Volts, Amps, & Watts

[PSU1981]

When hooking up to a 50 Amp outlet at a campground - where is the line below which the volt reading is too low?

Power (watts) = Volts * Amps

[TG Twinkie]

Usually a 10% drop or rise is acceptable. Anything more is not.

[dznf0g]

While the above is true, the shutdown on a good "surge protector" is around 98 volts, IIRC.

Edit: I stand corrected, it is 102 Volts....see here....

http://www.campingworld.com/browse/s...F84aAteD8P8HAQ

[HiJoeSilver]

If it's below 110vac then I'd start thinking of not using the air conditioning. As the voltage drops it gets harder for large loads to start, they try to compensate by drawing more current/amps, which can damage components.

Your questions are embarassing some fellow graduates. You're making us look bad!

[SteveSueMac]

When voltage drops below 104 or rises above 132, the Progressive EMS unit shuts off power. I've experienced this at several campgrounds, unfortunately. And there's one we visit annually that is always at 120-121 24x7. You just never know. Here are all the specs:


http://www.progressiveindustries.net...t50c-read-more

[cazual6]

Well, it depends on use.

50a x 120v = 6000w

AC, Hair Dryer, Humidifiers or razors as an example of beasts. They will work all the way down to 100v and above 130v. (most will)

Look at voltage as temperature. Voltage between 110 and 120 is ideal for equipment to work.

72 to 76 is ideal for most people to be comfortable (humidity aside). Can people work below 72 or above 76, sure they can. It all depends on application. A baby shouldn't be out at 90 degrees nor below 70.

Highly sophisticated equipment such as SmartTV's, Computers, Control systems want to stay between 110 and 120.

On the other hand, beast items mentioned above including power tools, will operate far beyond the ideal voltage.

[Alumineer]

Originally Posted by cazual6

AC, Hair Dryer, Humidifiers or razors as an example of beasts. They will work all the way down to 100v and above 130v. (most will)
(snip)
Highly sophisticated equipment such as SmartTV's, Computers, Control systems want to stay between 110 and 120.

On the other hand, beast items mentioned above including power tools, will operate far beyond the ideal voltage.

This is incorrect. Unfortunately, the reasons require a deeper insight into electrical theory than the usual voltage-is-like-pressure analogies can easily explain.

A hair dryer's main use of power is in the heating element. That component is purely resistive, and therefore the heating part absolutely doesn't care about the voltage (other than, when the voltage gets too high, you might have enough resulting heat output to melt things). The blower motor requires relatively low current and since it's usually built as a brushed "universal" motor, it actually doesn't care much about the voltage either. The motor speed will be proportional to the voltage.

The power draw of an electric razor is so low that its (universal) motor can cope with pretty much any input voltage, you'll just get more or less speed.

An Air conditioning unit has an induction motor to provide input drive to the compressor. This motor is an alternating-current split-phase device that requires a capacitor to be switched into the circuit in order to start the motor. This capacitor is switched out by centrifugal force once the motor hits a certain speed. The problem with low or drooping line voltage is that the motor will require excessively long to hit the capacitor cutout speed and this will eventually damage the starting circuit. If the voltage is low enough then the capacitor may never get switched out; the resulting power dissipation in the capacitor can cause it to overheat and explode.

Most computers, smart TV's and the like are (today) powered by high-speed-switching power converters that can accept any input voltage between 90 and 250 volts, and also don't much care about the line frequency within a broad range. The only thing they don't like is when the line voltage really doesn't look sinusoidal, and when there are large power transients.

[cazual6]

You're right if you want to get that deep. I gave OPs a general idea based on his post.

[HiJoeSilver]

"Well, it depends on use.
50a x 120v = 6000w"

Except in a RV 50A hookup, because there are actually two hot 50A wires in there. Sharing one neutral. So your RV 50A hookup is actually 100A.

The RV outlet is also what most would call a 240v outlet. It has two opposite phase 120v wires which could be used to make 240v. Really not much different from the dryer outlet except the RV outlet is wired in the RV circuit breaker panel so the opposite phases can't easily share opposite busses which would produce 240v. If they are wired wrong then you can get 240v in the RV.