A while back I did a real world comparison of the Viar 400P RV and the Viar 450P. One interesting note is that with compressors the lower the amp draw rating the more powerful the compressor is. For most other appliances the opposite is true.
You can read it here:
http://www.irv2.com/forums/f52/viair-400p-rv-and-450p-comparison-234981.html
I am copying my post here:
Hello everyone,
I finally gave in to find an easy solution to topping off my tires without turning on the engine. I have been reading good reviews about the viair 12 volt portable compressors and wanted to give them a try. The one problem was, I could not decide which of these two models would work best so I purchased both to test and would return the one that does not perform best.
Here are the specs for the two models:
Model 400 P-RV Automatic-
Duty cylce = 33% (can run for 10 minutes then must rest for 30 minutes)
CFM = 2.54 CFM
Advantage = greater CFM
Disadvantage = shorter duty cylce
Max amp draw = 30 amps
Model 450 P Automatic-
Duty cycle = 100% (can run continuously without stopping)
CFM = 1.66 CFM
Advantage = 100% duty cyle
Disadvantage = Lower CFM
Max Amp draw = 20 amps
(note on amp draw and compressors: the more efficient the compressor is the lower the amp draw is, so the lower number here is better than a higher number)
To be clear, I will never use this compressor to fill a flat RV tire, only to top them off with 5 to 10 psi. I needed something to reach 120 psi without struggling. My main concern and question with the 450P was would it take a ridiculous time period to top off a tire compared to the 400P RV.
Method:
I purged one tire to 117 psi and clocked the time to fill this tire to 122 psi. The ambient temperature was 75 degrees Fahrenheit
The 400 P-RV took 1 minute, 35 seconds.
The 450P took 1 minute, 55 seconds.
As it turned out the difference in time was not too significant. My choice was to keep the 450P in order to have the 100% duty cycle and will be sending back the 400P-RV.
I was particularly curious about the performance of these two models when I first watched a video recommending the 400P-RV from the RV GEEKS. I wonder if they ever tested the 450P model.
I hope this information is helpful to some and look forward to hearing your input and opinions on this subject.
