Wiring Question: Air Compressor Pressure Switch
-N.
been replaced by a 3HP 230/115VAC (FLA=26) motor. I have the
replacement motor wired for 115VAC . Everything checks out O.K.,
everything is up to code. One last issue is re-wiring the pressure
switch.
The pressure switch is a new Siemens unit and has a sticker on the
outside of the enclosure reading " 230/1/60", which I assume refers to
230VAC, 1 phase, 60Hz. Is this type of switch fully compatible with a
115VAC motor?
Inside the pressure switch enclosure is a sticker with the following
info:
56288806-01
1 Phase Ratings
Volts FLA LRA
120 34 144
240 26 130
69JG109748R 5/1
ON 145 PSI
OFF 175 PSI
My question is this. The pressure switch has 4 terminals: 2 for the
LINE and 2 for the MOTOR (and also a grounding terminal). The pressure
switch was originally wired for 230VAC. Is rewiring it for a 115VAC
motor straight forward? Do I just connect the 115VAC line hot to one
LINE TERMINAL, the line neutral to the other LINE TERMINAL, connect
the line ground wire to the enclosure, then simply wire the 2 MOTOR
TERMINALS to the motor's line terminals, and then terminate the ground
at the motor case?
Thanks a bunch.
Cheers,
Neal
Wilson Lamb
230 configuration? That will greatly reduce your running current and
starting surge. At 115V you need at least 10 GA wire.
The four terminals are intended for the 230V setup, where you must break
both sides of the line to avoid having power in a non running motor. If I
were doing your new setup (which I wouldn't), I would use the two pair of
contacts in parallel and not break the neutral. Then the failure of the
neutral pair of contacts could not leave you with voltage in a non running
motor, which might lead you to believe it was safe to work on.
Parallel means the hot line goes to both line contacts and one side of the
motor goes to both the load pair.
BTW, you will probably have to either reduce the max pressure or the size of
the motor pulley to stay within the motor's rating. It is smaller, after
all. But who knows, max power is only needed as the tank gets near full
charge, so it may survive limited use. To be safe, I'd get the cheap clamp
on ammeter from Harbor Freight and choose a max pressure or pulley size that
limited the max running current to about 110% of the nominal rating. You
really don't need 175 PSI anyway, since most tools are rated around
80-100PSI. So reducing the max pressure setting saves your having to
experiment with expensive belts and pulleys.
Wilson
Wilson
"-N." <purple...@yahoo.com> wrote in message
news:ca3cfb6c.0202...@posting.google.com...
Kevin Beitz
Your switch has two switches in one ....Thats for the 220 volt...
110 volt pulls more amps ....So just run two loops of wire to the other switch...
Bernard Randall
will always come into contact, or break, micro seconds before the other and
that's the time contact welding will occur. I you want additional safety,
connect the switches in series, that way if one set of contacts welds the
other will still operate.
"Wilson Lamb" <inf...@mindspring.com> wrote in message
news:a5bvv6$ddf$1...@slb1.atl.mindspring.net...
-N.
Thanks for the advise.
I don't want to get into why I'm using the motor I'm using, it's been
hashed to death here. My electrical service upgrade was halted
mid-stream when asbestos was found in the basement, second phase of
electricity was never hooked up, I only have 115VAC now and for the
forseeable future until the owner resolves the situation (the latter
is anyone's guess). Making the best of a great compressor in a less
than ideal installation. Hopefully, a temporary solution.
It's running on a circuit of which the weakest conductor is 10 guage
MC THHN/THWN.
>I would use the two pair of contacts in parallel and not break the
neutral.
>Then the failure of the neutral pair of contacts could not leave you
>with voltage in a non running motor, which might lead you to believe
it was >safe to work on.
>Parallel means the hot line goes to both line contacts and one side
of the
>motor goes to both the load pair.
I'm confused by your explanation.
Are you suggesting wiring the neutral directly to the motor without
connecting it to the pressure switch??
And that the 115VAC hot wire is conected to BOTH the LINE terminals of
the switch?? One side of the motor gets connected to BOTH motor
terminals in the pressure switch??
If I'm understanding you correctly, why bother to wire both sides
(contacts) of the pressure switch? Why not just eliminate one of the
switch's contacts: and just use one contact for the 115VAC -> motor.
Then, connect the neutral directly to the motor, bypassing the switch?
>BTW, you will probably have to either reduce the max pressure or the
size of
>the motor pulley to stay within the motor's rating. It is smaller,
after
>all. But who knows, max power is only needed as the tank gets near
full
>charge, so it may survive limited use. To be safe, I'd get the cheap
clamp
>on ammeter from Harbor Freight and choose a max pressure or pulley
size that
>limited the max running current to about 110% of the nominal rating.
O.K., I'm confused again. You will have to forgive me, I'm a baby when
it comes to understanding electricity and motors.
Do you mean limit it to 90%??? It sounds as if you are suggesting
INCREASING running current to 110%.
I'v got it set up with the stock pulley. If need be, I can have the
pump turn slower. Stock pump speed is 1500RPM, Ingersoll-Rand says I
can go down to a pump speed of about 800RPM without jepordising the
splash lubrication.
>You really don't need 175 PSI anyway, since most tools are rated
around
>80-100PSI. So reducing the max pressure setting saves your having to
>experiment with expensive belts and pulleys.
Is there a way to adjust the max pressure of this particular switch?
Thanks.
CHeers,
Naal
Wayne Cook
<bwjar...@cox-internet.com> wrote:
>I disagree with connecting both pairs of contacts in parallel, one contact
>will always come into contact, or break, micro seconds before the other and
>that's the time contact welding will occur. I you want additional safety,
>connect the switches in series, that way if one set of contacts welds the
>other will still operate.
The problem with not connecting them in parallel is that the
contacts could weld. Running a compressor that size off 110 draws a
lot of current. I've had problems in the past running a 2 HP with the
contacts actually welding together due to the higher current draw.
Parallel will help divide the current between the two contacts and
will probably be the most reliable in the long run. BTW is one
contacts welds then the other is never released because the first
contact holds the second together.
Wayne Cook
Shamrock, TX
Jerry
>
> >You really don't need 175 PSI anyway, since most tools are rated
> around
> >80-100PSI. So reducing the max pressure setting saves your having to
> >experiment with expensive belts and pulleys.
>
> Is there a way to adjust the max pressure of this particular switch?
>
> Thanks.
>
> CHeers,
> Naal
Naal
I suggest that you will be alot happier with a pressure switch designed
for the pressure range you intend to operate. I have tried to adjust the
pressure range of compressor switches and have never gotten them set right.
I would be much happier with 100 psi than with 175 psi. in my home shop.
And, the compressor would live alot longer at !00 psi too.
Jerry
Bernard Randall
"Wayne Cook" <way...@pan-tex.net> wrote in message
news:gmej7uk41fu6pjkl5...@4ax.com...
If wired in parallel, that's the reason for wiring in series.
Wiring contacts in parallel does not increase current capacity with relays,
for reason previously stated. High current contacts on relays are of special
mechanical design and materials.
As suggested in earlier post, why wire for 110 any way? Much bigger cables,
much higher current.
>
>
> Wayne Cook
> Shamrock, TX
Wayne Cook
<bwjar...@cox-internet.com> wrote:
>
>"Wayne Cook" <way...@pan-tex.net> wrote in message
>news:gmej7uk41fu6pjkl5...@4ax.com...
>> On Sun, 24 Feb 2002 21:00:53 -0800, "Bernard Randall"
>> <bwjar...@cox-internet.com> wrote:
>>
>> >I disagree with connecting both pairs of contacts in parallel, one
>contact
>> >will always come into contact, or break, micro seconds before the other
>and
>> >that's the time contact welding will occur. I you want additional
>safety,
>> >connect the switches in series, that way if one set of contacts welds the
>> >other will still operate.
>>
>> The problem with not connecting them in parallel is that the
>> contacts could weld. Running a compressor that size off 110 draws a
>> lot of current. I've had problems in the past running a 2 HP with the
>> contacts actually welding together due to the higher current draw.
>> Parallel will help divide the current between the two contacts and
>> will probably be the most reliable in the long run. BTW is one
>> contacts welds then the other is never released because the first
>> contact holds the second together.
>
>If wired in parallel, that's the reason for wiring in series.
>
Due to the design of these switches if wired in series if one side
welds the other side will never release. Both contacts are on the same
arm.
>Wiring contacts in parallel does not increase current capacity with relays,
>for reason previously stated. High current contacts on relays are of special
>mechanical design and materials.
>
It sure can't hurt. It will mean less heating during the run of the
compressor which in this case can be considerable since he's running
the switch close to rated capacity.
>As suggested in earlier post, why wire for 110 any way? Much bigger cables,
>much higher current.
>
This has been gone through for a long time here. He can't get 220V
service where he's at. He's limited to 110V.
Wayne Cook
Shamrock, TX
Loren Coe
> On Mon, 25 Feb 2002 01:38:26 -0800, "Bernard Randall"
> >> contacts could weld. Running a compressor that size off 110 draws a
> >> lot of current. I've had problems in the past running a 2 HP with the
> >> contacts actually welding together due to the higher current draw.
> >> Parallel will help divide the current between the two contacts and
> >> will probably be the most reliable in the long run. BTW is one
> >> contacts welds then the other is never released because the first
> >> contact holds the second together.
> >
> >If wired in parallel, that's the reason for wiring in series.
> >
> Due to the design of these switches if wired in series if one side
> welds the other side will never release. Both contacts are on the same
> arm.
>
> >Wiring contacts in parallel does not increase current capacity with
relays,
> >for reason previously stated. High current contacts on relays are of
special
> >mechanical design and materials.
let me weight in here, i agree with Bernard. sci.electronics.repair is a
good
bet, too. the contacts of 1hp rated relays do indeed weld when closed, it
is actually _required_ to establish a low resistance path.
Waynes suggestion may work but there probably is very little sharing
between the contacts, the one that makes first will arc and carry the
load. the other one will probably provide a hi-resistance path,
accomplishing
nothing. in fact, it could melt and stick, depending on gawd knows what..
my 2cents,
--Loren
Loren Coe
Jerry <j.jm...@verizon.net> wrote in message
news:N7je8.641$bZ4...@nwrddc02.gnilink.net...
> I suggest that you will be alot happier with a pressure switch designed
> for the pressure range you intend to operate. I have tried to adjust the
> pressure range of compressor switches and have never gotten them set
right.
> I would be much happier with 100 psi than with 175 psi. in my home shop.
> And, the compressor would live alot longer at !00 psi too. > >
Jerry
this is a good suggestion. my recent experience in resurrecting a 2hp
240vac was
discussed here. i now understand that my switch was likely the same,
150-175. the
problem is the low-on setting goes no lower than 150psi with the adjustment
fully ccw.
i would _not_ want to run a 120vac 2hp compresser at that pressure, even a
1hp....
120vac and compressors really don't mix well, IMHO. i ran a Sears unit for
years wired new for 110. finially, tiring of tripping breakers, i changed
it to 220,
man, what a difference!
anyhoo, good luck!
--Loren
.
>
>
Wilson Lamb
pressures the pump must run slower for a given HP. Just look at the $10
compressor that can inflate car tires for an example.
If he uses a 100-125 PSI cutoff, the 2HP may well do the job, even with the
same pulleys.
Wilson
"Loren Coe" <lore...@netscape.net> wrote in message
news:4eve8.5953$9o.151265@sccrnsc02...
Eastburn
a semi-insulative material - that keeps arcing down and the
closure presses through the film and makes a real un-pitted and
not oxidized surface.
I think it was in an U.S.A.F. manual - or motor repair..
Didn't see it in the motor repair manual. Humm.
Martin
--
NRA LOH, NRA Life
NRA Second Amendment Task Force Charter Founder
Martin Eastburn, Barbara Eastburn
@ home on our computer old...@pacbell.net