CA Traveler wrote:
For a motor to deliver a set HP with lower voltage it has to draw more amps.
But why ASSUME a RV A/C works that way??? Indeed my A/C tests years ago showed that the amps decreased with decreased voltage which leads to a vary obvious conclusion: The A/C was producing less cooling and/or air movement.
So you are saying that with lower voltage the motor speed drops?
Could be, although I was under impression that inductive motors regulate rpm by Hz and electric motors are rated at 110V for a reason.
When I have more time I try to use the meter Watts scale and play with different resistance extensions to compare.
Still the main fact is that ACs draw way less amp than they are rated by the factory.
usersmanual wrote:
how can anyone go by the factory suggested amp draws?
You will find people with narrow minds everywhere, that is why factory plays it safe and overrate the draw.
Theory and real life are seldom equal.
At start up electric motors do have to fight kinetic energy, higher friction, thicker oils and less efficiency.
That is why starting amps under the load is several times higher than running amp. If you observe air compressors - they have pressure relieve system that allows the motor to start with no pressure load and then build it gradually.
AC systems do have time delay that will not allow restart till pressure drops down. '
Starting compressor motor with pressure in the system is good way to burn it.
Than the law of physics say that if you need to deliver certain energy aka watts, when voltage drops, the amperage has to go up to compensate.
watts = volts x amps
That is why starting amps under the load is several times higher than running amp. If you observe air compressors - they have pressure relieve system that allows the motor to start with no pressure load and then build it gradually.
AC systems do have time delay that will not allow restart till pressure drops down. '
Starting compressor motor with pressure in the system is good way to burn it.
Than the law of physics say that if you need to deliver certain energy aka watts, when voltage drops, the amperage has to go up to compensate.
watts = volts x amps
I was always under impression that lower voltage = higher amp to compensate for watts. During my test voltage drop to 113V and was consistient with other meters I have.
When I can't calibrate watts on kill-a-watt, the voltage seem to be correct and the internet shows it as a pretty good gauge.
test
When I can't calibrate watts on kill-a-watt, the voltage seem to be correct and the internet shows it as a pretty good gauge.
test
dougrainer wrote:Kayteg1 wrote:
My 13500 AC draws 6.9 amp.
The 15k Carrier did draw 8.
The label is always saying much more because of starting current.
What outside temp were those amp draws taken at? There is NO WAY a 13.5 or 15k would draw less than 10 amps(compressor only). For a AC rated at compressor draw of 12.9 amps(average on most) you would have to have outside ambient of 45 degrees to get it down to 7.9 amps. At 45 degrees, why would you need the AC to run. The "label" has nothing to do with actual running amps. According to the Carrier specs, they have NO 13.5 or 15k that draws less than 12.7 amps(compressor only) at 95 degrees. Doug
I did not know outside temperatures play such big role and remember doing the test in the past in mild weather.
So having 92F outside right now, went to the camper to repeat the test.
My AC need 12V for operation, so had to hook up the battery to do test with converter off.
So final measurements, my attic fan takes 2.4amp and even switch shows 2-speed it operates with only 1.
When I turn on AC at full blast after initial peak the total amp were 7.8, meaning 5.4 amp for the compressor.
After few minutes the draw increased and start showing > 9.
Yes, the air is very cool.
Measurements done with Kill-a-watt.
BTW whole test done with extension cord having 10 amp breaker on it.
