View Full Version : Replacing compressor unit question?
After 35 years of faithful service, my Sears compressor has died. I
was blowing the water out of the motorhome plumbing, getting ready for
the freeze. It took about ten minutes of blowing air into the intake
while my wife bled all the water out of the various fixtures. The
compressor was running constantly and, just as we were finished, it
began clanking like a '49 Chevy beating the babbit out of a rod.
Well, I've been meaning to drag it out from under the bench - no small
job, gotta move a lot of stuff, car, motorcycle, etc. to check the
specs on it for replacement. One that old, there's no sense
rebuilding. Before I could get a roundtoit, we stopped into HFT today.
They have a "3-HP" twin compressor pump on sale for $89. Can't beat
that! Looks just like the one on my compressor. I don't remember the
hp of the 240 volt motor I replaced a few years ago, but it's about
that.
They swearch all over the store for one NIB. Nada. They won't sell the
display unit that's bolted to the counter. They will, however, give me
the "5-HP" unit for the "3-HP" price. Wow! That's a $139 pump. I
haven't seen it yet because they have none on display, but I take the
deal.
I get home and remove it from the car trunk where the gut put it. Oh
oh. It's a V-twin instead of an inline. Examination of my existing
compressor motor reveals my first guess was right on. It's a 240 V. 3-
hp 2350 rpm motor. The other pump would have been perfect. Now what do
I do?
Options -
A - just take this one back and trade it for the smaller unit when
they come in.
B - Install this one (not as easy by a bunch) and try it. If it
doesn't work, buy a 5 hp motor.
C - Sell this one on Craig's list, maybe make ten bucks or not, and
buy the smaller unit.
I like "A". If it's "B", will my 3 hp motor run this pump? A 5-hp
motor from HFT is $300.
I don't need any more air than the old compressor supplied.
Rich S.
Morgans[_2_]
January 7th 09, 01:39 AM
> wrote
> I like "A". If it's "B", will my 3 hp motor run this pump? A 5-hp
> motor from HFT is $300.
My bet is that it will work just fine. If it has a hard time, it would be
at start, or finishing topping off the tank. The worst thing that could
happen is that you would have to put a smaller pulley on the motor, or a
larger one on the compressor. That should not hurt any working ability,
since it would pump air more slowly than the bigger motor, but the bigger
pump will have the ability to pump more air, so it should be a wash.
The bonus of the whole thing is that if you can keep it the same, it will be
able to pump more air at the lower pressures. Even though you say you don't
need it to do more that you had, I've never met anyone that could not
occasionally do with more air!
--
Jim in NC
John Ammeter
January 7th 09, 03:43 AM
Rich,
I'm willing to bet you'll be fine with the "5" hp compressor. If your
old Sears motor is 36 years old it's probably REALLY 3 HP while the
newer ones rate their "hp" at the instant locked rotor amps... nowhere
near the actual hp.
I bought a 60 gallon compressor/motor combo rated at 5 hp but, looking
at the voltage current on the dataplate, it wasn't even close to an
actual 5 horsepower. In fact, I got a "settlement" from a class action
lawsuit that was brought against the company for their false claims. A
Horsepower is 746 watts (from memory, could be wrong) and a 5 hp motor
at 240 volts would draw at least 15 amps.
BTW, when are we going to go on that motorcycle trip?? My brother wants
me to go with him to Sturgis next year.. not sure I want to go that far
but, who knows, I might change my mind.
John
wrote:
> After 35 years of faithful service, my Sears compressor has died. I
> was blowing the water out of the motorhome plumbing, getting ready for
> the freeze. It took about ten minutes of blowing air into the intake
> while my wife bled all the water out of the various fixtures. The
> compressor was running constantly and, just as we were finished, it
> began clanking like a '49 Chevy beating the babbit out of a rod.
>
> Well, I've been meaning to drag it out from under the bench - no small
> job, gotta move a lot of stuff, car, motorcycle, etc. to check the
> specs on it for replacement. One that old, there's no sense
> rebuilding. Before I could get a roundtoit, we stopped into HFT today.
> They have a "3-HP" twin compressor pump on sale for $89. Can't beat
> that! Looks just like the one on my compressor. I don't remember the
> hp of the 240 volt motor I replaced a few years ago, but it's about
> that.
>
> They swearch all over the store for one NIB. Nada. They won't sell the
> display unit that's bolted to the counter. They will, however, give me
> the "5-HP" unit for the "3-HP" price. Wow! That's a $139 pump. I
> haven't seen it yet because they have none on display, but I take the
> deal.
>
> I get home and remove it from the car trunk where the gut put it. Oh
> oh. It's a V-twin instead of an inline. Examination of my existing
> compressor motor reveals my first guess was right on. It's a 240 V. 3-
> hp 2350 rpm motor. The other pump would have been perfect. Now what do
> I do?
>
> Options -
> A - just take this one back and trade it for the smaller unit when
> they come in.
> B - Install this one (not as easy by a bunch) and try it. If it
> doesn't work, buy a 5 hp motor.
> C - Sell this one on Craig's list, maybe make ten bucks or not, and
> buy the smaller unit.
>
> I like "A". If it's "B", will my 3 hp motor run this pump? A 5-hp
> motor from HFT is $300.
>
> I don't need any more air than the old compressor supplied.
>
> Rich S.
On Jan 6, 7:43*pm, John Ammeter > wrote:
> Rich,
>
> I'm willing to bet you'll be fine with the "5" hp compressor. *If your
> old Sears motor is 36 years old it's probably REALLY 3 HP while the
> newer ones rate their "hp" at the instant locked rotor amps... nowhere
> near the actual hp.
>
> I bought a 60 gallon compressor/motor combo rated at 5 hp but, looking
> at the voltage current on the dataplate, it wasn't even close to an
> actual 5 horsepower. *In fact, I got a "settlement" from a class action
> lawsuit that was brought against the company for their false claims. *A
> Horsepower is 746 watts (from memory, could be wrong) and a 5 hp motor
> at 240 volts would draw at least 15 amps.
>
> BTW, when are we going to go on that motorcycle trip?? *My brother wants
> me to go with him to Sturgis next year.. not sure I want to go that far
> but, who knows, I might change my mind.
>
> John
>
>
>
> wrote:
> > After 35 years of faithful service, my Sears compressor has died. I
> > was blowing the water out of the motorhome plumbing, getting ready for
> > the freeze. It took about ten minutes of blowing air into the intake
> > while my wife bled all the water out of the various fixtures. The
> > compressor was running constantly and, just as we were finished, it
> > began clanking like a '49 Chevy beating the babbit out of a rod.
>
> > Well, I've been meaning to drag it out from under the bench - no small
> > job, gotta move a lot of stuff, car, motorcycle, etc. to check the
> > specs on it for replacement. One that old, there's no sense
> > rebuilding. Before I could get a roundtoit, we stopped into HFT today.
> > They have a "3-HP" twin compressor pump on sale for $89. Can't beat
> > that! Looks just like the one on my compressor. I don't remember the
> > hp of the 240 volt motor I replaced a few years ago, but it's about
> > that.
>
> > They swearch all over the store for one NIB. Nada. They won't sell the
> > display unit that's bolted to the counter. They will, however, give me
> > the "5-HP" unit for the "3-HP" price. Wow! That's a $139 pump. I
> > haven't seen it yet because they have none on display, but I take the
> > deal.
>
> > I get home and remove it from the car trunk where the gut put it. Oh
> > oh. It's a V-twin instead of an inline. Examination of my existing
> > compressor motor reveals my first guess was right on. It's a 240 V. 3-
> > hp 2350 rpm motor. The other pump would have been perfect. Now what do
> > I do?
>
> > Options -
> > A - just take this one back and trade it for the smaller unit when
> > they come in.
> > B - Install this one (not as easy by a bunch) and try it. If it
> > doesn't work, buy a 5 hp motor.
> > C - Sell this one on Craig's list, maybe make ten bucks or not, and
> > buy the smaller unit.
>
> > I like "A". If it's "B", will my 3 hp motor run this pump? A 5-hp
> > motor from HFT is $300.
>
> > I don't need any more air than the old compressor supplied.
>
> > Rich S.- Hide quoted text -
>
> - Show quoted text -
John Boy ..........
The motor is probably ten years old. I got it from Graingers and it's
a Dayton rated at 3 hp 240 v. The main problem with mounting the V-
twin compressor pump is physical dimensions. One of the cylinders wil
interfere slightly with the air delivery tube from the pump to the
center top of the tank. This isn't too critical, but will call for a
double bend in 1/2" copper tubing to fit. The other cylinder will hang
out over the end of the tank, causing a problem in fitting the whole
compressor back under the existing bench. It'll be really long and
trying to jockey it under the 2X4 legs of my wood lathe bench will
probably require removing the handle off the other end and replumbing
the regulator/filter. That's kinda okay, because I would like a new
filter/regulator from HFT.
I will get the amp ratings off the motor tomorrow and check back with
you. The pulley on the motor is about 2-1/2" and the existing pump
pulley is ~10". I'm not sure of the diameter of the pump pulley on the
new unit, but I think it's 12". The new pump is rated at 1230 rpm,
IIRC. The old motor is rated at 2350. The new pump
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=93786
is a whopper.
I am trying to firm up plans for the summer. Following a motorhome
tour to Yosemite, Arizona, The Big Easy and Florida, I hope to fly to
OSH this year. After I get back, I have no plans until the Kite
Festival at Long Beach, Aug 17-23. How about following the Seafair
hydroplane race weekend? Weather should be as good as it gets!
Rich S.
John Ammeter
January 7th 09, 05:38 AM
Hey, I'm retired, too... as long as swmbo says ok I'm free to do what I
want...
John
wrote:
> On Jan 6, 7:43 pm, John Ammeter > wrote:
>> Rich,
>>
>> I'm willing to bet you'll be fine with the "5" hp compressor. If your
>> old Sears motor is 36 years old it's probably REALLY 3 HP while the
>> newer ones rate their "hp" at the instant locked rotor amps... nowhere
>> near the actual hp.
>>
>> I bought a 60 gallon compressor/motor combo rated at 5 hp but, looking
>> at the voltage current on the dataplate, it wasn't even close to an
>> actual 5 horsepower. In fact, I got a "settlement" from a class action
>> lawsuit that was brought against the company for their false claims. A
>> Horsepower is 746 watts (from memory, could be wrong) and a 5 hp motor
>> at 240 volts would draw at least 15 amps.
>>
>> BTW, when are we going to go on that motorcycle trip?? My brother wants
>> me to go with him to Sturgis next year.. not sure I want to go that far
>> but, who knows, I might change my mind.
>>
>> John
>>
>>
>>
>> wrote:
>>> After 35 years of faithful service, my Sears compressor has died. I
>>> was blowing the water out of the motorhome plumbing, getting ready for
>>> the freeze. It took about ten minutes of blowing air into the intake
>>> while my wife bled all the water out of the various fixtures. The
>>> compressor was running constantly and, just as we were finished, it
>>> began clanking like a '49 Chevy beating the babbit out of a rod.
>>> Well, I've been meaning to drag it out from under the bench - no small
>>> job, gotta move a lot of stuff, car, motorcycle, etc. to check the
>>> specs on it for replacement. One that old, there's no sense
>>> rebuilding. Before I could get a roundtoit, we stopped into HFT today.
>>> They have a "3-HP" twin compressor pump on sale for $89. Can't beat
>>> that! Looks just like the one on my compressor. I don't remember the
>>> hp of the 240 volt motor I replaced a few years ago, but it's about
>>> that.
>>> They swearch all over the store for one NIB. Nada. They won't sell the
>>> display unit that's bolted to the counter. They will, however, give me
>>> the "5-HP" unit for the "3-HP" price. Wow! That's a $139 pump. I
>>> haven't seen it yet because they have none on display, but I take the
>>> deal.
>>> I get home and remove it from the car trunk where the gut put it. Oh
>>> oh. It's a V-twin instead of an inline. Examination of my existing
>>> compressor motor reveals my first guess was right on. It's a 240 V. 3-
>>> hp 2350 rpm motor. The other pump would have been perfect. Now what do
>>> I do?
>>> Options -
>>> A - just take this one back and trade it for the smaller unit when
>>> they come in.
>>> B - Install this one (not as easy by a bunch) and try it. If it
>>> doesn't work, buy a 5 hp motor.
>>> C - Sell this one on Craig's list, maybe make ten bucks or not, and
>>> buy the smaller unit.
>>> I like "A". If it's "B", will my 3 hp motor run this pump? A 5-hp
>>> motor from HFT is $300.
>>> I don't need any more air than the old compressor supplied.
>>> Rich S.- Hide quoted text -
>> - Show quoted text -
>
> John Boy ..........
>
> The motor is probably ten years old. I got it from Graingers and it's
> a Dayton rated at 3 hp 240 v. The main problem with mounting the V-
> twin compressor pump is physical dimensions. One of the cylinders wil
> interfere slightly with the air delivery tube from the pump to the
> center top of the tank. This isn't too critical, but will call for a
> double bend in 1/2" copper tubing to fit. The other cylinder will hang
> out over the end of the tank, causing a problem in fitting the whole
> compressor back under the existing bench. It'll be really long and
> trying to jockey it under the 2X4 legs of my wood lathe bench will
> probably require removing the handle off the other end and replumbing
> the regulator/filter. That's kinda okay, because I would like a new
> filter/regulator from HFT.
>
> I will get the amp ratings off the motor tomorrow and check back with
> you. The pulley on the motor is about 2-1/2" and the existing pump
> pulley is ~10". I'm not sure of the diameter of the pump pulley on the
> new unit, but I think it's 12". The new pump is rated at 1230 rpm,
> IIRC. The old motor is rated at 2350. The new pump
> http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=93786
> is a whopper.
>
> I am trying to firm up plans for the summer. Following a motorhome
> tour to Yosemite, Arizona, The Big Easy and Florida, I hope to fly to
> OSH this year. After I get back, I have no plans until the Kite
> Festival at Long Beach, Aug 17-23. How about following the Seafair
> hydroplane race weekend? Weather should be as good as it gets!
>
> Rich S.
On Jan 6, 7:43*pm, John Ammeter > wrote:
> A Horsepower is 746 watts (from memory, could be wrong) and a 5 hp motor
> at 240 volts would draw at least 15 amps.
John ........
I was wrong about the electric motor on the compressor. It's not a
Dayton, it's a Doerr. Specs are 3450 rpm @ 60 Hz. 230 VAC @ 12 A.
You're right on the 746 W/HP. 230 * 12 = 2760 W 2760/746 = 3.7 hp
That should give it a good 3 HP continuous duty.
After looking carefully at the installation, I think I'll wait until I
can trade for the smaller unit. It'll be a "drop-in" install. The old
one did everything I needed except run a DA sander continuously. I
only use one of those when I do car repair - and I ain't gonna do that
anymore.
Rich S.
vBulletin® v3.6.4, Copyright ©2000-2025, Jelsoft Enterprises Ltd.