44 amps plus 44 amps equals 88 amps?

Reply

  #1  
Old 02-03-10, 10:04 AM
Member
Thread Starter
Join Date: Jan 2006
Location: Owen Sound Ontario Canada
Posts: 541
Received 0 Votes on 0 Posts
44 amps plus 44 amps equals 88 amps?

I opened up my breaker box and put my clamp on ampmeter on one of the black wires and started to turn off the individual load breakers. I noticed that both black wires read 44 amps and when I shut down the double pole 240 volt circuit for the heaters that both black wires amp reading went down. I take it this is normal being that each black wire is suppling 120 volts.
So my question is if both black wires are reading 44 amps then is my power draw from the meter 88 amps? Its a 200 amp box

Thanks
 
Sponsored Links
  #2  
Old 02-03-10, 10:34 AM
Gunguy45's Avatar
Super Moderator
Join Date: Dec 2007
Location: USA
Posts: 21,107
Received 0 Votes on 0 Posts
Nope...if this was feeding the heaters in a straight 240 circuit..your draw was 44 amps.

Remember in a 240 circuit current "flows" back and forth on the 2 hot legs. So the voltage (or potential) is additive 120+120 = 240.....but the current across both legs SHOULD be the same for a 240 only circuit. Now it might vary a bit for a 240/120 item like an electric dryer..since the motor(120) pulls a bit more on one leg..but that will flow on the neutral and one hot leg. Then you may see something like 20 on one leg (just the heater elements) and 23 (element and motor) on the other.

Now..this may not be an Pro's answer...but thats basically how it works. And If I'm way off, I'll be chastised severely...lol
 
  #3  
Old 02-03-10, 11:17 AM
Forum Topic Moderator
Join Date: Feb 2005
Location: Near Lansing, Michigan
Posts: 10,944
Received 42 Votes on 40 Posts
Originally Posted by frankiee View Post
So my question is if both black wires are reading 44 amps then is my power draw from the meter 88 amps?
Your power is 240 volts * 44 amps = 10560 watts
 
  #4  
Old 02-03-10, 03:21 PM
Member
Join Date: Aug 2008
Location: boston, mass
Posts: 60
Received 0 Votes on 0 Posts
your total load is 44 amps if thats what your reading then thats what you got, the reason your reading 44 on each is because those two wires are a complete circuit for instance what goes out must come back. One wire is the feed and the other is the return in a sense. but they alternate 60 times a second.
 
  #5  
Old 02-03-10, 05:11 PM
chandler's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Dec 2005
Location: USA
Posts: 39,967
Received 2 Votes on 2 Posts
That is why a 240 volt circuit (except with clocks, etc.) require no neutral. Each line is a neutral and each line is hot as the sine wave crosses in opposition to each other. Is it 60 times a second or 360 times a second?
 
  #6  
Old 02-03-10, 05:36 PM
Member
Join Date: Mar 2006
Location: NE Wis / Paris France{ In France for now }
Posts: 4,808
Received 0 Votes on 0 Posts
Originally Posted by chandler View Post
That is why a 240 volt circuit (except with clocks, etc.) require no neutral. Each line is a neutral and each line is hot as the sine wave crosses in opposition to each other. Is it 60 times a second or 360 times a second?

Normal format is 60 time a second so you have 60 plus pulses and 60 minus pulses.

Any other HZ system it will prorated properly.

Merci,Marc
 
  #7  
Old 02-03-10, 06:47 PM
Member
Thread Starter
Join Date: Jan 2006
Location: Owen Sound Ontario Canada
Posts: 541
Received 0 Votes on 0 Posts
Thanks people
44 amps sounds much better then 88 amps to pay for
 
  #8  
Old 02-03-10, 08:36 PM
Forum Topic Moderator
Join Date: Feb 2005
Location: Near Lansing, Michigan
Posts: 10,944
Received 42 Votes on 40 Posts
You don't pay for amps, you pay for energy. The power company bills in a unit called kilowatt-hours (kWH). One kWH is equal to a 1000W (1 kW) load running for one hour. If your 10kW heater runs for one hour you will be billed for 10 kWH, which is about $1.00 to $1.50 in most areas, but could be up to $3.00 in an area where electricity is expensive.
 
  #9  
Old 02-03-10, 08:57 PM
CasualJoe's Avatar
Member
Join Date: Jan 2010
Location: USA
Posts: 9,978
Received 22 Votes on 17 Posts
"So my question is if both black wires are reading 44 amps then is my power draw from the meter 88 amps? Its a 200 amp box"

As was mentioned, your power draw is measuered in and billed in KWHs, not in amps. You have a 120/240 volt panel rated at 200 amps. That would be 200 amps at 240 volts. If all you had was 120 volt circuits, in theory you could actually have a current draw of up to 400 amps, 200 amps on each leg and on each bus bar.
 
  #10  
Old 02-04-10, 05:04 AM
Member
Join Date: Aug 2008
Location: boston, mass
Posts: 60
Received 0 Votes on 0 Posts
Originally Posted by CasualJoe View Post
"So my question is if both black wires are reading 44 amps then is my power draw from the meter 88 amps? Its a 200 amp box"

As was mentioned, your power draw is measuered in and billed in KWHs, not in amps. You have a 120/240 volt panel rated at 200 amps. That would be 200 amps at 240 volts. If all you had was 120 volt circuits, in theory you could actually have a current draw of up to 400 amps, 200 amps on each leg and on each bus bar.
i suppose you could have 200 amps travelling on one leg but not both at the same time the double pole breaker will trip if both sides collectively have over 200amps or one side has over 200amps.

if all you had was 120v in theory you would only have 100amps, because if you can picture the transformer up at the pole, the secondary side as a whole is 240v with a center tap(neutral) to split it up into two legs of 120v. so technically you would be dividing it in half

and no your getting billed for the power consumption for 44 amps x 240volts. 88amps does not exist in this situation there is no way of looking at it that it will be 88 amps at all.

the more voltage the lesser the amps
example:
lets say a blow dryer runs at 10a at 120v so power is 1200watts
lets say that same blow dryer runs at 240 volts it would then draw only 5 amps, and its power would still be 1200watts. its all ratios
 
  #11  
Old 02-04-10, 11:10 AM
Member
Join Date: Aug 2008
Location: boston, mass
Posts: 60
Received 0 Votes on 0 Posts
hope this helps everyone understand it
 
  #12  
Old 02-04-10, 06:06 PM
CasualJoe's Avatar
Member
Join Date: Jan 2010
Location: USA
Posts: 9,978
Received 22 Votes on 17 Posts
"i suppose you could have 200 amps travelling on one leg but not both at the same time the double pole breaker will trip if both sides collectively have over 200amps or one side has over 200amps."

Ok, let's assume you have a single phase panel with a 200 amp MCB. You have all 120 circuits with a load of 110 amps on each side of the panel. Collectively you have a 120 volt load of 220 amps. What will happen?
 
  #13  
Old 02-04-10, 10:26 PM
Member
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 18,482
Received 25 Votes on 19 Posts
Originally Posted by chewylu103 View Post
lets say a blow dryer runs at 10a at 120v so power is 1200watts
lets say that same blow dryer runs at 240 volts it would then draw only 5 amps, and its power would still be 1200watts. its all ratios
Nope, the same hair dryer connected to 240 volts would draw 20 amperes until it burnt up, which would happen very quickly.

Ohms law states that voltage divided by current equals resistance. The hair dryer in question therefore has a resistance of 12 ohms. Transposing ohms law gives us the equation for current equals voltage divided by resistance. Therefore this same hair dryer on 240 volts will be 240 divided by 12 equals 20.

Power, being the product of voltage times current, would be 4800 watts or four times the power consumption of the same hair dryer when properly connected to the design voltage of 120.
 
  #14  
Old 02-04-10, 10:39 PM
Member
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 18,482
Received 25 Votes on 19 Posts
Originally Posted by CasualJoe View Post
by Chewylu103
"i suppose you could have 200 amps travelling on one leg but not both at the same time the double pole breaker will trip if both sides collectively have over 200amps or one side has over 200amps."
Ok, let's assume you have a single phase panel with a 200 amp MCB. You have all 120 circuits with a load of 110 amps on each side of the panel. Collectively you have a 120 volt load of 220 amps. What will happen?
The neutral conductor (transformer center tap) carries ONLY the DIFFERENCE between the two outside conductors. If the load from one outside conductor to the center tapped conductor was 110 amperes AND the load from the OTHER outside conductor to the center tapped conductor was also 110 amperes there would be no difference between the the loads carried on the two outside conductors and therefore NO CURRENT ON THE CENTER TAPPED (neutral) CONDUCTOR! The total load would be 110 amperes at 240 volts or 26,400 watts. This could be confirmed as a load of 13,200 watts on each 120 volt circuit which when added together equals the the 26,400 watts at 240 volts.

A 200 ampere, 240 volt service has a capacity (at least peak capacity) of 48,000 watts (48 kilowatts) therefore the load on the above example of 110 amperes is only 55% of the total capacity.
 
  #15  
Old 02-05-10, 04:57 AM
Member
Join Date: Aug 2008
Location: boston, mass
Posts: 60
Received 0 Votes on 0 Posts
Originally Posted by furd View Post
Nope, the same hair dryer connected to 240 volts would draw 20 amperes until it burnt up, which would happen very quickly.

Ohms law states that voltage divided by current equals resistance. The hair dryer in question therefore has a resistance of 12 ohms. Transposing ohms law gives us the equation for current equals voltage divided by resistance. Therefore this same hair dryer on 240 volts will be 240 divided by 12 equals 20.

Power, being the product of voltage times current, would be 4800 watts or four times the power consumption of the same hair dryer when properly connected to the design voltage of 120.
i understand ohms law, but bear with me here. This blow dryer at 120volts drawing 10 amps has a power rating of 1200w
now if you do the formula for power (P) over (I), (E)
P/E= I
1200w/120v = 10a
1200w/240v = 5a
the characteristics of the load change with the voltage as the voltage increase or "pressure increases" there is no need for as much amperage to push through the resistance.
 
  #16  
Old 02-05-10, 06:12 AM
Member
Join Date: Jul 2008
Location: Kingston, PA
Posts: 137
Received 0 Votes on 0 Posts
Furd is correct.

Originally Posted by chewylu103 View Post
there is no need for as much amperage to push through the resistance.
...using your terms...this statement is correct...but you have to continue


...there is no need for the same amperage in order to provide the same power, but it will push thru anyway and give it all she's got unless you increase the resistance to limit the power to the same 1200 watts you had before.


You are assuming the power (watts) will remain constant if you just change the voltage but it won't, because the resistance will not change itself in the opposite direction which would be necessary to equal the same watts.
 
  #17  
Old 02-05-10, 06:50 AM
Member
Join Date: Aug 2008
Location: boston, mass
Posts: 60
Received 0 Votes on 0 Posts
Originally Posted by williswires View Post
Furd is correct.



...using your terms...this statement is correct...but you have to continue


...there is no need for the same amperage in order to provide the same power, but it will push thru anyway and give it all she's got unless you increase the resistance to limit the power to the same 1200 watts you had before.


You are assuming the power (watts) will remain constant if you just change the voltage but it won't, because the resistance will not change itself in the opposite direction which would be necessary to equal the same watts.
After talking about this with a fellow electrician friend and what you said williswires I know now that i used a poor example and should have used a motor that can be run on either 120v/240v
the blower dryer is only rated for 120v and the resistance is fixed unlike the motor. where you can hook up the windings to work in parallel for 120v and series to work for 240v sorry about that but i'm sure you can see where the two formula's messed things up for me
i was aware of the outcome of the formula furd used aswell as mine.
 
  #18  
Old 02-05-10, 07:09 AM
Member
Join Date: Jul 2008
Location: Kingston, PA
Posts: 137
Received 0 Votes on 0 Posts
Originally Posted by chewylu103 View Post
After talking about this with a fellow electrician friend and what you said williswires I know now that i used a poor example and should have used a motor that can be run on either 120v/240v
the blower dryer is only rated for 120v and the resistance is fixed unlike the motor. where you can hook up the windings to work in parallel for 120v and series to work for 240v sorry about that but i'm sure you can see where the two formula's messed things up for me
i was aware of the outcome of the formula furd used aswell as mine.
...I figured as much...
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes
 
Ask a Question
Question Title:
Description:
Your question will be posted in: