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Palum

Palum

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TheNozz said:
Need some help gauging the efficiency of my grandma's wall mounted AC unit and whether or not we need to replace it.

It's pretty old, at least early 80's but likely older. Wood grain panel Kenmore Coldspot manufactured for Sears. Model Number on info plate doesn't yield any results online

I can't find the wattage rating on the info plate, but I know it runs at:

8000 BTU/HR
7.5 Amps AHAM
Rated Volts: 115
Operating Volts: Min - 103.5 Max - 126.5
1 Phase - 60 Hz

Apparently, the wattage can be found by multiplying volt to current rating. I'm guessing that means 115(rated volts) x 7.5(amps) = 862.5 watts?

Dividing BTU by the wattage leaves me with 9.28 EER. Apparently an EER of 10 or higher is more desirable?

It does a decent job of cooling, but we're wondering if there's anything better on the market that could cost less energy and reduce the electric bill every month.
Click to expand...

Well bumping up 1 EER at 8k BTU is an extra 84 watts. Which means you save 1 kwh for every 11.9 hours of runtime.

So if you save 1 kwh a day for 120 days in summer and pay say 15c/kwh you could pay off a new $500 wall unit in about 28 years.

However, this assumes the current unit is working well and you don't get other efficiencies with a new unit (such as an inverter that runs at lower speed more often so takes a lot less energy for similar low to moderate cooling).

So let's assume your old unit is nearly dead and 50% less efficient than when new and you would replace with a fancy inverter unit. Maybe you save 7kwh a day in that case, so your RoI on a $500 unit is like 4 years.

Honestly, I would focus on comfort (temp, air quality cycle time, noise, features) if you're looking because you'll probably not make the money back.
 
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BrutulTM

BrutulTM

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Electricity is so cheap that most things you do to conserve it will never pay for themselves. People spend 10's of thousands of dollars on new windows because they're "more energy efficient" but they probably save you about $100/year or something. Just say you wanted new windows.
 
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Lanx

Lanx

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BrutulTM said:
Electricity is so cheap that most things you do to conserve it will never pay for themselves. People spend 10's of thousands of dollars on new windows because they're "more energy efficient" but they probably save you about $100/year or something. Just say you wanted new windows.
Click to expand...
yea it's like buying an ev, the initial upfront cost would take 20years b4 it outperforms a regular ice sedan in price, and by then the batteries need replacing anyway.

just say you want to play w/ an ev car
 
Goatface

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BrutulTM said:
Electricity is so cheap that most things you do to conserve it will never pay for themselves. People spend 10's of thousands of dollars on new windows because they're "more energy efficient" but they probably save you about $100/year or something. Just say you wanted new windows.
Click to expand...
think that is a hold over from when upgrading really meant something.
 
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Kajiimagi

Kajiimagi

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Captain Suave said:
Just skimming some reviews, this one is 15 SEER for $250. That saves just under half the electricity for the same cooling. You can do the math on how long you think it runs and figure out a payback period.

Click to expand...
regardless of energy cost, cannot recommend that AC unit enough. I have the 12K version in my south facing game room window and they it's so quiet that half the time I forget to turn it off when I leave the room for the night. It's also pretty energy efficient. I replaced the ol battle axe unit (also 12K) and noticed a wattage reduction in year/month bills.
 
Fogel

Fogel

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If she gets a new AC it'll no longer match the TV. Need to look at all aspects including decor!


VPRN4-1470333286-embed-tvs_1969euclid.jpg
 
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Kobayashi

Kobayashi

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TheNozz said:
Need some help gauging the efficiency of my grandma's wall mounted AC unit and whether or not we need to replace it.

It's pretty old, at least early 80's but likely older. Wood grain panel Kenmore Coldspot manufactured for Sears. Model Number on info plate doesn't yield any results online

I can't find the wattage rating on the info plate, but I know it runs at:

8000 BTU/HR
7.5 Amps AHAM
Rated Volts: 115
Operating Volts: Min - 103.5 Max - 126.5
1 Phase - 60 Hz

Apparently, the wattage can be found by multiplying volt to current rating. I'm guessing that means 115(rated volts) x 7.5(amps) = 862.5 watts?

Dividing BTU by the wattage leaves me with 9.28 EER. Apparently an EER of 10 or higher is more desirable?

It does a decent job of cooling, but we're wondering if there's anything better on the market that could cost less energy and reduce the electric bill every month.
Click to expand...
You can only do a straight multiplication to get wattage at unity power factor. Since that thing consists of a bunch of motors and probably not perfect compensation, you're probably generously at about 0.9 power factor when operating. That would push your calculation above 10 since you would multiply your apparent power by that power factor to get your active power.

Now, is an almost 40 year old window unit operating anywhere close to peak efficiency, probably not, so, I'd guess you'd realize some definite savings with a new inverter u-shaped unit, might be a lot quieter too. At the same time, would you ever realize enough savings to justify the cost of the new unit? Probably not. There are other tangible benefits to consider like aforementioned noise. Downside is I'd probably bet on the 80s unit surviving another 20 years over the inverter unit. Also, if your mom listens to AM radio, you might have issues. Depending on the switching frequency and modulation method, the inverter based one might annoy the shit out of dogs and small children too. (Last two are just my experience with inverters in general, really would depend on how they've designed the system)
 
TheNozz

TheNozz

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So I need to install a new door knob but it looks like the existing door is so old, it looks like this with the knob off:
IMG_6764.jpeg


What kind of tool do I need to bore it out to this:
IMG_6763.jpeg
 
Lanx

Lanx

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it costs 25bucks, but you can get it for 10bucks less if all youre going to do is wood doors, but you might want to get that b/c that includes a bi-metal hole saw so you can do metal doors too (which is worth it)
 
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ToeMissile

ToeMissile

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Kobayashi said:
You can only do a straight multiplication to get wattage at unity power factor. Since that thing consists of a bunch of motors and probably not perfect compensation, you're probably generously at about 0.9 power factor when operating. That would push your calculation above 10 since you would multiply your apparent power by that power factor to get your active power.

Now, is an almost 40 year old window unit operating anywhere close to peak efficiency, probably not, so, I'd guess you'd realize some definite savings with a new inverter u-shaped unit, might be a lot quieter too. At the same time, would you ever realize enough savings to justify the cost of the new unit? Probably not. There are other tangible benefits to consider like aforementioned noise. Downside is I'd probably bet on the 80s unit surviving another 20 years over the inverter unit. Also, if your mom listens to AM radio, you might have issues. Depending on the switching frequency and modulation method, the inverter based one might annoy the shit out of dogs and small children too. (Last two are just my experience with inverters in general, really would depend on how they've designed the system)
Click to expand...
Looks like there are some on sale at Amazon right now, a few different BTU capacities(?)

Limited-time deal: Midea 8,000 BTU U-Shaped Smart Inverter Window Air Conditioner –Cools up to 350 Sq. Ft., Ultra Quiet with Open Window Flexibility, Works with Alexa/Google Assistant, 35% Energy Savings, Remote Control https://a.co/d/4cvdO3w
 
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