Use three 2-wire heater elements that draw 11 amperes each at rated line voltage. If you connected all three in parallel to a 2-wire source, the current on each line connection would be 11+11+11 or 33 amperes. Now with two heaters on the 2-wire source, the line current is 11+11 or 22 amperes.

Expand the setup from a single-phase two-wire source to three phase, and power the three heaters from a simple three-phase three-wire line. Voltage is immaterial for your answer, but most 3Ă¸ calculations assume [unless stated otherwise] balanced voltage and balanced current. Another way of describing it all is that everythingâ€™s symmetrical.

Doing only part of the connections and making some current checks along the wayâ€”rewire the heaters with one 2-wire heater connected AĂ¸-to-BĂ¸ and the second BĂ¸-to-CĂ¸. At this point only 2 heaters are connected, but at this point there is a *trick* in the line currents, although it isnâ€™t a balanced-3Ă¸ system right now. If the current in each 2-wire heater is tested, [say, with a clamp-on ammeter checking either of the heater leads] they will measure 11 amperes in each connection, or 11 amperes on AĂ¸, 11 amperes on CĂ¸, OK? With both heaters connected to BĂ¸, the current should intuitively be more than 11 amperes, for thereâ€™s two heaters running. For two 2-wire heaters connected with one wire each on BĂ¸, it may seem that the total BĂ¸ current might be 11+11 or 22 amperes.

But, through the *magic of three phase,* the current is only 86.6% of the expected 22 amperes, or about 19 amperes on BĂ¸.

Continuing for a complete 3Ă¸ circuit, connecting the third 2-wire heater on CĂ¸ and AĂ¸, thereâ€™s now three symmetrical or balanced currentsâ€”about 19 amperes {11x1.732} on each phase, and not 22 {11+11}. The three heaters are connected in sort of a triangle or delta connection.

H-oâ€™-P, there you are for the short version. Itâ€™s a lot to absorb at once, and has taken years of installation and current checks on real systems for me to learn that all those books arenâ€™t crazy or stupid, and that if you do it right, then you can predict the outcomeâ€”and most importantlyâ€”make money at it. Repetition, repetition, repetitionâ€¦

three 2-wire heater elements that draw 11 amperes each at rated line voltage. If you connected all three in parallel to a 2-wire source, the current on each line connection would be 11+11+11 or 33 amperes. Now with two heaters on the 2-wire source, the line current is 11+11 or 22 amperes.

Expand the setup from a single-phase two-wire source to three phase, and power the three heaters from a simple three-phase three-wire line. Voltage is immaterial for your answer, but most 3Ă¸ calculations assume [unless stated otherwise] balanced voltage and balanced current. Another way of describing it all is that everythingâ€™s symmetrical.

Doing only part of the connections and making some current checks along the wayâ€”rewire the heaters with one 2-wire heater connected AĂ¸-to-BĂ¸ and the second BĂ¸-to-CĂ¸. At this point only 2 heaters are connected, but at this point there is a *trick* in the line currents, although it isnâ€™t a balanced-3Ă¸ system right now. If the current in each 2-wire heater is tested, [say, with a clamp-on ammeter checking either of the heater leads] they will measure 11 amperes in each connection, or 11 amperes on AĂ¸, 11 amperes on CĂ¸, OK? With both heaters connected to BĂ¸, the current should intuitively be more than 11 amperes, for thereâ€™s two heaters running. For two 2-wire heaters connected with one wire each on BĂ¸, it may seem that the total BĂ¸ current might be 11+11 or 22 amperes.

But, through the *magic of three phase,* the current is only 86.6% of the expected 22 amperes, or about 19 amperes on BĂ¸.

Continuing for a complete 3Ă¸ circuit, connecting the third 2-wire heater on CĂ¸ and AĂ¸, thereâ€™s now three symmetrical or balanced currentsâ€”about 19 amperes {11x1.732} on each phase, and not 22 {11+11}. The three heaters are connected in sort of a triangle or delta connection.

H-oâ€™-P, there you are for the short version. Itâ€™s a lot to absorb at once, and has taken years of installation and current checks on real systems for me to learn that all those books arenâ€™t crazy or stupid, and that if you do it right, then you can predict the outcomeâ€”and most importantlyâ€”make money at it. Repetition, repetition, repetitionâ€¦

[This message has been edited by Bjarney (edited 01-25-2003).]