BTU sizes for air con

[pineapple01]

Dam it, i cant find the Hand Books. I think it was the Carrier Book who say Do Not expect any Savings over a Non Inverter unless the room is insulated correctly. Rather refreshing honesty these Days.

[stouricks]

1 hour ago, Antiparovian said:

Maybe I'm stupid falang but does height of room not enter the equation? i.e. measure room on metres cubed not squared?

 

I would have thought it would, but when I asked in the previous post no. 23, Pineapple laughed. Why?

[Rawairat]

I have found all salesmen will sell you the biggest most expensive unit they can, I have fallen for that on the prodding of my ex. The salesman did a great job. Also Homepro like many large Thai stores have a salesperson for each brand and they will push you that way. I have had Samsung, Carrier and Panasonic all worked fine.

[pineapple01]

22 minutes ago, stouricks said:

I would have thought it would, but when I asked in the previous post no. 23, Pineapple laughed. Why?

Such a funny question to Me, Like why does a Mini Car have a smaller Air Con than a 2 Level VIP Bus, made me smile Sorry.

[Andycoops]

19 hours ago, Pilotman said:

None of our 6 aircons in our various rooms are right for the rooms they are in, according to the formulas used by the sales staff. I would  estimate that they are all up to 20% less powerful than the figures suggest that they should be.  All work perfectly well and all cool the rooms they are in very well. Our elect bills are very reasonable. 

Same here with my 3 units.

I wouldn't give a toss what any salesman said.

I would have said that's the one I want and if you don't sell it to me now, I'll buy it somewhere else.

[Oldie]

47 minutes ago, pineapple01 said:

Dam it, i cant find the Hand Books. I think it was the Carrier Book who say Do Not expect any Savings over a Non Inverter unless the room is insulated correctly. Rather refreshing honesty these Days.

Perhaps because if an inverter runs at full capacity all the time it will need more power than a conventional aircon that runs at full capacity? 

[pineapple01]

Just now, Oldie said:

Perhaps because if an inverter runs at full capacity all the time it will need more power than a conventional aircon that runs at full capacity? 

Spot On Sir.

[Pilotman]

5 minutes ago, Oldie said:

Perhaps because if an inverter runs at full capacity all the time it will need more power than a conventional aircon that runs at full capacity? 

Is that true?  I was always told that the inverters were more efficient. My bills seem to be quite low in comparison to many of my friends, albeit, we usually only use air-con at night. 

[bankruatsteve]

34 minutes ago, stouricks said:

1 hour ago, Antiparovian said:

Maybe I'm stupid falang but does height of room not enter the equation? i.e. measure room on metres cubed not squared?

 

I would have thought it would, but when I asked in the previous post no. 23, Pineapple laughed. Why?

The height of a room will have an affect, but not much.  Unless there are fans moving the air around, the cooled air will stay lower in a room.

[bankruatsteve]

26 minutes ago, Pilotman said:

34 minutes ago, Oldie said:

Perhaps because if an inverter runs at full capacity all the time it will need more power than a conventional aircon that runs at full capacity? 

Is that true?  I was always told that the inverters were more efficient. My bills seem to be quite low in comparison to many of my friends, albeit, we usually only use air-con at night. 

That is not true.  An "inverter" AC is more efficient and therefore saves energy/money for exactly the same job.  My Daikin never runs at full capacity unless I turn on "Power Cool"; and that is for a unit way undersized, according to the witchcraft, for the area I am cooling.

 

Edit:  The only difference between normal operation and "maximum" is the fan speed in the condenser.

 

[stouricks]

2 minutes ago, bankruatsteve said:

The height of a room will have an affect, but not much.  Unless there are fans moving the air around, the cooled air will stay lower in a room.

My ceilings are about 2.5 metres high. AC units are usually fitted close to the ceiling, so in a room with 4 metre ceilings the cool air has almost twice as much distance to get to 'living level' as it does in mine. No?

[spidermike007]

A 12,000 btu inverter, is plenty for a 20 meter room. Especially if you have ceiling insulation, which is always a good thing to have here. I have a rental house, and I still insulated the whole ceiling with R-22, and it made a tremendous difference. Cost was 13,000 baht with labor, and it paid for itself in one year of electric savings, plus the rooms stay cool for hours after I turn off the AC now. 

 

It is natural for a salesman to attempt to upsell. I treat them like lawyers and doctors. They are simply advisors, and nothing more.  

[rvaviator]

2 hours ago, Antiparovian said:

Maybe I'm stupid falang but does height of room not enter the equation? i.e. measure room on metres cubed not squared?

 

Sure the height matter - But for most people the height is pretty standard (i.e. the same) in most houses .. so people tend to just talk m^2 not m^3

 

Make sure you have a minimum of 100mm insulation in the ceiling - Easy and not to expensive to put in place - even on a suspended type ceiling.  Get the type packed in 'silver foil' Easy to roll out.  12000 BTU should not be a problem

[bankruatsteve]

9 minutes ago, stouricks said:

My ceilings are about 2.5 metres high. AC units are usually fitted close to the ceiling, so in a room with 4 metre ceilings the cool air has almost twice as much distance to get to 'living level' as it does in mine. No?

I can't think of any reason for the condenser to be installed 4 meters high.  Even so, the cool air will drop.  I previously had a house with a large living area that had a vaulted ceiling about 9-10m.  I had a 24K BTU installed in the loft area and that would comfortably cool the living area.

[Max69xl]

20 hours ago, whiteman said:

But he insists on coming to the house this evening to check my measurements, I assume he thinks I’m a stupid Falang  and he may be casing the joint for his mates ???? to see if you got a 65 inch tv for his mates. ;0

 

You don't have to listen to his bs. You are the customer. Have you compared prices on Lazada with HomePro? Lazada is in my opinion always cheaper and now during corona times even cheaper. I've seen 40-50% discounts on air-con units. 

[Pilotman]

34 minutes ago, stouricks said:

My ceilings are about 2.5 metres high. AC units are usually fitted close to the ceiling, so in a room with 4 metre ceilings the cool air has almost twice as much distance to get to 'living level' as it does in mine. No?

cooler air  descends through warmer air, as it is denser, that is why air-cons are set high in the wall.  Height of your ceiling would make little difference.  

[ujayujay]

One Year ago I bought 3 Daikin Inverter Units for my new House: Livingroom 32m2 18k BTU, Masterberdroom 24m2 12k BTU, Guestroom 14m2 9k BTU. This is far enough. If you ask Thai Seller, they will sell you double BTU..................wonder why????

 

[448glb]

I did air-conditioning for over 10 years in the United States. My master bedroom is 40 m² and 70% windows with sun exposure all day and I have an 18,000 BTU unit. 12,000 BTUs is more than enough for you. 

[natway09]

I would always go one size bigger than recommended.

It will make the compressor work less,so reducing power bill, as it works less will last longer, 

& remember as it ages there will be a reduction in efficiency so the bigger unit will cope better.

The capital cost increase is minimal.

And as stated, outside influences make a difference such as condo or house with a roof above or another unit, floor on the ground or on foundations or another unit below etc

Penny wise, pound fooish sometimes

[Oldie]

1 hour ago, bankruatsteve said:

That is not true.  An "inverter" AC is more efficient and therefore saves energy/money for exactly the same job.  My Daikin never runs at full capacity unless I turn on "Power Cool"; and that is for a unit way undersized, according to the witchcraft, for the area I am cooling.

 

Edit:  The only difference between normal operation and "maximum" is the fan speed in the condenser.

 

If both inverter or a non-inverter run at full capacity the inverter will always use more energy. Please study how an inverter works. 

[bankruatsteve]

Just now, Oldie said:

If both inverter or a non-inverter run at full capacity the inverter will always use more energy. Please study how an inverter works. 

Nope.  Maybe you should take your own advice.

[maxpower]

2 hours ago, bankruatsteve said:

That is not true.  An "inverter" AC is more efficient and therefore saves energy/money for exactly the same job.  My Daikin never runs at full capacity unless I turn on "Power Cool"; and that is for a unit way undersized, according to the witchcraft, for the area I am cooling.

 

Edit:  The only difference between normal operation and "maximum" is the fan speed in the condenser.

 

A inverter AC with compressor running at full speed should be less efficient than its equivalent conventional type due to conversion losses within the inverter.

Savings are made and conversion losses offset when the inverter is allowed to control proportionally around the set temp.

We have inverter control systems in our data center with AC-DC conversion loss up to 5%.
 

[Pilotman]

There has not been much debate on this post about temperatures.  It surly all depends how cool, or cold, you want the rooms that you are cooling to be. Our bedroom air con starts off at 21 degrees as it cools the room and then we raise the temp to 25 to sleep and the fan to silent ( night) setting. We very rarely use air-con in the day, if we do, it is set around 5 or so degrees below the outside temperature, with the fan on a middle setting.   That's why we really don't need the max recommended air-con BTU for the rooms we cool, we just don't use our air-cons that way. 

[bankruatsteve]

21 minutes ago, maxpower said:

A inverter AC with compressor running at full speed should be less efficient than its equivalent conventional type due to conversion losses within the inverter.

Savings are made and conversion losses offset when the inverter is allowed to control proportionally around the set temp.

We have inverter control systems in our data center with AC-DC conversion loss up to 5%.
 

If they used the same motor, that could be true.  But, they don't.  The fact is, an inverter aircon will use about 30% less energy than the old-style for equivalent cooling and size is much less a factor.

[pineapple01]

3 minutes ago, bankruatsteve said:

If they used the same motor, that could be true.  But, they don't.  The fact is, an inverter aircon will use about 30% less energy than the old-style for equivalent cooling and size is much less a factor.

Who told You that?

[maxpower]

2 minutes ago, bankruatsteve said:

If they used the same motor, that could be true.  But, they don't.  The fact is, an inverter aircon will use about 30% less energy than the old-style for equivalent cooling and size is much less a factor.

As the DIY & Electrical Forum Expert , can you please explain how these inverter control motors use 30% less energy for the same load as applied to conventional AC motor.

 

Reminder, the comparison is for the inverter AC running at full speed.

[bankruatsteve]

27 minutes ago, maxpower said:

As the DIY & Electrical Forum Expert , can you please explain how these inverter control motors use 30% less energy for the same load as applied to conventional AC motor.

 

Reminder, the comparison is for the inverter AC running at full speed.

First of all, inverter ACs only run at "full speed" a relatively short period of time - usually just after start-up.  There is no reason to run at "full speed" once the coolant is doing its thing.  The major savings is running the compressor at lower speed and avoiding the constant start/stop of the old-style which result in large spikes in current.  The 30% less energy comes from numerous tests by the industry and validated by TV posters who have taken the time to evaluate.  

 

But, this type of discussion is really becoming nonsensical as it won't be long, if not already, that the old-style aircon is just not produced.  

[Lacessit]

I think it's a tradition for Thai salespeople to try and upsell air conditioners, bigger commission on the bigger units. I once had a sales guy trying to persuade me I needed a 40,000 BTU aircon for 36 sqm. I suggested to him if he didn't want to sell me what I wanted, there was always HomePro or Thai Watsadu I could go to instead.

In the OP's shoes, I'd be telling his sales guy to rack off. He's got a nerve, telling you he's coming to your house. Shop elsewhere.

[maxpower]

31 minutes ago, bankruatsteve said:

First of all, inverter ACs only run at "full speed" a relatively short period of time - usually just after start-up.  There is no reason to run at "full speed" once the coolant is doing its thing. 

There is a need to run at full speed if a control is struggling to reach set temperature. The controller logic will increase output eventually reaching max if it cant see expected results. This is often called PID control.

 

This sub discussion in the thread is about inverter AC's running at max speed compared to conventional AC's. There are some efficiency differences using DC motors (complex comparison) but the lions share of the saving is done when the system can proportionally control temperature.

 

The guy back at post #36 was simply pointing out a comparison when running inverter AC at full speed which is quite valid for someone's inverter AC struggling to reach set temperature.

 

The conventional AC in our workshops often runs flat out 24/7 as the doors are opening constantly.  I doubt installing an inverter controller would make much difference to the energy consumption. Get the "running at full speed" idea?
 

[bankruatsteve]

IMO, the consideration for size of AC based on whether it would run at "maximum capacity" full time, is just nonsense.  If an AC (old-style or inverter) runs at maximum capacity full time, then something is wrong with the AC or the space it is trying to cool is inadequately insulated from heat ingress.  Even the smallest of AC will eventually cool the largest of room (not talking mansions) if it is well insulated.  A large inverter unit only makes sense if one needs cold quickly or arctic temperatures are required.