my ancient 4hp sears craftsman air compressor needs a starting
capacitor, I've determined (through a process of elimination). I still
have the original owners manual, and the capacitor is "part of the
motor", not shown in the parts blowup, or parts list, as a seperate
orderable part. further, the friggin' thing seems to be a 'non-standard'
mfd rating, too (it doesn't 'fall into' any capacitor size-groups of any
maker's starting cap's I can find online. matter of fact, it's not even
close):

the one in it now is
110 volt, 485-580 mfd
mallory #139852-49
seems a slightly non-standard SIZE as well:
diameter: 1 13/16ths inch, and
length, overall, excluding 'spades': hair over 4 5/16ths (but clearly
under 4 3/8ths)

atttempts to locate same by the mallory part number on it entirely
unsuccessful. so (physical size and 'look' issues aside) can I "daisy
chain" two cap's and achieve the same net effect, somehow? appearance
"not an issue", I just need a working compressor. I know I can replace
the cap with a higher voltage cap, and that'd be fine (maybe even
desireble) but what about the mfd rating? if I must, is it best to go
'bigger mfd numbers' or lesser?

thanks for tips on this, guys :-)

On Oct 8, 9:03*pm, dave wrote:
my ancient 4hp sears craftsman air compressor needs a starting
capacitor, I've determined (through a process of elimination). I still
have the original owners manual, and the capacitor is "part of the
motor", not shown in the parts blowup, or parts list, as a seperate
orderable part. further, the friggin' thing seems to be a 'non-standard'
mfd rating, too (it doesn't 'fall into' any capacitor size-groups of any
maker's starting cap's I can find online. matter of fact, it's not even
close):

the one in it now is
110 volt, 485-580 mfd
mallory #139852-49
seems a slightly non-standard SIZE as well:
diameter: 1 13/16ths inch, and
length, overall, excluding 'spades': hair over 4 5/16ths (but clearly
under 4 3/8ths)

atttempts to locate same by the mallory part number on it entirely
unsuccessful. so (physical size and 'look' issues aside) can I "daisy
chain" two cap's and achieve the same net effect, somehow? appearance
"not an issue", I just need a working compressor. I know I can replace
the cap with a higher voltage cap, and that'd be fine (maybe even
desireble) but what about the mfd rating? if I must, is it best to go
'bigger mfd numbers' or lesser?

thanks for tips on this, guys :-)

It looks like the value of the cap is not that critical. They give
you a range 485 to 580 microfarads. The average value is
approximately 540 microfarads. If you order from McMaster Carr, this
should work: http://www.mcmaster.com/#7245k114/=3z7b3b

On Oct 8, 6:03*pm, dave wrote:
my ancient 4hp sears craftsman air compressor needs a starting
capacitor, I've determined (through a process of elimination). I still
have the original owners manual, and the capacitor is "part of the
motor", not shown in the parts blowup, or parts list, as a seperate
orderable part. further, the friggin' thing seems to be a 'non-standard'
mfd rating, too (it doesn't 'fall into' any capacitor size-groups of any
maker's starting cap's I can find online. matter of fact, it's not even
close):

the one in it now is
110 volt, 485-580 mfd
mallory #139852-49
seems a slightly non-standard SIZE as well:
diameter: 1 13/16ths inch, and
length, overall, excluding 'spades': hair over 4 5/16ths (but clearly
under 4 3/8ths)

atttempts to locate same by the mallory part number on it entirely
unsuccessful. so (physical size and 'look' issues aside) can I "daisy
chain" two cap's and achieve the same net effect, somehow? appearance
"not an issue", I just need a working compressor. I know I can replace
the cap with a higher voltage cap, and that'd be fine (maybe even
desireble) but what about the mfd rating? if I must, is it best to go
'bigger mfd numbers' or lesser?

thanks for tips on this, guys :-)

The capacitor values are a range because the caps are made with a
large tolerance. Even if you got one marked exactly 580 mfd, it could
actually be much smaller or much larger. I don't think Mallory has
made capacitors for many,many years.

One trick we used to do in a emergency is to get two DC electrolytic
capacitors of twice the needed AC capacity and connect them in series,
either both + leads or both - leads together and wire the remaining
leads to the motor to replace a single AC capacitor. Gets you going
while you look for the correct replacement.

Paul

I'd probably go with the next size larger (still within the specified
range), should give a bit more starting 'kick'
http://www.mcmaster.com/#7245k54/=3z859g

Denis G. wrote:
On Oct 8, 9:03 pm, dave wrote:
my ancient 4hp sears craftsman air compressor needs a starting
capacitor, I've determined (through a process of elimination). I still
have the original owners manual, and the capacitor is "part of the
motor", not shown in the parts blowup, or parts list, as a seperate
orderable part. further, the friggin' thing seems to be a 'non-standard'
mfd rating, too (it doesn't 'fall into' any capacitor size-groups of any
maker's starting cap's I can find online. matter of fact, it's not even
close):

the one in it now is
110 volt, 485-580 mfd
mallory #139852-49
seems a slightly non-standard SIZE as well:
diameter: 1 13/16ths inch, and
length, overall, excluding 'spades': hair over 4 5/16ths (but clearly
under 4 3/8ths)

atttempts to locate same by the mallory part number on it entirely
unsuccessful. so (physical size and 'look' issues aside) can I "daisy
chain" two cap's and achieve the same net effect, somehow? appearance
"not an issue", I just need a working compressor. I know I can replace
the cap with a higher voltage cap, and that'd be fine (maybe even
desireble) but what about the mfd rating? if I must, is it best to go
'bigger mfd numbers' or lesser?

thanks for tips on this, guys :-)

It looks like the value of the cap is not that critical. They give
you a range 485 to 580 microfarads. The average value is
approximately 540 microfarads. If you order from McMaster Carr, this
should work: http://www.mcmaster.com/#7245k114/=3z7b3b

That is a common value, either of these two will work at about $8 each

http://www1.mscdirect.com/CGI/NNSRIT...MT4NO=72152023

http://www1.mscdirect.com/CGI/NNSRIT...MT4NO=72152023


"dave" wrote in message
...
my ancient 4hp sears craftsman air compressor needs a starting capacitor,
I've determined (through a process of elimination). I still have the
original owners manual, and the capacitor is "part of the motor", not
shown in the parts blowup, or parts list, as a seperate orderable part.
further, the friggin' thing seems to be a 'non-standard' mfd rating, too
(it doesn't 'fall into' any capacitor size-groups of any maker's starting
cap's I can find online. matter of fact, it's not even close):

the one in it now is
110 volt, 485-580 mfd
mallory #139852-49
seems a slightly non-standard SIZE as well:
diameter: 1 13/16ths inch, and
length, overall, excluding 'spades': hair over 4 5/16ths (but clearly
under 4 3/8ths)

atttempts to locate same by the mallory part number on it entirely
unsuccessful. so (physical size and 'look' issues aside) can I "daisy
chain" two cap's and achieve the same net effect, somehow? appearance "not
an issue", I just need a working compressor. I know I can replace the cap
with a higher voltage cap, and that'd be fine (maybe even desireble) but
what about the mfd rating? if I must, is it best to go 'bigger mfd
numbers' or lesser?

thanks for tips on this, guys :-)

dave wrote:

my ancient 4hp sears craftsman air compressor needs a starting
capacitor, I've determined (through a process of elimination). I still
have the original owners manual, and the capacitor is "part of the
motor", not shown in the parts blowup, or parts list, as a seperate
orderable part. further, the friggin' thing seems to be a 'non-standard'
mfd rating, too (it doesn't 'fall into' any capacitor size-groups of any
maker's starting cap's I can find online. matter of fact, it's not even
close):

the one in it now is
110 volt, 485-580 mfd
mallory #139852-49
seems a slightly non-standard SIZE as well:
diameter: 1 13/16ths inch, and
length, overall, excluding 'spades': hair over 4 5/16ths (but clearly
under 4 3/8ths)

atttempts to locate same by the mallory part number on it entirely
unsuccessful. so (physical size and 'look' issues aside) can I "daisy
chain" two cap's and achieve the same net effect, somehow? appearance
"not an issue", I just need a working compressor. I know I can replace
the cap with a higher voltage cap, and that'd be fine (maybe even
desireble) but what about the mfd rating? if I must, is it best to go
'bigger mfd numbers' or lesser?

thanks for tips on this, guys :-)


CDE bought the Mallory capacitor business. Take a look at this
catalog page:

http://www.cde.com/catalogs/PSU.pdf

Thus looks to be the closest size:

460-552 MFD PSU46015A 110/125V 1-13/16" 3-3/8"


http://www.alliedelec.com/Search/ProductDetail.aspx?SKU=8523750&MPN=PSU46015A
$6.15 each, 42 in stock.


--
The movie 'Deliverance' isn't a documentary!

On Thu, 08 Oct 2009 21:03:20 -0400, dave
put finger to keyboard and composed:

http://www.instruction.greenriver.ed.../Shift_Key.jpg

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

On 10/8/2009 7:03 PM KD7HB spake thus:

One trick we used to do in a emergency is to get two DC electrolytic
capacitors of twice the needed AC capacity and connect them in series,
either both + leads or both - leads together and wire the remaining
leads to the motor to replace a single AC capacitor. Gets you going
while you look for the correct replacement.

That can't be safe, can it--running AC through two polarized capacitors?

(Hey: two explosions for the price of one!)


--
Found--the gene that causes belief in genetic determinism

"dave" wrote in message
...
my ancient 4hp sears craftsman air compressor needs a starting
capacitor, I've determined (through a process of elimination). I still
have the original owners manual, and the capacitor is "part of the
motor", not shown in the parts blowup, or parts list, as a seperate
orderable part. further, the friggin' thing seems to be a 'non-standard'
mfd rating, too (it doesn't 'fall into' any capacitor size-groups of any
maker's starting cap's I can find online. matter of fact, it's not even
close):

the one in it now is
110 volt, 485-580 mfd
mallory #139852-49
seems a slightly non-standard SIZE as well:
diameter: 1 13/16ths inch, and
length, overall, excluding 'spades': hair over 4 5/16ths (but clearly
under 4 3/8ths)

atttempts to locate same by the mallory part number on it entirely
unsuccessful. so (physical size and 'look' issues aside) can I "daisy
chain" two cap's and achieve the same net effect, somehow? appearance
"not an issue", I just need a working compressor. I know I can replace
the cap with a higher voltage cap, and that'd be fine (maybe even
desireble) but what about the mfd rating? if I must, is it best to go
'bigger mfd numbers' or lesser?

thanks for tips on this, guys :-)

Take the old one to the Grainger's nearest you and walk out with a suitable
replacement Easy.

If no Grangers nearby, look in the yellow pages under motor rebuilding and
they can set you up also.


--

Roger Shoaf

About the time I had mastered getting the toothpaste back in the tube, then
they come up with this striped stuff.

You shouldn't have too much trouble finding a suitable replacement from an
electrical jobber supplier.. Johnstone, or local independent electrical
supplies dealer.

If you have a local motor repair shop, they will know what you need by
referring to the 120VAC motor voltage and 4 HP motor rating.

Start capacitors need to be for AC usage, and are typically sized at about
500uF per HP.
The numbers on the original cap indicate that the actual value of that
series can be as low as the minimum value, or as high as the maximum value
shown.
The actual measured values (microfarad, or uF, or mfd) of start capacitors
can vary widely, as much as about 30%, especially on parts that are decades
old.

The voltage rating for start caps is generally higher than the AC line
voltage, and different manufacturers choose to use different rating numbers.
Another common marking is 377VAC.

The other source of problems in split-phase motors would be the centrifugal
switch for witching between the start and run windings.

--
WB
..........
metalworking projects
www.kwagmire.com/metal_proj.html


"dave" wrote in message
...
my ancient 4hp sears craftsman air compressor needs a starting capacitor,
I've determined (through a process of elimination). I still have the
original owners manual, and the capacitor is "part of the motor", not
shown in the parts blowup, or parts list, as a seperate orderable part.
further, the friggin' thing seems to be a 'non-standard' mfd rating, too
(it doesn't 'fall into' any capacitor size-groups of any maker's starting
cap's I can find online. matter of fact, it's not even close):

the one in it now is
110 volt, 485-580 mfd
mallory #139852-49
seems a slightly non-standard SIZE as well:
diameter: 1 13/16ths inch, and
length, overall, excluding 'spades': hair over 4 5/16ths (but clearly
under 4 3/8ths)

atttempts to locate same by the mallory part number on it entirely
unsuccessful. so (physical size and 'look' issues aside) can I "daisy
chain" two cap's and achieve the same net effect, somehow? appearance "not
an issue", I just need a working compressor. I know I can replace the cap
with a higher voltage cap, and that'd be fine (maybe even desireble) but
what about the mfd rating? if I must, is it best to go 'bigger mfd
numbers' or lesser?

thanks for tips on this, guys :-)

David Nebenzahl wrote:

On 10/8/2009 7:03 PM KD7HB spake thus:

One trick we used to do in a emergency is to get two DC electrolytic
capacitors of twice the needed AC capacity and connect them in series,
either both + leads or both - leads together and wire the remaining
leads to the motor to replace a single AC capacitor. Gets you going
while you look for the correct replacement.

That can't be safe, can it--running AC through two polarized capacitors?



Why? You have no idea how it actually works. Look up 'Electrolytic
Rectifier'. What happens when you have two series connected rectifiers,
with both cathodes connected? Nothing, if you don't exceed the PIV of
either diode.


(Hey: two explosions for the price of one!)


Sorry, but you're the biggest loser.


--
The movie 'Deliverance' isn't a documentary!

On Oct 8, 10:51*pm, RoyJ wrote:
I'd probably go with the next size larger (still within the specified
range), should give a bit more starting 'kick'http://www.mcmaster.com/#7245k54/=3z859g



Denis G. wrote:
On Oct 8, 9:03 pm, dave wrote:
my ancient 4hp sears craftsman air compressor needs a starting
capacitor, I've determined (through a process of elimination). I still
have the original owners manual, and the capacitor is "part of the
motor", not shown in the parts blowup, or parts list, as a seperate
orderable part. further, the friggin' thing seems to be a 'non-standard'
mfd rating, too (it doesn't 'fall into' any capacitor size-groups of any
maker's starting cap's I can find online. matter of fact, it's not even
close):

the one in it now is
110 volt, 485-580 mfd
mallory #139852-49
seems a slightly non-standard SIZE as well:
diameter: 1 13/16ths inch, and
length, overall, excluding 'spades': hair over 4 5/16ths (but clearly
under 4 3/8ths)

atttempts to locate same by the mallory part number on it entirely
unsuccessful. so (physical size and 'look' issues aside) can I "daisy
chain" two cap's and achieve the same net effect, somehow? appearance
"not an issue", I just need a working compressor. I know I can replace
the cap with a higher voltage cap, and that'd be fine (maybe even
desireble) but what about the mfd rating? if I must, is it best to go
'bigger mfd numbers' or lesser?

thanks for tips on this, guys :-)

It looks like the value of the cap is not that critical. *They give
you a range 485 to 580 microfarads. *The average value is
approximately 540 microfarads. *If you order from McMaster Carr, this
should work: *http://www.mcmaster.com/#7245k114/=3z7b3b- Hide quoted text -

- Show quoted text -

Roy, you're probably right, however, I wonder that if you skew the
value to the higher end if you pay a price by decreasing the life of
the contacts on the centrifugal switch.

Hi!

The capacitor values are a range because the caps are made with
a large tolerance. Even if you got one marked exactly 580 mfd, it
could actually be much smaller or much larger. I don't think
Mallory has made capacitors for many,many years.

Funny you'd mention that. I bought an old furnace fan assembly ($10)
and found that not only was the motor rusty inside, but the start cap
was bad. The motor cleaned up well and that got it starting a lot
better, but it was still stubborn at times.

So I popped the cap out and looked at it. Turned out it was a Mallory
capacitor. I took another look at it and said "that's been a long
time". What I took as a date code suggested 1983 or 84 (don't remember
which). I'm sure that little motor started up lots of times between
then and now.

One trick we used to do in a emergency is to get two DC electrolytic
capacitors of twice the needed AC capacity and connect them
in series, either both + leads or both - leads together and wire the
remaining leads to the motor to replace a single AC capacitor.

I'm going to have to remember that! (Or at least remember to try it
and see the next time a capacitor drops out.)

I'd have thought that finding a replacement capacitor for my fan would
have been easy. (Find one at the hardware store, right?) Nope. Struck
out at various hardware stores, Farm and Fleet (now, come on!) and
only had any luck at a little hole-in-the-wall motor repair shop.

$7 later I had a slightly larger "Rotom" ("motor" spelled backwards--
clever, huh?) capacitor and everything was fine once again. I was
fortunate in that it did fit the capacitor compartment perfectly.

If the OP can't find an exact replacement, mounting it elsewhere on
the motor should be acceptable.

William