just to add: not just outside temp is important. you should also consider how well insulated your room is, how many people usually occupy it and what desired temp you want to chill down the room to.

in a well insulated room, a 1 HP aircon can easily handle a 25 sqm room. however if there is lot of traffic through the room (i.e. moving a lot of chilled air out) or a lot of people inside the room then you might need more power. same goes for equipment in the room that generates heat (PCs, lights, fridge, whatnot).

unless you know precisely how the room will be utilised it will be hard to give a good recommendation for the size of AC required.

FYI: 7,5 HP of a/C capacity *can* easily cool 550-650 cubicmetres of air to actual 25°C in a 3-5 person household if the rooms are insulated and windows ducted in normal malaysian climate (also in hot season!).

as i said: it will totally depend on many factors. major factor overlooked: how well or badly is the room insulated and how big is the air-exchange? 25 sqm is absolutely enough if the room is insulated.

the problem with EER and inverters is that it doesnt totally reflect the true savings. if i understand it correctly, EER will be calculated under full load which is not the optimal usage point for inverter a/cs. under partial load the effective EER would be a lot higher.

that beeing said my point on the issue is this:

make sure you slightly oversize the inverter ac for the room so that it always runs on partial load. if you care to research, choose one with the highest EER under 1/2 and/or 3/4 load.

consider:

desired room temp

degree of insulation (no need for it to be airtight. my example the room has one or two doors open, PC running 24/7, people run through a couple of hours per day, usually 12 hours per day one person inside only though. a/c cools to actual 25°C (setting 28° dry gives actual 25° across the room) and is mostly on lowest partial load once the room is chilled down)

amount of people

level of air-exchange

amount of appliances

how many windows (and how much heat from there)

ceiling insulation

if you do that, you'll be able to choose the right choice of A/C (hopefully). all the installers suggested that we hopelessly underpowered the ACs for the rooms but they dont break a sweat. i cool a 45 sqm hall (3,5 ceiling height) with 1 (!) 2 HP inverter ac and a ceiling fan to distribute the cool air properly in the hall. even on a hot day the ac is on minimum load almost all the time. windows tinted, ceiling insulated, heat reflecting paint, draft-safe windows etc. all add up.

very specific question. what's sure: R22 is beeing phased out because it harms the ozone layer. that for me is enough reason no to use ACs with R22 and i dont.

now to your question: R401A tends to be more energy efficient than R22. if i remember correctly by 10-15% but i really dont have the supporting figure at hand anymore. i looked into this around 4 years ago when i changed my ACs to 401A inverters. i found an interesting read on the issue here:

https://docs.google.com/viewer?a=v&q=cache:...zusFVDI_EZB-DUg

dry mode is actually the same as cool mode with one difference: the rotor will run extra slow. this has two effects: a) it makes operation more quiet and mostly b) it will give the air more time with the cooling fins. that way more moisture can be extracted from the air. this will lead to (my house, continous usage - never off) to approx. 10% less humidity in the air than the same temp. setting in cool mode.

this can be good or bad. i dont cool much (28° in almost all rooms) so i tend to have in excess of 65% humidity. using dry mode i can get around 60-65% which is ideal because it a) makes the air feel cooler than the same temp air with a higher humidity (save money) b) less noise c) 65% or less prevents mould and fungus growth and d) air never feels stuffy.

conclusion: all rooms have a/c set to dry 24/7 and create a pleasant environment. but yes, lower settings (probably 24 or so) will yield air that might be too dry. experient and see what suits you best. for me i find that malaysian air is always too humid. i prefer 65% humidity.

weikee,

true. but try 27° dry mode. 27° with 75% humidity i cannot tahan - but 28° with 60% is just nice. feels much lower (maybe like 24°C).

if service really needed i usually call joo fen enterprise. they are quite carefull and so far have not done any screwups with my aircons. they are a bit pricey but then again i normally clean my aircons myself so i only call for service on the 2 HP panasonic which is almost impossible to clean the rotary fan.

03-62752619