Awl --

With single phase, what are the pro's/cons with having a 3 ph compressor
motor with starting caps, vs swapping it out for a single phase motor?

The tradeoff I see is a wiring pita vs. the grunt/mechanical pita and $$ of
a single phase motor, with likely a modified mounting.

I would like to put the starting caps/running caps on relays, that switch
in/out, as well.

--
DT

DrollTroll wrote:
Awl --

With single phase, what are the pro's/cons with having a 3 ph compressor
motor with starting caps, vs swapping it out for a single phase motor?

The tradeoff I see is a wiring pita vs. the grunt/mechanical pita and $$ of
a single phase motor, with likely a modified mounting.

I would like to put the starting caps/running caps on relays, that switch
in/out, as well.

How big is it, and have you considered a VFD running your 3 phase motor
off of single phase power?

I'm running a 15hp 3 phase motor on my compressor. Admittedly, I need a
100 amp line to do it though.

"Todd Rich" wrote in message
...
DrollTroll wrote:
Awl --

With single phase, what are the pro's/cons with having a 3 ph compressor
motor with starting caps, vs swapping it out for a single phase motor?

The tradeoff I see is a wiring pita vs. the grunt/mechanical pita and $$
of
a single phase motor, with likely a modified mounting.

I would like to put the starting caps/running caps on relays, that switch
in/out, as well.

How big is it, and have you considered a VFD running your 3 phase motor
off of single phase power?

No, I hadn't. But it is an idea. About 5 hp.

Certainly caps will be cheaper, but wiring relays, start/run is going to be
a pain as well.
Plus, I will have to de-rate the motor, and possibly put a smaller pulley on
it.

Keep in mind that this is a scenario where the motor is starting under
near-full load, which might be some electrical wear/tear on a VFD.

At least I *think* it is starting under full load (tank pressure).
Is there a way to set up an air compressor so that the motor starts under no
load? Only with a clutch, I would imagine, or "almost no-load", where some
vent bypasses the compressor head to air, or sumpn, and then closes.

So much drama....
--
DT




I'm running a 15hp 3 phase motor on my compressor. Admittedly, I need a
100 amp line to do it though.

On 2008-10-06, DrollTroll wrote:
Awl --

With single phase, what are the pro's/cons with having a 3 ph compressor
motor with starting caps, vs swapping it out for a single phase motor?

The tradeoff I see is a wiring pita vs. the grunt/mechanical pita and $$ of
a single phase motor, with likely a modified mounting.

I would like to put the starting caps/running caps on relays, that switch
in/out, as well.


Most likely it will not develop enough power to start the pump at
your restarting pressure.

Mounting on compressors is usually very forgiving and you can mount
any motor on a tupical belt driven compressor. At most you need to
drill a few holes.
--
Due to extreme spam originating from Google Groups, and their inattention
to spammers, I and many others block all articles originating
from Google Groups. If you want your postings to be seen by
more readers you will need to find a different means of
posting on Usenet.
http://improve-usenet.org/

On Mon, 6 Oct 2008 11:43:28 -0400, "DrollTroll"
wrote:


"Todd Rich" wrote in message
...
DrollTroll wrote:
Awl --

With single phase, what are the pro's/cons with having a 3 ph compressor
motor with starting caps, vs swapping it out for a single phase motor?

The tradeoff I see is a wiring pita vs. the grunt/mechanical pita and $$
of
a single phase motor, with likely a modified mounting.

I would like to put the starting caps/running caps on relays, that switch
in/out, as well.

How big is it, and have you considered a VFD running your 3 phase motor
off of single phase power?

No, I hadn't. But it is an idea. About 5 hp.

Certainly caps will be cheaper, but wiring relays, start/run is going to be
a pain as well.
Plus, I will have to de-rate the motor, and possibly put a smaller pulley on
it.

Keep in mind that this is a scenario where the motor is starting under
near-full load, which might be some electrical wear/tear on a VFD.

At least I *think* it is starting under full load (tank pressure).
Is there a way to set up an air compressor so that the motor starts under no
load? Only with a clutch, I would imagine, or "almost no-load", where some
vent bypasses the compressor head to air, or sumpn, and then closes.

So much drama....

Many (if not most) compressors do not start under full load. There is
an "unloader" in either the pump output or in the controller.

On Oct 6, 5:57 pm, Don Foreman wrote:
On Mon, 6 Oct 2008 11:43:28 -0400, "DrollTroll"
wrote:





"Todd Rich" wrote in message
...
DrollTroll wrote:
Awl --

With single phase, what are the pro's/cons with having a 3 ph compressor
motor with starting caps, vs swapping it out for a single phase motor?

The tradeoff I see is a wiring pita vs. the grunt/mechanical pita and $$
of
a single phase motor, with likely a modified mounting.

I would like to put the starting caps/running caps on relays, that switch
in/out, as well.

How big is it, and have you considered a VFD running your 3 phase motor
off of single phase power?

No, I hadn't. But it is an idea. About 5 hp.

Certainly caps will be cheaper, but wiring relays, start/run is going to be
a pain as well.
Plus, I will have to de-rate the motor, and possibly put a smaller pulley on
it.

Keep in mind that this is a scenario where the motor is starting under
near-full load, which might be some electrical wear/tear on a VFD.

At least I *think* it is starting under full load (tank pressure).
Is there a way to set up an air compressor so that the motor starts under no
load? Only with a clutch, I would imagine, or "almost no-load", where some
vent bypasses the compressor head to air, or sumpn, and then closes.

So much drama....

Many (if not most) compressors do not start under full load. There is
an "unloader" in either the pump output or in the controller.



Methinks that an 'unloading check valve' is a standard commercial
item, useful for smaller compressors. This valve is placed between
the compressor and air receiver. After compressor shut-off this valve
bleeds off the pressure between it and the compressor, allowing the
compressor to start against atmospheric, instead of tank, pressure.

Wolfgang

wrote in message
...

Methinks that an 'unloading check valve' is a standard commercial
item, useful for smaller compressors. This valve is placed between
the compressor and air receiver. After compressor shut-off this valve
bleeds off the pressure between it and the compressor, allowing the
compressor to start against atmospheric, instead of tank, pressure.

Wolfgang


Also with many VFD's it is simple enough to program an output relay to
control a solenoid dump valve that closes when the motor reaches speed.
Greg

On Mon, 6 Oct 2008 16:25:51 -0700 (PDT), wrote:


Many (if not most) compressors do not start under full load. There is
an "unloader" in either the pump output or in the controller.



Methinks that an 'unloading check valve' is a standard commercial
item, useful for smaller compressors. This valve is placed between
the compressor and air receiver. After compressor shut-off this valve
bleeds off the pressure between it and the compressor, allowing the
compressor to start against atmospheric, instead of tank, pressure.

Wolfgang


My Emglo 5hp gasoline powered air compressor has such a valve


Whenever a Liberal utters the term "Common Sense approach"....grab your
wallet, your ass, and your guns because the sombitch is about to do
something damned nasty to all three of them.

wrote in message
...
On Oct 6, 5:57 pm, Don Foreman wrote:
On Mon, 6 Oct 2008 11:43:28 -0400, "DrollTroll"
wrote:





"Todd Rich" wrote in message
...
DrollTroll wrote:
Awl --

With single phase, what are the pro's/cons with having a 3 ph
compressor
motor with starting caps, vs swapping it out for a single phase
motor?

The tradeoff I see is a wiring pita vs. the grunt/mechanical pita and
$$
of
a single phase motor, with likely a modified mounting.

I would like to put the starting caps/running caps on relays, that
switch
in/out, as well.

How big is it, and have you considered a VFD running your 3 phase
motor
off of single phase power?

No, I hadn't. But it is an idea. About 5 hp.

Certainly caps will be cheaper, but wiring relays, start/run is going to
be
a pain as well.
Plus, I will have to de-rate the motor, and possibly put a smaller
pulley on
it.

Keep in mind that this is a scenario where the motor is starting under
near-full load, which might be some electrical wear/tear on a VFD.

At least I *think* it is starting under full load (tank pressure).
Is there a way to set up an air compressor so that the motor starts
under no
load? Only with a clutch, I would imagine, or "almost no-load", where
some
vent bypasses the compressor head to air, or sumpn, and then closes.

So much drama....

Many (if not most) compressors do not start under full load. There is
an "unloader" in either the pump output or in the controller.



Methinks that an 'unloading check valve' is a standard commercial
item, useful for smaller compressors. This valve is placed between
the compressor and air receiver. After compressor shut-off this valve
bleeds off the pressure between it and the compressor, allowing the
compressor to start against atmospheric, instead of tank, pressure.

Is the loud air exhaust noise when the compressor shuts off this "unloading"
valve at work?

--
DT



Wolfgang

On Tue, 7 Oct 2008 01:28:51 -0400, "DrollTroll" wrote:
wrote in message
...
On Oct 6, 5:57 pm, Don Foreman wrote:
On Mon, 6 Oct 2008 11:43:28 -0400, "DrollTroll" wrote:

No, I hadn't. But it is an idea. About 5 hp.

Certainly caps will be cheaper, but wiring relays, start/run is going
to be a pain as well. Plus, I will have to de-rate the motor, and
possibly put a smaller pulley on it.

Keep in mind that this is a scenario where the motor is starting under
near-full load, which might be some electrical wear/tear on a VFD.

At least I *think* it is starting under full load (tank pressure).
Is there a way to set up an air compressor so that the motor starts
under no load? Only with a clutch, I would imagine, or "almost
no-load", where some vent bypasses the compressor head to air, or
sumpn, and then closes. So much drama....

Many (if not most) compressors do not start under full load. There is
an "unloader" in either the pump output or in the controller.

Methinks that an 'unloading check valve' is a standard commercial
item, useful for smaller compressors. This valve is placed between
the compressor and air receiver. After compressor shut-off this valve
bleeds off the pressure between it and the compressor, allowing the
compressor to start against atmospheric, instead of tank, pressure.

Is the loud air exhaust noise when the compressor shuts off this "unloading"
valve at work?

Yes, that hiss is the unloader, it's usually built into the pressure
switch and has an 1/8" tubing to the output check valve right at the
tank. The check valve keeps the air from coming back from the
receiver, and the unloader valve relieves the pressure in the output
tubing between the compressor and the check valve when the pressure
switch cuts the motor.

The length of the output tubing gives a time delay before the
compressor starts working against the main receiver pressure - and the
delay can be lengthened with longer output tubing or a small
accumulator chamber made from large pipe.

Or if your VFD has auxiliary contacts, you can put a solenoid valve
that vents the output tubing until the motor is up to speed.

-- Bruce --

"Bruce L. Bergman" wrote in message
...
On Tue, 7 Oct 2008 01:28:51 -0400, "DrollTroll" wrote:
wrote in message
...
On Oct 6, 5:57 pm, Don Foreman wrote:
On Mon, 6 Oct 2008 11:43:28 -0400, "DrollTroll" wrote:

No, I hadn't. But it is an idea. About 5 hp.

Certainly caps will be cheaper, but wiring relays, start/run is going
to be a pain as well. Plus, I will have to de-rate the motor, and
possibly put a smaller pulley on it.

Keep in mind that this is a scenario where the motor is starting under
near-full load, which might be some electrical wear/tear on a VFD.

At least I *think* it is starting under full load (tank pressure).
Is there a way to set up an air compressor so that the motor starts
under no load? Only with a clutch, I would imagine, or "almost
no-load", where some vent bypasses the compressor head to air, or
sumpn, and then closes. So much drama....

Many (if not most) compressors do not start under full load. There is
an "unloader" in either the pump output or in the controller.

Methinks that an 'unloading check valve' is a standard commercial
item, useful for smaller compressors. This valve is placed between
the compressor and air receiver. After compressor shut-off this valve
bleeds off the pressure between it and the compressor, allowing the
compressor to start against atmospheric, instead of tank, pressure.

Is the loud air exhaust noise when the compressor shuts off this
"unloading"
valve at work?

Yes, that hiss is the unloader, it's usually built into the pressure
switch and has an 1/8" tubing to the output check valve right at the
tank. The check valve keeps the air from coming back from the
receiver, and the unloader valve relieves the pressure in the output
tubing between the compressor and the check valve when the pressure
switch cuts the motor.

The length of the output tubing gives a time delay before the
compressor starts working against the main receiver pressure - and the
delay can be lengthened with longer output tubing or a small
accumulator chamber made from large pipe.

Or if your VFD has auxiliary contacts, you can put a solenoid valve
that vents the output tubing until the motor is up to speed.

That is all very ingenious!
Quite motor-friendly, as well.
A baffle sounds like a good idea, a good safety hedge for the motor.
--
DT







-- Bruce --