MCB is Tripping While Starting A/C

Isolate the equipment and do not permit it to be used until it has been rendered safe. It us either a phase-to-earth fault or a neutral-to-earth fault. Consult a qualified Electrician for testing to local electrical regulations and removal of the fault.

Hi ,

Thanks for the suggestion.

But after giving the earthing, there is no electric shocks or jerks observed on the body of A/C. The problem now is only the tripping of MCB. Do you think is there any problem on the compressor part of the A/C ?

Best Regards,

Venkata Ramakrishna

See #1 above.

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You were getting the jerk and MCB was not tripping before because earthing of AC was not good and there is a leakage to earth in AC.

Once good earth was provided, your body and AC are at earth Voltage (which is practically Zero) hence you are not getting the shock. Note earlier when AC earthing was not good, you were at earth (Zero Voltage) and AC after switching on was at near supply voltage (say 110V) and you were getting shock (current moving via your body from AC which was at 110V and earth which was at Zero).

Once good earth is connected to equipment - heavy current due to faulty insulation flows directly from power supply to earth (Remember Power Supply has huge capacity in kilo amps to feed in to earth once the insulation fails) which is resulting in tripping of MCB.

I am writing above explanation, thinking that you are not electrically qualified to understand and analyse the behavior of mcb tripping or you getting shock.

Your AC is faulty and must be checked by a qualified technician. By frequent resetting of MCB and feeding fault by starting AC you are causing more damage to equipment. We shall at the most reset only once and if trips again - call the expert.

Good luck

isolate or shutdown your system, then test your MCB between phases and against earth, if its not grounded then do the same on your wiring. hope you know how to go about it

use this to isolate-your loads NEVER guess

You have what could progress to a deadly situation. From the content of your OP this situation is beyond your abilities to diagnose/correct the situation. We all need to work within our capabilities (that's why I don't do dental work or brain surgery). The a/c technician apparently is in the same lack of knowledge on the subject. They best thing for you to do is simply unplug the air conditioner and leave it alone until you can have an electrician look at it and accurately determine what the source of the problem is. If you are satisfied with his explanation have him fix it, if not find a better electrician.

At this point nobody knows what the problem is. To risk using the unit at this point is very dangerous. Electrical shock and fire, two potentially fatal occurrence's, are possibilities and not worth the risk. Call the electrician, go to the refrigerator and get some cold water, wet a cloth and put it on your forehead for now and think cold thoughts. Enjoy the quite with the air conditioner turned off!

Good Luck, Old Salt

Aside from the above safety issues, the initial problem may have been caused by the "welding", if by that you mean any type of electric discharge welding. The technician could have caused damage to the motor windings by welding on an i grounded system, where the welding current found its way to ground through the weakest link, the motor winding insulation. If that is the case, grounding it after the fact just gave a cleaner path for the subsequent fault and is not making your breaker trip. It will only get worse from here on, and as was said, this is now a life/safety issue.

If he repaired it by gas brazing or soldering, that is less likely, unless the work was done too close to some electrical portion of the AC unit to where the damage was caused by heat alone.

Any chance the AC cable was connected reversed compared to before the gas leakage "fixing"? Reverse it again and test if breaker stays ON. That would not mean there is no problem, just that the electricity leak is small and leak path is shorter to the "other side". So if this way breaker stays always ON while AC is GROUNDED (should have been grounded from the beginning), you 're OK until you get a good technician (from another village maybe?) to inspect it. S.M.

Well it's pretty much impossible to troubleshoot remotely without a qualified technician on hand....You might try changing the CB as a shot in the dark, but once an unqualified tech has messed about inside, it then becomes a real crapshoot, and a dangerous situation, even for a qualified tech.....there are just too many variables...I have to concur with others here that recommend unplugging the device until you can procure the services of a qualified tech.....outside of that, another A/c unit might be the way to go....

Since you was getting small electrical shock earlier, which vanished after providing earthing, necessarily means some thing in your AC has some Partial connection with earth.. it can be Harness, Motor, Switches or the Electronics.

Get the Expert to resolve the issue....ISolate the System till time..

Regards,

Vishram

I can understand your situation.

What probably has happened is that the insulation has gone bad which can only be checked using a MegOhmmeter/Insulation tester commonly called Meggar.

This is not for a noob to solve.

Gajanan Phadte

In any case you may have to get in touch with a good electrician. The problem could be over current and rating of MCB. If, you have purchased new A/C, chances of loading due to wear is ruled out. Could be as doubted by others welding has caused issue for lack of precaution. First get load current measured. In an air conditioner you have a fan motor and a compressor as main components. Earthinhg you have done ( have you checked for effectiveness of earthing?). Could be some insulation damage has been caused. Pls do not allow life to be affected .. get it checked prior to putting to regular use. Load currecnt may provide you some guide See if air ducts are clear and open. Might be the earthing issue remained in the old Airconditioner you bought(???) and that is the cause of its disposal by eariler owner. If earth fault is noted you may have to locate it and correct the part of Airconditioner for reuse effectively.

Basically it is a very simple problem. When the technician do the gas welding on your A/C gas leakage pipe, the copper pipe is heated up by the gas welding works and the heat of the copper pipe will travel along the copper pipe and damage some of the electrical wire insulation. The wire insulation is not 100% damage but I believed that some of the wire insulation is already burnt and carbonised. Once the wire insulation is carbonised, leakage current will occur and that why the body of the A/C get some electricity.

By putting earthing to your A/C, the earthing will make even a better conductor for the current or voltage flow to the earth and that why it causes the return circuit unbalance and trip your MCB. You need to check all the wiring of your AC to solve this problem.

You should get a better professional gas welder to do the welding job.

Hi,

Thanks all for the advise and suggestions.

Since our A/C guy told solving problem with compressor is difficult, i tried by replacing with 30 amps MCB ( older one is 20 amps MCB), and now the MCB is not tripping.

I am also planning to replace the A/C itself , once my financial budget gets stabilized.

Thanks once again to all.

Best Regards,

Venkata