Roger (K8RI) wrote:
>
> On 8/8/2010 3:00 AM, Brahmangou@aol.com wrote:
>> Check the Seer ratings on the 3 phase eqpt vs single phase before making so
>> bold a statement.
>>
>
> I think you will find that this is most likely due to equipment design
> rather than the ability to run on 3 phase.
> At work we only used single phase on the "small stuff".
> 3 phase motors are just plain more efficient than single phase for the
> same HP. With very small motors the difference becomes less and small
> single phase motors are cheap due to market volume.
> "I would guess" that as 3 phase powered small airconditioners are
> *relatively* rare here in the US compared to single phase that changes
> in implementing new designs may lag the implementation of new designs
> for single phase, as I can see no reason that the efficiency (seer
> rating) of a single phase airconditioner would be better/higher than a 3
> phase. The seer rating is determined almost wholly by the laws of
> thermodynamics.
>
not exactly..
The SEER rating is determined more by how well the AC can handle varying
loads. For a given number of joules/BTUs being pumped with a given
temperature differential, Roger's statement is true.. you can optimize
the size of the motor, condenser, evaporator, and expansion valve for
that operating point and pretty much everybody is in the same boat
(whether your electric motor is 90% or 95% efficient isn't going to make
much difference...)
But, when the condenser (outside) temperature (e.g. the differential
temp) is changing, which it does, with the seasonal adjusting (the S in
SEER), it's trickier. Do you run the system at constant differential
(with the evaporator running colder than normal when outside temp is
lower) and cycle it on and of more? (that's fairly inefficient) or do
you put in a fancy variable speed compressor (that's more efficient)..
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