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On 31 Jul 2005 04:01:14 -0400, email@example.com wrote:
Well... a BTU is a BTU per hour for an hour,
making it a BTU per hour hour.
So, what you are saying is a BTUH is a btu per hour hour hour.
Since "per hour" and "times hour" cancel out,
a BTU per hour hour hour equals a BTU per hour.
Therefore, BTU/hr == BTUH. :-)
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Elaborating on this answer, for lights, power is watts times
amps. This is still true *instantaneously* for everything,
but for motors the current and voltage or not in phase.
These means that part of each cycle voltage and current are of the
same sign, resulting in positive power consumption, just like lights.
But for the rest of the cycle,they are of opposite sign, so that
the power is negative. In other words, the motor is actually returning
power to the power company for this portion of the cycle.
You only care about the average power consumed over an entire
cycle, which for a motor running at full speed is considerably
less than the rms current times rms voltage.
Rick Matthews firstname.lastname@example.org
Department of Physics http://www.wfu.edu/~matthews
That's correct: The SEER is calculated to include the
phase shifts etc. introduced by the loads, which is why
direct calculations such as the OP used won't wash.
In addition, nameplates & labelling isn't always
accurate. It's often stated to be even higher than the
actual draw, just to account for the possible
variations in the production of multiple units. So
they use a max number on the plates and for the saftey
agencies. Plate numbers are only for sizing wiring to
If it has a SEER rating, and a safety label (UL,
CSA, CE, et al), which is a requirement, then the
numbers are correct.
On the current draw side:
1) volts X amps is not watts in AC. It is volt-amps (VA). Actual watts will
2) 7 amps on a 240 volt blower motor? It is probably a 120 volt motor.
3) As the other guy said, amps on the name plate is usually maximum load.
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