You have been sent to a new home. The homeowner reports that sometimes the electric furnace trips the 240-V, 60-A circuit breaker connected to it. Upon examination, you find that the furnace contains three 5000-W heating elements designed to turn on in stages. For example, when the thermostat calls for heat, the first 5000-W unit turns on. After some period of time, the second unit will turn on, and then, after another time delay, the third unit will turn on. What do you think the problem is, and what would be your recommendation for correcting it? Explain your answer.

Question

Physics

Boston Jensen

23 December, 21:43

You have been sent to a new home. The homeowner reports that sometimes the electric furnace trips the 240-V, 60-A circuit breaker connected to it. Upon examination, you find that the furnace contains three 5000-W heating elements designed to turn on in stages. For example, when the thermostat calls for heat, the first 5000-W unit turns on. After some period of time, the second unit will turn on, and then, after another time delay, the third unit will turn on. What do you think the problem is, and what would be your recommendation for correcting it? Explain your answer.

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Answers (1)

Know the Answer?

Aubrey Potter · Answer 1

Power rating of circuit breaker = volt x current

= 240 x 60

= 14400 W

When two 5000W unit are turned on total consumption becomes 10000 W. circuit breaker will not trip. But as soon as third unit is switched on total consumption becomes 15000 W so it exceeds the limit and circuit breaker will trip.

The recommendation is not to use all the three furnace at a time. At a particular time use only two furnaces together. We can not use them in series as they will not receive 240 V each.

Another recommendation is that use a circuit breaker of higher power rating or more than 15000 W. In that case also, there will not be any tripping.