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MN Renovator · 04-17-17, 08:02 PM

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.

04-17-17, 08:02 PM	#7
MN Renovator Less usage=Cheaper bills Join Date: Nov 2010 Location: Minneapolis, MN Posts: 939 Thanks: 41 Thanked 116 Times in 90 Posts	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.