I am going to put my 120v, 15A compressor in the back of my garage. I
would like to control it's outlet with a wall switch near my entrance
door. I was doing some research first, and found this post
saying that motor powered appliances (specfically air compressors)
should never be controlled by a wall switch. If I use a heavy duty
20A switch, is this ok? I am using a 20A breaker and 12g wire.
I was doing some research first, and found this post
I don't know about that but here's something else to consider. When your
compressor is switched off by the pressure controller it opens a valve that
releases pressure from the head so that it can start more easily the next
time. If you flip off the lever on that switch (assuming yours has one) it
has the same effect.
I'm not sure but I believe that if you just kill power this won't happen so
if you still have pressure on the head the next time you switch it on you
will put a considerable bit of extra stress on the motor plus you'll
probably pop the circuit breaker and of course that will give your wall
switch an extra workout too.
Hopefully someone that knows more about it will chime in. :-)
"I'm not grown up enough to be so old!"
You need a switch specifically rated for the HP of the motor you're
Switch ampere ratings are all about lighting loads. Some of the more
expensive borg-grade switches are HP rated as well. If you can find
one, then Bob's your uncle.
You can also get the right switch (or contactor, if needed) from any of
the industrial supply houses. Their catalogs usually have a bunch of
As another twist on this, I've setup my compressor on a mechanical wall
switch timer rated for the HP. When I initially put it on a simple switch, I
happened to forget to turn it off a couple of times, only to have it cycle
as it bled off in the middle night -- once was enough.......woke the whole
house. 4 hour timer ensures pressure is in range while working, but no
middle-of-the-night surprises should I forget.
if you are really worred, you can use a 15 A circuit breaker for the
switch - but a contactor (which is a giant relay) is cheap, particularly
when you buy one surplus. what I would recommend is that you put a
contactor near the compressor and place the switch anywhere you want - since
the switch will only carry an amp or less, it will then not be a problem.
And, you won't have to worry about the voltage drop in the wires to/from the
switch box. If you use a 24V contactor you could actually make life easier,
because the wiring now is low voltage and you can use cheap speaker wire and
a small toggle switch.
firstname.lastname@example.org (Ryan) wrote in <e7d49913.0310090700.50afc7f1
I've had my 240volt compressor on a wall switch for twenty years with no
problems. If you kill the switch while the compressor is running you should
manually release the pressure release switch. Making sure the wiring for the
switch leg and the capacity of the switch matches the draw of the compressor
is needed but not difficult.
This allows to easily deal with leaky connections when not using the
I will get a lot of flames on this but yes "I" would. make sure the
outlet is also rated at 20AMP to keep the NEC fanatics at bay.
If you cycle the switch 10 - 15 times a week while the compressor is
running then you might only get 2 - 3 years of life out of the switch.
The most common failure (if it fails) will be... it won't run. the
other failure mode, that might happen in 1 out 50000 switches is... it
won't shut off. In that case unplg the compressor and replace the
switch in the morning.
Find the beefiest switch you can find. My dad gave me his old 8"
a 3/4 horse motor. He had wired a conventional switch inside a metal
was mounted on the saw (I guess the original had died). Anyway, I
usually end up replacing
the switch every few years since it gets fried and either wont turn on
or wont turn
off (about the same percentage). I use the red bodied "commercial" 20
from the Despot that cost about $3-$4 each. The saw is not used much but
I'd guess maybe
500-1000 cycles between failures.
A compressor is usually 1 horse minimum so life will be shorter than
what I have experienced
(inductive motor loads are hell on switches).
After saying that (and heeding the other advice about the compressor
unloading) I'd say buy the
switch that is rated for the highest current draw (at least 20 amps) and
preferably has mercury
wetted contacts. Expect to replace it every few years if switching on a
low power compressor daily.
Not really. You're using your switch on your saw to start and stop the
motor. He won't be doing that with his compressor. The pressure switch on
the compressor will still serve that function. All he is doing is
interrupting the power in the circuit. Provided that the compressor is
not running, or that the tank is not bled below the pressure cutoff while
the power is off, he will never be switching the power to a running (or
starting ) motor. I have switched my compressor like this for lots of
years while no failure of any switch.
another voice of practicality, thank you. If we were all high volume
shops with multiple employees then this discussion would be different.
We are, for the most part, amateurs that try and get to our shops 2 - 3
times a week. The MTBF for switchs, compressors.... falls off the chart
with these usage rates. yes is you by the $0.43 switch it will probably
fail in a year but it will also fail in the same time if you put it on
your kitchen light.
That would be the ideal way to use the switch. Problem is though many
won't want to wait for the motor to stop before switching power off.
the system is 100% air tight, the first switch-on in the morning will
kick the motor
The _proper_ way to set this up is with a remote switch wired to a
switch (has the bleed off mechanism), but the prices are not friendly.
is accessible easily enough and I just use the switch installed on it (6
HP 60 gallon unit).
If I was to make a remote switch I'd just use an old contactor switch
designed for big motors
If the HP was under 2 I'd just deal with replacing a good wall switch
every so often or do what the
Squirrel does and switch it only when the motor is not running.
The stress on a switch is when you turn it off, not when you turn it in.
(extinguishing the arc).
Since this compressor will shut itself off when the pressure switch is
satisfied I doubt it will be running when the switch is thrown unless he races
over the the wall to do it.
At any rate a HP rated switch should handle it anyway. One poster has said that
switch is 7 bucks at Ace. That means it is probably less than 5 at the Borg.
Why are we spending so much time on this?
Buy a commercial grade switch and let's get back to making sawdust.
How do you spell "never"?? The start surge on that thing is probably close
to 50 A! If you just have to do this, wire the power straight in and add a
magnetic starter...Griz has them, among others. But, it's a lot of money.
Why not just leave it on? If you don't have leaks it doesn't matter.
Mine's been on for years. I crack the drain valve to keep the condensate
from accumulating, so it runs once or twice a day to keep the pressure up.
If you don't use it often, just leave it off and start it five minutes
before you need it.
email@example.com (Ryan) wrote in message
The other replies offer practical advice about the switch ratings and
the unloader. As for the unloader you can get around that at worst if
you switch off the compressor only after it has cycled off on its own.
But the code safety issue with a wall switch or any other remote
switch is on account of the risk of the switch being turned on while
you are working on the equipment. Particularly if the switch is out
of sight of the equipment. So at worst anything remotely switched
like that should still have a cord and plug you can unplug at the
equipment, or a separate disconnect switch again at the equipment.
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