Total amps don't match?

[as000ll]

We just came back from Arizona. I thought winter was pretty much over so I decided not to winterize my View. But, Canada being Canada, a few cold days are among us. Last night, it went down to -8 C (14 F) and today, it is -6 C. I did not want my pipes to freeze so I decided to use my 1500W space heaters to keep the rig warm.

I cannot connect my rig to a 30 amp hookup. So I use a regular switch which is on a 15 amp breaker.

So if Watt=amp*volt, my 1500w space heater should only pull 12.5 amps, right? I assume that it would even give me a buffer for the rest of the usage of power (like the inverter/charger for example). So everything worked fine.

Then I tried to put another space heater (this time, using it at half is capacity). Is it 750W? I do not know. But it is still a fairly decent amount of heat. It continued to work just fine. I thought I would overcharge the circuit but no breaker tripped (I have two 15 amp breakers on that circuit, one outside the house, one in my main power box). How could it be possible?

 

[powercat_ras]

Circuit breakers operate in 2 ways

- instantaneously if short circuit current is seen (magnetic trip)

- Due to overload that is not a short circuit being seen, after a delay. (thermal trip) The breaker is designed to trip before wiring overheats to the point of damaging the insulation or overheating switches and outlets operating at their maximum rated load.

So, beware of intentionally overloading that circuit you might find it tripped if both space heaters come on and stay on continuously for longer than a few minutes.

The colder the breaker box and circuit breakers inside of it are the longer the delay will be for the thermal trip device inside the breaker to heat to the point where it trips the breaker.