Advantage of 230v wall unit AC vs. 115v same 12K BTU?

537 Views 14 Replies 6 Participants Last post by rjniles, Jun 1, 2020

justplumducky

Discussion Starter · May 31, 2020

Advantage of 230v wall unit AC vs. 115v same 12K BTU?

I've already taken delivery of a 12K BTU thu-the-wall unit, and running a dedicated circuit for it soon, because I wanted to not add any load to the bedroom circuit (same as living room circuit where AC goes) to which a buyer later might want to add a small wall unit in order to keep the bedroom door closed at night, or even occasionally in daytime.

If the circuit resistance for 230v 12K BTU unit is same as a 115v 12K BTU unit, then the only advantage is lower amp draw (I = E/R)?

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user_12345a

· #2 · May 31, 2020

Less amp draw and the circuit can deliver more current without larger/lower gauge wire, can support a bigger a/c unit or one with electric heat exceeding 1500w.

SeniorSitizen

· #3 · Jun 1, 2020

I've had that question. I don't do math very well. How much less amp draw?

user_12345a

· #4 · Jun 1, 2020

Half, twice as much energy dissipated per electron passed though the circuit with 240v compared to 120v.

justplumducky

Discussion Starter · #5 · Jun 1, 2020 (Edited)

SeniorSitizen said:
I've had that question. I don't do math very well. How much less amp draw?

All I know is a few formulas, so decided to see if the Rated Input (w) from the Technical Specs page would work in my Power formula (P=EI) for comparison of amp draw for the 115v model and the 230v model.

115v model
P=EI
P(power in watts) = E(volts) x I (amps)
So I = P/E
I = 1142w*/115v
*1142w is the Rated Input (w) from tech specs page for this 115v model
https://www.emersonquietkool.com/ttw-2/eatc12re1/ Scroll down to tech specs.

I = 1142w/115v, or 9.93 amps
--------------------------------------------

230v model
Using the same above formula:
I = P/E
I = 1142w*/230v
*1142 is also the Rated Input (w) from tech specs page for this 230v model https://www.emersonquietkool.com/ttw-2/eatc12re2/ Scroll down to tech specs.

I = 1142/230v, or 4.96 amps

I have the 230v 12K BTU model, and the data label on the right side of the unit says: "5.2/56 Amps, so since my calculation of the 230v unit is 4.96 amps, does this comparison of amps work? The data label on the 115v model will read approximately 9.93 amps per the 115v calculation above?

In other words, 230v unit is less amp draw, because of higher voltage and same Rated Input (w) as the 115v model, and not because of same resistance as I first mentioned, or does this comparison not work at all?

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user_12345a

· #6 · Jun 1, 2020

240v is half the amps as 120v to deliver the same power.

Fan motors are rated in FLA, full load amps. Usually, the motor is not run fully loaded and rpm is limited by motor characteristics.

Compressors are rated in RLA, rated load amps. They take the amperage required to trip the thermal overload and adjust it with a formula.

Amp ratings don't always reflect draw in the real world. A/c compressors typically draw 80% or less of rated amps unless it's really hot.

justplumducky

Discussion Starter · #7 · Jun 1, 2020 (Edited)

user_12345a said:
240v is half the amps as 120v to deliver the same power.

Fan motors are rated in FLA, full load amps. Usually, the motor is not run fully loaded and rpm is limited by motor characteristics.

Compressors are rated in RLA, rated load amps. They take the amperage required to trip the thermal overload and adjust it with a formula.

Amp ratings don't always reflect draw in the real world. A/c compressors typically draw 80% or less of rated amps unless it's really hot.

OK, I believe you've found no fault with my comparison numbers used and the result, which is 4.96A for the 240v model is approximately half of the 115v model of 9.93A? I'm talking in general here, aside from the other variables you mention.

In other words the 115v model could be expected to draw about 10A, correct? Aside from the other variables you cite.

user_12345a

· #8 · Jun 1, 2020

No fault.

If the efficiencies are the same, the real world amp draw would be half for the 240v.

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Joeywhat

· #9 · Jun 1, 2020

I understand that it uses half the amps, but it still uses the same total power (more or less...). Are there any benefits when comparing "identical" units where the only real difference is voltage?

I'm curious as I'm tempted to switch my old 240v unit to a 120v as it's a little cheaper and doesn't need to be huge (only 12k btu max). It's wired for 240 but wouldn't be difficult to change as it's a couple feet from the breaker. Is there a benefit to staying with 240?

I may look into units with heat... I'm sure at that point 240v will make a lot more sense.

justplumducky

Discussion Starter · #10 · Jun 1, 2020

user_12345a said:
No fault.

If the efficiencies are the same, the real world amp draw would be half for the 240v.

OK, I'll remember that word "efficiencies," point taken.

justplumducky

Discussion Starter · #11 · Jun 1, 2020 (Edited)

Joeywhat said:
I understand that it uses half the amps, but it still uses the same total power (more or less...). Are there any benefits when comparing "identical" units where the only real difference is voltage?

I'm curious as I'm tempted to switch my old 240v unit to a 120v as it's a little cheaper and doesn't need to be huge (only 12k btu max). It's wired for 240 but wouldn't be difficult to change as it's a couple feet from the breaker. Is there a benefit to staying with 240?

I may look into units with heat... I'm sure at that point 240v will make a lot more sense.

User_12345a may not have noticed your post yet, or just hasn't gotten to it. Maybe this post will help.

From this conversation with User~, seems like the only difference, as you've said also, is the higher amp draw with the 240v unit, but I'm not an expert, obviously.

Are you having to replace your 240v unit (not working well?) If so, What 115v 12K BTU unit are you considering? I'm just asking, because if y ou're having to replace the 240v unit, I got mine 240v/12K BTU at Walmart/free shipping for only 425.00 plus tax; normally 629.00 elsewhere. Mine is a through the wall unit. However, some time later I finally noticed the 120v units/same brand were at good prices also at Walmart. Still happy to have the lower amp draw of the 240v model, even though it's on a dedicated circuit and not interfering in the least with another circuit. And like you said, maybe the buyer of this home (my current home/selling it soon) will want to switch it to a cool/heat unit one day.

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surferdude2

· #12 · Jun 1, 2020

There will be a slight increase in efficiency using the higher voltage unit due to less line current producing less voltage drop and consequently less wire heat loss.

On a personal note, the 240 volt units (we called it 220 back then) were the greatest thing that happened to business in the 50's and 60's. I made big bucks upsizing the many 60 amp 120 volt (110) services as a sweatheart deal from my buddy at Montgomery Wards who did the selling and passed the installation work my way. I made enough money to finally escape the bonds of that small town and relocate to SoCal and the rest is history. Actually all that is history... including Montgomery Ward (Monkey Wards it was called) which the young whipper snappers today never heard of.

A typical 100 amp 240 service billed out at $150. with a net profit of $120 for an easy day's work. In today's dollars, that would be equal to charging roughly $1300 for the job and netting $1000. (still good money for an easy 1 man day)

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justplumducky

Discussion Starter · #13 · Jun 1, 2020

surferdude2 said:
There will be a slight increase in efficiency using the higher voltage unit due to less line current producing less voltage drop and consequently less wire heat loss.

On a personal note, the 240 volt units (we called it 220 back then) were the greatest thing that happened to business in the 50's and 60's. I made big bucks upsizing the many 60 amp 120 volt (110) services as a sweatheart deal from my buddy at Montgomery Wards who did the selling and passed the installation work my way. I made enough money to finally escape the bonds of that small town and relocate to SoCal and the rest is history. Actually all that is history... including Montgomery Ward (Monkey Wards it was called) which the young whipper snappers today never heard of.

A typical 100 amp 240 service billed out at $150. with a net profit of $120 for an easy day's work. In today's dollars, that would be equal to charging roughly $1300 for the job and netting $1000. (still good money for an easy 1 man day)

I remember Monkey Wards, but only vaguely. Can't even remember why I remember it

... what I bought there in other words.

This current mobile home I bought to resell had a 60 amp 120v panel. 50-year old trailer built better than than similar new ones. However, panel door was kept open with a bag of fuses from the flea market hanging on it! You missed one!

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SeniorSitizen

· #14 · Jun 1, 2020

user_12345a said:
240v is half the amps as 120v to deliver the same power.

The way i'm reading the above quote, to operate a 12 BTU unit the operating cost of a 240 V would be half as much as 120 V because the 240 V draws half the amps a 120 V draws and this would be apparent on a electric bill if each had their own meter?

rjniles

· #15 · Jun 1, 2020

SeniorSitizen said:
The way i'm reading the above quote, to operate a 12 BTU unit the operating cost of a 240 V would be half as much as 120 V because the 240 V draws half the amps a 120 V draws and this would be apparent on a electric bill if each had their own meter?

Nope, you pay for power in watts not amps. The power use is roughly the same except for difference in efficiencies (minor)

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