Ok, after checking eBay and Craigslist and some other sources, I've
decided I'd rather get a new compressor that is delivered to my door (or
in the case of Grizzly Freight, my driveway). So given that I need about
20 CFM @ 100psi, and trying to save a buck, is there any reason to NOT
go for this Porter Cable compressor:
http://www.grizzly.com/products/H3719

as opposed to this Campbell Hausfeld compressor:
http://www.grizzly.com/products/G2815

The PC is about $160 less delivered.

You gets what you pays for with this machine.

If you'd like one that runs quiet and lasts forever:
http://www.quincycompressor.com/products.html


I bought two el-cheapos first. Would have been better to buy the good one
like I finally did the third time.

Karl

Todd Rich wrote:

Ok, after checking eBay and Craigslist and some other sources, I've
decided I'd rather get a new compressor that is delivered to my door (or
in the case of Grizzly Freight, my driveway). So given that I need about
20 CFM @ 100psi, and trying to save a buck, is there any reason to NOT
go for this Porter Cable compressor:
http://www.grizzly.com/products/H3719

as opposed to this Campbell Hausfeld compressor:
http://www.grizzly.com/products/G2815

The PC is about $160 less delivered.

Have you ever stood next to a cheap compressor running? They're LOUD!
And they smell HOT. I once owned a DeVilbiss "6.5hp" vertical unit
which looked great and spec'd out great. But when it started at night
(it was in a huge basement space surrounded entirely by foundation
and thick walls) it woke up my neighbors. And the damn thing wouldn't
run a die grinder without running out of air, because of the phony
specs. The specs are more believable these days but when you buy these
import compressors and they wear out in 2 or 3 years what are you going
to do?

I sold my import and bought a used Quincy 5 horse 2-stage. When it runs,
it's quiet and solid sounding. It's about 30 years old and runs like a
top. I paid $150 for it and put another $400 or so into upgrading the
motor to single phase. Works great for everything I need it for. And yes,
it will run a die grinder!

GWE

I also had a misfortune of buying a cheap compressor first. Promptly
sold it because it was unusable for the reasons that Karl and Grant
mentioned. Bought a used Curtis 5 HP and have been very happy.

I would say that with about $400, and some patience, you can get
yourself a very nice vertical compressor.

i

second the Quincy - I paid 850 for mine, 21 cfm at 160 psi, 5 hp motor,
single phase, delivered
"Karl Townsend" wrote in message
anews.com...
You gets what you pays for with this machine.

If you'd like one that runs quiet and lasts forever:
http://www.quincycompressor.com/products.html


I bought two el-cheapos first. Would have been better to buy the good one
like I finally did the third time.

Karl





--
Posted via a free Usenet account from http://www.teranews.com

Karl Townsend wrote:
You gets what you pays for with this machine.

If you'd like one that runs quiet and lasts forever:
http://www.quincycompressor.com/products.html


I bought two el-cheapos first. Would have been better to buy the good one
like I finally did the third time.

Karl

Unfortunately I expect it will be more than $1600 retail from what I've
seen on the used prices for ones large enough. I simply can't afford any
more than that for the forseeable future.

I was offered a used one when I posted an earlier compressor related
question, and it was far enough away that transportation costs would have
pushed me over my limit... Otherwise I would have jumped on it.

Todd

seen on the used prices for ones large enough. I simply can't afford any
more than that for the forseeable future.

Yea, I understand. I did the same thing on many items. But, it would have
been cheaper in the long run to buy the good unit the first time around. In
my case, I went through three cheap tractors and tons o' repair bills before
buying a John Deere orchard tractor. Now, I bought it too late in my career
to come anywhere close to wearing it out.

karl

"Todd Rich" wrote in message
...

Ok, after checking eBay and Craigslist and some other sources, I've
decided I'd rather get a new compressor that is delivered to my door (or
in the case of Grizzly Freight, my driveway). So given that I need about
20 CFM @ 100psi, and trying to save a buck, is there any reason to NOT
go for this Porter Cable compressor:
http://www.grizzly.com/products/H3719

as opposed to this Campbell Hausfeld compressor:
http://www.grizzly.com/products/G2815

The PC is about $160 less delivered.

You don't have a local supplier that can beat those prices?? Grizzly is high
on their prices compared to buying local, at least in my area. Ported cable
is carried by Mills Fleet Farm and Campbell Hausefeld by Tractor Supply.
Home depot units are Campbell Hausefeld last I checked.
Greg

Karl Townsend wrote:
seen on the used prices for ones large enough. I simply can't afford any
more than that for the forseeable future.

Yea, I understand. I did the same thing on many items. But, it would have
been cheaper in the long run to buy the good unit the first time around. In
my case, I went through three cheap tractors and tons o' repair bills before
buying a John Deere orchard tractor. Now, I bought it too late in my career
to come anywhere close to wearing it out.

karl


Well, with the encouragement here, I looked again, and there was one that
was use, but local to me and what I could afford.

http://cgi.ebay.com/ws/eBayISAPI.dll...m=150167291768

I'll be picking it up in 8 days. Of course since I don't have 3 phase,
it looks like I'll finally be getting around to building a phase
converter. Fortunatley I've found a 15 hp motor that is about as close
and cheap enough that it will still be less than the Porter Cable one I
was looking at.

Time to research the best way to make a rotarty phase converter.

Todd

On 2007-10-04, Todd Rich wrote:
Karl Townsend wrote:
seen on the used prices for ones large enough. I simply can't afford any
more than that for the forseeable future.

Yea, I understand. I did the same thing on many items. But, it would have
been cheaper in the long run to buy the good unit the first time around. In
my case, I went through three cheap tractors and tons o' repair bills before
buying a John Deere orchard tractor. Now, I bought it too late in my career
to come anywhere close to wearing it out.

karl


Well, with the encouragement here, I looked again, and there was one that
was use, but local to me and what I could afford.

http://cgi.ebay.com/ws/eBayISAPI.dll...m=150167291768

I'll be picking it up in 8 days. Of course since I don't have 3 phase,
it looks like I'll finally be getting around to building a phase
converter. Fortunatley I've found a 15 hp motor that is about as close
and cheap enough that it will still be less than the Porter Cable one I
was looking at.

Time to research the best way to make a rotarty phase converter.


Wow. I am rather speechless. A very impressive compressor. Do not make
a phase converter, this compressor would be best run from an
electronic drive, especially if it has unloader valves.

Running it will take about 70 amp from single phase under the best
case (electronic drive).

What source of electric power do you have (200 amp service?)

It may not necessarily handle starting load of this compressor, unless
you soft start the motor with a drive.

You really should plan carefully as to how you wire this very large
unit.

I am not saying that I know the above for sure, but you should
research it.

i

Ignoramus8571 wrote:
(snip)
Wow. I am rather speechless. A very impressive compressor. Do not make
a phase converter, this compressor would be best run from an
electronic drive, especially if it has unloader valves.

Electronic drive as in inverter/variable frequency drive? Why is it
it better than a phase converter. I was under the impression from
articles I've read here that a balance rotary phase converter was the next
best thing to having true 3 phase power. Also, every VFD I've seen
requires 3 phase input for units over 3-5 HP.

Running it will take about 70 amp from single phase under the best
case (electronic drive).

What source of electric power do you have (200 amp service?)

200 amp service at the house, 100 amp subpanel in the garage where this is
going.

It may not necessarily handle starting load of this compressor, unless
you soft start the motor with a drive.

You really should plan carefully as to how you wire this very large
unit.

I am not saying that I know the above for sure, but you should
research it.

i

I'll be researching. I'm not necessarily that up on electrical theory,
but I'm pretty good at following directions.

Todd

Ignoramus8571 wrote:
(snip)
Wow. I am rather speechless. A very impressive compressor. Do not make
a phase converter, this compressor would be best run from an
electronic drive, especially if it has unloader valves.
(snorp)

Sorry to follow up again, but I just got confirmation that I can pick up
the motor in person and don't have to have it shipped. I really don't
want to waste $150 for the motor, but I have to make a decision in the
next few hours.
Todd

On 2007-10-04, Todd Rich wrote:
Ignoramus8571 wrote:
(snip)
Wow. I am rather speechless. A very impressive compressor. Do not make
a phase converter, this compressor would be best run from an
electronic drive, especially if it has unloader valves.

Electronic drive as in inverter/variable frequency drive?

Yes.

Why is it it better than a phase converter.

Let's see. I have a phase converter with a 10 HP idler motor (there is
another idler, that starts at a different time, but that is beside the
point). When it starts, it draws about 120 amps.

You would need a bigger idler than than, my guess about 25 HP
idler. If it draws proportionally more current at startup, it has a
need for about 120*25/10 = 300 amps. I am not sure if you can get that
much from your service.

I was under the impression from articles I've read here that a
balance rotary phase converter was the next best thing to having
true 3 phase power.

You have some size issues here, besides other issues. Other issues are
that the compressor is intermittent, so your phase converter would be
either spinning idly a lot, or you would need some complicated
starting arrangement to start it prior to kicking in the compressor
motor.

Also, every VFD I've seen requires 3 phase input for units over 3-5
HP.

Not the case with ones I have seen (Siemens up to 60 HP)

Running it will take about 70 amp from single phase under the best
case (electronic drive).

What source of electric power do you have (200 amp service?)

200 amp service at the house, 100 amp subpanel in the garage where this is
going.

It may not necessarily handle starting load of this compressor, unless
you soft start the motor with a drive.

You really should plan carefully as to how you wire this very large
unit.

I am not saying that I know the above for sure, but you should
research it.

i

I'll be researching. I'm not necessarily that up on electrical theory,
but I'm pretty good at following directions.


This is a very interesting machine that you bought. Let us know how it
goes.

i

On 2007-10-04, Todd Rich wrote:
Ignoramus8571 wrote:
(snip)
Wow. I am rather speechless. A very impressive compressor. Do not make
a phase converter, this compressor would be best run from an
electronic drive, especially if it has unloader valves.
(snorp)

Sorry to follow up again, but I just got confirmation that I can pick up
the motor in person and don't have to have it shipped. I really don't
want to waste $150 for the motor, but I have to make a decision in the
next few hours.

Todd, ask around, your application is a little unusual due to size.

i

Todd Rich wrote:
Ignoramus8571 wrote:
(snip)
Wow. I am rather speechless. A very impressive compressor. Do not make
a phase converter, this compressor would be best run from an
electronic drive, especially if it has unloader valves.

Electronic drive as in inverter/variable frequency drive? Why is it
it better than a phase converter. I was under the impression from
articles I've read here that a balance rotary phase converter was the next
best thing to having true 3 phase power. Also, every VFD I've seen
requires 3 phase input for units over 3-5 HP.

There is a hack for this: derate the drive unit by 50%, hook up
two of the three inputs to one leg of 220 and the other input to
the other leg. A 30HP drive is a big one but there is a big advantage
to using one: no starting surge. It's not clear that you could start
it from your 200amp service without a soft start unit or an electronic
motor drive.
Running it will take about 70 amp from single phase under the best
case (electronic drive).
At full load and 220 volts, over 100A.
The electrical code & the motor starter would require one heckuva (technical
term) feed for that baby! It would have to be fused for 120A according
to the code at my reading, maybe more.

Program the motor drive to ramp up over 5-10 seconds and there's no
problem. You will have to wire the pressure switch to the control input
of the motor drive and bypass the starter. The motor drive will NOT
work (for more than a day or so) with the compressor turning itself
on and off without telling the motor drive!!!!

I did something very like this with a 4HP unit running off a single
20A breaker (240V). Worked like a charm. Remember, the motor drive MUST
control the power to the compressor motor directly, with no relays or
anything else in the way. A listed motor drive qualifies as a motor starter
and a protective device under the electrical code, so you don't need them.
You MUST connect any overheating sensor and the pressure sensor to the drive.

Hope this helps.
geoff

Ignoramus8571 wrote:
(snip)
Also, every VFD I've seen requires 3 phase input for units over 3-5
HP.

Not the case with ones I have seen (Siemens up to 60 HP)

I see them now...weird I didn't find them before, but then again, I wasn't
looking for them before when I got my 3HP VFD.

(snip)

This is a very interesting machine that you bought. Let us know how it
goes.

i

Well, not sure where the original article I was looking at, but it looks
like I read it wrong...double checking several others I see I would need a
larger motor anyway, so I'll pass on this one. Thanks for the kick to
check again.

I've found at least one model of 15 HP VFD that takes single phase input.
However they want $1400 for it, which I can't afford. I'll have to see if
I can find a used one for less.

On the plus side, there is an electrician who is marrying into my wife's
side of the family. I can see how much it would take to do a 3-Phase drop
from the power company....

On 2007-10-04, gwes wrote:
Todd Rich wrote:
Ignoramus8571 wrote:
(snip)
Wow. I am rather speechless. A very impressive compressor. Do not make
a phase converter, this compressor would be best run from an
electronic drive, especially if it has unloader valves.

Electronic drive as in inverter/variable frequency drive? Why is it
it better than a phase converter. I was under the impression from
articles I've read here that a balance rotary phase converter was the next
best thing to having true 3 phase power. Also, every VFD I've seen
requires 3 phase input for units over 3-5 HP.

There is a hack for this: derate the drive unit by 50%, hook up
two of the three inputs to one leg of 220 and the other input to
the other leg. A 30HP drive is a big one but there is a big advantage
to using one: no starting surge. It's not clear that you could start
it from your 200amp service without a soft start unit or an electronic
motor drive.

Agreed.

Running it will take about 70 amp from single phase under the best
case (electronic drive).
At full load and 220 volts, over 100A.

I have a 25 amp single phase 5 HP motor (Baldor). Multiplying this by
(15 HP per OP's compressor) 3 gives you 75 amps. Use of a VFD and a
efficient 3 phase motor could yield a bit more savings. Hence my 70
amp number.

The electrical code & the motor starter would require one heckuva
(technical term) feed for that baby! It would have to be fused for
120A according to the code at my reading, maybe more.

Good question.

Program the motor drive to ramp up over 5-10 seconds and there's no
problem. You will have to wire the pressure switch to the control input
of the motor drive and bypass the

Yes.

I did something very like this with a 4HP unit running off a single
20A breaker (240V). Worked like a charm. Remember, the motor drive MUST
control the power to the compressor motor directly, with no relays or
anything else in the way. A listed motor drive qualifies as a motor starter
and a protective device under the electrical code, so you don't need them.
You MUST connect any overheating sensor and the pressure sensor to the drive.

The drive can be programmed to work as an overload, also.

i

On 2007-10-04, Todd Rich wrote:
Ignoramus8571 wrote:
(snip)
Also, every VFD I've seen requires 3 phase input for units over 3-5
HP.

Not the case with ones I have seen (Siemens up to 60 HP)

I see them now...weird I didn't find them before, but then again, I wasn't
looking for them before when I got my 3HP VFD.

By the way, I used to sell such drives, bnut I no longer do so, so
there is no profit motive in suggesting a VFD.

This is a very interesting machine that you bought. Let us know how it
goes.

Well, not sure where the original article I was looking at, but it looks
like I read it wrong...double checking several others I see I would need a
larger motor anyway, so I'll pass on this one. Thanks for the kick to
check again.

What motor exactly are you talking? The possible motor for an idler?
What kind?

I've found at least one model of 15 HP VFD that takes single phase input.
However they want $1400 for it, which I can't afford. I'll have to see if
I can find a used one for less.

You need a VFD rated for 30 HP three phase input. Basically you need a
drive that

1) Can be run from single phase

2) Has motor FLA rating at least 150% of the FLA of your compressor's
motor

As for the cost, those Siemens drives sold for $400 apiece, more or
less, up to 60 HP rating. With a little bit of looking, you can find
a suitable drive for a lot less than $1400. You would need to do a
little bit of research.



On the plus side, there is an electrician who is marrying into my wife's
side of the family.

That's great, as long as he does a little more beyond house wiring.

I can see how much it would take to do a 3-Phase drop
from the power company....

A lot more than the drive.

i

Wow. I am rather speechless. A very impressive compressor. Do not make
a phase converter, this compressor would be best run from an
electronic drive, especially if it has unloader valves.

WOW, I'm GWE (green with envy) What a unit.

Iggy's right, get a VFD to run this. Set it up to accelerate slow and not go
to full speed. Then this compressor will run quiet and last forever. If
you're short on electric line amp size, just running it slower with the VFD
will solve the problem.

Bet ya Iggy will help out with finding a suitable VFD and directions to set
up.

Karl

On 2007-10-04, Karl Townsend wrote:

Wow. I am rather speechless. A very impressive compressor. Do not make
a phase converter, this compressor would be best run from an
electronic drive, especially if it has unloader valves.

WOW, I'm GWE (green with envy) What a unit.

Me too.

Iggy's right, get a VFD to run this. Set it up to accelerate slow and not go
to full speed. Then this compressor will run quiet and last forever. If
you're short on electric line amp size, just running it slower with the VFD
will solve the problem.

Just make sure that the motor is sufficiently cooled, as its fan may
not be sufficient at lower speeds. (adding an extra fan is all that is
necessary, if that)

Bet ya Iggy will help out with finding a suitable VFD and directions to set
up.

I do not have any for sale in his size (mine are all 0.5-5 HP), but I
saw several on eBay that may work, for a lot less money than $1,400.

VFDs are not that expensive if you make an effort looking.

i

Karl Townsend wrote:

Wow. I am rather speechless. A very impressive compressor. Do not make
a phase converter, this compressor would be best run from an
electronic drive, especially if it has unloader valves.

WOW, I'm GWE (green with envy) What a unit.

Iggy's right, get a VFD to run this. Set it up to accelerate slow and not go
to full speed. Then this compressor will run quiet and last forever. If
you're short on electric line amp size, just running it slower with the VFD
will solve the problem.

Oh he definately convinced me. The other option I'm pondering is if I can
get a 10 hp motor and either use the 15 hp it comes with as the idler
motor, or use a VFD with that one. I'm not as up on the mechanics as I
would prefer to be at the moment.

Bet ya Iggy will help out with finding a suitable VFD and directions to set
up.

Karl

Well, I can go about $400-500 right now given my savings on the Quincy
unit.
Todd

On Thu, 4 Oct 2007 23:03:27 +0000 (UTC), Todd Rich
wrote:

Karl Townsend wrote:

Wow. I am rather speechless. A very impressive compressor. Do not make
a phase converter, this compressor would be best run from an
electronic drive, especially if it has unloader valves.

WOW, I'm GWE (green with envy) What a unit.

Iggy's right, get a VFD to run this. Set it up to accelerate slow and not go
to full speed. Then this compressor will run quiet and last forever. If
you're short on electric line amp size, just running it slower with the VFD
will solve the problem.

Oh he definately convinced me. The other option I'm pondering is if I can
get a 10 hp motor and either use the 15 hp it comes with as the idler
motor, or use a VFD with that one. I'm not as up on the mechanics as I
would prefer to be at the moment.

Bet ya Iggy will help out with finding a suitable VFD and directions to set
up.

Karl

Well, I can go about $400-500 right now given my savings on the Quincy
unit.
Todd

Starting a 10hp motor with a 15hp idler is kinda dicey according to
motor folks I've spoken to. If the 10hp motor can be started with a
small load it would probably work fine. Starting the 15hp idler will
draw lots of current unless it is already spinning. This is a common
way of starting 3 phase converters. In fact, you can even wrap a rope
around the shaft of the motor and pull it to spin the motor up. Might
be hard to spin up a 15hp motor that way though. Some folks use a
single phase motor mounted on a hinge to start the larger motor
spinning. Once it's up to speed the idler motor is energized and the
belt from the single phase motor to the idler is flipped off by
raising the smaller motor to relieve the belt tension. I have a
converter that is well balanced and is based on a 15hp idler motor. It
runs the whole shop and starts 2 10hp lathes with DC drives. But the
starting is adjusted a little soft, about 1.5 seconds. Before I got
the big converter I used one built around a 7.5hp motor and it could
only start the lathes with a 6 second soft start. These are DC drives
though and the motors are shunt wound DC units and so may draw less
current when starting than an AC induction motor. I don't know. You
could use the 10hp motor with a smaller motor pulley in order to
lessen the starting current. This would mean the compressor would not
pump as fast but maybe that isn't a problem for you.
ERS

On Thu, 4 Oct 2007 23:03:27 +0000 (UTC), Todd Rich
wrote:

Karl Townsend wrote:

Wow. I am rather speechless. A very impressive compressor. Do not make
a phase converter, this compressor would be best run from an
electronic drive, especially if it has unloader valves.

WOW, I'm GWE (green with envy) What a unit.

Iggy's right, get a VFD to run this. Set it up to accelerate slow and not go
to full speed. Then this compressor will run quiet and last forever. If
you're short on electric line amp size, just running it slower with the VFD
will solve the problem.

Oh he definately convinced me. The other option I'm pondering is if I can
get a 10 hp motor and either use the 15 hp it comes with as the idler
motor, or use a VFD with that one. I'm not as up on the mechanics as I
would prefer to be at the moment.

Bet ya Iggy will help out with finding a suitable VFD and directions to set
up.

Karl

Well, I can go about $400-500 right now given my savings on the Quincy
unit.
Todd

You also might consider a smaller motor pulley for a greater
reduction, lower top speed to reduce the power requirement (also the
output).

Pete Keillor

On 2007-10-04, Pete Keillor wrote:

You also might consider a smaller motor pulley for a greater
reduction, lower top speed to reduce the power requirement (also the
output).


Also, the high power draw of the compressor at full speed may limit
what other tools you can run when it kicks ni (e.g a plasma cutter).

i

Ignoramus8571 wrote:
(snip)
Bet ya Iggy will help out with finding a suitable VFD and directions to set
up.

I do not have any for sale in his size (mine are all 0.5-5 HP), but I
saw several on eBay that may work, for a lot less money than $1,400.

VFDs are not that expensive if you make an effort looking.

i

I'm not doing that well with my search strings. Any suggestions for what
to look for? There are some used Allen-Bradley stuff I'm seeing that
looks like it might work that is only a little over my budget. (And way
oversize on capacity)

Stuff like:
http://cgi.ebay.com/ws/eBayISAPI.dll...m=330171342159

On Thu, 04 Oct 2007 17:05:11 -0500, Ignoramus3531
wrote:
On 2007-10-04, Todd Rich wrote:
Ignoramus8571 wrote:

You need a VFD rated for 30 HP three phase input. Basically you need a
drive that

1) Can be run from single phase

2) Has motor FLA rating at least 150% of the FLA of your compressor's
motor

As for the cost, those Siemens drives sold for $400 apiece, more or
less, up to 60 HP rating. With a little bit of looking, you can find
a suitable drive for a lot less than $1400. You would need to do a
little bit of research.

I'd go for a VFD for a compressor, because that tends to be
automatic equipment that will start and stop unattended. Much less to
go wrong with a VFD than with a homebrew rotary converter.

And if you need to derate the 15 HP compressor to use a smaller
motor, you can slow down the compressor with a smaller motor pulley
and reduce the HP needed to drive it. Check the paperwork on the
compressor head first, some of them have a minimum speed and HP draw.

On the plus side, there is an electrician who is marrying into my wife's
side of the family.

That's great, as long as he does a little more beyond house wiring.

I can see how much it would take to do a 3-Phase drop
from the power company....

A lot more than the drive.

Yes, but Iggy gets enough "Interesting Stuff" through Mil-Surp bids
and other "finds" that having a 277V/480V 3-Ph 4-wire service
installed in his shop area would be very useful. If for nothing else
than testing items before resale so he can say "It Works."

The bugaboo is if the utility will /allow/ him to have a 3-Ph
service installed at a residence, and that varies wildly by the
utility rules and state/local laws & codes.

And once you have a 480V service, dropping it down to 240V or 208V
is as simple as a dry transformer or three. Taking voltage down is
easy, up is hard - you run out of amps on the service way fast.

-- Bruce --

On 2007-10-05, Todd Rich wrote:
Ignoramus8571 wrote:
(snip)
Bet ya Iggy will help out with finding a suitable VFD and directions to set
up.

I do not have any for sale in his size (mine are all 0.5-5 HP), but I
saw several on eBay that may work, for a lot less money than $1,400.

VFDs are not that expensive if you make an effort looking.

i

I'm not doing that well with my search strings. Any suggestions for what
to look for? There are some used Allen-Bradley stuff I'm seeing that
looks like it might work that is only a little over my budget. (And way
oversize on capacity)

Definitely do NOT use search strings. Look in two categories: "AC
drives" and "inverters".

Stuff like:
http://cgi.ebay.com/ws/eBayISAPI.dll...m=330171342159


It is a soft starter. Here's a brochure for it:

http://literature.rockwellautomation...r021_-en-p.pdf

Based on a quick look, it is not a VFD, it is more like a gradual
solid state switch. It does not make three phase, it simply increases
amount of three phase available to the motor gradually. Someone else
may be able to comment more accurately.

i

On 2007-10-05, Bruce L Bergman wrote:
On Thu, 04 Oct 2007 17:05:11 -0500, Ignoramus3531
wrote:
On 2007-10-04, Todd Rich wrote:
Ignoramus8571 wrote:

You need a VFD rated for 30 HP three phase input. Basically you need a
drive that

1) Can be run from single phase

2) Has motor FLA rating at least 150% of the FLA of your compressor's
motor

As for the cost, those Siemens drives sold for $400 apiece, more or
less, up to 60 HP rating. With a little bit of looking, you can find
a suitable drive for a lot less than $1400. You would need to do a
little bit of research.

I'd go for a VFD for a compressor, because that tends to be
automatic equipment that will start and stop unattended. Much less to
go wrong with a VFD than with a homebrew rotary converter.

And if you need to derate the 15 HP compressor to use a smaller
motor, you can slow down the compressor with a smaller motor pulley
and reduce the HP needed to drive it. Check the paperwork on the
compressor head first, some of them have a minimum speed and HP draw.

The OP Can check this out

http://cgi.ebay.com/DANFOSS-VLT6000-...QQcmdZViewItem

If he can find a 10 HP motor and a smaller pulley, this drive would
make his compressor into a useful 10 HP compressor. I am not saying
that it is the way to go -- I would look for a 30 HP drive to run the
15 HP motor, but just showing what is out there.



On the plus side, there is an electrician who is marrying into my wife's
side of the family.

That's great, as long as he does a little more beyond house wiring.

I can see how much it would take to do a 3-Phase drop
from the power company....

A lot more than the drive.

Yes, but Iggy gets enough "Interesting Stuff" through Mil-Surp bids
and other "finds" that having a 277V/480V 3-Ph 4-wire service
installed in his shop area would be very useful. If for nothing else
than testing items before resale so he can say "It Works."

The bugaboo is if the utility will /allow/ him to have a 3-Ph
service installed at a residence, and that varies wildly by the
utility rules and state/local laws & codes.

And once you have a 480V service, dropping it down to 240V or 208V
is as simple as a dry transformer or three. Taking voltage down is
easy, up is hard - you run out of amps on the service way fast.

Ignoramus8571 wrote:
(snip)
If he can find a 10 HP motor and a smaller pulley, this drive would
make his compressor into a useful 10 HP compressor. I am not saying
that it is the way to go -- I would look for a 30 HP drive to run the
15 HP motor, but just showing what is out there.
(snorp)

Well, I called up the local Quincy service rep, and found out that it has
already been sized down as far as the motor goes. The compressor is a 20
HP model. So the 15 HP motor is about as low as it will go. The service
rep said that a 10 HP motor won't run that cylinder. So, 30 HP VFD it is.
Just need to find a good one.

Btw, thanks for all the help and suggestions.

Todd

On 2007-10-05, Todd Rich wrote:
Ignoramus8571 wrote:
(snip)
If he can find a 10 HP motor and a smaller pulley, this drive would
make his compressor into a useful 10 HP compressor. I am not saying
that it is the way to go -- I would look for a 30 HP drive to run the
15 HP motor, but just showing what is out there.
(snorp)

Well, I called up the local Quincy service rep, and found out that it has
already been sized down as far as the motor goes. The compressor is a 20
HP model. So the 15 HP motor is about as low as it will go. The service
rep said that a 10 HP motor won't run that cylinder. So, 30 HP VFD it is.
Just need to find a good one.


Todd, I routinely monitor the drives categories for good deals, and I
will keep an eye open for 30 HP drives.

i

Ignoramus23835 wrote:
On 2007-10-05, Todd Rich wrote:
(snip)
Well, I called up the local Quincy service rep, and found out that it has
already been sized down as far as the motor goes. The compressor is a 20
HP model. So the 15 HP motor is about as low as it will go. The service
rep said that a 10 HP motor won't run that cylinder. So, 30 HP VFD it is.
Just need to find a good one.


Todd, I routinely monitor the drives categories for good deals, and I
will keep an eye open for 30 HP drives.

i

Well, I just noticed this:
http://cgi.ebay.com/Toshiba-E3-varia...mZ280026158272

Probably a 480V model, but I've got a question into the seller anyway.
All the bad image links in the description make me a bit nervous though...

On 2007-10-07, Todd Rich wrote:
Ignoramus23835 wrote:
On 2007-10-05, Todd Rich wrote:
(snip)
Well, I called up the local Quincy service rep, and found out that it has
already been sized down as far as the motor goes. The compressor is a 20
HP model. So the 15 HP motor is about as low as it will go. The service
rep said that a 10 HP motor won't run that cylinder. So, 30 HP VFD it is.
Just need to find a good one.


Todd, I routinely monitor the drives categories for good deals, and I
will keep an eye open for 30 HP drives.

i

Well, I just noticed this:
http://cgi.ebay.com/Toshiba-E3-varia...mZ280026158272

Probably a 480V model, but I've got a question into the seller anyway.
All the bad image links in the description make me a bit nervous though...

Call him at his phone listed at http://www.smilecaribbeancolor.com/
(602-358-****), and find out. I think that he messed up his website
and URLs (they contain bad characters etc).

i