power consumption question

[SithZedi]

You could benefit more from some gonzo true floating isolation transformer designs out there....

Thanks. I would buy almost anything with the name gonzo in it..

 

[highfigh]

thanks guys!

It's a digital pinball machine, PC inside, 4K screen.

OK, so it's using a relatively insignificant amount of power.

If you want to KNOW the power consumption of anything like this, buy a Kill A Watt- $30 and it shows current, Watts, KW-Hr and other details-

 

[tony.silveira]

OK, so it's using a relatively insignificant amount of power.

If you want to KNOW the power consumption of anything like this, buy a Kill A Watt- $30 and it shows current, Watts, KW-Hr and other details-

View attachment 54289

Thanks man! I did actually buy one and I have begun the sloooowwww process of checking each piece of equipment in the room.

A quick question to the group. I have a mini fridge connected to the same breaker as my arcade machines. Typically, the thing draws about 1.4 amps. but when the motor kicks in to keep the temp, it can go as high as 6 amps for about 30 seconds and then drops down to about 1.1 - 1.4.

if i had all those machines on and the fridge at base line, i'm drawing about 12 amps. when the fridge kicks on, that would increase to 17 amps for about 30 seconds. do you think a short peak like that would trip the breaker or more importantly, be a fire hazard (if it's only 30 seconds).

apologies if that is an ignorant question, I'm just trying to learn and keep everything safe

 

[-Jim-]

The surge of current from the fridge is due to the starting cycle of the compressor's motor, and nothing to be worried about. The Breaker in your panel is sized to handle that inrush.

I hope this is helpful.

 

[tony.silveira]

Hi Jim,

It does relieve me a bit. everything i have been researching says that you shouldn't be pulling at an amps peak power (15 amps in this case) but instead target 80%, which is right where i'm at (12 amps) with the fridge at base line.

as i am still learning, is there a point where a breaker trips if there is a rush of power that takes it over it's max? meaning, a 15 amp breaker can handle that 17 amp load for two minutes (i'm pulling that number out of the air) but will trip if it continues after that?

thank you guys for all of the input and helping me learn!

 

[-Jim-]

Tony,

This may be getting a bit geeky so bear with me. Remember earlier on I advised your local electrical code typically limits fridges to their own circuit. I'm not familiar with your local code regarding mini-fridges but I wouldn't suggest you add more load to that circuit as you are at a good base line now, if your local code allows a mini-fridge to be connected with other devices.

Breakers are rated to trip (to clear the fault) for both Long-Time and Instantaneous current levels. In that manner they can handle in-rush of inductive loads (typically motors) for short durations (instantaneous current can be 6-7 times full load current but it only typically lasts for a few seconds) without tripping. A circuit with an overload (just beyond the breaker rating) that is more constant, will trip some time after 300 seconds (for a BR type 120 VAC / 15 Amp single pole breaker at 25°C ). The more it's overloaded the shorter the time before it trips. And yes, temperature affects the time to trip. You can usually look up the trip curves for your breakers on line.

As per Schneider Electric/Square D/Merlin Gerin Circuit Breakers:

"Inverse time tripping is a characteristic of circuit breakers in which the breaker trips in more time with lower overcurrent, and less time with higher overcurrent. For the US, Article 100 of the National Electric Code defines it as follows: "Inverse Time (as applied to circuit breakers). A qualifying term indicating that there is purposely introduced a delay in the tripping action of the circuit breaker, which delay decreases as the magnitude of the current increases."

IMHO, I try to be very conservative with circuit design. In my past life I did Breaker calibration and testing on large and small industrial breakers => 3 Phase Air and Vacuum types, Contactors, & their related Relays for a few years. To me it's never worth the risk to overload a circuit and rely on a 25 year old breaker to trip.

(By the way, I exercise the breakers in my house yearly. That means I turn them off and on 3 or 4 of times each after turning off the main breaker. I've heard too many stories of breakers failing to act as they've never moved in 20 years and were "frozen".)

I hope this is helpful.

 

[fmw]

I side with those who say you are overthinking it. How much current your speakers draw depends on their efficiency and the volume to which you drive them. So let's take speakers rated at 90 db. What that means is that 1 watt of amplifier power witll drive them to a sound level of 90 db at a 1 meter listening distance. If you are standing next to gas powered lawn mower, you are experiencing a sound level of around 90db. That is pretty loud. it will take up about 1/100th of an amp of your 15 amp circuit at the electrical outlet for each amplifier. My 55" LCD screen draws about 1/2 of an amp of your 15 amps. You can continue on with the calculation.

With each 3db of additional volume the power used by your speakers doubles. 93 db takes 2 watts of amplifier power. 96 db takes 4 watts and so on. Things are now getting very loud indeed. Being further than 1 meter from the speakers reduces the decibel level you experience from the speakers which is likely to make your listening more pleasant.

The point is that it is really hard for a home theater to draw anywhere near 15 amps from the circuit. Even my 15" subwoofer doesn't draw a meaningful amount of current - way less than the screen. Relax. Put the brakes on your power worry. Hook it all up and and enjoy the entertainment.