Why does my room air conditioner trip ELCB?

I would start by checking if the feed is coming directly from the panel this is a start, then I would check all of the connections from where you feed is coming from. A lot of times if you have a bad connection it can cause the breaker to heat up causing it to trip. I recommend you run a straight from the panel to feed you A/C.

Hope it helps,

If the problem is not in the connections, then the motor to the compressor has an intermittent issue. Check all of the connections first. By all of the connections, I mean lugs that are crimped on, wire nuts, any break in the wire.

A connection doesn't have to be very loose to become a big headache. Look closely for evidence of heat buildup on one wire more than another. This is usually a giveaway.

Do you have access to an infrared camera. It will show the temperature of all of the components. The hot spot is the problem. The compressor should have a maximum temperature. If it exceeds this temp it is bad.

Recently an A/C service man touched the compressor and felt it was too hot just after running for 8-10 minutes only.???

Gents,

Could you check the tripping curve of the MCB, this seemse to be a starting current or an earth leakage problem that occurs when the compressor starts.

Three causes:

1-As said above the MCB tripping curve is not adapted to the compressor starting current

2-The compressor hydraulic system has a problem and the compressor starts at full load

3- There is an eath fault on the compressor circuit

The MCB has been there for several years. It is 16 Ampere rated. In the last 3 years, and even today the MCB does not trip. It is the ELCB/RCCD that is tripping.

How do i get the hydraulic system of the compressor checked?

My electrician checked the power supply point of the AC and the earth is not leaked there at least. The compressor is just one block in which the 3 wires lead and there is no problem there as well.

Breakers are cheap and they wear out. Air conditioners run a lot and the breakers get hot. Change it out if that does not solve probem then hire electrician!

I have bought new breakers that were no good!

Poor quality since most are imported from who know where.

Replaced 2nd time everything ok.

It seems you have covered all the power input possibility's, this then leads back to the compressor itself.

The starting load has possibly increased due to faulty operation of said compressor, in which case to confirm this a data logging meter should be inserted in the input lines to get some comparable readings .

Garth

Going with the information that you have already listed as tried. It looks to me like you may have one of the following. A bad compressor or the thermal shut off on the compressor is bad. If the compressor is tyring to restart before the system has had time to equalize its pressure (say you turn the thing back on right after it went off) the compressor will draw large amounts of current the thermal will at this point shut the compressor off. If it doesn't it would possibly trip the breaker. The other is a bad winding on the compressor. Note if it would shut off while running I would check to make sure the outside condenser coil was clean. One other possibility would be the thermostat points or start relay if it has one could be bad.

A senior A/C service man was here today. He checked the following;

1) While the A/C was on, he deliberately reduced temperature to cause the compressor to start. It started. Then over a period of 30-40 mins, the compressor turned off and and turned on twice automatically. All this while, the current measurement was in the normal range. He has come to the conclusion that the compressor's functioning is normal. The ELCB did not trip in his presence. That's the real problem. The ELCB trips mostly at night when the A/C has been turned on and run for at least 6-7 hours

Neverteless the ELCB has been replaced and doesn't trip anymore, I strongly advice that you have that airconditioner checked. A device that makes an ELCB trip is dangerous !
BTW. ... Does your new ELCB have the same mA rating than the original one ? (30mA, 100mA, 300mA) I suppose that for airconditionners a 30 mA is necessary because of the moist.

I have bought the same ELCB/RCCD of the same rating that was installed earlier.

Didn't see it posted anywhere but have you put an ammeter on it and know how much current it is drawing? Compressor may be starting to go bad. What is the current rating on the compressor/fan/total? Would be a good starting point. Check total resistance and it should be close to the sum of the start and run windings.

Didn't see it posted anywhere but have you put an ammeter

See post 6

More than likely one of two reasons:

1. The compressor is "short-cycling"; re-starting before the refrigerant pressure has had enough time to sufficiently decay (maybe your thermostat load anticipation is not set/programmed correctly?).

2. The compressor is "worn-out" and the bearings, vanes, and/or piston (depending on design type) mechanical interference fits are too great causing mechanical binding at random intervals.

The AC service man says that the compressor is working fine. He suggested me that I always keep the temperature setting between 20-25 degree celcius even though the A/C remote can take it down to 16 degree celcius. He says that keeping at 16 degrees, the compressor is always running and does not get time to 'rest' in which case it could get hot and trip. However its been 3 years since i've been running this A/C and never has such a thing occurred. Secondly, he has taken current ampere readings while the A/C has been runing and they seem to be in normal range.

What should I do to objectively rule in/out the two possibilities you mentioned? I mean how can i surely decide to say that the compressor is "worn-out" Cause a faulty compressor means a big issue.

A competent A/C service shop should have the the equipment necessary to measure & record the running and starting characteristics of your compressor. (voltage, amperage, and the high & low pressure sections)

Most residential A/C units have two windings; one for starting and one for running. It is very possible that the starting winding or one of it's components is bad. To check for this have the service tech install a amperage recorder on the starting circuit and record for a few days. In some cases the starting switch "sticks" and does not clear the starting winding in adequate time.

Other concerns that I have are:

Most residential outlet circuits are rated at 15 amps and are designated for intermittent loads less than 15 amps. If your A/C unit is rated at 16 amps you may well be tripping on an overload condition during high heating loads.

A/C units should have a dedicated circuit that does not supply power to any other device. You can verify this by turning the A/C supply CB off and checking all of your other outlet circuits for abscense of power. It may be that the outlet servicing your A/C unit is providing another outlet that now has something plugged into it and the combination of loads is greater than the breaker is designed for.

You need to verify that the ELCB feeding the A/C outlet provides the necessary time delay amperage curve to account for the compressor starting inrush. Normally the motor inrush current is nominally 2.5 - 3 times the compressor nameplate running amperage rating. For instance: In this case the compressor is rated at 16 amps so a standard residential circuit breaker rated at 15 amps nominal would have to sustain a starting load of 48 amps and a constant running load of 16 amps x (design derating factor). Obviously having the A/C unit plugged into a standard, non-dedicated outlet might work for a while but not for a long period of time. When the compressor was new and for the period of time it is in the "bathtub" (maintenance free performance time period) it would pull less amperage. As the A/C unit ages it has to work harder to handle the same heat load and will therefore pull more current. Hence one day the unit suddenly starts tripping the feeder breaker.

Another simple thing that often gets overlooked is that all of the A/C unit components affect the amperage draw, not just the compressor. If your condenser is restricted due to dirt, paper, plastic, bent cooling fins, etc. it will significantly add to the total current draw. Condenser fan mechanical binding and/or failure will cause high amperage conditions also. Evaporator fan abnormal conditions will also affect the total amperage draw and cause the feeder breaker to trip. Shut the power off the unit, and rotate the fans by hand feeling for rough vibrations and/or resistence. All of the fans should "free-wheel" for a few seconds after being activated by hand. If they do not do so, change them out. If your unit has a separate condenser fan control switch and the switch is not operating correctly, the unit will experience high pressure conditions that will cause higher than normal amperage. Verify that any time the compressor is running, the condenser fan is also running.

This is probably an overwhelming amount of information for most laymen and would best be served by being reviewed and administered by a competent service technician. Hopefully though it will give you some ammunition for asking the right questions. Good luck.

The Tripping still continues. Recently another A/C serviceman was here to check. After putting on the A/C, and observing for a few minutes (8-10 mins) he felt that the compressor was overheated by touching the outside of the compressor. He reckons that refuelling a small quanitity of the refrigerant R-22 (about 150-200 grams) will add some efficiency to the compressor.

Is this possible? I mean can a worn-out refrigerant be the reason for tripping?

If your compressor is running all the time then it could be low on gas assuming it is big enough to cool your room in the first place. In this case the compressor will be running hotter than it should be as low gas return will not be helping to cool the compressor, also will damage your motor if left like this.You will soon know that after the gas is added if your cooling does not improve your compressor is damaged.

The refrigerant is not warn out. It may have leaked a small amount. or there could be a restriction, causing thr flow to be deminished resulting in warmer return freon to the compressor.

The first thing to check is that the cable downstream of the <...ELCB...> is in good enough condition for a trip not to occur. Did the <...electrician...> carry out a test on the cable?

It wouldn't be the first time a dead mouse has appeared across line and earth, or across neutral and earth, for example. A qualified Electrician will be able to determine where the problem is on the cable by measurement.