I m having a 12 Btu/hr AC 1280 w, 6.5 amp but current in main wire is 11 amp. why so much cost?

Question

the wire leading to outdoor unit is having a 8.5 amp. i want to ask where this 4.5 amp is going. is it a wiring problem? which type of wiring should i use?

Answer 1

The 12 BTU/Hr or 12,000 BTU/Hr has nothing to with the electrical requirement.  It is the amount of heat that can be moved from the inside to the outside of the home.  1280 Watts and 6.5 Amps tells me that the circuit is a none-US voltage of 240 volts.  Which means 1,560 VA or a Power Factor of 0.82.  This is about right for motors.  

Current measured at the Main is 11 Amp; this could be that there are other circuits there, so the measurement may not be accurate or useful.  Try measuring the voltage at the AC (outdoor) and at the same point you measured the 8.5 Amp.  If the voltage at the AC unit is around 190 volts or less, and the voltage at the 8.5 Amp point is 240 volts, then it is your wiring too low in gauge.  Try using a thicker wire, i.e. 18 or 15 gauge.

Answer 2

It's not a wiring problem, too small a wire will overheat, and you will get less current, not more. Or a fire.

12 BTU/hr is only 3.5 watts, perhaps it is 12000 BTU/hr, which translates to 3500 watts, which at 240 volts is 15 amps? or is it 3 phase?

So clear up the numbers and provide more details and you may get an answer.

What is the voltage and number of phases?

What is "main wire"?

What is "outdoor unit"?