The compressor(Item No. 90385-4VGA) works fine when plugged into a
115v outlet, but not when connected with an extension cord. Even a
heavy duty cord causes the push-button circuit breaker to blow when it
trys to restart after the pressure falls and the unit tries to kick
in. When you push the button, the unit tries to start but kicks the
breaker after about 1 second. Sometimes it just whines without
turning over before it kicks the breaker. With an extension cord, you
can only restart it by bleeding off the back pressure.
There are two capacitors, a start capacitor and a run capacitor.
The documentation states that the compressor warranty is void if you
connect it to an extension card. And of course, if you run it without
Heavy duty 2.5 HP rated motor
Air delivery: 5.6 SCFM @ 90 PSI; 7.2 SCFM @ 40 PSI
Oil lubricated pump
Thermal overload protection
Dual capacitors for fast, easy starts
Easy-to-read pressure regulator gauge
Clear view oil window for easier maintenance
High impact ABS shroud protects the motor
120V, 60Hz, 3400 RPM; Single stage pump, 120 PSI max; Air outlet:
1/4''-18NPT; Weight: 65 lbs.
You think a hard start kit would help?
: Use more hose, less extension cord. Tom
Eggzactly. Also no one has mentioned the voltage loss in the
plug/outlet combination. Cleaning the bright clean might of
might not help but it wouldn't last even if it helped
Sound like it doesn't have an "unloader valve" on the compressor to
relieve it of having to work against pressure in the tank when it's
trying to start. That's why it will restart when you drain it down to
zero gage pressure, but not when you are just down to the "start" pressure.
What do you mean by "heavy duty" extension cord? What gage wire does it
have in it? And how long is it? There is no theoretical reason why you
can't make an extension cord of even several hundred feet length that
would support the starting load. But there are practical reasons like
weight and flexibility. If your extension cord is made with less than
No. 12 gage wire, get a heavier one.
BTW, that 2.5 HP rating is a BS "peak horsepower" number, just before
the motor stalls out and burns up. You can't get a 2.5 HP motor to run
continuously off a "normal" 115 volt circuit.
You get what you pay for. A better and more expensive compressor will
have an unloader system to prevent just what you are experiencing.
Google up "unloader valve" and see what you can buy to add to your
Kind of sums it up. You should always being using
a cord that is at least 12 gauge with a heavy
motor and preferably a cord as short as possible.
However, I have a DevilBiss compressor 20 gallon,
5 hp (course it isn't 5 hp) that I have run on
from a building that is powered by a 90 foot 10
gauge underground wire and the compress hooked to
that with a 25 foot 12 gauge or 14 gauge extension
cord. It has also run fine with extension cords
in all of the outlets in the house (15 A circuits
with 14 gauge wire) and some are fairly long. So
I would say that compressor motor draws a lot of
current at start, whether designed that way or
because something is not right with the compressor
: > The compressor(Item No. 90385-4VGA) works fine when plugged
: > 115v outlet, but not when connected with an extension cord.
: > heavy duty cord causes the push-button circuit breaker to
blow when it
: > trys to restart after the pressure falls and the unit tries
: > in. When you push the button, the unit tries to start but
: > breaker after about 1 second. Sometimes it just whines
: > turning over before it kicks the breaker. With an extension
: > can only restart it by bleeding off the back pressure.
: > There are two capacitors, a start capacitor and a run
: > The documentation states that the compressor warranty is
void if you
: > connect it to an extension card. And of course, if you run
: > oil.
: > info:
: > Heavy duty 2.5 HP rated motor
: > Air delivery: 5.6 SCFM @ 90 PSI; 7.2 SCFM @ 40 PSI
: > Oil lubricated pump
: > Thermal overload protection
: > Dual capacitors for fast, easy starts
: > Easy-to-read pressure regulator gauge
: > Clear view oil window for easier maintenance
: > High impact ABS shroud protects the motor
: > CSA certified
: > 120V, 60Hz, 3400 RPM; Single stage pump, 120 PSI max; Air
: > 1/4''-18NPT; Weight: 65 lbs.
: > You think a hard start kit would help?
: Starting current is very high on these motors. Extension cords
: much voltage drop at start. It says not to use a ext. cord
right in the
: Also the 2.5 HP is BS. No 2.5HP motor plugs into a 15 or 20 amp
: outlet. The rating is bogus.
===> Sort of; it's "peak" hp, not continuous. Bass turds in marketing do that sort of crap.
On Tue, 13 Sep 2005 22:14:23 +0000, JohnR66 wrote:
2.5HP is about 1850W, or about 15.5A, so it *is* possible on a 20A
circuit. ...though not likely. I have a 2KW bathroom heaters on
20A 120V circuits.
Though I agree, the starting current will be *MUCH* higher. Compressors
are like that.
You are correct on the wattage, but you didn't include the motor's
efficiency, and a NEMA B motor in the 1-4 HP range will have an
efficiency of about 79%. So, to get the motor to produce a true 2.5 HP
of mechanical output the current would be about 19.9 amps. That's
theoretically possible on a 20 Amp circuit, but really pushing it. :-)
But almost everybody in the "shop world" knows that there was and still
is far too much liberty taken with HP ratings on compressors. It was so
bad that class action suits were started and settled in favor of purchasers:
Your 2KW bathroom heaters are 100% efficient and thus should draw only
16.7 amps on a 120 volt line, certainly OK for use on a 20 amp circuit.
Particularly when they don't have an "unloader valve" and have to start
against tank pressure.
I just realized it's a little like trying to PUSH a nail into wood with
a hammer, it works much better if you get the hammer moving BEFORE it
touches the nail head.
Also, motors are said to typically have a power factor of .8. So that
19.9 amps becomes almost 25 amps (for a supposedly typical figure).
Heaters have a power factor of 1, hardly less if they also have a fan or
- Don Klipstein ( firstname.lastname@example.org)
Well, I definitely overlooked the power factor issue, and I won't even
try to BS you by saying that it's because I've fitted power factor
correction capacitors to every motor in our home. :-)
But while I'm bloviating on the subject, during the energy crisis in the
70s, some guys at China Lake looked into improving the efficiency of
fractional horsepower induction motors by putting an AC capacitor across
the starter switch contacts, which rurned the motor into a two phase one
as soon as those switch contacts opened. 20% eenergy savings were
reported when using this technique on motors with relatively constant loads.
When that energy crisis cooled off that idea went away too. But I always
tought it was a darned clever approach.
The only reference to it I've seen is a letter published in Electronic
Design magazine in 2001, the last one on this page:
You've had some good responses, but if I might, when (not if) this
compressor goes south on you, and you are in the market for another,
I'd suggest you spend a bit more money. Harbor Freight is fine for
many things, including a compressor with which to air up basketballs
and car and bicycle tires. If it is a compressor with which you hope
to do much actual work, buy a good one. With excess capacity over and
above what you will be using it for. And I don't mean go to Home Depot
because most all their offerings come from the same kind of Chinese
factory as what you already have.
When I need lots of air, I hook up two or more of the Thomas air
compressors we use in our roofing business. Look them up. They are
made in the USA and they last. The ones we run have no oil, use Teflon
rings, and we've never had a motor burn up. And you can run them
plugged into extension cords. (Although, as the others have already
advised, I prefer using a heavy gauge cord.) These compressors are
rated at 10,000 hours of use between rebuilds. That works out to eight
hours a day, five days a week, for five years. We've never gotten rid
of one of these compressors, although we've thrown away cheaper kinds
like you would find at Harbor Freight or Home Depot!:~)
(Remove the Primes before e-mailing me)
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