What is this Dry Mode Control in Air Conditioner?

Those who have newer air conditioners bought in recent years will notice that there is an additional button in the remote controller.  This button is called "Dry Mode".  Some like it as they claimed it could save energy; some just ignore it completely.   This button is not available in the older models. What is this button and how does it work to provide cooling?

Why The Button?

Our body is sensitive to temperature as well as humidity. When the temperature is hot or cold, our bodies can feel it immediately. When the humidity is high or low, we might not feel it immediately but over time, our body will react to it. 

This is because 1/2 to 3/4 of our bodies are full of water. When water evaporates fast enough from our bodies, we will feel the sensation.  The feeling is just like we are under a fan.  The air blowing towards us evaporates vapor from our bodies.  The faster the airflow,  the higher the evaporation, the better will be the cooling. 

The air conditioner is also an air dehumidifier but not as efficient as a real dehumidifier.  When it cools the air,  it also removes water vapors from the air.  This is a natural cooling process. The dry mode button will instruct the air conditioner to operate more like a dehumidifier.

 

The dry mode will be particularly useful in tropical countries where humidities are usually high.  The dry mode can help to lower humidity in the room more quickly than the normal cooling mode.

 

How Does it Work?

As a simple illustration of how airconditioning and dry mode works,  if the air conditioner's airflow is strong, it is working as an air conditioner; on the other hand, if the airflow is reduced, it is working as a dehumidifier.   It appears that the airflow is forcing the air conditioner to change from air conditioning mode to dry mode. 

Slow Fan Speed Not Freeze Coil?

Of course, its controls are not so simple.  The control involves also the speed control of the compressor.  There is also a need to make sure the cooling coil will not freeze when the airflow is reduced.  This is why the dry mode button is not always available in older models that have fixed-speed compressor motors.

This is one possible control strategy:

The Best Design Strategy for Dry Mode?

Dry Mode slows down the fan speed so that the evaporator coil can condense more vapor out of the air when the air passes through the coil.  It will use some energy and be able to lower the humidity faster than usual to an acceptable and comfortable level.    

Different manufacturers have different design strategies for dry mode; some adjusted also temperature as well as the airflow in their cooling strategies. The idea is to achieve a desired comfortable cooling condition.

It has been commonly accepted by researchers that the most comfortable room cooling condition is 25^oC@ 55% humidity. This is the room condition that most manufacturers are using to design their air conditioners.  For the angle of saving more energy,  there is a tendency for the professional to pick 65% humidity level as the new comfortable humidity level.  

Anyway,  different people might have different feelings and reactions towards temperature and humidity.  For this reason,  most manufacturers will still allow users to adjust the temperature in the dry mode.  If temperature adjustment is available in dry mode,  most users will still use 25^oC as the setpoint temperature.   This does not necessarily save energy.  This is because the energy to maintain the room at the comfortable setting of 25^oC@ 55% humidity will more or less remain the same. 

Will Dry Mode Save Energy?

The dry mode lowers the fan speed allowing moisture in the air that flows through the evaporator coil to be removed more quickly.  It still consumes about the same energy to maintain the room's humidity at the desired comfort level of 55%.  However,  if one finds it comfortable to allow the room temperature to be set higher than the usual 25^oC, one will be able to save some energy.

Operating an air conditioner at econ cooling mode or auto mode will save more energy as the air conditioner is always set to run at the most efficient designed load capacity under this operating mode. Depending on the design, the airconditioner's efficiency can vary a lot at different load capacities.

Difference between Cool, Dry, and Econ Modes?

The newer air conditioner having an inverter or otherwise to control the speed of the compressor motor allows 2 additional modes of control,  namely Dry Mode and Econ Mode.  The differences between them are briefly described in this table:

Mode	Mode Description	Usage	Energy Saving
Cool Mode	Default mode	in hot and humid weather to maintain constant temperature control	Saving Depend on selected temperature;
Dry Mode	New Function	In not too hot weather or raining season to lower humidity to achieve comfort cooling	Save energy if the temperature can be allowed to be set higher.
Econ Mode	New Function	In not so hot weather to run the air conditioner at a most efficient level	Prevent excessive low-temperature cooling to lower electricity bills

Why Singapore has a Sudden Increase in Covid New Case?

Jump to:

3) Update : 11 December 2021 

Lastest chart update about Covid situation in Singapore

2) Update : 8 December 2021 

Expert said Antigent Rapid Test or LFT works with Omicron

1) Update : 28 November 2021 

South Africa Adds Antigen Test

24 October 2021

Abstract:

Lockdown is an effective way to curb Covid from spreading.  It works by isolating all or part of the community,  trying to force the infected,  especially those asymptomatic to stay away from the rest of the community;  hopefully,  by testing or otherwise,  these infected people will disappear over time. 

Instead of using the Lockdown method,  Singapore implemented free and easily accessible Antigen  Rapid Test Kits (ART) in September 2021.  This has managed to flush out thousands & thousands of asymptomatic patients,  who otherwise will stay hidden in the Community,  spreading Covid silently.  The success will depend on whether this new method can flush out the asymptomatic patients in the Community.

Introduction

Singapore used to be one of the best in handling the spread of Covid pandemic disease.   It used to have the lowest Covid infection rate as well as the death rate.  Many countries have taken it as a model.    Lately,   Singapore's infection rate has risen exponentially;  at the same time, the death rate has also increased slightly as shown in the following chart.  It has recorded infection new cases hovering at around 3,000 to 5,000 recently.

Possible Reasons

The following might be the reasons:-

1.  Increase in a spread of Covid infection; 

2.  Increase awareness in the community to carry out frequent testings;

3.  Management lapse and negligence.

There were active web discussions about the reasons why.  Many are clueless.  Some attributed this to the pervasive Mandatory Fast and Easy Testing (FET) rules in September 2021.  Others blamed the mismanagement.  There are also people saying the mRNA vaccine is not effective.  This article will make an attempt to explain.

Why?

The recent rapid increase could be due to a combination of the above reasons.  

There could be a real increase in the spread of infection.  Many countries that opted to live with Covid also experienced the same. But many countries,  especially the European countries, are using  Antigen (ART) testings as an alternative to do away with Lockdowns.  This is because of the frequent street protests from the residents.

Singapore has just introduced this new rule using Antigen testing in September.  The new rule makes it mandatory for the residents,  especially those workers,  to do self-testing at regular intervals or whenever they are feeling unwell.   This move must have flushed out many hidden cases that otherwise will go unrecorded,  spreading Covid in the community.    

Sudden increase Not by Variants

The sudden increase in Singapore is not caused by variants.  If it was so,  the Authority would have reported it, and such statistics would have been reflected in the GISAID webpage

Click picture to go to the GISAID webpage

The "Silent Covid Spreaders"?

Although there was no known statistical testing done,  this technical article using a decision analytical model estimated that about 59% of Covid transmission came from people without any symptoms.  These people without any symptoms are known to be "Silent Covid Spreaders".

These people are always living real in the community,  spreading and transmitting Covid silently every day.  The Covid virus can also grow stronger by the day.   That is the reason why many countries failed to contain the disease.  Many countries have conceded and changed their strategies from "Zero Tolerance" to "living with Covid".

How Can We Flush Out these Silent Covid Spreaders?

Mass testing is always done to flush out these  "Silent Covid Spreaders".   Following up with Lockdowns is the way to complete the job.

In the past,  residents & visitors to the infection areas or clusters are always troubled and made to line up under the hot sun or corridors for many hours to get their Covid testing done.  This was when only a few hundred infected people were found daily. 

 

Today,   this scene is no more around but many thousands were found.   Some more,   about 99% of those found infected are without symptoms or with mild symptoms.  Why it is so?

Brought-in-Dead (BID)

Many countries with very high Covid infection rates often use BID (Brought-in-Dead) or DOA (Dead on Arrival) to measure the gaps in health services or the seriousness of the pandemic disease in the field.  It measures how many people are brought in Dead before any effort is put into resuscitation.  This indicator will often stand up when the health services are so loaded that they cannot handle the pandemic disease.  

Malaysia was reported to have 370 BIDs in June when it had about 5,000 to 6,000 new infection cases.  There were nearly 200 BIDs between May 14 to June 14.

So far,  there were no such BID reports in Singapore even though the new infection cases have been hovering around 3,000 to 4,000 daily at the moment.  The health services were still able to handle the new cases.   Why is it so?

Case Fatality Rate (CFR) vs Infection Rates

CFR is a ratio between confirmed deaths and confirmed cases.   CFR can be used roughly to indicate how serious is pandemic in a country.  Therefore,   countries with higher CFR can mean countries are having pandemic that is more serious than those with lower CFR.  The country with a higher CFR might have a lot of very sick people.   Presently,  Singapore has very high infection cases but very low CFR.  One reason is that 99% of the infection cases are asymptomatic.   How do they do it?

For more details,   please refer to this webpage.

The Possible Answer

The sudden increase in infection rate happening in Singapore can be viewed as the result of the latest move by the Government to live with Covid and do away with "Circuit Breakers" aka lockdowns.  But at the same time,  they are flushing out the "Silent Covid Spreaders".  

First,  Singapore announced a new Covid testing rule in August/September.   It introduced and started ART,  the Antigen Self Covid Testing in September.  It made ART testing mandatory in some establishments in early September.  The month-long result must be good for them to extend mandatory ART testing to the rest of the community including the residents by 1st October.  Offenders would be taken to task and cases publicized.  

Second,  it has given every household a free blood oxygen meter and some free ART Self-Test kits to start with.    After that,  more ART Self Test kits were made available for free.

In addition,  the Government is making sure:-

a)  The free Self-Test kits are made readily available also to those infected.  They can draw the test kits from vending machines located all over the island on a 24/7 basis;

b)  The kits are also distributed to companies, factories,  construction sites,  offices & establishments for them to test each and every worker regularly daily.  

All those who tested positive using self-test kits & display symptoms (mild or otherwise) will have to submit the results to the Authority for PCR confirmation as required.  Once confirmed,  the patients will have to wait for the quarantine instruction from the Authority.  Home quarantine is only allowed for those aged below 60.  

Most Singaporeans are generally aware of the strict law enforcement in Singapore.   They don't want to be caught by the laws.  Many must have diligently carried out the self-testing at their premises. 

After such a move started on Sept/Oct,   PCR testing centres,  information service, and treatment facilities were overwhelmed and overloaded.   Those waiting for Authority's instructions were often seen complaining in the forum about the long waiting time.   The infection rate suddenly shot up.    It would appear that the Singapore Government's latest strategy of flushing the "Silent Covid Spreaders" started working.  

With ART testing kits easily available,  people are aware if they have been infected by the deadly Covid and seek medical attention at the earliest instant.  Hence, no BID reports so far.

Corresponding Increase in Hospitalisation and Death Rate

Although there was a corresponding increase in the number of hospitalization and deaths putting some pressure on the medical system,  this could be due to the emergence of a new infection wave or pattern.   But this did not attract the Authority to sound any alarm or raise the DORSCON (Danger) level because:- 

1)  The hospitalization number is rising slightly

This chart shows the number of infections vs the number of hospitalization. It indicates that the hospitalization number has risen only slightly. This was after they introduced ART testing.  It is not rising in tandem with the infection. 

2)  The majority of those infected were having either mild or no symptoms.  They have been put either in-home quarantine order or in Community Care Centre for observation.  

3)  The death rate per 100,000 is still very low. 

4)  The Weekly Ratio of Infection in the Community is falling

The Ratio of community cases in the past week over the week before has been falling gradually ever since August.

This Could be What Happen

1.  Before ART Testing is in place

The "Silent Covid Spreaders" would stay at home and would not pay money to visit the clinic when they have had flu-like symptoms,  like fever or sore throat.  They would visit the clinics only when they became very sick.  

Mass testing done can get at most,  a few hundred "Silent Covid Spreaders"

2.  After ART Testing is in place

The same "Silent Covid Spreaders"  will usually use the free blood oxygen meter to test for fun.  When reading is low,  they become curious and use the free ART testing kit to confirm.   With positive readings from ART testing,  they will get panic.   wondering if the sickness will get worst and they will want to visit the clinic or the testing centres in the next very first hour.  As a result,  clinics are lately seeing a lot more infection cases.

This explains why no mass testing was done but Authority can get several thousand in a day. 

 

What about Cost-Effectiveness?

Giving out free blood oxygen meters and ART testing kits to every household may look to be a wasteful and overkilled effort initially.  Many people did not expect it to be well-received because Singaporeans,  by nature,  are always reluctant to share personal information voluntarily even though submitting the test results is mandatory.    

Now it turns up that this strategy of self-testing is not only successful,  it is also cost-effective.  The Government can save at least the cost of the following items:-

a)  The first PCR testing which otherwise would cost another US$100/=.  This is because 2 PCR testing will be needed to confirm the infection;

b)  The cost of setting up and manning of field testing stations;

c)  The manpower and admin for tracing,  calling up & monitoring all the testing work.  The majority might not be even infected and PCR testings are always wasted.

As for the Singaporeans,  they can save themselves from the agony of spending valuable time,  lining up for hours to get mandatory PCR testing done.

Results:  

1) Flushed out Thousands of  "Silent Covid Spreaders" 

The following chart using Data from Our-World-in-Data illustrates that Singapore was able to use the latest ART testings strategy to successfully detect about 5,000 cases a day on 27 October.  They have not only reduced the frequency of PCR testings but also did it without using mass testing and other methods.  Thousands were found with no or mild symptoms.  The chart shows clearly that the infection rate increased in tandem with the increase in the positive rate in testings;  at the same time,  the testing rate was declining.  The positive rate went up 18 times from about 1% to about 18% with a 60% decline in testing rates.  This is not possible without the help of ART testings.

Note:  Positive Rate is the % ratio between Confirmed Case over the number of tests carried out

2) Rapid Increase and falling in Covid cases

Our World in Data compares countries in terms of how rapidly a country's Covid cases have doubled.  Singapore came second next to Barbados,  doubling the cases in 35 days.  Although there was no report in our World in Data about the rapid fall in Covid cases,  Singapore just announced to say that the new cases were only 1,723 on 14 November.  They managed to cut down by half the number of new cases from the record of 5,000 new cases on 29 October.  That is in less than 16 days.  

What Others Are Still Doing

The attached Appendix is showing some examples of what other countries are now doing to flush out the "Silent Covid Spreader".  Although some ideas like mobile testing are good, it is doubtful it will be as effective as giving out free ART Test kits idea.  

In Conclusion

We are of the view that this sudden increase in the infection rate in Singapore is mostly due to the Government's latest move to make self-testing mandatory.   It is good,  timely, efficient, and cost-effective.  

The "Silent Covid Spreaders" in the Community must always be flushed out as much as possible to stop Covid from having a chance to spread and grow stronger every day.  Singapore should be able to see very low new cases very soon.

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3)  Update: 11 December 2021

This updated chart taken on 11 December shows that Singapore was able to tame the Covid in about 109 days;  this is less than half of the ttime taken by its neighbour,  Malaysia.  Both Malaysia and  Singaopre are having predominantly the Delta variant.   

The  abundant use of ART test kits must have help Singapore to achieve this better than expected results.

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2) Update: 8 December 2021

• Experts say that COVID-19 tests should be able to detect all variants of COVID-19, including the Omicron variant of COVID-19.

• Individuals getting tested will likely not know which specific variant of the virus they have based on a basic PCR or antigen test.

for more information:  Read here

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1) Update 28 November

South Africa Adds Antigen Test

South Africa Health Authority found 20,000 new cases by Nov 8 and this is about 26% of the 75,000 Antigen tests (ART) done.  They are now adding Antigen testing to the National count.   They said " Analysis of the mutations in the nucleocapsid (N gene) of B.1.1.529 viruses suggests that rapid antigen tests should be unaffected, however, verification of this is underway."

References:

1.  Our World in Data

2.  Latest Update of Singapore's Covid-19 Charts]

3.  Straits Times report about BID in Malaysia 

4.  New Straits Time report about BID in Malaysia

5.  59% Transmission by "Silent Covid Spreaders" in community

6.  Singapore's MOH Highlights

7.  Collection Actions to slowdown Community Transmission

Appendix:   What others are still doing

Beijing residents queue in Cold Weather Beijing's mile long testing queue Testing remains unsatisfactory Lockdown & Mass Testing Not Efficient Good Idea but Less Effective slight drop only after hours' afford Big Operation with little results Business not so good Everyone suffering Moving away from Mass Testings Mass Testing Is it Worth? Thousands lining up?

Why UK's Vaccinated Has Higher rate of Infection than the Unvaccinated?

10 October 2021

Jump to 

1) Update : 13 December 2021

Introduction

The UK Heath Security Agent (UKHS) has regularly published COVID-19 vaccine surveillance reports weekly.  In its week 42 report,  it attached this table:

It also attached this chart

The table clearly shows the rate of hospitalisation and death  of those vaccinated is higher than that of the unvaccinated for age above 30. In some cases,  twice as much. Many netizens especially those anti-vax took & cited this table and the chart to mock the pro-vax.  

What Could be the cause?

UKHS explained that it could be due to a variety of reasons, including differences in the population of vaccinated and unvaccinated people as well as differences in testing patterns.  But what exactly does this mean and why does this happen?

What does it mean and Why?

The infection rate discrepancy between the vaccinated and unvaccinated always happen and is commonly found when the majority of the population is vaccinated.   This also happened recently in Singapore.  The Singapore Authority had to stop publishing such information in late September when such data become meaningless and misleading.   We are not comparing the effectiveness of vaccines.

To understand why it happens,  lets us examine a simple and extreme example.  Imagine we have a population of 10,000 people.  9,000 are fully vaccinated and stay active with constant human-to-human contacts and interactions.   The other 1,000 are unvaccinated and always stay in isolation or in a rural area away from busy streets.  In this case,  it is always likely that the rate of infection of the vaccinated is always higher than the unvaccinated in this population.

If we must compare the vaccine effectiveness,  we must make sure the comparison is always done on the fairground.  We must know if the vaccinated and unvaccinated are exposed to Covid on an equal and fair basis.   This is only possible only when the unvaccinated are not aware they were not vaccinated.   

This was exactly what the vaccine manufacturers had done when they first carried out the vaccine efficacy test earlier.  Then,  all participants were jabbed;  half with vaccines & others half with placebo.  The unvaccinated always thought they were vaccinated  They were expected to behave the same when they returned back to the community.    

Using the raw real-world data,  the remaining few unvaccinated,  knowing they are more vulnerable,   will always take extra precautionary steps to prevent themselves from exposing themselves to Covid infection.  If we were to use such raw real-world data for comparison,  we are actually not comparing vaccinated against unvaccinated but other things like vaccinated against the various Covid control measures. By using the same argument,   if the vaccinated were to take the same and stringent control measures as the unvaccinated,  quite sure the results would be much different.

Then How Do We Rate them?

When a situation like the above extreme example was to happen and we must rate them,  a fairer rating system is to compare the rate of infection (or the attack rate) of the vaccinated against a known benchmark,  An example is shown on this webpage.

In Conclusion

It is always important to know what we are comparing.  Sometimes, it is better to omit and ignore such data instead of comparing them and getting meaningless results or answers.

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Update: 13 December 2021

One can always take all extra precautions to avoid being infected but one cannot cheat death.  This superimposed chart from Our-World-in Data shows that the unvaccinated has 5 times the death rate compared to the vaccinated.  The ratio was 8:1 at the peak just a week ago.

References:

1.  UK's week 42 report;

2. Example on vaccine effectiveness comparison

Latest Update of Singapore's Covid-19 Charts

Updated Daily from 20 October 2021

MOH  resumed publishing Covid data by vaccination status again in early October after a brief stop in September.  This time,  they concentrate on reporting the data for hospitalization and severely sick patients.  The latest data are shown by vaccination status in terms of vaccinated(V) and Not-Fully-Vaccinated (NFV).   

This article will resume tracking the vaccine effectiveness.  The charts will be updated daily. 

1)  Vaccination Rates

2)  Attack Rate for Hospitalisation

This chart shows the Hospitalisation attack rates of vaccinated(V) and the Not-Fully-Vaccinated (NFV)The data is extracted from MOH's chart. The rate is worked out based on this formula

The working of such a formula is explained in this wiki. 

The chart shows the % of people who are hospitalised after having exposed to Covid-19. The right axis shows the ratio between vaccinated and not fully vaccinated.  The attack rate assumes:

1.  The population of NFV excluded those whose age is less than 12 years old (the minors) and also,  their infection figures adjusted to reflect the same.  The population of the minors is about 250,000;

2.  Those having infected will have natural immunity and 40% of them are NFV

3)  Attack Rate for Patients in O2 or ICU Beds 

Similar to Chart 1 but for patients who are severely sick requiring O2 support or ICU beds.

The chart shows the % of people who become severely sick after having been exposed to Covid-19. The right axis shows the ratio between vaccinated and not fully vaccinated.

4)  Full-Doses Vaccine Effectiveness for hospitalised & those required O2 & ICU )

This chart works out the Full-Doses' vaccine effectiveness for those who are severely sick & in O2 or ICU beds. It uses the data extracted from MOH's chart. The effectiveness is worked out based on the same formula in this wiki.

The chart shows that Fully Vaccinated people have more than 80% chances of avoiding hospitalisation & 90% chances of becoming severely sick as compared to Not Fully Vaccinated people.

Note 1:  The sudden dip could have been caused by spikes and delays in testings

Note 2:  The Chart was split to show ICU(unstable) & ICU(critical)  on 30 October 2021.

5)  Booster-Dose Vaccine Effectiveness for hospitalised & those required O2 & ICU ) 

This chart works out the Booster-Dose's vaccine effectiveness who are severely sick & in O2 or ICU beds. It uses the data extracted from MOH's chart.

The chart shows that people with Booster-Dose have more than 95% chances of avoiding hospitalisation & severely sick as compared to Not Fully Vaccinated people.

Note 1:  MOH's started to provide booster shot information on severely sick patients from 6 October 2021

Note 2:  The Chart was split to show ICU(unstable) & ICU(critical)  on 30 October 2021.

6)  Infection Number vs Hospitalisation/Dead  Numbers

This chart shows the number of Infections vs Hospitalisation published by Singapore MOH.   If the infection is due to new waves,  hospitalisation figures will usually rise in tandem.

7)  Number of Deceased

This chart shows the number of deceased as published by Singapore MOH

8)  Imported as % of Local Cases

The imported cases have cropped up the end of December 2021.  This  chart shows the import cases as % of local cases

9)  Weekly Infection Growth Rate

This Chart from MOH Singapore shows how serious is the spreading of the infection and if the infection spread has been controlled.  If the growth rate is less than 1.0,  it will mean that the infection spread has slowed down.

10)  % of people severely sick and Dead according to Vaccination Status 

This MOH Singapore chart shows the % of people becoming severely sick (Requiring O2 support and ICU) and Dead after having exposed to Covid infection.   For the period (1 May to 31 Oct 2021) as shown in this MOH webpage

11)  Daily new Cases and Case Fatality Rate (CFR)

Our World in Data has published 2 useful comparison charts that will tell how serious is the present pandemic in various countries.  These 2 chart shows the situation in ASEAN Countries.   It will be less worrying if a country has very high new Cases but very low CFR especially when the country has a lot of new asymptomatic cases.  This is presently the case in Singapore.

Reference:

1.  MOH Twitter

2.  Covid-19 Situation Report (Summary)

3.  Covid-19 Situation Report (Detail)

4.  News Highlight (Daily)

5.  Statistic

6.  Download MOH Singapore Data

a)  Raw from MOH/Data.sg

         

b)  Extracted