Armed Polite Society
Main Forums => The Roundtable => Topic started by: 230RN on June 25, 2017, 10:19:24 PM
-
Harbor Freight is advertising an electric pole saw and they say it is 1.5 horsepower and draws 7 amps.
Hm. 7 amps X 125 volts = 875 watts.
Hm. 875 watts ÷ 746 watts per horsepower = 1.17 horsepower.
Hm. 1.5 horsepower advertised ÷ 1.17 horsepower by the numbers = 128% efficiency.
Apart from mere "advertising hype" and pure "typographical error," can anyone see how they could make such a technical mistake in the arithmetic?
???
I've got a cortex vortex over how they could screw up this one, even using Occam's razor and just saying "it was a boo-boo."
I've been a little off my stride lately, but that one kind of leaped out at me. I know I'm going to feel like an idiot when someone points out my error in thinking. :facepalm:
Terry
REF:
Page 6, middle right, their "Super Coupon, June 2017, Issue 8724-2," but you can take my word for it: "7 Amps, 1.5 HP."
-
1.5 HP is its maximum power output. It can't sustain that for very long but it can achieve it.
7 amps is what it pulls under no load. HTH
-
Honestly, many motor ratings on consumer products are vastly over-inflated.
I have a shop vacuum that advertises on it, 5 peak horsepower. That plugs into a 120V receptacle using a length of 16awg cord....
The CPSC finally started coming down on small engine manufacturers for the same reason. Now you'll only find CC's of displacement listed on a small engine.
-
Honestly, many motor ratings on consumer products are vastly over-inflated.
I have a shop vacuum that advertises on it, 5 peak horsepower. That plugs into a 120V receptacle using a length of 16awg cord....
The CPSC finally started coming down on small engine manufacturers for the same reason. Now you'll only find CC's of displacement listed on a small engine.
I was part of a class action settlement a few years ago on air compressor ratings. We won the case, but I didn't get a damn thing. Not even a worthless coupon. I assume the lawyers made $millions.
-
I thought maybe they were screwing up with power factor or something, but that seems to work out backwards. You'd need even more (measured, lagging) current to develop 1.5 HP than 7 amps. Getting kinda rusty on this stuff, though. I no longer do it on a day-to-day basis.
Sounds ike that's the no-load value, though, as mentioned. Also sounds like a "hyoe," as also mentioned.
-
Honestly, many motor ratings on consumer products are vastly over-inflated.
This.
Those ratings are only accurate on brand-new, lab tested equipment. Nothing in the real world comes close. That applies to cars, planes, boats, women, tools, lawn mowers, and everything else.
-
Sometimes called ILS power ratings. If Lightning Strikes.
-
Sometimes called ILS power ratings. If Lightning Strikes.
:rofl:
I guess that's the case. I got "triggered" by the advertised numbers, though. Even without a calculator, they didn't "look" right...
"Hmmmm. Seven times one hundred equals seven hundred watts. That's even less than a horsepower. Oh, wait, seven times one hundred ten is seven hundred and seventy watts... still not even close."
Terry reaches for one of the many calculators around the house, each one parked near a gun, all for instant access....
"Hmmm... that's for DC, though. I wonder if they screwed it up with power factors... let's see, a running motor ought to have about an 0.80 PF..."
At about that point, I realized how rusty I was on that stuff. I just wanted to know how they could make that mistake and decided to consign the problem to the hive mind here.
Terry