Question about old A/C and electric usage

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semperfiguy
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Question about old A/C and electric usage

Post by semperfiguy » April 25, 2019, 9:36 am

My 8 year old LG 18,000 BTU living room unit recently sprang a Freon leak in the outside unit, and rather than buy a new system I opted for an older reconditioned 21,000 BTU outside unit. It's guaranteed for 6 months and works great, but this month's electric bill was 1000 Baht higher than my previous highest bill in 8 years. Of course, this has been an unusually hot April, but could it be that this older unit is not as energy efficient, and thus the higher bill? Is it possible for an older unit to use that much more electricity to maintain the same inside temperature?


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Re: Question about old A/C and electric usage

Post by Doodoo » April 25, 2019, 9:53 am


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Re: Question about old A/C and electric usage

Post by tamada » April 25, 2019, 10:05 am

It is possible for an older, bigger unit in increasingly hot conditions to cost more.

Are you comparing this latest April electric bill with the last 7 April's?

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Re: Question about old A/C and electric usage

Post by semperfiguy » April 25, 2019, 10:07 am

tamada wrote:
April 25, 2019, 10:05 am
It is possible for an older, bigger unit in increasingly hot conditions to cost more.

Are you comparing this latest April electric bill with the last 7 April's?


Yes! My units of electric usage went from 452 last April to 826 this April. Sure, it's hotter this year, but certainly not that much hotter.
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Re: Question about old A/C and electric usage

Post by saint » April 25, 2019, 10:14 am

Do not forget that electricity prices went up by around 12 % this month .

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Re: Question about old A/C and electric usage

Post by sometimewoodworker » April 25, 2019, 11:19 am

saint wrote:
April 25, 2019, 10:14 am
Do not forget that electricity prices went up by around 12 % this month .
That doesn't affect the units used only the cost of them
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Re: Question about old A/C and electric usage

Post by bluejets » April 25, 2019, 11:22 am

Just because it says 21,000 btu on the label does not mean given it is old, that it is efficient.
Probably worn out, huffing and puffing to keep up with the load.

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Re: Question about old A/C and electric usage

Post by glalt » April 25, 2019, 11:33 am

I think you picked an expensive way to save money. New units are more efficient and your electricity saving would have quickly returned the money difference between an old unit and a new unit.

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Re: Question about old A/C and electric usage

Post by parrot » April 25, 2019, 12:21 pm

Apples and oranges, I understand. But we cashed in our 10 year old Toyota truck last year for a new Revo. Smaller engine, more power, and easily 10% better gas mileage. Oh, and new truck smell!

More on ACs, over 10 years ago we cashed in an antique Fujitsu AC for new Daikin inverters. Our house is much cooler, the new acs are near silent, they suck out many liters of moisture each day during the rainy season, and our electric bills are lower despite a significant increase in use.
I never complained about my 386 desktop when I had one, but I'd never go back to one now!

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Re: Question about old A/C and electric usage

Post by tamada » April 25, 2019, 12:50 pm

If the % increase in the bill is less than the % increase in units used, then factoring in the rates increase, maybe the OP's choice of buying a pre-owned, larger aircon isn't so significant an issue here?

Possibly using aircon more than the previous 'high' April? Despite being away for most of the year so far, I know that Mrs tam is firing up the bedroom aircon earlier and running it for longer than she normally would when I am away. We also added a second unit in the kids bedroom in March. I think there's been maybe a 6.5% increase over March's billing? I am on another top-secret mission overseas right now so can't compare the units or the April '18 and April '19 units/costs.

Good to learn that rates increased last month though, I had missed that. I will tell Mrs tam but she probably knows already.

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Re: Question about old A/C and electric usage

Post by RLTrader » April 25, 2019, 1:07 pm

My elect for Mar - last yr 483kw this yr 490kw

for April last yr 500kw this yr 688kw

because of the heat this year was expecting the increase, for been turning on 2 AC in afternoon for a few weeks now. Can never ever remember doing this since I have lived here.

When figured out it does seem that electric has gone up. Last month 4.19 per kw this month 4.31 per kw

Anyways my bill went up by 911฿ and I used 198 kw more than last month.

Think you just might want to wait for normal weather, then see if there is a difference.

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Re: Question about old A/C and electric usage

Post by tamada » April 25, 2019, 1:23 pm

semperfiguy wrote:
April 25, 2019, 10:07 am
tamada wrote:
April 25, 2019, 10:05 am
It is possible for an older, bigger unit in increasingly hot conditions to cost more.

Are you comparing this latest April electric bill with the last 7 April's?
Yes! My units of electric usage went from 452 last April to 826 this April. Sure, it's hotter this year, but certainly not that much hotter.
On the premise that the bill doesn't lie, you used 83% more electricity which would be hard to attribute to one air conditioner unless it's a real fossil and a lot OLDER than the 8 year-old one it replaced.

My first home build in Naklua around 1980 had new aircon installed. When I relocated back to Thailand some 23 years later, I rented my old house from my mate who I had sold it to (he was on top-secret foreign assignments as well). It still had the original aircons installed and part of the deal with my mate/landlord was that the much-needed refurbishments would come off the rent. The aircons were the first to go and IIRC, that made a whopping +1000 baht break on the monthly electric bill.

It was a great deal BTW, after I terminated the 16-month lease to relocate to Udon, he got a hugely refurbished home, aircon, wiring, breaker box, shower units, water pump, plumbing, lawn and sprinklers, new doors, new roof on the maids quarters and he only had to pay me around 65,000 baht to leave!

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Re: Question about old A/C and electric usage

Post by pf-flyer » April 25, 2019, 2:09 pm

The issue is a matter of mismatched Condenser and Evaporator.
You have an 18000 BTU Evaporator and a 21000 BTU Condenser. The system can only cool at the rate that the 18000 BTU Evaporator can provide. You have a what would be a larger capacity compressor running in the outside 21000 BTU Condenser unit. That is why you used more energy to cool the same room because the 18000 BTU evaporator can only absorb the heat at the rate of an 18000 BTU unit and you are feeding the 18000 BTU evaporator with a 21000 BTU outside unit. The physics of heat transfer. If you had a 21000 BTU rated evaporator that matched the Condenser you would see a difference.
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Re: Question about old A/C and electric usage

Post by tamada » April 25, 2019, 2:30 pm

pf-flyer wrote:
April 25, 2019, 2:09 pm
The issue is a matter of mismatched Condenser and Evaporator.
You have an 18000 BTU Evaporator and a 21000 BTU Condenser. The system can only cool at the rate that the 18000 BTU Evaporator can provide. You have a what would be a larger capacity compressor running in the outside 21000 BTU Condenser unit. That is why you used more energy to cool the same room because the 18000 BTU evaporator can only absorb the heat at the rate of an 18000 BTU unit and you are feeding the 18000 BTU evaporator with a 21000 BTU outside unit. The physics of heat transfer. If you had a 21000 BTU rated evaporator that matched the Condenser you would see a difference.
Well spotted! If indeed the OP has only replaced the external condenser with a larger unit and retained the original, smaller, internal evaporator unit, then yes, the frustrated physics of heat transfer is EXACTLY what's eating his lunch.

No need to pass on the number of the Einstein that proposed and facilitated this money-saver!

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Re: Question about old A/C and electric usage

Post by semperfiguy » April 25, 2019, 3:24 pm

I want to take this opportunity to thank all of those who have contributed their comments here. I think I understand the problems now. Yea, I really screwed up when I let the A/C guy tell me that he couldn't replace the leaking coil in my original unit, and he suggested that I replace the entire outside unit with a refurbished unit that he could find for me. After he installed the refurbished unit and was walking away carrying my original unit to his truck, I knew something was wrong when I saw that big grin on his face like he got some real joy from screwing over the farang...and I fell for it. No doubt he later repaired the coil in my original unit and convinced the next sucker to buy a refurbished unit...mine!
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Re: Question about old A/C and electric usage

Post by tamada » April 26, 2019, 10:55 am

semperfiguy wrote:
April 25, 2019, 3:24 pm
I want to take this opportunity to thank all of those who have contributed their comments here. I think I understand the problems now. Yea, I really screwed up when I let the A/C guy tell me that he couldn't replace the leaking coil in my original unit, and he suggested that I replace the entire outside unit with a refurbished unit that he could find for me. After he installed the refurbished unit and was walking away carrying my original unit to his truck, I knew something was wrong when I saw that big grin on his face like he got some real joy from screwing over the farang...and I fell for it. No doubt he later repaired the coil in my original unit and convinced the next sucker to buy a refurbished unit...mine!
You may take succor in the hope that he may have fobbed-off your repaired 18 kbtu condenser unit on some sucker local who has a 14 kbtu evaporator.

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Re: Question about old A/C and electric usage

Post by bluejets » April 26, 2019, 2:38 pm

Many of these units are made from materials that quite simply, do not take any sort of "leak repair" with any amount of success.

Any aluminium used is usually of a type that will not weld successfully and any steel lines are "rolled" and as soon as one hits it with a brazing torch, the tube splits open.

As Glalt says, false economy.

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