Air-Conditoner - How Does System 4 Works?

[uris 0]

Hi All,

Am planning for a new flat and I am looking at a system 4.

I am wondering how a system 4 works cos my contractor states that a system 4 will have lesser power even though only 1 unit is turned on.

Our household is unlikely to be a high user of air-con. In fact, we have no air-con in our current flat so air-con is more like a just in case.

I was thinking, usually, if the living room air-con is turned on, the rest of the rooms are unlikely to be on (or at most 1 room).

Let's take for example, the Mitsubishi MXY-4A28VA condenser which can serve 30k+ BTU/hr with 3x MSY-GE10VA (8k BTU/hr) and 1x MSY-GE13VA (12k BTU/hr).

Obviously, if all 4 are on, it's 36k BTU/hr which means all will be lowered. But what if 1 bedroom and 1 living room is on? That is only 20k BTU/hr. Does it mean both units will get their full potential or is there a hard cap on each unit due to the fact that the condenser needs to be split for 4 units?

Don't really wish to spend on a system 3 + split single as we do not use the air-conditioner often, especially the living room. What are your opinions?

Thanks!

[neubie 2]

yes, u answered most questions correctly. dun really need to find out how the compressor distribute cooling power to the rooms. what's impt is your usage habits n patterns. just buy something that suits u.

[terumo 0]

Inverter aircon will adjust its energy consumption according to the number of fancoils u turn on. If you on only one, the aircon will consume less electricity compared to on 3.

[Simontsh 0]

but inverter aircon only helps to save money if you on it over an extended period daily.

i.e. u reach home u switch on

u go out of house for one hour, you still leave it on.

if you on off on off, then the energy usage no diff from non-inverter.

correct me if i am wrong but if u seldom use perhaps non-inverter can save more $$$

[airconlin 0]

but inverter aircon only helps to save money if you on it over an extended period daily.

i.e. u reach home u switch on

u go out of house for one hour, you still leave it on.

if you on off on off, then the energy usage no diff from non-inverter.

correct me if i am wrong but if u seldom use perhaps non-inverter can save more $$$

If you usage pattern is on off on off, then better choose inverter. The non-inverter motor need a few times more current just to restart, that is major drawback for non-inverter.

[Simontsh 0]

If you usage pattern is on off on off, then better choose inverter. The non-inverter motor need a few times more current just to restart, that is major drawback for non-inverter.

but what matters is how much you pay at the end of the day no?

i.e. does the amount of savings you get from electrical bills > the amount of money you pay for installing inverter aircons

i am not a technical guy, more of a finance guy.

as long as room is cold whenever I want, ultimately it boils down to how much additional money i need to spend on inverter versus how much money i can save.

Do note we also have to take into account time value of money. You might need to invest maybe $1000 more by choosing inverter. the savings per month needed for the next 5 years will be $16.66

given the light usage of the aircon, will you be able to save that amount?

thus it really depends on how often the aircon will be switched on. so far i see, only the ones who switch on everyday see the most savings.

[Simontsh 0]

The second point to consider is the repairs of inverter vs non-inverter.

IIRC inverter aircons have more parts to repair and repair parts are more expensive....need the aircon experts to verify this.

[airconlin 0]

but what matters is how much you pay at the end of the day no?

i.e. does the amount of savings you get from electrical bills > the amount of money you pay for installing inverter aircons

i am not a technical guy, more of a finance guy.

as long as room is cold whenever I want, ultimately it boils down to how much additional money i need to spend on inverter versus how much money i can save.

Do note we also have to take into account time value of money. You might need to invest maybe $1000 more by choosing inverter. the savings per month needed for the next 5 years will be $16.66

given the light usage of the aircon, will you be able to save that amount?

thus it really depends on how often the aircon will be switched on. so far i see, only the ones who switch on everyday see the most savings.

1: Generally speaking, inverter save 30% more in electricity bill, so if you using aircon more, definitely need inverter; if not so often use, then non-inverter is fine.

For one off buying cost, inverter may be 30% higher.

2: The inverter motor starting way make it more durable, and Singapore labor cost is high, reduce potential repairing cost is important;

3: In old HDB, non-inverter sys 3 or 4, the running current easily exceed HDB limit which is only 8.5A;

4: Inverter is much quieter, this is hard to value it by money, depends.

5: most inverter is using R410a, and non-inverter r22, which will be banned after 2020

Edited September 14, 2011 by airconlin

[Simontsh 0]

1: Generally speaking, inverter save 30% more in electricity bill, so if you using aircon more, definitely need inverter; if not so often use, then non-inverter is fine.

For one off buying cost, inverter may be 30% higher.

2: The inverter motor starting way make it more durable, and Singapore labor cost is high, reduce potential repairing cost is important;

3: In old HDB, non-inverter sys 3 or 4, the running current easily exceed HDB limit which is only 8.5A;

4: Inverter is much quieter, this is hard to value it by money, depends.

5: most inverter is using R410a, and non-inverter r22, which will be banned after 2020

$3000 30% is already $900. if non-frequent aircon user......good luck trying to save the amount to justify the $900

now all the new non-inverters also R410a liao.....no future upgrade headaches etc etc

[airconlin 0]

$3000 30% is already $900. if non-frequent aircon user......good luck trying to save the amount to justify the $900

now all the new non-inverters also R410a liao.....no future upgrade headaches etc etc

Of course, if you don't use, the 30% will never be recovered.

http://els.nea.gov.sg/mels/aircon.asp

non-inverter

Brand Model Type Green Ticks Cooling Capacity (kW) COP* Annual Energy Consumption (kWh)1 Estimated Energy Cost ($)2

Mitsubishi Electric MUX-4BD26VB Multi-split (non-inverter) 2 7.44 2.93 7388 2250

Brand Model Type Green Ticks Cooling Capacity (kW) COP* Part Load COP# Annual Energy Consumption (kWh)1

Estimated Energy Cost ($)2 Full Load Part Load Full Load Part Load

Mitsubishi Electric MXY-4A28VA, MXY-4A28VA-R7 Multi-split (inverter) 4 7.52 3.44 5.08 6395 2132 1947 649

When it is part load, one year's difference is SGD1500, if full load, then difference only S$303, need 3 years to recover. most aircon can use 8-10 years

this is based on Sys 4, inverter 7.5KW cooling capacity, non-inverter 7.44KW, usage pattern is 8 hours per day

Edited September 14, 2011 by airconlin

[Simontsh 0]

yep...so IMO the person need to define his usage pattern.

are you a can-don't-eat-but-cannot-no-aircon kind, the switch-on-MBR-only kind, or the once-in-a-blue-moon kind.

the 1st type, no need brains. just go full inverter.

the second type...maybe use multisplit inverter for bed rooms then non-inverter for living.

once in a blue moon non inverter R410a all the way to save money. next time got money but nowhere to spend then upgrade to inverter.

[airconlin 0]

yep...so IMO the person need to define his usage pattern.

are you a can-don't-eat-but-cannot-no-aircon kind, the switch-on-MBR-only kind, or the once-in-a-blue-moon kind.

the 1st type, no need brains. just go full inverter.

the second type...maybe use multisplit inverter for bed rooms then non-inverter for living.

once in a blue moon non inverter R410a all the way to save money. next time got money but nowhere to spend then upgrade to inverter.

living room can use non-inverter if you only use it once in a week, bedroom should get inverter because most people will turn on it all night if aircon is there, even the initial plan is to keep it off and save money.

[Simontsh 0]

living room can use non-inverter if you only use it once in a week, bedroom should get inverter because most people will turn on it all night if aircon is there, even the initial plan is to keep it off and save money.

no leh

my MIL install system 4. all the rooms aircon switched on less than 10 times last year. in fact this year.....only switched on ONCE during chinese new year

[uris 0]

Wah so much info. Ya lor I now totally don't use but also worried that next time have it become a habit...

Based on http://els.nea.gov.sg/mels/aircon.asp, on 4 hrs usage a day average, a sys-3 non-inverter (3 ticks) is around $964 a year (based on $0.40/kwh which is very likely in next 5 yrs). A sys-3 inverter is around $1244 (more!!!) but half load is only $432. (the inverter 1 has higher cooling capacity means can on 3 units no problem)

Say 1/4 of the time full load and 3/4 of the time half load hor, means average is $635. Save $300 a year which mean 3-4 years break even liao? So even if I use only average 2 hrs a day (meaning 1-2 times a week on air-con), 6 years break even? Hmmm.

Also read that condenser for non-inverter is split into 2 niah. So any 1 of the 3 bedrooms (or 2 if using sys-3) turns on means full power for that condenser liao. When inverter, if only on 1 means it draw lesser than what is stated right???

Scared the non-inverter compressor gone case faster as well. Then if I do sys-3 + single split means must consider standby power of 2 condensers. Does higher cooling power condenser use more standby power?

Also just to confirm, if the condenser is rated 20k BTU, if have 3 units 9k each. Doesn't mean each unit hard cap 6666 BTU right? If I on 1, can get 9k. 2 is 9k each but 3 will drop to 6666 each?

Maybe will give up living room and do a sys-3 instead....

Edited September 14, 2011 by uris

[forgotten 1]

no leh

my MIL install system 4. all the rooms aircon switched on less than 10 times last year. in fact this year.....only switched on ONCE during chinese new year

My aircon usage pattern is like your MIL hehe. My area rains almost daily, so fan is sufficient for me.

I know I won't get to save much on the electricity bill. But I will still get inverter aircon for my next house. Reason is that the noise from my current non-inverter aircon compressor is very loud, especially if it is right outside my bedroom windows. I want a good night sleep.