Electricians help needed

[vhato]

I have been to a few Generator sizing sites and they all lead to huge generators.

 

My Home's Air Conditioner is a 47,000 BTU unit (3.91 Tons). According to the manufacturer, the running current is 24.7 AMPS @ 230 Volts. The maximum current listed is 40 AMPS. So I assume the most amount of power I need is between 9200-9600 watts to get it started and 5700-6000 to keep it running.

 

The Sizing charts I have found show my running power at 12,000 Watts and my starting power at over 22,000 Watts for a typical single phase, single stage, 4 ton unit.

 

What am I doing wrong??? I was always taught Voltage x Amps = Watts

 

One more question: Generators list a continuous and surge ability. In my case 15,000 Watt continuous and 22,000 Surge. If the generator has a 62 AMP circuit breaker how can it allow more than the continuous power without triping the breaker?

 

Thanks,

Vhato

[PaulieK]

Ohm's Law

 

Ohm's Law defines the relationships between (P) power, (E) voltage, (I) current, and ® resistance. One ohm is the resistance value through which one volt will maintain a current of one ampere.

 

( I ) Current is what flows on a wire or conductor like water flowing down a river. Current flows from points of high voltage to points of low voltage on the surface of a conductor. Current is measured in (A) amperes or amps.

 

( E ) Voltage is the difference in electrical potential between two points in a circuit. It's the push or pressure behind current flow through a circuit, and is measured in (V) volts.

 

( R ) Resistance determines how much current will flow through a component. Resistors are used to control voltage and current levels. A very high resistance allows a small amount of current to flow. A very low resistance allows a large amount of current to flow. Resistance is measured in ohms.

 

( P ) Power is the amount of current times the voltage level at a given point measured in wattage or watts.

 

 

Hope this helps, I am a power Engineer but I am mostly DC and not AC.

Sorry

[vhato]

Ohm's Law

 

Ohm's Law defines the relationships between (P) power, (E) voltage, (I) current, and ® resistance. One ohm is the resistance value through which one volt will maintain a current of one ampere.

 

( I ) Current is what flows on a wire or conductor like water flowing down a river. Current flows from points of high voltage to points of low voltage on the surface of a conductor. Current is measured in (A) amperes or amps.

 

( E ) Voltage is the difference in electrical potential between two points in a circuit. It's the push or pressure behind current flow through a circuit, and is measured in (V) volts.

 

( R ) Resistance determines how much current will flow through a component. Resistors are used to control voltage and current levels. A very high resistance allows a small amount of current to flow. A very low resistance allows a large amount of current to flow. Resistance is measured in  ohms.

 

( P ) Power is the amount of current times the voltage level at a given point measured in wattage or watts.

 

 

Hope this helps, I am a power Engineer but I am mostly DC and not AC.

Sorry

 

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Wow ok!! That is cool stuff. I now understand the role impedance plays and see all equations. The problem is, when I try those equations I get 5.75 as the impedance, I always get 230 volts as voltage and 40 as amperage and 9200 as Watts. So the sizing charts are wrong?? Thanks for the pic!!

[vhato]

I have been doing more reading and now have more questions. Apparently A/C Compressors have a unit called LRA and this number determines how many AMPS are pulled to start up. My 4-ton unit needs 102 AMPS @ 230 volts (23,000 Watts) just to start, then falls to 18.3 RLA @ 230 volts (4200 Watts) of continuous power.

 

Now I am SUPER DUPER confused. I found a Generac Ultra Source Generator with a surge of 23,000 Watts and a continuous power of 15,000 Watts. It sounded like the perfect match for me, but the generator only has a 62.5 AMP Circuit breaker on the 230 Volt line. Thats just under 15,000 Watts of power.

 

So how on earth is the generator gonna put out a surge of 23,000 advertised watts when the breaker is gonna trip at 15,000 watts????????????????????????????????????????

[mmmikkke]

Because the circuit breaker has some sort of inertia that prevents it from tripping during the surge.

[vhato]

Because the circuit breaker has some sort of inertia that prevents it from tripping during the surge.

 

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Really? Sounds reasonable to me. Would you happen to know how much time can pass before tripping? Less than a second, 1-2 seconds, 3 or more??

 

Thanks!

[mmmikkke]

Probably 1-2 seconds. It's hard to know, all circuit breakers are different.