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Old 04-16-17, 10:10 AM   #1
oil pan 4
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Default Higher efficiency window unit?

I am looking for a big 18,000btu 220v powered window unit that has a SEER rating greater than 12.
Are there any window units out there higher than 12?

I'm finding big window A/C units that have dreadfully low SEER ratings of like 9, 10 and barely over 11.

Even the cheapest non inverter split unit I can find has a SEER of around 15.

I may have to do a creative through the garage split install with condensation pump if I can't find a decent window unit.

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Old 04-16-17, 11:25 AM   #2
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Window units are not rated in SEER. They are rated in EER.

Central air conditioners are rated in both. There is a difference.

EER is a rating determined by a single standard condition, which SEER ratings are determined with multiple conditions, including conditions where it is cooler and the units operate more efficiently.

As a very rough figure, 13 SEER is roughly 11.5(+/- 5 depending on the system) EER in the standard split-system central air setups.
Usually the window AC units that are energy star that you can find on Craigslist are around 10.7 EER, this is around the 12-12.5 SEER range. The Energy Star standards changed about 2 or 3 years ago, but before that, the standards on the smaller units was around 10.7 EER.

Compared to the window air conditioners from the 70's and 80's that most older apartments still have installed today, the new energy star units are a significant improvement.

I think that the newest units out today that are roughly a 13 SEER or close to it are pretty good for a unit the size of a large luggage carry-on. These things have small coils in relation to their output and have their outlets in close proximity to their inlets.

I was actually disappointed when I saw non-inverter mini-splits with only 13 SEER, it seems with a ductless system that 15+ SEER should be close to automatic with large coils and no ductwork.
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Old 04-16-17, 12:01 PM   #3
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So it's still low efficiency compared to a good split inverter unit.
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Old 04-17-17, 01:42 AM   #4
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For a rough estimation, add 3 to the EER rating to get the SEER rating for window units. EER is measured at static conditions (95 degF outdoor / 75 degF indoor or close to it) and is directly equivalent to COP. SEER is not directly related to COP at many moments in time, it's just an average value that is calculated to yield higher numbers out of units that don't perform as well when it gets above 95 degF outside.

The industry does this to confuse the general population. For example, a 9000 btu window unit will generally have an EER that is 3 less than the SEER of a mini-split that has the same performance. Believe it or not, that 3 points sells lots of people into a mini-split that costs twice or three times as much. To be fair, there are more aspects to consider than raw performance. Apples versus oranges and such.

Window units without capacity control aren't going to have heavenly efficiency numbers. Manufacturers aren't highly interested in cramming inverter compressors and electronic expansion valves into window units. They are more interested in reducing the size and weight of window units to reduce handling difficulty and raw production cost. The energy star standard of 10.2 to 11 (depending on capacity) is good enough for 99 percent of everyone, so the cheaper and quieter and lighter that units can be designed, the more they will be competitive in this low-cost sector. In other words, they are not cost effective to improve much.

A new number, CEER, is the new EER for digital control board having room a/c units. It includes the standby power loss (5115 hrs x 1.4W vs. 750 hrs active load W) in the rating. I don't imagine it would be significantly different from EER, but it is a new number to further confuse the innocent.
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Old 04-17-17, 12:11 PM   #5
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Yes that's what it looks like, with the window units it's like who can make the cheapest one in compliance with government energy standards.

Wife doesn't mind spending the $ on a 2 ton inverter split.
We're looking at ones on ebay with 20 and 21 SEER rating. Since it will be quieter and use less energy than a window unit.
20 to 21 SEER seems to be the normal rating for the larger 2 ton and up inverter units.

I have never heard of or seen a window unit that does something more advanced than just turn on and off.
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Old 04-17-17, 12:27 PM   #6
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A 2 ton window unit at home Depot has a CEER of 9.8, that seems kind of low.

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Old 04-17-17, 08:02 PM   #7
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Packing 24000 BTUhr of capacity into a window unit is asking for a pile of heat exchange to occur in a very small package with small condensing and evaporator coils. I really don't see needing that kind of capacity at a single point source unless that is in an area with a significant amount of glass, cooking loads, or some other high load environment. I think most people who probably buy one of these huge window units either thought 'bigger is better', or 'hey, this fits the measurement of the window, I don't need to build or buy a spacer'. There are some niche applications for a single point air conditioner of a 2 ton capacity but I don't think many people buying these are buying the proper size.

My 2100sq ft house should have a 1.5 ton central air system, but has a 2 ton 8.5 SEER(yes, SEER) system built in 1986. If I didn't have roommates living in the house, I'd toss my 5350BTUhr(500 watt 10.7 EER) unit back into the bedroom window and keep the bedroom door shut and call it good. I don't mind using my bedroom as a living space when I'm the only one here, saves a pile of money. The air conditioner was either $20 or $40 on Craigslist, was an EER rating that was still Energy Star compliant at the time I bought it, and cools the bedroom with the door shut just fine. I've never actually seen it use 500 watts, it's usually under 450 watts and the capacity at lower than the 95 degree test conditions is probably higher. I'm getting a rough SEER of probably 12-12.5. At 450 watts and a worst case day where it runs for 18 hours, it's consuming about 8kwh. My central air burns that much power in about 3.4 hours and if I'm cooling the whole house, it will use way more than that on even an 80 degree sunny day.

For the price I bought it for and my niche single room use for air conditioning, a mini-split wouldn't pay off. If I open the bedroom door and let it cool the rest of the house off and use the existing 2 ton for a few hours to supplement on the hottest days, a 1 ton mini-split would be great and if I use it for heating with the door shut method, keeping the rest of the house cooler, it would save quite a bit on heating in the shoulder months. The natural gas in my area is dirt cheap (65 cents per therm) and electric heat is currently 4.5 times the cost. Getting a COP of 4.5 at temperatures that I actually need heat in Minnesota is not easy, even with a mini-split, so heating a smaller space while letting the rest of the space be colder would be the only real way to be cost positive.
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Old 04-17-17, 10:30 PM   #8
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Quote:
Originally Posted by oil pan 4 View Post
A 2 ton window unit at home Depot has a CEER of 9.8, that seems kind of low.
Down from 10 EER on account of the digital control. Twisty knobs don't add any vampire load.

What is the intended purpose of the unit? Temporary, permanent, seasonal, year-round? What area will it serve? Why a window unit? It sounds like you're steering towards a mini-split or split system, so the cost and scope increases in that general direction. Better research is justified in this case.

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Old 04-19-17, 11:39 AM   #9
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If I installed a heat pump inverter split like I did in the bedroom I would use it year round.

The window unit is just a quick and dirty way to cool off the house.
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Old 04-24-17, 06:53 PM   #10
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I bought the 2 ton senville inverter split, 20 SEER.
No window unit.

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