Air conditioning question

[dddave]

I hope this is the appropriate forum.

I live in a rented, 50 S/M (150 cubic/M) studio condo in Bangkok, One longitudinal, south facing wall that gets warm to the touch in daytime. Other 3 walls are sheltered from direct sun. (9th floor, large, older apartment bldg).

When I rented this unit 10 years ago it had no air and it was understood that if I wanted air, purchase and installation would be at my own expense. I found a used inside/outside unit, not marked but about 25,000 BTU and had it installed, B15000 all in.

It has worked pretty well over the 10 years, costing me about B5000 since for maintenance and repairs. Now it is beginning to have increasingly more problems and has become much noisier.

I buy electricity at the condo rate of about B4.2/unit including taxes and surcharges. Up until two years ago my elect bill was about B3000 p/m spread over a year. I usually run the AC whenever I am in the room, maybe about 15 to 18 hours a day.

Lately my elect. bill has been climbing to beyond B5000 p/m and I suspect the inefficiency of my old unit bears the blame.

I need advice on what size I actually need as I am getting a lot of conflicting information. I would like to keep the cost down but do want to buy new this time...no more 2nd hand. Research I did on the internet suggests I could get away with a 18,000 to 22,000 BTU unit but local salespeople in stores like Emporium, Best Buy and Home Pro consistently suggest 35,000 BTU's for 50 s/m. That puts cost close to B40,000 for a decent, major manufacturers unit, which is out of my range.

What are the trade-offs if I get a smaller 20,000 +- unit? Will it cost me appreciably more in the long run by having to work harder. Is the 35,000 BTU overkill or is it actually the size that is necessary?

Most of the websites I used for calculating what I needed were Australian based...I know it can get pretty hot there but would their guidelines be adjusted lower because of an overall cooler climate? Should I not rely on what they suggest?

Also, any personal experiences with various brands available here would also be appreciated. i know DAIKIN is the gold standard but they seem to be fully half again as expensive as comparably sized units. Also, is it worth the 30 to 50 % premium to go for a unit with an inverter?

I know they are said to be more efficient but are they that much more efficient to justify the added cost?

All information appreciated.

[IMHO]

If 25,000 BTU worked for you before, it will work for you again, simple

An inverter will save electricity when 100% cooling power isn't needed.

The price of electricity has gone up quite a bit over the last few years, so that could explain the increase in your monthly bill actually. Are you sure you're only paying 4.2 Baht/unit? I haven't seen domestic electric rates that low for several months now, Last month's bill worked out to about 4.5x Baht/unit, including ft and VAT.

[KittenKong]

If 25,000 BTU worked for you before, it will work for you again, simple

That's how I did my calculation when I replaced my clapped-out old unit a year ago, and it worked for me. 24KBTU for approx. 50sqm living space.

An inverter will save electricity when 100% cooling power isn't needed.

My savings come to around 60-70% of my previous bills, though I cant be sure how much is down to the inverter and how much is just down to newness. The saving is there though, no doubt about it.

There is also the question of the complete absence of start-up/shut-down noise with outdoor unit of the new inverter aircon, and little noise whilst it's running, and the general quietness of the indoor unit which is presumably down to newness only.

Having had inverter units in Europe also (the hot-cold sort) I would never consider a non-inverter aircon again.

[ksamuiguy]

Pay back is very long, over 8 years on average for an A/C unit. That said they are great energy savers. We use inverters on all motors over 2 HP in many applications.

[dddave]

"The price of electricity has gone up quite a bit over the last few years, so that could explain the increase in your monthly bill actually. Are you sure you're only paying 4.2 Baht/unit? I haven't seen domestic electric rates that low for several months now, Last month's bill worked out to about 4.5x Baht/unit, including ft and VAT".

You're right..I recalculated my last 2 months bills and it is indeed closer to B4.5/unit.

Thanks to all for the comments and information.

[MichaelJohn]

From the little I know I think 18-22k is too small for your room and would tend to agree with the shop calcs at 35k BTU's. But, you can't fault the logic that if you have 25k and it works then have another 25k unit?!

I have just installed 3 x Mitsubishi "Mr Slim" Inverters (87 SqM condo) and I can say they are very quiet and cheap to run. I have the morning sun directly in my windows and even so it's sometimes hard to know they're on they're so quiet.

My elec bill for 2 x 24k and 1 x 12k has been B2,300 per month for the last 2 months since installation. The big two are both on for 10 hours during the day and the little one is on 9 hours at night.

Cost approx B45k each fitted.

[ToddinChonburi]

I have an 18000 in 40 sqm condo and It seems to do OK. My condo faces the north and do not get any direct sun light but the bathroom is by the door the farthest away from ac and that is always warm. just moved in here on December 1st.

I had the big Mitsubishi Heavy duty commercial in the old place and had the hot afternoon sun. The fan was much stronger and it cooled down the 39 sqm much faster. My highest electric bill was just under 1700 baht . When working on computer in condo I could shut it off for 30 minutes or more at a time to save on bill. I have not had air on in new place much at all during the day . I let run at night when sleeping .

[dddave]

From the little I know I think 18-22k is too small for your room and would tend to agree with the shop calcs at 35k BTU's. But, you can't fault the logic that if you have 25k and it works then have another 25k unit?!

I have just installed 3 x Mitsubishi "Mr Slim" Inverters (87 SqM condo) and I can say they are very quiet and cheap to run. I have the morning sun directly in my windows and even so it's sometimes hard to know they're on they're so quiet.

My elec bill for 2 x 24k and 1 x 12k has been B2,300 per month for the last 2 months since installation. The big two are both on for 10 hours during the day and the little one is on 9 hours at night.

Cost approx B45k each fitted.

Thanks. I am beginning to consider going your route with multiple a/c units. It is really wasteful for me to cool the entire room at night when I am sleeping in one corner. I tried floor to ceiling drapes enclosing my sleeping area and it helps somewhat but not all that much.

I could actually wall off my sleeping area using lightweight panels and create a bedroom. I could install a much smaller unit there (10,000+-) for night time use and a larger, maybe 18,000 unit at the other end of my room for the remaining area...never needing to use both simultaneously.

From reading these responses, it's clear to me I am spending way too much with my old unit....plus the thing is as loud as locomotive.

Food for thought.

[KittenKong]

Thanks. I am beginning to consider going your route with multiple a/c units. It is really wasteful for me to cool the entire room at night when I am sleeping in one corner. I tried floor to ceiling drapes enclosing my sleeping area and it helps somewhat but not all that much.

I could actually wall off my sleeping area using lightweight panels and create a bedroom. I could install a much smaller unit there (10,000+-) for night time use and a larger, maybe 18,000 unit at the other end of my room for the remaining area...never needing to use both simultaneously.

This seems like a lot of work and inconvenience for little reward.

My 24kBTU inverter aircon cools my entire studio (similar size to yours) for a total monthly electricity bill (including hot water, big TV, PC, fridge-freezer etc) of well under 2000B.

[KittenKong]

Pay back is very long, over 8 years on average for an A/C unit. That said they are great energy savers.

I estimate that my new inverter air-con will pay for itself in under a year. Of course it does rather depend on how bad the old air-con unit was.

[Naam]

go for inverter! general consensus of Thaivisa experts is that your dogs will salivate less, your wife will demand more sex and the electricity company might send refunds because of negative consumption

[dddave]

go for inverter! general consensus of Thaivisa experts is that your dogs will salivate less, your wife will demand more sex and the electricity company might send refunds because of negative consumption

Well, If I had either, I'd get the inverter today and reap the benefits you describe, but being a fully unencumbered old fella, I only have myself to please.

KittenKong...That's really interesting that your bill runs in the B2000 range. I'm very jealous. Are you in the Bangkok area? I've figured I can partition the room with 100cmX250 cm panels for about B10000. A neighbor in my building did this a few years ago and the craftsman who built the panels is still available so I do have something to base it on. The panels rest in channel tracks so little real construction required.

Even considering a 25,000 BTU inverter unit, wouldn't is still cost considerably less to cool a 20 s/m room with a 10 to 12,000 BTU unit for 8 to 10 hours a night rather than cooling the whole 50 s/m room at night with the larger?

Buying 2 smaller units, installation included in the price seems really no more expensive than a single 25 K BTU unit with inverter.

[bartender100]

18 hours a day in your room, are you in self imposed jail?

[KittenKong]

KittenKong...That's really interesting that your bill runs in the B2000 range. I'm very jealous. Are you in the Bangkok area? I've figured I can partition the room with 100cmX250 cm panels for about B10000. A neighbor in my building did this a few years ago and the craftsman who built the panels is still available so I do have something to base it on. The panels rest in channel tracks so little real construction required.

Even considering a 25,000 BTU inverter unit, wouldn't is still cost considerably less to cool a 20 s/m room with a 10 to 12,000 BTU unit for 8 to 10 hours a night rather than cooling the whole 50 s/m room at night with the larger?

Buying 2 smaller units, installation included in the price seems really no more expensive than a single 25 K BTU unit with inverter.

I'm in Jomtien. I run the aircon more or less 24/7 except during the couple of cool months, but I set it at 28 degrees. I also have two ceiling fans running 24/7 at the lowest speed.

My bill used to be around 3000B but climbed to 5000B or more during the last year of using the old air-con unit, even though it was serviced correctly. Since installing the new one it hovers around 1700B. I prefer to have one large unit because I dont want the extra clutter of two units and two compressors (I suppose one could fit a model that has a single compressor with two outputs and two indoor units).

I certainly would not want to build walls in my condo: the main thing I like about it is the panoramic view from everywhere inside (one entire wall is glass) and the space and the open-plan setting. If you dont mind having walls then logic suggests that it would be cheaper to cool just half the condo for half the time rather than all the condo all the time.

[IMHO]

go for inverter! general consensus of Thaivisa experts is that your dogs will salivate less, your wife will demand more sex and the electricity company might send refunds because of negative consumption

Maybe that explains it! I thought it was just her going through the "dirty thirties". No more inverter AC's for me then