Tuesday, May 18, 2010

RV Basics : An Electrical Primer : Power or Watts

In this previous article I took some time and explained how volts and amps work and tried to give you a guttural sense of the two 'things' so you might get a more intuitive feel for electricity. I ended by explaining that amps and volts work together to provide power and that power is what gets things done.

The measurement of power is called a Watt. Again this is named after a fellow named, well, Watt.

Power is the most important thing to think about in almost every sense of electricity for a number of reasons. You can power up and get a 'power budget'. You can just about figure out what things will make you 'hot' because they waste power in the form of heat instead of utilizing power in the form of 'getting something done'.

You can roughly figure that the RV power budget for a 30 Amp circuit will be 3600 Watts. The reason the circuits are stated in 30 Amps is because the circuit breaker protection is set for looking for how many Amps go through the system. Amps through systems cause damage, but you can never lose sight of the idea that the total power needed by the system is what causes the demand for the amps and because the voltage is 'known' typically people don't worry about stating the voltage. People will go back and forth a little bit, but for subtle reasons you'll use one term or the other.

For a 50 Amp RV, the power budget is 6000 Watts, although I think the 50 Amp units may actually be 50 Amps on TWO sources of power which means you might get to 12,000 Watts. Our trusty Puma is a 30 Amp unit so I've never looked.

Lots of RV gadgets consume POWER. Your microwave, refrigerator, TV and so on and so forth. When the engineers designed them they made assumptions about available power (delivered as Amps/Volts) and the system usually tries to maintain a constant power internally. As the circuitry tries to maintain a constant power, if either the available Amps or Volts changes, then there will be a corresponding change in Volts or Amps.

So, if voltage is lowered to your system, the system will generally compensate by consuming more Amps. That keeps the power constant and everything working.

Except for one small problem. If you remember, Amps is like a very large current of water. It can be destructive. Most waterways are designed to hold so much water/current. If you have lots more water going through them, they overflow their banks and cause trouble.

Its the same with amps. If your current drops, amps goes up and trouble starts. Many circuits are designed to only carry or handled so many amps. If you 'up' the amps by just 10% you could reduce their life by 90% of the maximum. You will increase the heat everywhere in systems and heat is a problem too that wears things out. You might also have many more circuit breaker trips which are good that your system is being protected, but unnecessary breaker trips can wear things out too.

So if you learned one or two things from this article it should be that most things want to consume power and that if voltage is dropped, power demand is constant, so the amps go up and that is a bad thing overall.

Oh yea, amps going through wires, exceeding the ratings can cause fires. That is good to know too.

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