Decisions, decisions - New aircon or more solar?

[Crossy]

In our bedroom is a 10 year old, 12,000 BTU Samsung conventional A/C. It's run for about 8-9 hours every night set to 28C. It's working just fine, although it's getting a little long in the tooth it's not really had a tough life.

 

I have 22k Baht burning a hole in my pocket (ok gently singeing a hole).

 

Do I :-

1. Buy a new inverter A/C and move the existing one to my workshop (which currently has no A/C).
2. Spend the $$$ on another 2.3kW of solar panels (I have the inverter already).
3. Do nothing.
4. Do something else.

 

Thoughts?

 

 

[Surelynot]

15 minutes ago, Crossy said:

Do I :-

1. Buy a new inverter A/C and move the existing one to my workshop (which currently has no A/C).
2. Spend the $$$ on another 2.3kW of solar panels (I have the inverter already).
3. Do nothing.
4. Do something else.

Stick it all on Bitcoin....what the hell......and sweat it out.

Edited July 4, 2021 by Surelynot

[carlyai]

Seeing you are going all green (eventually), option 2.

[Excel]

My advice would be leave the a/c there if it is still working OK. Invest the 22,000 via an online site, currently the odds being 15/8 on to win the Euros. Then with those winnings invest in England winning the world cup next year, currently quoted as 10/1. So by the end of next year you could potentially have turned your 22,000 of hole burning baht into 373,333 baht. With that you could afford new a/c and solar upgrade.

[jvs]

22000 Thousand?

Go for option a.

You will still have some money left over to buy nice things for your shop,some nice tools .

A shop with aircon will make you very happy and you will spend more time there doing things

that save money.

Wait until next year to buy more panels,they will be cheaper then.

 

 

 

[2 is 1]

Buy one small fan and drink rest money. Put that in bedroom and move AC from there in your workshop. If you feel hot sleep there whit all beer.

Edited July 4, 2021 by 2 is 1

[blackcab]

Option 1.

 

It's important to do something for yourself every now and then.

[tjo o tjim]

Crossy… I expected you to be more data driven!  ;)  Conventional wisdom is that you are best off reducing load first; my modification to the theorem is that you are best off reducing night-time load first.

 

I’m actually in a similar situation, and while I don’t have sufficient data to really tell me what is best, my 13-year old (iirc 24,000 btu/h) aircon seems to be the most likely candidate.  It generally only runs at night, but the screenshot below is from a particularly hot day that we turned it on early and sat in the bedroom until sunset.  Most days have a similar profile where we have a high pull-down load for the first hour and generally decreasing loads for the remainder of the night.  The unit mainly handles latent load; it can only get the room temperature 1-2C below outside temperature (which is fine for us).

 

My expectation is that through tying the setpoint into my home automation system, and going wiith a dual-inverter unit the long tail load should drop by close to 50%, and I should be able to save about 20% on the pull-down load.  I need to be able to compare it to room and outside temperature though to be more confident.

[Yellowtail]

Save another 20K and upgrade to a cassette unit...

[Crossy]

9 hours ago, Yellowtail said:

Save another 20K and upgrade to a cassette unit...

 

Do they make them as small as 12k BTU? Besides a cassette wouldn't fit in with our cathedral ceilings in the upstairs rooms.

[sezze]

What's different in a cassette unit ? I do know they are large and can be put horizontal and vertical ( like on floor lvl ) but is there any other reason to buy a cassette unit ?

 

in OP question , 12000 btu / 28c setting , shouldnt be working hard . Idk his electric consumption , but for 2.3 kWh it should be plenty to make up for the AC consumption of it .

[mudcat]

Option 1.  We replaced an old Samsung non-inverter A/C with a Daikin inverter unit, moving the Samsung to another room.

Did not use the Samsung on a regular basis until an accident caused us to add a  hospital bed to that room which made it a comfortable 'sick' room.  The Daikin we use to cool the room off down to outside early-nighttime temperature (~26 degrees) at which point we move the temperature up to 29 to keep the air dry and avoid using the  wall mounted fan. 

[Crossy]

1 minute ago, mudcat said:

Option 1.  We replaced an old Samsung non-inverter A/C with a Daikin inverter unit, moving the Samsung to another room.

Did not use the Samsung on a regular basis until an accident caused us to add a  hospital bed to that room which made it a comfortable 'sick' room.  The Daikin we use to cool the room off down to outside early-nighttime temperature (~26 degrees) at which point we move the temperature up to 29 to keep the air dry and avoid using the  wall mounted fan. 

 

That is very similar to our situation, did you notice a decrease in your power bill after switching to the inverter unit?

[Yellowtail]

2 hours ago, Crossy said:

Do they make them as small as 12k BTU?

 

 

 

 

 

2 hours ago, Crossy said:

Besides a cassette wouldn't fit in with our cathedral ceilings in the upstairs rooms.

 

You could hang with all-thread and box it, but going with another wall unit would certainly be easier.

[Yellowtail]

2 hours ago, sezze said:

What's different in a cassette unit ? I do know they are large and can be put horizontal and vertical ( like on floor lvl ) but is there any other reason to buy a cassette unit ?

 

No. I think you are referring to:

This is a cassette unit:

The cassette units hang from the ceiling, and are generally in the center of the room, rather than on the wall/perimeter the primary benefits are:

1. Propeller rather than wheel fan (quieter, more efficient) 

2. Fan never gets wet (Stays clean for years) 

3. Condensate is pumped out rather than relying on gravity to drain (locate anywhere, never clogs)

4. Return air drawn from top center of the room

5. Cool air is distributed about the perimeter of the room evenly, or can be directed to any part of the room

6. Larger filter area

7. Less frequent service

8. High capacity

 

Cons

1. Higher cost

2. Fewer installers are familiar with them, but they are getting much more popular, and will continue to do so.

 

 

 

[mudcat]

Yes, the KWh shown on our bills have dropped because of the regular use of a modern inverter unit and irregular use of the older non-inverter Samsung.  That said we use the inverter unit to cool off the bedroom in the early evening and then set the temperature to just above late-night ambient temperature (~29-degrees) so the unit primarily serves a fan and de-humidifier, so it is not the same usage as the wife setting the temperature on the older Samsung unit it replaced to ~24-degrees.

[Crossy]

5 minutes ago, mudcat said:

Yes, the KWh shown on our bills have dropped because of the regular use of a modern inverter unit and irregular use of the older non-inverter Samsung. 

I know it's difficult with varying usage etc. etc. but do you have an idea of payback time for the inverter unit vs energy savings?

[Yellowtail]

4 minutes ago, Crossy said:

I know it's difficult with varying usage etc. etc. but do you have an idea of payback time for the inverter unit vs energy savings?

Payback on the cost differential between conventional and inverter, or payback on replacing an existing conventional unit the is operating and sized correctly? 

 

 

[Crossy]

7 minutes ago, Yellowtail said:

Payback on the cost differential between conventional and inverter, or payback on replacing an existing conventional unit the is operating and sized correctly? 

We are talking about replacement of a currently functional unit, so the latter.

 

[Yellowtail]

12 minutes ago, Crossy said:

We are talking about replacement of a currently functional unit, so the latter.

Assuming the old unit is in good repair and reasonably efficient (it should be as it is a "name brand" and only ten years old) in a bedroom situation as you describe you would do very well to see a 20% reduction. 

 

It would be interesting to see a one month chart of what the existing unit draws vs what the new unit draws...

 

Even better if the inside and outside temps were charted as well.

 

How much is the compressor running now? The less it is actually running, the less savings you are going to see. At 28 C I doubt it's running much, so even if you saved 100% the payback period would be significant. 

 

Installing more panels would certainly make better economic sense, but buying new stuff is always fun. The best reason to buy anything is because you want it. I was skeptical of the inverters but I love the "quiet comfort" of mine.  

 

There is no magic. 

[Crossy]

19 minutes ago, Yellowtail said:

... but buying new stuff is always fun ...

Buying new TOYS is fun, new A/C isn't really a toy ???? 

[Yellowtail]

1 hour ago, Crossy said:

Buying new TOYS is fun, new A/C isn't really a toy ???? 

You don't enjoy going through the specs and whatnot? And being married, it is one of the only things I get to pick put by myself...

[tjo o tjim]

5 hours ago, Crossy said:

I know it's difficult with varying usage etc. etc. but do you have an idea of payback time for the inverter unit vs energy savings?

Do you know your current SEER? I would assume 1kWh/h/ton for a 12-SEER, and half that for a 24-SEER, so just estimate your running hours to get your payback. 
 

If the unit is oversized then payback can be better (while maintaining a fast pull-down time).

Edited July 8, 2021 by tjo o tjim

[Crossy]

3 minutes ago, tjo o tjim said:

Do you know your current SEER?

With some research I could probably find it and that of a potential replacement. How would that help?

 

[Muhendis]

Have you considered going geothermal?

 

[Yellowtail]

55 minutes ago, Crossy said:

With some research I could probably find it and that of a potential replacement. How would that help?

 

A good seer would be able to predict what your savings will be, along with winning lottery numbers and whatnot. 

 

I think what he is sawing is that give the way SEERs are calculated, you can calculate your savings as a percentage by dividing the old SEER by the new....

[tjo o tjim]

1 hour ago, Crossy said:

With some research I could probably find it and that of a potential replacement. How would that help?

 

If it is 10 years old, 12-14 is reasonable assumption. A 24 SEER should save you around 1,500kWh/year if run 9 hours/night at 28C. 

[Crossy]

The cheapest 24 SEER I can find with a quick search is 34k Baht (DAIKIN FTKZ12VV2S) the 22k Baht units are around 17-18 SEER.

 

So with an assumed saving of 1,500 units per annum (6,750 Baht @ 4.5 per unit). That's a payback of 5 years on energy usage.

 

Adding 330W solar panels at 2,890 Baht a piece (I already have the inverter) would generate roughly 400 units (1,800 Baht @ 4.5 per unit) per year per panel. Payback of 1.6 years on energy generation.

 

Purely on energy savings there's only one winner, but ...

[Amusements]

22K is heavy! My last place had a really old air con in it, and the landlord changed it as it was starting to break down, and the bills were massive.

When I moved here a couple of years ago, I bought a Mr Slim (MSY-KT09VF specs) from that electric store near Makro in Chewang. My bills are usually around 1k a month. I have my AC set on 26 with the fan on static/minimum, and have it on for around 8-9 hours a day. I do however only have a fairly small bedroom.

 

[Muhendis]

3 hours ago, Crossy said:

The cheapest 24 SEER I can find with a quick search is 34k Baht (DAIKIN FTKZ12VV2S) the 22k Baht units are around 17-18 SEER.

 

So with an assumed saving of 1,500 units per annum (6,750 Baht @ 4.5 per unit). That's a payback of 5 years on energy usage.

 

Adding 330W solar panels at 2,890 Baht a piece (I already have the inverter) would generate roughly 400 units (1,800 Baht @ 4.5 per unit) per year per panel. Payback of 1.6 years on energy generation.

 

Purely on energy savings there's only one winner, but ...

Longevity comes into it too.

 

Solar panels are good for well over twenty years.

 

Air con.? More bits to give trouble and in any case why change something that works.