Jump to content


Photo

Amps, Amp Hours, Watts, what? :)

12V electrical Amps furnace blower Amp draw

  • Please log in to reply
11 replies to this topic

#1 ExploreWithDon

ExploreWithDon

    Member

  • Members
  • PipPip
  • 21 posts
  • LocationMichigan's Upper Peninsula & Alaska

Posted 09 February 2017 - 07:58 PM

Hi all. I've been busy doing this and that to the camper (that will be another post), but I have a question about amps...

 

I ran an extension cord from my generator, plugged in a Kill-A-Watt meter, then ran another cord to my camper 110VAC input. It was 10F and I basically wanted to see how well the generator and hydraulics would work in the cold. For those wondering, the generator did great. The hydraulics were very slow.

 

Curiously, there was a .96 to .98 amp draw. I'm not concerned with that, but am curious why. Inverter maybe? Or even the WattsUP meter even? Anyway, when I turned on the furnace I read 1.45 to 1.64 amps at start up, and then it settled down to 1.40 to 1.42 amps.

 

So my question, which may be a silly one, is, would the 1.42 amp draw be per hour, and therefore would that draw be 14.2 amps drawn from a battery bank in a 10 hour period if the furnace is going non-stop? That doesn't seem right to me, but would be great if it's the case ^_^ .

 

And if that is indeed the case, I don't think I'd have a problem running the furnace non-stop for 10 hours using my two Trojan J-186AC batteries, although I don't quite understand what the amp hour rating is of those. The amp specs on the Trojan web page are confusing to me  :blink: .


  • 0

#2 PackRat

PackRat

    Senior Member

  • Members
  • 651 posts
  • LocationNovato, CA

Posted 09 February 2017 - 09:36 PM

Does the furnace have a FAN/BLOWER in it? That is probably the difference between the two readings. What the .98 draw is is beyond my pay grade.


Edited by PackRat, 09 February 2017 - 09:37 PM.

  • 0

1988 Ford F-250 HD Lariat 4x4 8 Ft. bed

1976 Alaskan 8 Ft. CO camper


#3 ExploreWithDon

ExploreWithDon

    Member

  • Members
  • PipPip
  • 21 posts
  • LocationMichigan's Upper Peninsula & Alaska

Posted 09 February 2017 - 10:00 PM

Does the furnace have a FAN/BLOWER in it? That is probably the difference between the two readings. What the .98 draw is is beyond my pay grade.

Yep. What I'm wondering though is how many amps I'd use in a 10 hr period if running constantly if something is drawing 1.42 amps. MY thinking is it would take 14.2 amps in that 10 hr period, but I'm not sure if that's correct.


  • 0

#4 Vic Harder

Vic Harder

    Get's a "charge" out of camping!

  • Members
  • 2,070 posts
  • LocationCalgary, Alberta

Posted 09 February 2017 - 10:03 PM

Hi all. I've been busy doing this and that to the camper (that will be another post), but I have a question about amps...

 

I ran an extension cord from my generator, plugged in a Kill-A-Watt meter, then ran another cord to my camper 110VAC input. It was 10F and I basically wanted to see how well the generator and hydraulics would work in the cold. For those wondering, the generator did great. The hydraulics were very slow.

 

Curiously, there was a .96 to .98 amp draw. I'm not concerned with that, but am curious why. Inverter maybe? Or even the WattsUP meter even? Anyway, when I turned on the furnace I read 1.45 to 1.64 amps at start up, and then it settled down to 1.40 to 1.42 amps.

 

So my question, which may be a silly one, is, would the 1.42 amp draw be per hour, and therefore would that draw be 14.2 amps drawn from a battery bank in a 10 hour period if the furnace is going non-stop? That doesn't seem right to me, but would be great if it's the case ^_^ .

 

And if that is indeed the case, I don't think I'd have a problem running the furnace non-stop for 10 hours using my two Trojan J-186AC batteries, although I don't quite understand what the amp hour rating is of those. The amp specs on the Trojan web page are confusing to me  :blink: .

Your Kill-a-watt meter is measuring the AC current.  Power used is 1.4 amps x 120v = 168 watts.  To get those watts back out of your battery you need to divide by the 12v the battery is putting out = 168/12 = 14 amps.  10 hour draw would be 140AH.  If you want to avoid killing your batteries, you should have 2x that capacity available to keep them charged at 50% or above, = 280 AH.  If you factor in that the batteries might be cold (or do they get warmed by the furnace?) then your AH available is actually much less.


  • 0

2006 Silverado 3500 ext cab 8' bed LBZ, FASS, EGT delete, 5" exhaust, FTE Resonator, MotorOps 50 HP Tow Tune

2005 Hawk Shell built the way I like it - SOLD

2012 ATC Puma (Grandby) shell - build started!


#5 ExploreWithDon

ExploreWithDon

    Member

  • Members
  • PipPip
  • 21 posts
  • LocationMichigan's Upper Peninsula & Alaska

Posted 09 February 2017 - 10:26 PM

Your Kill-a-watt meter is measuring the AC current.  Power used is 1.4 amps x 120v = 168 watts.  To get those watts back out of your battery you need to divide by the 12v the battery is putting out = 168/12 = 14 amps.  10 hour draw would be 140AH.  If you want to avoid killing your batteries, you should have 2x that capacity available to keep them charged at 50% or above, = 280 AH.  If you factor in that the batteries might be cold (or do they get warmed by the furnace?) then your AH available is actually much less.

Ahhh. Well, I figure it was too good to be true. Thanks for explaining it to me Vic, much appreciated.


  • 0

#6 Vic Harder

Vic Harder

    Get's a "charge" out of camping!

  • Members
  • 2,070 posts
  • LocationCalgary, Alberta

Posted 09 February 2017 - 10:28 PM

Ahhh. Well, I figure it was too good to be true. Thanks for explaining it to me Vic, much appreciated.

still seems like a really high draw rate to me though, for just your furnace.  Do you have any metering on the DC/Load side in your rig?


  • 0

2006 Silverado 3500 ext cab 8' bed LBZ, FASS, EGT delete, 5" exhaust, FTE Resonator, MotorOps 50 HP Tow Tune

2005 Hawk Shell built the way I like it - SOLD

2012 ATC Puma (Grandby) shell - build started!


#7 ExploreWithDon

ExploreWithDon

    Member

  • Members
  • PipPip
  • 21 posts
  • LocationMichigan's Upper Peninsula & Alaska

Posted 09 February 2017 - 10:47 PM

still seems like a really high draw rate to me though, for just your furnace.  Do you have any metering on the DC/Load side in your rig?

Yeah, I was thinking that too. I just went out and pulled off the cover, and I see that it has a rating of 4.6 amps, 55 watts. So... 46 amps would be used for a 10 hour draw?


Edited by ExploreWithDon, 09 February 2017 - 11:11 PM.

  • 0

#8 Vic Harder

Vic Harder

    Get's a "charge" out of camping!

  • Members
  • 2,070 posts
  • LocationCalgary, Alberta

Posted 10 February 2017 - 12:17 AM

Yeah, I was thinking that too. I just went out and pulled off the cover, and I see that it has a rating of 4.6 amps, 55 watts. So... 46 amps would be used for a 10 hour draw?

That is usually the max draw, not average.  And your furnace is unlikely to run full time... unless it is really cold out?  And yes. at a maximum, you would have 46AH draw.


  • 0

2006 Silverado 3500 ext cab 8' bed LBZ, FASS, EGT delete, 5" exhaust, FTE Resonator, MotorOps 50 HP Tow Tune

2005 Hawk Shell built the way I like it - SOLD

2012 ATC Puma (Grandby) shell - build started!


#9 ExploreWithDon

ExploreWithDon

    Member

  • Members
  • PipPip
  • 21 posts
  • LocationMichigan's Upper Peninsula & Alaska

Posted 10 February 2017 - 11:01 AM

That is usually the max draw, not average.  And your furnace is unlikely to run full time... unless it is really cold out?  And yes. at a maximum, you would have 46AH draw.

Ok good, and thanks. Now I better understand amp hours. It was hard for me to comprehend that if something draws X amount of amps constantly, then that amount would be an amp hour. My Trojan batteries will accommodate that well. I was thinking the worse case scenario of running the furnace constantly for 10 hours. Now I know I'll have heat for the night in the Canadian Rockies when I pass through. Thanks a bunch Vic. Again, much appreciated.


  • 0

#10 Ripperj

Ripperj

    Senior Member

  • Members
  • 229 posts

Posted 10 February 2017 - 12:14 PM

You had the right idea, but were mixing up AC amps and DC amps. The power in watts is essentially the same on both sides, but the DC amps have to be much higher to produce the same power with 1/10 the voltage.
  • 0





Also tagged with one or more of these keywords: 12V, electrical, Amps, furnace blower, Amp draw

0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users