On 10/11/23 22:16, John Dammeyer wrote:
From: gene heskett [mailto:ghesk...@shentel.net]
I blew up old bucket-vac by putting a larger diameter hose on the
intake. This raised the air flow and the amps it drew, and apparently
tripped a one time thermal fuse about 9 minutes into a 12 minute job.
This one claims 4 hp peak but that is likely only for short term use and
this may run for a day at a time, possibly even longer. Sucking up swarf
or saw dust as my go704 works.
I have no clue how to translate 4hp into the amps I'd see on an Amprobe
which would equal 4hp on a 125 volt circuit.
I really dislike the term HP to describe equipment as it's so misleading.
We used to joke about Sears HP in shopvacs and compressors.
The simple reality is that the equivalent of 1HP is roughly 750W of
electrical power. Divide that by 115VAC and you get about 6.5A. That means
2HP is about 13A. Although your circuit breaker is rated at say 15A you
don't find to many gizmos drawing that. Think of that space heater that is
1500W. You don't see many 1725W space heaters.
So when buy a shopvac that states 4HP they are lying to you. What it means
is that for a brief moment as the motor starts turning it draws way more
than the breaker can handle but not long enough to pop the breaker. That
number may work out to 3000W or 4HP for a fraction of a second but that's
it.
So the important number on the machine is voltage and amperage. Multiply to
get watts and then derate it to 85% and divide by 750. Now you have real
continuous HP.
I'm sure someone will come up with a more detailed explanation but
essentially this back of the envelope in ink calculation.
John
Thanks John. I did turn it on w/o anything plugged into it, for about 15
seconds but with 2.25" open ports, no restrictive 1" cheap hose, I'd bet
it was drawing close to 20 amps, the air blast out of the exhaust was
seriously more than I ever felt out of the old one. So I'll do whatever
it takes to get the amps down to a reasonable level. Something it can
comfortably do for several hours.
This moving air costs horsepower is a lesson I've had to learn several
times so it should be burned in by now.
You would be amazed at the air conditioner people who never learn that.
Lennox made a 22 ton unit for the KXNE transmitter building, but I was
adding a 20 lb bottle of F22 to it to run in cooler weather, and
bleeding it back out in the spring as it warmed up. I finally got tired
of that and put my gauges on it, It had 2, 1 hp 1750 motors on the
outdoor condenser, and ten minutes staring that the gauges said it
needed more fans. I picked a cool day when it might run on one fan, took
the other out, mounting brackets and all and found me a welding shop in
Norfolk who would modify the brackets to hold a 10 horse 3450 motor and
bought two fan blades of about an inch less pitch and rated for 4k revs,
wrote a P.O. for the motors and blades and two days later I adjusted the
charge in that system for the last time. It was still running right 7
years later when I got bored and left for a higher paying CE position in
New Mexico. I called up Lennox and asked for the designer who bid that
system and gave him a good sized piece of my mind.
Thanks John, take care & stay well.
Cheers, Gene Heskett.
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
Genes Web page <http://geneslinuxbox.net:6309/>
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