Team-BHP - The Home Appliance thread

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Originally Posted by graaja (Post 4769768)

No. There is no mechanical timer. Everything is electronically controlled. The service technician replaced three temperature sensors (NTC thermistors). All these are connected to the controller board which has a microcontroller that implements the measurement and control logic.

In that case, do they not have a diagnostic scan for the main controller board. The sensors shouldn't be the culprits as they are very simple devices.
I hate how complex these simple devices have become. That's why my next fridge is going to be a commercial one as they are much more repair friendly.
My current 18 yr old LG fridge is also showing the same issue as yours. There seems to be a short somewhere in the wirinv which is not allowing the heater to be turned on even when the timer is working fine. This can't be repaired without ripping out the whole wiring which is embedded in the poured insulation. So for the time being, I manually defrost the freezer coils with a hair dryer.
The commercial versions allow the whole component area to be pulled out like a drawer and repair can be carried out very easily.

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Originally Posted by rdst_1 (Post 4769764)

ELCBs used to check earth leakage current. They have now been replaced by RCCBs (Residual Current Circuit Breakers) which check for the difference between the currents of the live wire and neutral wire. For any power point, you will need an individual RCCB which trips if the difference is 30mA, because 30mA is all it needs to stop a human heart.

You can get them for the distribution box. I had one thus fitted in my London house in 1980-something.

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Edit - The vendors whom I have dealt with have told me that both these devices are a constant nuisance as one usually doesn't have perfect earthing at home and these devices keep tripping. They told me that they only install them because it is needed to get an electric connection and they remove them afterwards because of the constant tripping.

No, they do not constantly trip (although experience with our wiring here may differ!) but it is strongly recommended that equipment like fridges and freezers are not connected to these devices.

I have one of these things here. It covers the line to our submerged drainage pump. I don't think it has ever tripped.

This is from the Wikipedia article on RCD/RCCBs

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Whole installations on a single RCD, common in older installations in the UK, are prone to "nuisance" trips that can cause secondary safety problems with loss of lighting and defrosting of food. Frequently the trips are caused by deteriorating insulation on heater elements, such as water heaters and cooker elements or rings. Although regarded as a nuisance, the fault is with the deteriorated element and not the RCD: replacement of the offending element will resolve the problem, but replacing the RCD will not.

From another website -

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Some of the most common appliances that tend to trip are electric kettles, toasters, range-hoods, Hair appliances, fridges and freezes as they tend to be used a lot, which causes them to wear out faster.

Not using a RCCB with a device which you touch regularly and has a metal body defeats the purpose of such devices.
There are companies which have developed RCCBs which can handle higher inrush currents and surges without tripping.

It is better to have individual RCDs installed at appropriate power points because that makes sure that the whole home doesn't lose electricity when a particular device causes the RCD to trip.

Even I wasn't willing to believe the shopkeepers but if you search online you will find that 'nuisance tripping' is definitely something that happens. It is not the device which is wrong but it is just not smart enough to differentiate between actual current fault and other faults which can cause the same current difference.

RCDs were an improvement over Current sensing ELCBs which were themselves improvement over Voltage sensing ELCBs. The RCDs are better over ELCBs because they work even if your earthing is incomplete or broken. So if one of your connections was leaking current to the plumbing and eventually to earth an RCD would trip but an ELCB won't.

So eventually we might get smarter RCDs.

Quote:

Originally Posted by rdst_1 (Post 4769764)

The vendors whom I have dealt with have told me that both these devices are a constant nuisance as one usually doesn't have perfect earthing at home and these devices keep tripping. They told me that they only install them because it is needed to get an electric connection and they remove them afterwards because of the constant tripping.

Thanks for the info on RCCB. And I love the part about earthing. Reminds me of our PWDs which puts speed breakers on main roads, at intersections rather than on the minor roads.

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Well, as I said, mine did not nuisance trip. Although, as I also said, connection of fridges and freezers was not recommended.

But I have my own story about the thing. It was late evening. I was stuck behind a washing machine, waiting to be pushed back into its kitchen gap, doing something with the electricity supply, which I knew was turned off. I cut a cable to length, and poof! The rcb tripped. Despite the live being disconnected it sensed something from the earth/neutral. And there I was. In the dark.

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Originally Posted by meerkat (Post 4769032)

Let me see, ... a bulb in such a testing device would draw how much power? 100W max? How is that supposed to trip even a 6A MCB?! such a bulb connected between live and earth is supposed to light, if the earthing is done even minimally right, no cause for worry! The neutral wires themselves are connected to earth somewhere upstream after all! -- Or is this "jugad" device something special in some unexplained way?

.

The intent of this jugaad is to check the RCCB/ELCB for it's leakage tripping ability and not for it's load tripping one. Also, this is a easy way to find out if a plug point has proper grounding or not.

I do not know any tool/tester available which will be able to load test a circuit which is controlled by a RCCB/MCB to above it's specified load and see if it trips or not.

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Originally Posted by sagarpadaki (Post 4770112)

Some RCCB/ELCB's come with a inbuilt test button. One such example is shown below. The trip amps limit ( delta current ) is usually 30mA.

The Home Appliance thread-somb751160_abcd751160_5d1b220b5e19f.jpg

The above is just an random internet image.

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Originally Posted by srini1785 (Post 4770886)

Some RCCB/ELCB's come with a inbuilt test button. One such example is shown below. The trip amps limit ( delta current ) is usually 30mA.

The above is just an random internet image.

Yes, the test function tests the tripping by introducing some leakage current. I was talking about a device which will make the MCB/RCCB trip when it goes beyond it's rated load.

For example if a MCB/RCCB is rated at 16 Amps, then there is no test device that i know of that will hook onto the MCB/RCCB and draws >16Amps load to check if it trips or not.

Quote:

Originally Posted by rdst_1 (Post 4769775)

In that case, do they not have a diagnostic scan for the main controller board. The sensors shouldn't be the culprits as they are very simple devices.

My current 18 yr old LG fridge is also showing the same issue as yours. There seems to be a short somewhere in the wirinv which is not allowing the heater to be turned on even when the timer is working fine. This can't be repaired without ripping out the whole wiring which is embedded in the poured insulation. So for the time being, I manually defrost the freezer coils with a hair dryer.

The engineer did not run any diagnostic scan. I doubt if there is such a process or if the engineer is capable of this.

So, I decided to take up things in my own hands and opened up the freezer compartment which has the cooling coil behind the wall. This is what I saw. Definitely a problem.

Then I opened up the control panel and checked if there is continuity between the defrost sensor and the input connector.

I was able to read the same resistor at the input connector as at the sensor's connector inside the freezer compartment.

Then I removed the board and checked if the traces from the input connector to the microcontroller are good. No disconnect in tracks. But I found possible dry solder in the input connector (marked yellow).

The Home Appliance thread-dry-solder.jpg

I cannot be 100% sure, but such a dry solder can cause random issues (I had seen a defrost sensor error indication on the display console a couple of times - the temperature indicator flashes).

So, I have done a re-flow soldering of the input connector and have put back the board inside the fridge. Will observe a couple of days and see if the problem is solved.

If the problem is not solved, I plan to revert back to the age old method of periodic defrosting by adding a smart plug and scheduling to turn off the fridge every day for a short while.

EDIT: Not sure how defrosting works in this fridge. There are a couple of blowers inside the freezer, but these look like for circulating air than to defrost.

Quote:

Originally Posted by sagarpadaki (Post 4770902)

Yes, the test function tests the tripping by introducing some leakage current. I was talking about a device which will make the MCB/RCCB trip when it goes beyond it's rated load.

For example if a MCB/RCCB is rated at 16 Amps, then there is no test device that i know of that will hook onto the RCCB and draws >16Amps load to check if it trips or not.

A few things :

Dead short : Phase touches neutral. MCB to the rescue.

Earth fault : Phase touches the metallic part of the appliance. ELCB to the rescue.

MCB and ELCB are two different devices. While a MCB is a safety device against a short,i.e when phase touches the neutral, the ELCB is a device that trips when there is a "earthing" i.e when phase touches the metallic part of the appliance. The earth wire is specifically designed to conduct this current safely to the ground.

During a dead short, the current is significantly greater than the rated current of 16A. While during a earth fault, its normal volts and current except that the circuit gets completed through the person who touches the metallic part of appliance. A MCB is unable to detect a earth fault. Hence the need for a ELCB.

The 10/12/16A MCB's are the rating of the MCB's , i.e what current they can safely conduct. I don't think they would trip if a 16A MCB conducts 17A for a long time. They follow what is called as the IDMT curve. If current raise suddenly withing a very short period of time then a MCB trips.

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Originally Posted by srini1785 (Post 4770919)

A few things :

The 10/12/16A MCB's are the rating of the MCB's , i.e what current they can safely conduct. I don't think they would trip if a 16A MCB conducts 17A for a long time. They follow what is called as the IDMT curve. If current raise suddenly withing a very short period of time then a MCB trips.

I was not aware of this part. Thanks for the info. I was under the impression that the MCB/RCCB trips if the current through it goes beyond the rated value.

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Originally Posted by graaja (Post 4770916)

EDIT: Not sure how defrosting works in this fridge. There are a couple of blowers inside the freezer, but these look like for circulating air than to defrost.

Your refrigerator symptoms are common with many micro controller controlled refrigerators. Typically, the iced metal fins show that the fans behind it is not running. Most of the time, the fan motor is a shaded pole motor. The same kind you will find in your microwave turntable and its cooling fan. They are low power induction motors with little to go wrong.

How to proceed:
1. Turn off the power supply. Use your hair dryer to heat the iced fins free.

2. Sometimes, there is no path left for the fan to move the air. When you defrost the fins, the motor might start and everything will become normal for the timebeing.

3. The shaded pole motor still uses bush bearings. It works long hours. So in a few years, the bearing will come slightly skewed. It will continue to work, but will have starting problem. Substitute the motor. They don't cost much - around Rs.600-900 depending upon the size.

4. If the motor doesn't run, Check if it gets its supply. No supply and you are in trouble. It means a problem with your control board.

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Originally Posted by Prowler (Post 4770932)

Your refrigerator symptoms are common with many micro controller controlled refrigerators. Typically, the iced metal fins show that the fans behind it is not running.

Thanks a lot for the detailed troubleshooting tips! I will check this as well.

I have also downloaded the fridge's service manual (paid $4.5 for this) which has all the details of diagnostics available in the fridge with detailed flowcharts to diagnose various systems. Will also perform some diagnostic checks and update.

Actually the fan you see in front of the coils when you open the freezer part has little to no role in defrosting. It is only to recirculate the cold air from the coils to the refrigerator portion. The system actually has a heater element which switches on and off and stops ice from depositing on the coils. In older refrigerators, it was done with a mechanical timer which switched on the heater for a fixed time after every few hours. These new fridges seem to have a sensor for the same.