How can an appliance work better when the AC Mains stabilizer is removed?

[Wrichik Basu]

I don't know whether this question is suited to this forum specifically, but since it deals with electronics, I am putting it here.

We have an old air-conditioner, bought in 2007. As you can understand, it is one of the old models running on R22 gas and it switches off the compressor when the proper room temperature is reached (rather than varying the compressor speed).

In our region, voltage fluctuations are major problems for our appliances. So, all costly appliances have to be protected with a voltage stabilizer. The AC also has one.

Recently, this stabilizer started malfunctioning. The relay is electromechanical, and it often gets stuck on one side, resulting in either a very high voltage or a very low voltage.

Yesterday, I removed the stabilizer. And all of a sudden, the AC started working brilliantly. For the last few months, it was not cooling properly, something that indicated gas leak or low gas pressure. But all tests were fine, so we were thinking about changing it. But when I removed the stabilizer, the AC started cooling in a much better way. It seemed we were back in 2007 or so.

In India, the rms AC is around 220V to 230V, which dips to around 200V at night and sometimes surges all of a sudden to 250V. During the last world cup, we have experienced voltages as low as 140V. That is why we had to install the stabilizers.

The work of a stabilizer is to maintain the potential difference. If it gives a proper voltage output (in the range of about 210V to 230V), how can it affect the performance of the AC? Is it just coincidence, or is there science behind this?

 

[Borek]

If it gives a proper voltage output

If.

Are you sure it does it all the time, regardless of the load?

 

[Wrichik Basu]

If.

Are you sure it does it all the time, regardless of the load?

When the compressor starts, there is a voltage drop, and the line voltage falls to 200V. The stabilizer then steps up the voltage to 230V. The stabilizer has a display which shows these readings. Moreover, I have checked through a multimeter as well. The only problem that I have faced is the relay getting stuck. Otherwise, it worked fine. The voltage supply was good irrespective of the load, and in the range 210V to 230V.

 

[anorlunda]

The work of a stabilizer is to maintain the potential difference. If it gives a proper voltage output (in the range of about 210V to 230V), how can it affect the performance of the AC?

Your stabilizer is not familiar to us in the Western World. But it sounds like an automatic tap changing transformer.

If it is malfunctioning and giving your AC the wrong voltage, that would affect the performance of the AC. The relay and the taps are both mechanical, and subject to wearing out or failing. The voltage sensing device, no matter what type, can also fail.

It is possible that the quality of your local power grid has improved over the years, making a stabilizer unnecessary. It is also possible that the stabilizer is needed only certain times out of the year when the grid is most strained.

If you want to troubleshoot that stabilizer, measure the voltage at the AC at times when it performs poorly. There is also a repair technique that was familiar to us who grew up prior to 1980. Kick the stabilizer. If the AC performance changes, you have direct evidence that the stabilizer is the cause.

 

[Wrichik Basu]

If it is malfunctioning and giving your AC the wrong voltage, that would affect the performance of the AC. The relay and the taps are both mechanical, and subject to wearing out or failing. The voltage sensing device, no matter what type, can also fail.

The cooling of the AC had decreased before the relay got stuck. So, apparently the efficiency of the AC had decreased when the stabilizer was working fine.

It is possible that the quality of your local power grid has improved over the years, making a stabilizer unnecessary. It is also possible that the stabilizer is needed only certain times out of the year when the grid is most strained.

The quality has not improved, and at times, we do get voltages around 190V. This is mainly in summer when all the neighborhood ACs are working. Don't know what happens in winter.

 

[anorlunda]

The cooling of the AC had decreased before the relay got stuck.

But you said

And all of a sudden, the AC started working brilliantly.

That suggests that the AC is OK.

The stabilizer can malfunction even if the relay is not stuck. The stabilizer still sounds like the most likely source of trouble.

 

[Wrichik Basu]

The stabilizer can malfunction even if the relay is not stuck. The stabilizer still sounds like the most likely source of trouble.

That could be true. I wanted to test the stabilizer with a variable AC voltage generator. Let me see if I can get hold of one from somewhere, otherwise I will call the service personnel. The reason I want to test it myself is that, these people often lie about what is actually faulty. So, I wanted to find that out by myself.

 

[sophiecentaur]

That could be true. I wanted to test the stabilizer with a variable AC voltage generator. Let me see if I can get hold of one from somewhere, otherwise I will call the service personnel. The reason I want to test it myself is that, these people often lie about what is actually faulty. So, I wanted to find that out by myself.

This sounds like a specific problem and there are many possible answers.
I have found, in cases like yours, that it's often worth while to trawl around the Internet for appropriate forums . The most unlikely forums can sometimes be found. There's a UKWhiteGoods forum which has dug me out of a hole on several occasions when a Fridge Freezer was dodgy, for instance. The problem was a well known one amongst Hotpoint owners and I was given the right advice. The item worked well for another fifteen years. I doubt that UKWhiteGoods will help with a system like yours but you should consider spending a half hour or so, searching. Of course, you may need to be inventive with your search criteria but do include the specific make and model. You might be pleasantly surprised. You may be unpleasantly surprised at the unpleasant language and rudeness on some such forums but hell, the advice would be free!

 

[anorlunda]

Did you try the kick test first?

Edit: I don't see where a variable AC supply will help much in diagnosis. It certainly can't help with repair.

 

[Wrichik Basu]

Did you try the kick test first

Can you elaborate a bit on that?

Actually, I don't want to repair it. I want to find the fault, and let the service person repair it properly.

 

[anorlunda]

Can you elaborate a bit on that?

There is also a repair technique that was familiar to us who grew up prior to 1980. Kick the stabilizer. If the AC performance changes, you have direct evidence that the stabilizer is the cause.

 

[Wrichik Basu]

@anorlunda I had already read that from your first post. Do you mean to say I should literally kick the stabilizer?

 

[anorlunda]

@anorlunda I had already read that from your first post. Do you mean to say I should literally kick the stabilizer?

YES!

I used to have a voltage regulator in my car that stopped working. I hit it with a tire iron and it worked OK for a few more weeks. I did that every few weeks for the remainder of the life of that car.

Relays and transformer taps are moving part mechanical devices. They can stick. The shock of a hit can unstick them.
Electrical contacts can be intermittent. The shock of a hit can shake them making new contact. Grabbing the wires and shaking does the same thing.

 

[Borek]

Yep. Especially when it comes to TV sets made here, hitting them was a common thing. There even was a recurring joke: drawing with a TV set, hammer and a sign "vertical bands - hit once, horizontal bands - hit twice".

 

[Wrichik Basu]

I used to have a voltage regulator in my car that stopped working. I hit it with a tire iron and it worked OK for a few more weeks. I did that every few weeks for the remainder of the life of that car.

Relays and transformer taps are moving part mechanical devices. They can stick. The shock of a hit can unstick them.

I could free the relay by a slightly different trick. After kicking once, I switched it on and off a large number of times. The relay could come back to normal, but whenever a load is applied, it is again stuck. That's where I am afraid. For example, if it gets stuck, giving high output voltage, and at that point of time I am sleeping, not only will the appliance be damaged, but there will be a chance of fire due to overvoltage. I will call the service centre some time next week and ask them to change the relay.

Meanwhile, I am designing an Arduino circuit with a solid state relay to measure and control the output voltage of the stabilizer, so as to prevent any mishap. SSRs work better than EMRs in the sense that they do not get stuck like these. I don't know why stabilisers don't use SSRs.

 

[Tom.G]

I don't know why stabilisers don't use SSRs.

1. Relays are much more robust to both overvoltage and overcurrent
2. Relays are usually lower cost
3. Relays are more readily available
4. If using a double throw relay, many inherently can not have both the Normally Open and Normally Closed contacts closed concurrently. This can happen with SSRs and could be rather dangerous, as in shorting two taps on the transformer.

If the SSR is in a moderately benign electrical environment they have a longer life than a mechanical relay.
A typical 10Amp rated relay has a rated life of 100 000 to 500 000 electrical operations (resistive load, load dependent for reactive loads)
(life data from pg.9 of: http://literature.rockwellautomation.com/idc/groups/literature/documents/td/700-td552_-en-p.pdf)

Cheers,
Tom

 

[anorlunda]

Based on what you said, you don't have enough evidence to prove that a sticky relay is the problem. There can be malfunctions in the voltage sensor, and in the transformer taps.

Is there just one relay? Single throw? Single pole?
How many taps are there?
Our guess for the mechanism was that a auto tap changing transformer. Is that confirmed?

Can you find nameplate information, make/model/ratings/schematics for this device?

 

[Wrichik Basu]

Based on what you said, you don't have enough evidence to prove that a sticky relay is the problem. There can be malfunctions in the voltage sensor, and in the transformer taps.

Relay is just one of the problems. There should be others that I don't know about.

Is there just one relay? Single throw? Single pole?
How many taps are there?
Our guess for the mechanism was that a auto tap changing transformer. Is that confirmed?

Can you find nameplate information, make/model/ratings/schematics for this device?

Schematics are not shared with customers. https://www.microtekdirect.com/product/microtek-em-4150/ is the web site. See if it can help you. I can open up the stabilizer an post an image. I will do it soon.

 

[anorlunda]

I'm afraid that you have no choice other than to call the repair technician.

It was interesting to see the difference between and Indian and American technology vendor. American vendors provide more information, manuals, and forums under the "customer service" department. I suppose it relates to the competition between multiple vendors and the power that gives to consumers.

 

[Wrichik Basu]

It was interesting to see the difference between and Indian and American technology vendor. American vendors provide more information, manuals, and forums under the "customer service" department. I suppose it relates to the competition between multiple vendors and the power that gives to consumers.

True. In many cases, it is so difficult to contact the customer service that people get frustrated and call in local electricians to do the job.

I'm afraid that you have no choice other than to call the repair technician.

Ok. However, thanks for the support.

 

[sparkie]

True. In many cases, it is so difficult to contact the customer service that people get frustrated and call in local electricians to do the job.

Ok. However, thanks for the support.

And we are always happy to help for a small phenomenal fee :). Generally, when calling an electrician, we like to be given symptoms and ideas, not what you *think* is wrong. We will troubleshoot the devices ourselves using your symptoms as a starting point.

That voltage stabilizer looks like it uses caps to produce a DC voltage and then has IGBT's to synthesize smooth power from there. This is pretty common on VFD's and phase converters these days. Had to add something useful so I could get my joke in.

Also, I just noticed the OP's original question. The bottom line is that your device is working better because it is getting proper power. Your voltage stabilizer may be giving your device proper RMS voltage, but you are not getting proper, clean POWER for whatever reason, and there are many that it could be.

Clues that lead me to this starting point from your initial concerns: The relay doesn't always pull in / stay pulled in. The compressor is not running properly, but runs just fine without the stabilizer. These lead me to believe that your stabilizer is having issues with inductive loads.