[IshaanIan]

Originally Posted by GTO

My AC tech tells me to avoid inverter ACs as they are too efficiency-focussed. He says that, being how particular about room temperatures as I am, it's best to buy a conventional type AC, even if the power usage is higher. True?

Might be some truth in this considering it is not the first post I am reading mentioning the same. That said, I have had an excellent experience with Daikin JTKJ series inverter ACs. They are super efficient, maintain temps well, streamer function helps eliminate smoke and other odors. I find overall that they work as advertised and offer trouble free performance. My dad had a very crippling brain stroke few years back and one of the quirks he developed is that he is extremely temperature sensitive to the point where he gives instructions on opening or closing windows, turning on or off fans in adjacent rooms as well. But he sleeps well and has no complaints about the Daikin JTKJ unit in his bedroom whether used in the summer or in the winter. I am considering buying a cheaper yet seemingly very efficient Onida unit for another room in the house but such posts are making me wonder if I should just cough up the extra money and go for another Daikin JTKJ unit.

[Turbanator]

My AC tech tells me to avoid inverter ACs as they are too efficiency-focussed. He says that, being how particular about room temperatures as I am, it's best to buy a conventional type AC, even if the power usage is higher. True?

Inverter ACs unlike regular, always keep the compressor running, at variable speeds depending on the temperature you set and the actual room temperature. Regular Airconditioners, on the other hand, work on On & Off (compressor) so you will see room temperatures getting cool and then after the compressor trips, getting hot before the compressor turns on again. I dont like this variation and also sometimes the noise associated with this. Electric saving is usually a byproduct. I will not buy another regular AC ever, in fact, even at the slightest fault, I replace the regular with an Invertor type.

Originally Posted by GTO

The new Mitsubishi AC (their flagship model, apparently) is still unable to consistently maintain temperatures all through the night. Whether in auto mode or in manual mode (22 or 23 with blower level 2), it's all fine until 0430 - 0500 hours in the morning. Then, depending on the setting, things either get too cold or too warm.

I usually keep around 25 on most of the inverter ACs. But assuming you are already feeling hot at 23, this may not work for you. Nevertheless, give it a shot tonight at 25-26

The only reason in your case can be the mismatch in controlling the grill temperature vs room temperature, I will wait for the change to be done by the technician.

Secondly, I will also try to sleep in another bedroom and see if there is something else disturbing your sleep and not just the AC.

Originally Posted by Sheel

This is what I was / am thinking, but the BHPians made me cancel this [(time will tell)] and have ordered a Daikin 4 star inverter unit.
Room temperature, completely dark room and complete silence is what I need, any fluctuation which disturbs my sleep cycle and my day is ruined. Hence no phones in bedroom.

Daikin inverters or for that matter most inverters work well when the Voltage is constant, in case of fluctuations, these go kaput very easily. I will avoid a Daikin and instead pick a Mitsubishi from the longevity point of view besides the extra cooling on the latter.

[Sheel]

Originally Posted by Turbanator

I usually keep around 25 on most of the inverter ACs. But assuming you are already feeling hot at 23, this may not work for you. Nevertheless, give it a shot tonight at 25-26

I keep it at 26 with fan at low setting. That is my ideal.

Originally Posted by Turbanator

Secondly, I will also try to sleep in another bedroom and see if there is something else disturbing your sleep and not just the AC.

Yup, this is what I suggested, may help in knowing the cause.

Originally Posted by Turbanator

Daikin inverters or for that matter most inverters work well when the Voltage is constant, in case of fluctuations, these go kaput very easily. I will avoid a Daikin and instead pick a Mitsubishi from the longevity point of view besides the extra cooling on the latter.

With a new 200KV transformer barely 100 meters from my home, voltage is almost constant and I should be getting 3 phase armored cabling till my home in few months, should eradicate any further fluctuations. May fit a stabilizer till then. (Looks very ugly to me, those stabilizers).

Unsure of longevity in modern appliances, my old AC is going strong at ~15 years, we all have seen refrigerators / washing machines working well at ~20 years, but, now, nothing barely lasts for ~ 5 years, with ever increasing price.

[@og_adi]

Originally Posted by GTO

My AC tech tells me to avoid inverter ACs as they are too efficiency-focussed. He says that, being how particular about room temperatures as I am, it's best to buy a conventional type AC, even if the power usage is higher. True?

I'm not the kind of person who'd dive deep into technical stuff but from my personal experience, I would recommend otherwise. We have two 1.5 tonne ACs functioning in different rooms (Voltas (inverter) and a Panasonic (conventional)). While I agree the conventional ones can really bring down the temperature in a room, I hate how the airflow is stopped abruptly everytime a particular temperature is reached. It's a real pain especially when one is sleeping and trust me, tucking yourself in and out of a comforter is painful . With inverter ACs, though the room doesn't turn as chilly as the one with the conventional ones, the room is pleasant and remains so until the AC is switched off. If you need an absolute chiller, get yourself a more powerful AC or set a lower temperature. Another point to note is the sound that the conventional ones make. It isn't the same with inverter ones and when you have a fan switched on, you can barely hear one. My dad who isn't really a fan of ACs has finally made peace with our Voltas thanks to it being really silent. Voltas is easily a recommendation from my end. Their service has been good and the AC performs well.

P.S- Do they still sell conventional ACs? Last I visited Croma, they said normal ones were no longer sold.

[Thad E Ginathom]

Originally Posted by GTO

The new Mitsubishi AC (their flagship model, apparently) is still unable to consistently maintain temperatures all through the night. ...

We have three, and I have been one of those praising the brand on this thread, so apologies if due!

Actually, with the 2.2-ton model we have in our main hall, which is almost TOTL, I have noticed that it never stops cooling. This is fine in the day, but given my night-bird hours, it can get a bit cold at 3.00am. I don't like to cold: we keep it on 28. On 30, the room does warm up a bit.

Our first inverter machine, Sharp, was brilliant: perfect temperature control. Sadly, it was a complete disaster for reliability/service, and we literally threw it away.

Originally Posted by @og_adi

P.S- Do they still sell conventional ACs? Last I visited Croma, they said normal ones were no longer sold.

I'm sure they are still available. Mitsubishi still sold them last time I looked.

[thanixravindran]

Originally Posted by GTO

Guys, this is really becoming a royal pain. Would appreciate suggestions.

My AC tech tells me to avoid inverter ACs as they are too efficiency-focussed. He says that, being how particular about room temperatures as I am, it's best to buy a conventional type AC, even if the power usage is higher. True?

Looks like the AC thread is heating up rather than cooling people

I have not had any issues with the temperature control with my inverter ACs. I hate the Fixed speed ACs that they switch OFF or ON and impacting my sleep. If it is possible please ask to install external temperature sensors with display in your room by the AC people or ask them to take your AC away and log the temperature with a data logger in their testing lab for 24 hours. This will provide the temperature variation graph to see whether AC is controlling or not.

I believe there is a possibility of humidity control issue affecting your air conditioner. In the early night, your humidity may be comparatively less and AC is just switched ON. So it is removed using the evaporator coil properly. In the early morning, outside temperature itself would have dropped but with increased humidity and your humidity control becomes less effective. So please ask the technician to check the evaporator coil or humidity control.

Originally Posted by Sheel

This is what I was / am thinking, but the BHPians made me cancel this.

I am one of them. I am a big fan of inverter ACs as in Residential AC's, it is one of the significant invention to become energy efficient as well comfort.

Originally Posted by Turbanator

most inverters work well when the Voltage is constant, in case of fluctuations, these go kaput very easily.

The only comparable difference in PCBs is there is a Power board in ODU in Inverter ACs. They have large IGBTs similar to inverters and heat dissipation is a problem and there were failures earlier due to that. I believe we have crossed that phase with the latest ACs.

[Mr. Nobody]

What's a good Stabilizer brand to protect a split AC ? Is the voltage range like 170-270 all that is to be checked when comparing between them ?

[Behemoth]

Originally Posted by Mr. Nobody

What's a good Stabilizer brand to protect a split AC ? Is the voltage range like 170-270 all that is to be checked when comparing between them ?

Go for Vguard stabilizers - they are very good and last very long. I have been using on all my Acs and till date not even one has failed. (In 10 years of usage too).

[r_devakumar]

Originally Posted by Turbanator

Inverter ACs unlike regular, always keep the compressor running, at variable speeds depending on the temperature you set and the actual room temperature. Regular Airconditioners, on the other hand, work on On & Off (compressor) so you will see room temperatures getting cool and then after the compressor trips, getting hot before the compressor turns on again. I dont like this variation and also sometimes the noise associated with this.

I am very sensitive to change in temperature and noise during sleep (and also when I listen to music). It is a big relief for me after I changed from regular AC to Inverter AC. Inverter ACs are best suited for Bedrooms.

[Thad E Ginathom]

I can't say, but I would have thought that compressors on inverter ACs should be able to turn off, as in no cooling needed. The controller would then turn them on again, at a low RPM, voiding the spike of starting up to full speed.

Comments?

[Gansan]

^^ I have a 3 star Whirlpool inverter ac in the bedroom, and the outdoor unit is placed just outside the window. During night times I can hear the out door unit's fan stop and start from time to time. I don't know how it will do that if the compressor keeps on running continuously.

[GTO]

Thanks guys for all the suggestions. Am discussing them with Mitsubishi. They are in the process of changing the PCB & indoor / outdoor sensors.

@ Turbanator: Been sleeping in a different room since 2 nights. Slept like a baby for 8 hours .

Originally Posted by thanixravindran

I believe there is a possibility of humidity control issue affecting your air conditioner. In the early night, your humidity may be comparatively less and AC is just switched ON. So it is removed using the evaporator coil properly. In the early morning, outside temperature itself would have dropped but with increased humidity and your humidity control becomes less effective. So please ask the technician to check the evaporator coil or humidity control.

Thanks! Forwarding this to them right away.

[sagarpadaki]

Originally Posted by GTO

Thanks guys for all the suggestions. Am discussing them with Mitsubishi. They are in the process of changing the PCB & indoor / outdoor sensors.

@ Turbanator: Been sleeping in a different room since 2 nights. Slept like a baby for 8 hours .

Thanks! Forwarding this to them right away.

AFAIK, there is no humidity control mechanism in an AC. The humidity in the air is condensed onto the evaporator coil and drained out via the drain hose.

Since you say you slept well in another room, is the room size vs the AC type/brand/tonnage different from your regular room?

I suggest you get a digital thermometer and keep it on your bedside. See if the temperature of the room is around the same as the one set on the AC.

Also check if the evaporator coil in the indoor unit is clogged with dust. That also impacts cooling when the AC is run for long time .

[thanixravindran]

@Thad - You are 100% right. Inverter compressors do switch OFF like Fixed speed compressors. It is a myth that service technicians tell that inverter compressor never switches OFF.

I will write little bit more on the ACs in the post.

In normal operation, when we set a temperature (Set Point temp), there will be a 'Hysteresis' band of Hi and Low cut off points (Technical term is temp differential). This will remain irrespective of whether it is Fixed Speed or Inverter compressors as after all they are PID controllers. Generally the regulated temp of any space is between 20 to 30 deg C (68 to 86 F). The hysteresis manufacturers set is +/- 1 deg C (2 F) which is the acceptable standard for human comfort/discomfort though humans can sense a change of +/- 0.5 deg C. AC can easily sense +/- 0.5deg C (1 F) and can be allowed as finer set point (Blue star has one precision inverter) but tighter control with +/-0.5 deg C will make frequent switching ON/OFF the compressor and its driver motor which will result in premature failure.

One advantage of temperature is, it is slow time varying phenomenon to be sensed by us and there is good time to control unlike lights which is visual and needs instant control. The time to reach the limits (and sensed) is determined by the heat load added to the room (not only by us but also the seepage through wall/doors). General design practice is compressors are not shut down within 10 minutes. So, the control algorithm allows 'overshoot' in a fixed speed compressor to prevent this and you will see a little cold or warm at that time (Prolonged turn ON or Prolonged turn OFF) some times. Inverter compressors can start up at any speed and can easily modulate the temp swing and is energy efficient. Main savings come from this maintaining temperature after reaching the steady state operation initially. Refer the Bijilibhacho article I shared that shows the calculations which are correct.

There is another energy efficiency technique called 'Dead band hysteresis' which is used to keep the compressor cut off at a higher range say within +/- 2 deg C rather than allowing adjusting to the set-point temperature during seasonal change over months (It is a pain to change set-point schedules). This is mostly done in Thermostats as 'configurable auto' mode. As end user you can choose within a range once and leave it. I do not know whether Indian AC do this in auto mode.

One additional information - Some times in small server room instead of a central HVAC, a packaged air conditioner is installed to maintain the temperature. Here human comfort is not needed but needs the set-point to be made with very less temperature differential. This does not mean compressor is always ON. Rather the algorithm is reworked to always allow overshoot of - 2deg C or more (overcooling) to cut the compressor OFF and the Hi temp point is set point itself which will trigger the compressor to switch ON. So the hysteresis graph will get shifted below the Set-point.

PS: All of this is only Residential air conditioning (Packaged air conditioner and Thermostats) and the commercial HVAC is completely different with multi stage heat dissipation and recovery. So the techniques are different but principles remain same.

Edit: Adding a point about Humidity. We always had Humidity sensor to sense and control of humidity (Relative Humidity) though there is no setting for end user to set a value. It is exactly as I told earlier or sagarpadaki has explained in post too. Our ACs do operate as dehumidifier in dry mode and general setting is 50% RH. This is very useful in rainy/cold days and prevent the condensation/ice formation in evaporator oils. My old Samsung AC used to show the humidity as well in display while toggled. I agree humidification action is not there but we generally don't need it in cooling.

[Thad E Ginathom]

Originally Posted by sagarpadaki

AFAIK, there is no humidity control mechanism in an AC. The humidity in the air is condensed onto the evaporator coil and drained out via the drain hose.

I agree with that. There is no monitoring or specific control of humidity. Lowering of humidity is equally desired to lowering of temperature, but it is also a side effect. Simply, water from the air condenses out as it is cooled by the indoor unit. Warm, damp air in; cool, drier air out.

It happens even at lower cooling rates, to the extent that, at night, lower humidity is actually more important than lower temperature. That (and the white noise covering external noise) is why I sleep with AC 365 days a year. I could live with 1/2 to 2/3rds of Chennai's night temperatures (but wife couldn't) but not with the humidity,