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Old 08-11-2019, 11:54 AM   #61
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I am enjoying one right now, and have been monitoring its operation.

....

PS. Because I did the installation myself and did not ask for any quote, I do not know what the normal charge is. In my case, it involves quite a bit of work to run the 33-ft refrigerant lines through the attic.
Was running the drain line from the interior unit a problem? We had a mini-split with two head units installed and were able to locate them in spots that were acceptable aesthetically and that allowed a downward slope on the drains to piping runs that were also acceptable. I would consider installing a mini-split in a rental we have, but most of the ceilings are coved. The one decent location is in the house interior - and I don't think running a drain line up into the attic would be very functional!

We are pleased with the mini-splits - not a lot of AC weather in Oregon, but installing and removing the window air unit we had was an experience, and the noise level was way way beyond the mini split. Also like having a heat backup to the gas furnace (which was down when we had to come back up in January), fireplace, and portable electric heaters.
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Old 08-11-2019, 12:42 PM   #62
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Yes, the condensation drain line would be a problem for some installations.

In my case, the indoor unit is mounted high in the vaulted entrance hall, next to the garage. The unit is mounted higher than 8 ft meaning above the garage ceiling, which allows a gently sloped PVC line to be installed in the garage attic to drain to the outside. The high location of the unit puts it out of view and makes it not obtrusive to the eye, particularly as it is fairly big for being a 18,000 BTU/hr unit.

For most installations, people will have the unit on an exterior wall, and the refrigerant lines and drain line simply go through the wall to reach the exterior where the compressor is located. That will make things very simple.
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Old 08-11-2019, 03:12 PM   #63
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...

I have observed the power drawn of this 18,000 BTU/hr unit being the max at 1.4 kW in midday to 300W in the morning. No "bang-bang control". It's just beautiful.

When it gets cooler in a couple of months, I expect to see the outdoor fan and compressor completely stop in the morning, while the indoor fan runs at a very low speed to circulate the air. ...

So almost a 5:1 operating range - impressive. Do you know if the efficiency (COP) is similar across that range? I suppose it drops off at the low range, and that's why they switch to on/off control.

Oh, for those unfamiliar with the term, "bang-bang" is a control systems term for ON-OFF control, like you find in a typical single stage furnace/AC, a toaster, water heater, etc. Any system that is truly ON-OFF rather than varying the level, like you do with the gas pedal on a car.

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Old 08-11-2019, 08:08 PM   #64
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Similarly to fuel efficiency of a car, it is reasonable to expect that COP of a variable-speed compressor will peak at an intermediate speed, then drops off at a low speed. The manufacturer certainly does not want to run the compressor below a certain minimum speed, similarly to having a car crawling along at idle speed will not get you very good mpg.

COP of an AC will also rise when the outdoor temperature drops. It is not just the lower speed of the compressor that results in the low power consumption in the morning. The refrigerant can liquefy at a lower pressure when the temperature at the condenser drops, and the reduced head pressure presented to the compressor will result in a lower electrical load for the same speed.

By the way, I did a quick look into how EER and SEER must be measured by manufacturers, so that everyone plays by the same rule.

In the old days, EER is measured at indoor temperature of 80F and outdoor temperature of 95F. For a single speed motor, that is it.

For SEER, the EER is measured at 8 different outdoor temperatures, and the values are combined in a weighted average, hence the name "Seasonal EER" to account for the fact that it is not always that hot.

For dual-capacity ACs, the tests are specified to allow for the automatic switching of the unit to the lower speed when the conditions are favorable for the latter. For variable-speed units, the tests are even more involved.

PS. This morning at 7AM, I saw the mini-split running at 700W. The outdoor was around 90F. The time I saw the low 300W power drawn was more than a month ago, when I first installed the unit. It was a lot cooler in the morning then.
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Old 08-17-2019, 09:06 AM   #65
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I can tell that I'm not in the same league as you all! I'd probably just buy a window air conditioner and leave it at that.

I admit that the rest of my house does have central AC. But this is just one room that isn't intended to be used a whole lot from what I am reading between the lines.
Not only the least expense upfront but also when repair is needed you can buy another for the price of a service call. The smallest units should do the job on such a small space and cost around $200 for a better brand.
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Old 08-18-2019, 11:53 AM   #66
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Since I haven't seen this mentioned, here is one other thing to keep in mind. If you go the route of closing off the existing supply and return ducts, you will want to make sure that the existing AC will still operate correctly. When the indoor coil doesn't have enough air moving over it, it can ice over at which point bad things start happening. So if you have a contractor put in a mini split and close off the existing ducts, get it in writing from them that they'll guarantee there won't be issues with the existing coil icing over.

Ask me how I know, I have two townhomes built in 2015 that I'm in the middle of spending $2k each to add more ductwork as the original contractor didn't put enough in. Thus, both places start having issues on days when the tenants are running the AC quite a bit (but not trying to get to any kind of unusual temperate setting, just the hot days of summer)
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Old 08-18-2019, 12:16 PM   #67
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Not only the least expense upfront but also when repair is needed you can buy another for the price of a service call. The smallest units should do the job on such a small space and cost around $200 for a better brand.


I would not mind a window AC for a small room. But when you have a large window that slides horizontally, it is not amenable to mount a window AC.

The OP does not even have any window. The wall is also masonry, else knocking out a rectangular hole in a stud wall would not be hard either.
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Old 08-18-2019, 01:07 PM   #68
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I agree there is no easy way to get a window unit installed. Without a thermostat control for the room it will be warmer than the part of the house that is regulating the temp setting due to the higher heat gain in the room. Increasing the air exchange with the rest of the house could help but is probably in the cost range of the mini split system already mentioned.
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Old 08-18-2019, 03:59 PM   #69
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Definitely will bring it up, and if they claim "no problem," ask for it in writing.

Now, would there be any issues using the mini-split with the ducts left open?

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Since I haven't seen this mentioned, here is one other thing to keep in mind. If you go the route of closing off the existing supply and return ducts, you will want to make sure that the existing AC will still operate correctly. When the indoor coil doesn't have enough air moving over it, it can ice over at which point bad things start happening. So if you have a contractor put in a mini split and close off the existing ducts, get it in writing from them that they'll guarantee there won't be issues with the existing coil icing over.

Ask me how I know, I have two townhomes built in 2015 that I'm in the middle of spending $2k each to add more ductwork as the original contractor didn't put enough in. Thus, both places start having issues on days when the tenants are running the AC quite a bit (but not trying to get to any kind of unusual temperate setting, just the hot days of summer)
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Old 08-19-2019, 08:24 AM   #70
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Check out a split system. We have one in our office and it's great. It wasn't that expensive either.
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Old 08-19-2019, 09:05 AM   #71
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Check out a split system. We have one in our office and it's great. It wasn't that expensive either.
The nomenclature is important. A "split system" is what most homes in the US have had for decades, and what is already in the home of the OP. A "mini-split" is newer to the US market, it normally has separate evaporator coils/fans/thermostats in each room where there is an evap coil/fan.
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Old 08-19-2019, 09:16 AM   #72
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The mini-split is also called ductless.

In exchange for the ungainly exposed airhandler, the blower is more efficient because it does not have to push air through long and narrow ducts. There's also no heat gain or loss due to the ducts being in the attic with the old central system.

There are now airhandlers that are flush-mounted in the ceiling, and look just like a ceiling vent. These allow the temperature in each room to be set individually.
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Old 08-19-2019, 09:40 AM   #73
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LG has a picture frame airhandler unit that hangs on the wall. Manufactures of the split systems are getting more creative and realize some people don't like the look of bread boxes hanging on the wall. Minisplit systems with the variable speed inverter technology are amazing.

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Old 08-19-2019, 10:26 AM   #74
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Oh, my. That heat load calculator asks for a lot of info that we can't lay our hands on. Especially insulation - except for the attic, which has about 16-18" of loose insulation, there's no telling what's in the walls, floors, ceilings. Even the garage under the Frog is drywalled.
If you know the age of the home (look at your toilet lid!) you may be able to google building code for that era. Most homes would be built & insulated at that level. Building code = the worst home you can legally build
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Old 08-19-2019, 03:00 PM   #75
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Thank you for letting me know the units do not have to be ugly. I'm sure there's a beauty premium, though.

The 2 contractors I've interviewed, pushed Haier pretty hard. Something felt odd about this, as I've never heard Haier called a great quality brand. I figure Haier must be offering them incentives (maybe to overcome tariffs).
I've called a halt to the mini-split project until we can look into everything you all have told me about.
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Old 08-21-2019, 08:39 AM   #76
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The OP said this room will be used as a studio. Perhaps it can also serve as a lab to experiment with a novel AC concept as laid out here in this video.

No, this Youtuber is not a crank. He explored some novel ideas that will need more refinement before it becomes practical. It's something for the OP and her husband to occupy their time and have some fun.

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