ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Shout Box
Recent Posts
Single phase and what you call it.
by dsk. 11/12/18 11:10 AM
220/230/240V 60Hz Systems
by Albert. 11/07/18 12:48 AM
Black & Decker Recalls Hammer Drills
by Admin. 11/01/18 07:22 PM
Having around 30 projectors to dump
by gfretwell. 10/31/18 10:54 PM
Installing a small swimming pool
by TimothyHallam. 10/30/18 10:42 PM
New in the Gallery:
What is this for?
Plug terminals
Who's Online Now
0 registered members (), 15 guests, and 25 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Page 1 of 2 1 2
Window air conditioner #127998
05/10/02 01:09 PM
05/10/02 01:09 PM
F
Frank Cinker  Offline OP
Member
Joined: Jul 2001
Posts: 311
Pennsylvania
15,000 BTU, 115 volt air conditioner. What is the formula to convert to amps?

Frank

[This message has been edited by Frank Cinker (edited 05-11-2002).]

Tools for Electricians:
Re: Window air conditioner #127999
05/10/02 03:01 PM
05/10/02 03:01 PM
P
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
Frank,

The conversion factor is 1kW = 3413 BTU/hr.

Thus 15,000 / 3413 = 4395 watts

Calc. current = 4395/120 = 36.625 amps.

Actual current will be higher of course, depending upon the efficiency and power fsctor of the A/C unit in question.

Re: Window air conditioner #128000
05/10/02 03:17 PM
05/10/02 03:17 PM
Bill Addiss  Offline
Member
Joined: Oct 2000
Posts: 3,903
NY, USA
Paul,

(That doesn't even sound close)

Bill

Re: Window air conditioner #128001
05/10/02 08:38 PM
05/10/02 08:38 PM
P
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
Quite right Bill, I've just looked at a catalog and seen a 1-ton (12000 BTU) A/C unit that draws 11.5 amps @ 120V. Oops!

I just took the straight watts-to-BTU/hr conversion which would be valid for HEATING, but not for A/C. We don't have much need for A/C over here, so I guess I just wasn't thinking hard enough -- Sorry folks.

According to my data, you put an EER (Energy Efficiency Rating) on your A/C units, which works out as BTU/hr (of COOLING power) divided by input wattage.

So electrical power would be BTU / EER.

Obviously the exact figure would then depend upon the EER, but from the listings I have somewhere around 9 to 10 seems to be typical for a 15,000 BTU unit. That would result in a current of around 12.5 to 14A @ 120V, plus a little for power factor.

Sound better?


[This message has been edited by pauluk (edited 05-10-2002).]

Re: Window air conditioner #128002
05/11/02 06:06 AM
05/11/02 06:06 AM
F
Frank Cinker  Offline OP
Member
Joined: Jul 2001
Posts: 311
Pennsylvania
Please post foumula you used to obtain amps. Just the simplified version, excluding efficiency and power factor. For example, if the only information you had on a window air conditioner was 15,000 BTU, 115 volts.
I'm aware all you have to do is look at the nameplate. I just want to learn a very basic formula to convert BTU to amps for air conditioner units.

I divided the BTUH (4395) / 3.4 to get 1292 and then divided by 115 volts to get 11.23amps. Am I even close??

[This message has been edited by Frank Cinker (edited 05-11-2002).]

Re: Window air conditioner #128003
05/11/02 09:33 AM
05/11/02 09:33 AM
P
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
Hmm, slightly new territory for me here; as I said we don't get involved with A/C much over here.

If the EER of the unit is not available, I would guess you would just have to resort to an estimate of a typical value to get a rough idea of the current.

I did a Google search on keywords "air condition efficiency," and came up with several links which seem to agree that around 10 is a reasonably good EER on modern A/C units.

If we plug that into the formula, it becomes (ignoring p.f.):

Amps = (BTU / 10) / voltage

That will simplify down to:

Amps = BTU / 1200 (for a 120V unit), or

Amps = BTU / 2400 (for a 240V unit)

Would any A/C experts agree with these figures?

Re: Window air conditioner #128004
05/11/02 11:59 AM
05/11/02 11:59 AM
F
Frank Cinker  Offline OP
Member
Joined: Jul 2001
Posts: 311
Pennsylvania
Paul,

Thank you for reply. If we stay with my original example: Window air conditioner: 15,000 BTU, 115 volts. How would you apply your formula to get amps? Also, what does EER mean? One more question....What is the average power factor for a window air conditioner?

[This message has been edited by Frank Cinker (edited 05-11-2002).]

[This message has been edited by Frank Cinker (edited 05-11-2002).]

Re: Window air conditioner #128005
05/12/02 10:11 AM
05/12/02 10:11 AM
P
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
I've seen EER listed as both Energy Efficiency Rating and Energy Efficiency Ratio, although they amount to the same thing.

Assuming the EER of 10, your original figures would then be:

Current = 15000 BTU / 1200 = 12.5 amps.

But keep in mind that that figure is based on my quick search showing that 10 is a reasonably good EER.

I'm not sure what the average p.f. would be on these units, although I would guess that they're capacitor-corrected to keep it as high as possible.

There must be some of you other guys with experience of these units. Anyone???

Re: Window air conditioner #128006
05/12/02 10:20 AM
05/12/02 10:20 AM
F
Frank Cinker  Offline OP
Member
Joined: Jul 2001
Posts: 311
Pennsylvania
Paul,

I appreciate you staying with me on this. Little by little I'll gain more knowledge on the subject. I wonder if the EER is around 10 if that indicates 100% power factor.

Frank


[This message has been edited by Frank Cinker (edited 05-12-2002).]

Re: Window air conditioner #128007
05/12/02 03:56 PM
05/12/02 03:56 PM
P
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
It's more knowledge for me as well. As I said, we don't have much A/C in this land of cool weather and warm beer, hence my initial goof of just converting BTUs to watts as though it was for heating.

The EER won't represent the power factor of the system, just the efficiency with which the electrical power is converted to cooling power. Some of the links I found show some super-efficient A/C units with an EER of 12 or more.

I have a couple of U.S. catalogs here with A/C units in them. I'll see if I can find any with enough data to work out the p.f.

Page 1 of 2 1 2

Featured:

2017 Master Electrician Exam Preparation Combos
2017 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
Radar
Radar
Los Angeles, CA
Posts: 349
Joined: April 2004
Show All Member Profiles 
Top Posters(30 Days)
Admin 8
Popular Topics(Views)
251,414 Are you busy
188,637 Re: Forum
178,341 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.6.1
(Release build 20180101)
Page Time: 0.027s Queries: 15 (0.006s) Memory: 1.0254 MB (Peak: 1.2020 MB) Zlib enabled. Server Time: 2018-11-13 22:26:27 UTC