Why are the lights flickering when the a/c is on?

Question

The lights flick on and off when the a/c is on and the sound of a/c is too noisy and look like it's going to blow.

I already checked the connection if they have a short circuit. Did not found any trouble

Answer 1

Im going to assume you are talking about either a window air conditioner or portable unit - not central AC.

The lights flickering means the voltage is dropping. Incandescent bulbs are particularly sensitive to that. Most CFL and LED bulbs flicker less, though some may still flicker.

The voltage is dropping because of a large current draw. It is normal for there to be a momentary large draw as the compressor starts up. Fridges and freezers do the same thing. Its part of the reason for having a dedicated circuit for such appliances. The manual for your AC may even say it requires a dedicated circuit.

If its doing this when the AC first turns on, its not a problem. If it were drawing too much power for too long your circuit breaker would trip. If the compressor is starting and stopping rapidly causing constant flicker, your AC unit needs servicing or replacing. The noise might be the compressor or a fan dying, or just vibrations. Hard to tell without hearing it.

Answer 2

Although this is a very common issue you have to totally be certain that the flickering is only taking place by switching on the A/C.

For the condenser to start it can take up to 100+ Amps of current for the first few milli seconds(aka locked rotor amps). This energy is much much greater than full load amps. As soon as the motor is up and running the current drawn decreases to a much lesser value(around 2 - 5A).

Coming to the flickering of your bulb. When the A/C is switched on, the large amount of current drawn causes the current across the bulb and other electrical devices to decrease and hence the bulb either switches off momentarily or goes dim. As soon as the motor is running at normal speed the bulb glows starts to glow at normal brightness. Hence, you feel the bulb is flickering.

This should happen only when the motor/condenser starts and not throughout the working of the A/C. If this is happening throughout then there is a problem with the A/C and it is probably pulling too much of current. In that case you need to contact your technician immediately!

Answer 3

large inductive loads can cause out of sync pulse

power goes into the the compressor motor does the work intended and comes out a fraction of a second later this anomaly is calculated by what is known as a power factor for motors this is mostly a non issue but say you put 2 transformers in parallel so they are drawing power from the same source and output to the same load if the transformers are of the same rating you might think all is good but unless they are manufactured in the exact same way they will more or less short out into one another back to motors its gonna contribute to flickering its more then a simple heavy load and yes its almost like you have a out of phase generator hooked up to the grid but that would be a 1000 times worse and likely result in damage to generator and house hold wiring

Answer 4

I would get a electrical multi tester and verify the A/C unit is not drawing more amps/volts that it should, I would also wonder if the A/C unit is disrupting flow and possibly reversing the current. Electricity flows to the path of least resistance which is the purpose of the earth.