Can a device use more wattage than it's rated for?

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    Device Wattage
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Discussion Overview

The discussion revolves around whether devices can consume more wattage than their rated specifications, particularly focusing on high-wattage appliances like heaters and motors. Participants explore the implications of power ratings, operational conditions, and potential malfunctions.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants suggest that devices should not consume more power than their rated specifications under normal operation, although malfunctions can lead to higher consumption.
  • Others argue that power ratings are often approximate and can vary, with some devices potentially drawing more power due to factors like voltage fluctuations or initial power spikes during startup.
  • A participant mentions that a heater will draw more power when cold and less when hot, indicating that power consumption can change based on the device's operational state.
  • There is a discussion about motors drawing more power initially and then stabilizing at a lower consumption once operational, with examples provided regarding specific devices like refrigerators and vacuum cleaners.
  • Some participants express curiosity about the mechanisms that limit current draw in various devices, indicating that the topic is complex and not easily summarized.
  • One participant shares personal experience with laptops and power supplies, highlighting the risks of using under-rated power supplies with devices that require more power.

Areas of Agreement / Disagreement

Participants generally agree that devices should not exceed their rated power under normal conditions, but multiple competing views exist regarding the impact of malfunctions, initial power spikes, and operational variations. The discussion remains unresolved on the specifics of how and when devices might exceed their rated wattage.

Contextual Notes

Participants acknowledge that the rated wattage is typically the steady running wattage, but initial power draw can be higher for certain devices. There are also mentions of specific conditions under which power consumption may vary, such as mechanical load on motors or heating elements cycling on and off.

  • #31
K^2 said:
You think there is no capacitor at all to improve power factor? Seems kind of wasteful.
It isn't common because a single device with bad power factor isn't wasteful in and of itself. Residentially, you aren't charged for bad power factor and commercially it is cumulative for the meter, so if the overall isn't below .9 it doesn't matter what the individual devices are.
 
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  • #32
It just seems like such an easy thing to fix for individual appliance that even the extra heating in the wiring between outlet and motor seems like a waste in comparison.

On the second point, though. The meter does charge based on RMS current, not power, doesn't it? Would it be at all practical to try and correct the power factor of the household? It'd have to be adaptive, of course, but the controller would be cheap. So long as capacitor banks required wouldn't be prohibitively expensive... I mean, we are talking 5-10% of the power bill here. That's not change.
 
  • #33
Electric meters measure real power, not current. So a slight increase in amperage for something with very little resistance doesn't change the power enough to matter. It isn't like the manufacturer of the device is paying for the power anyway -- they'd rather pocket the extra $.50 per vacuum cleaner.

And adaptive power factor correctors -- commercial ones anyway -- are still pretty absurdly expensive.
 

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