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10-10-2016, 06:04 PM
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#15
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Senior Member
Winnebago Owners Club Solo Rvers Club
Join Date: May 2015
Posts: 1,834
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Quote:
Originally Posted by twinboat
An electric mixer
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X2. Or, something like a pancake air compressor.
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Randy - Manhattan, Kansas
2015 Vista 27N
2020 Ford Escape Hybrid
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10-10-2016, 06:19 PM
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#16
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Senior Member
Join Date: Nov 2014
Posts: 133
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I don't have either. Would a drill work?
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2002 Diplomat
2017 F-150 Toad
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10-10-2016, 06:35 PM
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#17
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Senior Member
Join Date: Jan 2011
Location: Pensacola, FL
Posts: 2,457
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A variable speed drill uses an electronic circuit that may well affect draw on a MSW. An old-fashioned single speed drill would work. A small vacuum cleaner should also be a simple motor circuit.
FWIW, I did tests on a K-A-W, an old Fluke DMM without True RMS, and a newer Fluke with True RMS. As expected, the old fluke read about 100 VAC, the New Fluke read 120 VAC, and the K-A-W also read 120 VAC. That is only volts - I do not know how the K-A-W does on amps.
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2008 Itasca 37H
2011 & 2012 Len & Pat's "One lap of America"
27K miles & 41 states in 13 months
Yellowstone Lake 6-1-2012
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10-10-2016, 06:46 PM
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#18
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Senior Member
Join Date: Jul 2014
Posts: 35,349
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Try the AC on fan only, if you can.
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10-10-2016, 06:52 PM
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#19
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Senior Member
Join Date: Nov 2014
Posts: 133
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The AC fan will not operate on the inverter. Also, I have no way to wire in the Kill A Watt. What about a simple fan? We have one of those.
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2002 Diplomat
2017 F-150 Toad
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10-10-2016, 07:30 PM
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#20
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Senior Member
Join Date: Jul 2014
Posts: 35,349
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As a test, a fan could work. Not much load though.
With the AC fan, dog bone the power cord to 15 amps, shut off all, but the AC breaker and bring the cord in the door and plug it in an inverter outlet.
Crazy idea, I know.
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10-10-2016, 08:03 PM
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#21
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Senior Member
Join Date: Nov 2014
Posts: 133
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I am not sure I understand? Why can’t I just plug the fan into the Kill A Watt on an inverter outlet (like the refrigerator is now), record the amps reading while on the inverter. Then, turn on that 120 supply (the inverter has pass through), and record that reading?
Then, I have exactly what I have now, except I am replacing the refrigerator with the fan.
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2002 Diplomat
2017 F-150 Toad
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10-10-2016, 08:21 PM
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#22
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Senior Member
Winnebago Owners Club Solo Rvers Club
Join Date: May 2015
Posts: 1,834
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Quote:
Originally Posted by Krash
I am not sure I understand? Why can’t I just plug the fan into the Kill A Watt on an inverter outlet (like the refrigerator is now), record the amps reading while on the inverter. Then, turn on that 120 supply (the inverter has pass through), and record that reading?
Then, I have exactly what I have now, except I am replacing the refrigerator with the fan.
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Should work, run it on high to max out the load. Another thing might be to use a vacuum cleaner it would generate a bigger load than a residential fan will.
Since you said you could tell DC amps drawn by the inverter I still think you would be better off telling the actual watts being used while on the inverter by the DC current draw, converting to watts by multiplying amps by voltage. This will be slightly high because the inverter is not 100 % efficient. The actual AC watts used by the AC load will be 5 to 20 watts less than the DC watts due to the power consumed internally inside the inverter and the fact it is not 100% efficient.
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Randy - Manhattan, Kansas
2015 Vista 27N
2020 Ford Escape Hybrid
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10-10-2016, 08:32 PM
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#23
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Senior Member
Join Date: Nov 2014
Posts: 133
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Yes, I will run the fan on high. I also will look at both amps and watts because the Kill A Watt displays both.
And, I will absolutely measure the DC side of things with my Tri-Metric tomorrow. I am guessing that all will be fine, and the Kill A Watt is giving me some erroneous readings on the actual power consumption on the fridge when on the MSW inverter.
You are correct, the DC draw is actually what I should be concerned with most.
Thanks for all the suggestions.
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2002 Diplomat
2017 F-150 Toad
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10-11-2016, 06:44 AM
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#24
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Moderator Emeritus
Join Date: Jan 2000
Location: West Palm Beach, FL. USA
Posts: 27,563
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While its true that inductive loads are different than resistive loads, I don't think you care if the purpose is to validate the KOW measurement technique. A toaster uses amps, and what you are seeking to learn is whether the KOW measures MSW amps the same as PSW amps. Doesn't make any difference how many amps - just how the KOW reacts to MSW vs PSW (shore power).
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Gary Brinck
Former owner of 2004 American Tradition and several other RVs
Home is West Palm Beach, FL
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10-11-2016, 06:57 AM
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#25
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Senior Member
Join Date: Sep 2012
Posts: 8,055
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Quote:
Originally Posted by Gary RVRoamer
While its true that inductive loads are different than resistive loads, I don't think you care if the purpose is to validate the KOW measurement technique. A toaster uses amps, and what you are seeking to learn is whether the KOW measures MSW amps the same as PSW amps. Doesn't make any difference how many amps - just how the KOW reacts to MSW vs PSW (shore power).
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Inductive and capacitive loads change the phase relationship between the current and the voltage applied. That is why places with large motor loads (inductive) also put large capacitor banks on their lines to correct the phase shift.
The change in phase can effect both the measured output and the wave shape on any inverter.
The input current required is the significant issue with supplying an inverter but the output measured current will be different with different inverters because of the efficiency factor for each one.
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10-11-2016, 01:34 PM
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#26
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Senior Member
Join Date: Nov 2014
Posts: 133
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Just in case someone can shed some light on this problem for me, I have included the results of a few tests using the Kill A Watt meter.
Testing MSW Power Readings Using Kill A Watt and a small electric fan.
1) Plug fan into inverter outlet with AC on.
2) Record amps and watts
3) Turn off 50 amp breaker, so circuit is on inverter.
4) Record amps and watts.
5) Compare results.
Results: Sorry, I couldn't get the formatting right.
............ Amps Watts
Inverter 0.43 51.4
AC Power 0.53 63.6
This seems with reason to me, although approximately a 20% loss through the inverter.
Here are the results doing the same test with the refrigerator replacing the fan.
Results:
............ Amps Watts
Inverter 2.07 149
AC Power 0.92 108
This seems way out of line from what I was expecting. Also, the watts do not track? There is over 100% increase in amps, while less than a 50% increase in Watts. Very strange readings that I don’t understand.
DC Power Draw Measured with the Tri-Metric while on the inverter.
13.2 Amps @ 12.5 volts = 165 Watts
This almost tracks with the 149 Watts measured with inverter using the Kill A Watt, but is way out of line for what I hoped for. If, and only IF the Kill A Watt is correct, then my conclusion is that my MSW inverter is wasting a ton of power, and I need to get a PSW inverter for the fridge. This fridge is rated at 350 KWH per year, or say, 1 KWH per day. And it does, when on shore power. But it is using more than twice that much on the inverter. Do my conclusions make sense?
If there are other explanations, please toss them into the mix for me.
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2002 Diplomat
2017 F-150 Toad
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10-11-2016, 01:57 PM
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#27
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Senior Member
Monaco Owners Club
Join Date: Sep 2014
Posts: 4,569
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I recently did an inventory of the DC/AC power used and I seem to remember where a few of the readings on my Trimetric meter didn't match up with the kill-a-watt reading. (after converting)
Unfortunately I just did a reset on my phone and lost the excel file. If I'm at the RV again this week I'll do a couple of quick checks.
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1996 Tioga Class C
2007 Monaco Diplomat 40 PDQ
TOAD 2012 Cadillac SRX 4
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10-12-2016, 06:52 AM
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#28
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Senior Member
Join Date: Sep 2012
Posts: 8,055
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I think you are getting caught up in the non sinusoidal wave form coming out of the MSW Inverter. I will go back to my first post, put a True RMS Amp meter in series with the power cord. Most DMM's will do 10 A so that should not be more than a bit of wiring to make a way to connect the meter. Put it in a small box if you are worried.
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