AC 20amp breaker trips mid day

road-runner wrote:
Hard for me to tell what some of the posts are saying. I'll throw in that from actual measurements I made on a 13.5 kbtu Dometic air conditioner, in the voltage range of 98 to 122, I found the following:

-As voltage goes down, current draw increases
-As voltage goes down, power factor improves. Worst case was .93 at 122 volts.
-As voltage goes down, total power consumption goes down

With this particular air conditioner, my take is that boosting the voltage is good for the air conditioner, at the expense of slightly higher power consumption.

“As the voltage goes down, the power factor improves”

Wrong, as the voltage goes down, the sinusoidal relationship between current and the voltage begins to widen thereby worsening the power factor - in the ideal, the power factor should be at 1, this is what the capacitor corrects for to keep this relationship in phase (while discharging at 180 deg of sag) and also why its important to use the ‘right sized’ capacitor to overcome this reactance...But you didn’t say how you are determining the p/f...

BTW, at 98v your air conditioner may start to think its a toaster!!

road-runner,

I hope you did not operate the unit long at 98 volts.

What happens to the "numbers" after the AC has been running for many hours?

My own "wattage" goes up and up as the ambient temperature gets warmer. It starts at about 1200 and I've seen as high as 1900 watts.

Hard for me to tell what some of the posts are saying. I'll throw in that from actual measurements I made on a 13.5 kbtu Dometic air conditioner, in the voltage range of 98 to 122, I found the following:

-As voltage goes down, current draw increases
-As voltage goes down, power factor improves. Worst case was .93 at 122 volts.
-As voltage goes down, total power consumption goes down

With this particular air conditioner, my take is that boosting the voltage is good for the air conditioner, at the expense of slightly higher power consumption.

With or without the autoformer apparent power should be the same, but with the autoformer ‘true power’ stays within design parameters thereby safeguarding the compressor - it’s this important point that makes the difference.

Haycamper wrote:
The autoformer increases the output voltage but it doesn't increase the output power so the output current actually drops. The autoformer input current goes up when the input line voltage drops. So even though the output current may be 28 amps, the input current could be over 30 amps. The increase in voltage is not free it's not a power station where you can just turn up the boiler.

when your driving an induction motor, as the voltage goes down the current goes up, opposite of what one might think. As voltage drops, the motor "back emf" drops causing current to rise. So in a case like this the autotransformer actually can actually reduce current draw, especially as voltage drops down near 100V when driving a motor.

On a pure resistive load then good old ohms law for pure resistive loads applies.

Haycamper wrote:
3 Tons
The autoformer increases the output voltage but it doesn't increase the output power so the output current actually drops. The autoformer input current goes up when the input line voltage drops. So even though the output current may be 28 amps, the input current could be over 30 amps. The increase in voltage is not free it's not a power station where you can just turn up the boiler

“The autoformer increases the output voltage but it doesn't increase the output power so the output current actually drops”...

Isn’t this rather self evident, but you dismiss the fact that the ‘power factor’ is corrected to near unity thus the air conditioner sees no (or minor) voltage sag...It’s this voltage sag that can burn out compressor windings...

“The autoformer input current goes up when the input line voltage drops. So even though the output current may be 28 amps, the input current could be over 30 amps. The increase in voltage is not free it's not a power station where you can just turn up the boiler”...

I know of no single rooftop air conditioner that uses that many amps, but thats just me with my smallish truck camper - quite naturally outliers do exist (especially when only on a 30a pedestal) when running multiple appliances, high ambient temps, etc....This is exactly where one should instead opt for a 50a pedestal... Judgement plays a large role here...

BTW, recall that your OP question was in reference to a 20a breaker - just saying...

3 Tons
The autoformer increases the output voltage but it doesn't increase the output power so the output current actually drops. The autoformer input current goes up when the input line voltage drops. So even though the output current may be 28 amps, the input current could be over 30 amps. The increase in voltage is not free it's not a power station where you can just turn up the boiler

The autoformer increases the output voltage but it doesn't increase the output power so the output current actually drops. The autoformer input current goes up when the input line voltage drops. So even though the output current may be 28 amps, the input current could be over 30 amps. The increase in voltage is not free it's not a power station where you can just turn up the boiler.

DFord wrote:
Trouble with the a device like the autoformer mentioned is that to increase the voltage, the amperage also increase and you're more susceptible to tripping the pedestal breaker - there's no free lunch and you won't be able to draw more than 24 amps (80%) through a 30 amp breaker for any length of time with it tripping.

In order to make long distance transmission of electricity efficient and affordable Nikola Tesla figured out that AC was the way to go...So when voltage goes UP current is proportionally driven down, and wires that are used get waaaay smaller... So how does use of an autoformer cause the pedestal CB to trigger open, and why does the autoformer ‘make possible’ the use of my honda genny while loafing along under LOAD when in the eco mode??....Maybe Tesla got it awfully wrong...

Where is your AC breaker panel located? Is it hot to the touch? Mine is in a closet and it gets incredibly hot. Breakers trip at lower currents when they get hot.

I chased this issue a long time and used a current meter. Removing the cover of the AC panel found it far to hot inside. I made a tiny modification and the problem has subsided. At one time I kept the closet door open and an AC vent blowing on the face of the panel.