be consuming 1846 watts. At 240 volts that would be 7.69 amps.

The 2 ton three phase would be consuming 1846 Watts. At 240 volts that would be 4.44 amps.

If the thre phase was on a 480 volt service. It would still use 1846 Watts. Just its amp draw would be 2.22 amps.

If the three phase service was a 208 volt service. It would still be 1846 Watts. With the amp draw being 5.13

[John E]

thanks, u da man

[Super Tech JJ]

Dudes,

3 Phase is cheaper to operate than single phase. 1/3 the power just bounces around the windings and is therefore 150% cheaper to run a 3 phase motor than a single phase motor at the same power range.

You can google it if you want or you can read this article to see that the guys here that believe 3 phase is cheaper to operate are correct!

Read this page to see exactly what we are talking about. Yes, watts are watts but, 1/3 of the power just bounces between the windings.
http://www.windstuffnow.com/main/3_phase_basics.htm

JJ. OUT!