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7.5 hp 220 volt push on off switch

easlers

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getting ready to install new quincy 7.5 hp air compressor. where in the world do you have to go to get a push on/off button for this compressor. 220volt single phase. iwant to run power to switch then to compressor so i can turn on and off . I could use a disconnect but I figure the arcing on disconnect would not hold up with frequent on and off. Anybody got any idea where to get one. The only ones I see are 3hp max. I really do not want it running when not in use.
Any one with a suggestion or info would be greatly appreciated.
 
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mm08822

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Interrupt the control circuit. Put extra switch in series with existing pressure switch. No need to get into the power circuit.
 

Bert_

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Does this compressor use a contactor/starter to control the motor? Usually it would for a motor of this size.
If so just put a switch in series with the coil. You could then use any cheap switch because you would only be switching the contactor not the full current of the motor.

A disconnect would be a perfectly fine option. Most are made to hold up to frequent switching. For a 7.5 hp motor you would need a 60A disconnect.
 

American Locomotive

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Why not just switch the disconnect when the compressor has cycled off?

Also, there's no reason to switch the compressor off if your air system is leak free. I've seen leak-free compressors hold air for literally months without leaking down. Even if your air system does have a bit of leak somewhere, you could just put a ball valve.
 

OccupantRJ

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A standard household light switch will do it if you attach it to the pressure switch wiring. I use one on mine. It is only switching the contactor coil on or off.
 

wyliesdiesels

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getting ready to install new quincy 7.5 hp air compressor. where in the world do you have to go to get a push on/off button for this compressor. 220volt single phase. i want to run power to switch then to compressor so i can turn on and off . I could use a disconnect but I figure the arcing on disconnect would not hold up with frequent on and off. Anybody got any idea where to get one. The only ones I see are 3hp max. I really do not want it running when not in use.
Any one with a suggestion or info would be greatly appreciated.

U will not find a push button switch that is rated for interrupting the high current of a motor that size.

As said above, wire the switch into the control circuit.

A cheap snap switch would work.
 
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easlers

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Ok do you interupt L1 or L2 wire.I'm not sure of the voltage going to the contactor. I could probably mount a togle switch on the side of the box the motor starter is in. I take it you would only interupt 1 of the line wires, Correct?
 

wyliesdiesels

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Ok do you interupt L1 or L2 wire.I'm not sure of the voltage going to the contactor. I could probably mount a togle switch on the side of the box the motor starter is in. I take it you would only interupt 1 of the line wires, Correct?

U need to know the voltage of the coil.

Is there a transformer?

Its most likely 240v.

Doesnt matter which one u interupt.
 

EOC_Jason

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I don't see why a normal disconnect box would not be an option? It's not going to arc when the compressor is off. Plus they are spring loaded to minimize arcing, that's why you hear the loud THUNK every time you flip them on / off (well, for higher amp boxes at least). That's what a guy I know uses in his machine shop for their air compressor, they flip it off every night just to be safe in case an air line leaks or something so the pump isn't running all night.
 

manwithtools

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A disconnect switch would be an option Jason, it's just a very expensive one. A toggle (wall) switch in series with the control circuit is only switching a very small load. A $1.50 switch in a handy box is much cheaper than a properly sized disconnect switch.

It will provide exactly the same kind of protection the disconnect switch does in case of a air line failure.
 

AntonLargiader

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Easlers, what hardware do you already have for control? Just bare motor leads? Normally a motor of this size has a "motor starter" which is a set of contactors for the power leads. Basically a relay. Do you have one for that motor?

For example:
https://www.amazon.com/dp/B00GGPZ9P4/?tag=atomicindus08-20

All of the turning on and off is done on the control side of that, and the starter handles the actual full-power switching.

EDIT: OK, I see you have one. If you follow the line from the pressure switch, that will be the one that turns it on and off. If you want a single push on/off control, the easiest would be to buy a switch control that you like and use it to feed power to the pressure switch. You can also build a control with relays to do the same thing. Is there an existing control that you like?
 
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EOC_Jason

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I realize the switch would work, that cuts power to keep the pump from coming on (assuming something doesn't fuse the coil closed). But it doesn't actually kill power to the machine.

Being a 7.5HP it's going to have to be hard-wired. Typically code also requires a means to disconnect the power nearby the machine. So unless the breaker panel is close by, a disconnect box would be the proper way to do it.

A 60A disconnect new isn't *that* bad, it's a one-time expense too. You can also check electrical supply places that sell used equipment (disconnects, breakers, lights, etc) and save some money that way. Or CL if you are lucky.

No trying to be an ***... Just trying to err on the side of safety.
 
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easlers

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Thanks guys for the imput. I just dont under stand this is a quincy 7.5 hp max package compressor (not cheap by no means) It comes with a prewired motor starter it would seem like it would have a off on switch. Im wanting to do it right. I will consider putting a disconect. my breaker box will be about 40 feet away. But here is the ting. If something was to go south more than likely I will be in the main part of the shop and more than likely would be closser to the breaker box than the disconnect. You never know though when or where you'll be. All advise is well taken and thanks but there must be more with the wire to the pressure switch than the disconnect. The issue here is more safety than convienience. I was a Maint. Suppervisor for 30 years and if it were at the plant I know for a fact the dissconect would be the way to go. Thanks guys. This compressor takes a 75 amp breaker so I guess an 80 amp disconnect will be the way to do it. Thanks again.
 

PT Doc

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Leviton makes a 60 amp switch. A believe it is ms602 for single phase and ms603 for 3 phase. These is part of a series of motor rated switches. They have really nice special switch boxes to mount these specialty switches in although a had the 602 mounted in a 4.5" steel junction box with a cover. From the exterior it looked like a simple toggle switch. Hope this helps.
 

AntonLargiader

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Every time I have seen compressors like this they are rigged with a disconnect which is used to turn it on and off for the weekend, overnight, whatever. Or a breaker.

With a motor starter, the disconnect isn't exactly starting the compressor anyway. It's energizing the starter which may or may not get pulled in by the pressure switch. It happens pretty quickly but the final connection should be in the starter. Unless you are talking about old knife switches, your disconnect will snap closed quickly.

It would not be so hard to add another control to give you the push on/off thing you were talking about in the beginning. Rig it to send power to the pressure switch. You can buy complete units like that (I see them on woodworking equipment all the time), or you can roll your own with two buttons, a relay and a small enclosure. This would keep the compressor from starting automatically when you energize the system with low pressure.

http://www.ebay.com/bhp/start-stop-switch
 

matt_i

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Here is how I would solve your problem. I have the control ladder listed as 120vac but it can also work for 240vac. The light bulb would not, however, work on 240vac. You would have to eliminate that or else find an indicator rated for that voltage.

You already have the contactor/starter, all you are doing is adding another logical element to take control of the coil, exactly like a billion other industrial systems out there.



Here is the control circuit which you will break into with the wall-switch (this one is wired with an overload element)

 
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wyliesdiesels

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I realize the switch would work, that cuts power to keep the pump from coming on (assuming something doesn't fuse the coil closed). But it doesn't actually kill power to the machine.

Being a 7.5HP it's going to have to be hard-wired. Typically code also requires a means to disconnect the power nearby the machine. So unless the breaker panel is close by, a disconnect box would be the proper way to do it.

A 60A disconnect new isn't *that* bad, it's a one-time expense too. You can also check electrical supply places that sell used equipment (disconnects, breakers, lights, etc) and save some money that way. Or CL if you are lucky.

No trying to be an ***... Just trying to err on the side of safety.

code requires a disconnect if compressor is further than 50' and not within sight of panel.

And a pull out AC disconnect accomplishes the same thing for a lot cheaper.

But OPs panel is 40' away so nether is required. The breaker suffices.

Thanks guys for the imput. I just dont understand this is a quincy 7.5 hp max package compressor (not cheap by no means) It comes with a prewired motor starter it would seem like it would have a off on switch. Im wanting to do it right. I will consider putting a disconnect. my breaker box will be about 40 feet away. But here is the thing. If something was to go south more than likely I will be in the main part of the shop and more than likely would be closer to the breaker box than the disconnect. You never know though when or where you'll be. All advise is well taken and thanks but there must be more with the wire to the pressure switch than the disconnect. The issue here is more safety than convenience. I was a Maint. supervisor for 30 years and if it were at the plant I know for a fact the disconnect would be the way to go. Thanks guys. This compressor takes a 75 amp breaker so I guess an 80 amp disconnect will be the way to do it. Thanks again.

why would it seem "like it would have an off on switch"? Nothing requires them. But perhaps the PS has one. Can u post pics?

Is breaker panel within sight of the compressor?

If so U dont need a disconnect since panel is 40' away.

BTW the disconnect is for servicing of the compressor and to prevent someone from getting shocked because of another person coming along and turning the breaker back on while someone is working on it. Has nothing to do with possible potential dangerous situations.

Dont waste money on a disconnect. Breaker is suitable for this. Or if it makes u feel safer, wire a light switch in series with the compressor starter coil and place the switch next to your other light switches. Label it compressor.

And again, a plant setting makes no difference as far as disconnects go. If the machine was within 50' of and in sight of the panel, then its not required by code.

If u think there is more to the PS why dont u take some pics and post them. At this point its all guessing over the internet for us.

Ya know what they say. "A picture is worth a thousand words." Probably more so.

:needpics:

Leviton makes a 60 amp switch. A believe it is ms602 for single phase and ms603 for 3 phase. These is part of a series of motor rated switches. They have really nice special switch boxes to mount these specialty switches in although a had the 602 mounted in a 4.5" steel junction box with a cover. From the exterior it looked like a simple toggle switch. Hope this helps.

Those are more geared towards motors without starters. The OP doesnt need to waste money on that for many reasons including breaker panel is within 40' and most likely in sight of the compressor, an AC pull out disconnect is cheaper if the OP insists on having a disconnect for servicing the compressor, and as has been said numerous times a cheap snap switch and some wire will accomplish what he is looking for which is an "On-off switch".

People in this thread are confusing "on-off" switch with disconnect. The Op asked about an "on-off" switch. An on-off switch is just that. A disconnect is for servicing and removes power from the machine which isnt necessary since breaker panel is within 50'.
 
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gungatim

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matt_i

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I don't think the General Electric TG3221 is the right manual disconnect.

Note it is only 1.5HP @ 240vac rated with standard fuses, thus the old "snap the disconnect up/down while under load" is going to cause some problems. It would take a 60A or 100A disconnect to service a 7.5hp motor depending on what style fuses are available. I don't think the -CP version uses fuses.




source: http://apps.geindustrial.com/publib...NR=Brochures|DET-845|PDF&filename=DET-845.pdf
 

wyliesdiesels

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this is what I used for mine: https://www.menards.com/main/electr...m?tid=2424219660203224892&bargainStoreId=3144

$20, plus whatever the cartridge fuses cost (I forget). works great. it says 30 amp, not sure what amp you need but you could probably put whatever cartridge fuses you need in it. just may not be "code".

I made a bracket off the motor mount to hang it by the pump.

What is the HP rating on your comp?

If more than 1.5HP as Matt pointed out above, then thats the wrong disconnect.

And a fusible disconnect in this application is a waste of money.
 

md21722

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Magnetic starter coils are not fool proof. One of their failure modes is that they can stick on. To protect against that, a full load disconnect could be used. If you're not worried about that, a remote mounted switch wired into the control circuit could be used. Some magnetic starters have a blank for controls, but you can do the same with a simple toggle switch for about $130 less..
 
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matt_i

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Magnetic starter coils are not fool proof. One of their failure modes is that they can stick on. To protect against that, a full load disconnect could be used. If you're not worried about that, a remote mounted switch wired into the control circuit could be used. Some magnetic starters have a blank for controls, but you can do the same with a simple toggle switch for about $130 less..

If worried about the contact failing via welding, I would use a "NEMA size 1" startern (for 7.5hp @ 240vac). The NEMA rating is a very severe duty device (iow conservatively rated) in my opinion as compared to the downsized IEC devices that are used all over because they cost less and are physically more compact.

Likely if you did have a contact weld, you'd find it via the mechanical pressure reliefs opening up and the motor still running away. At that point I would go and shutoff the circuit breaker. A localized manual disconnect would be handy if you want to follow lockout/tagout procedures but in a 1 man personal shop, its a bit of extra expense.
 

AntonLargiader

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Home Depot has this....wouldn't it work. Not crazy expensive either...8.00.

If it has a HP rating, yes. From what I have read, if it only has an amp rating it is not permitted as a motor disconnect per 430.109.

I've never seen a pull-out used as a compressor disconnect so I did a bit of reading (I have a compressor to install in the next month or so). 430.109 seems to require a HP rating to function as a required disconnect, and documents like this PDF seem to back that up:

http://www.cooperindustries.com/con...ary/BUS_Ele_Tech_Lib_Molded_Case_Switches.pdf
 

kevs79

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If it has a HP rating, yes. From what I have read, if it only has an amp rating it is not permitted as a motor disconnect per 430.109.

I've never seen a pull-out used as a compressor disconnect so I did a bit of reading (I have a compressor to install in the next month or so). 430.109 seems to require a HP rating to function as a required disconnect, and documents like this PDF seem to back that up:

http://www.cooperindustries.com/con...ary/BUS_Ele_Tech_Lib_Molded_Case_Switches.pdf

Good info! Looks like it does have a 10 hp rating so it should work. If you look in the lower right hand corner.......kind of hard to see.
http://www.homedepot.com/catalog/pdfImages/5c/5ccaf388-daae-44eb-af9d-4f0cfb34ccfe.pdf
 

wyliesdiesels

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If it has a HP rating, yes. From what I have read, if it only has an amp rating it is not permitted as a motor disconnect per 430.109.

I've never seen a pull-out used as a compressor disconnect so I did a bit of reading (I have a compressor to install in the next month or so). 430.109 seems to require a HP rating to function as a required disconnect, and documents like this PDF seem to back that up:

http://www.cooperindustries.com/con...ary/BUS_Ele_Tech_Lib_Molded_Case_Switches.pdf

They are made for disconnecting air conditioner condensers which can have high HP motors....
 

gungatim

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What is the HP rating on your comp?

If more than 1.5HP as Matt pointed out above, then thats the wrong disconnect.

And a fusible disconnect in this application is a waste of money.

it is probably wrong, but it's a 6hp single stage 60 gal. I don't use it as a true on/off switch, as I don't disconnect it under a load. it is to disconnect power (have a light wired to it when on) so I don't forget when I leave the shop. I think I put 30amp fuses in it.

it's not a waste of money for me, because I needed a way to make sure I turned it off at night. there is a little on/off plastic switch on the pressure switch but it is tiny and hard to get to (unless you like burning your hand fumbling around the intake piping).
 
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wyliesdiesels

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it is probably wrong, but it's a 6hp single stage 60 gal. I don't use it as a true on/off switch, as I don't disconnect it under a load. it is to disconnect power (have a light wired to it when on) so I don't forget when I leave the shop. I think I put 30amp fuses in it.

it's not a waste of money for me, because I needed a way to make sure I turned it off at night. there is a little on/off plastic switch on the pressure switch but it is tiny and hard to get to (unless you like burning your hand fumbling around the intake piping).

does your compressor have a starter?
 

rrangus

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If it were mine, I would install the disconnect at the compressor. If I am working on it I want to be darn sure that it does not get turned on. I operate on the premise Murphy was a optimist. If any thing can go wrong, it will, and at the worst possible time.
 

GarageGuy89

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If it were mine, I would install the disconnect at the compressor. If I am working on it I want to be darn sure that it does not get turned on. I operate on the premise Murphy was a optimist. If any thing can go wrong, it will, and at the worst possible time.

+1

I did this on mine, even though it was within 10' of breaker. Took all of 2 min. to hook it up and have it mounted. I put it right next to the compressor so I treat it as an on/off switch. I believe it was $10. It is also inline with the main power, so there is no need to run additional wiring or have wiring flopping around everywhere for a light switch if you choose that route.

I also find that for what ever reason stuff gets put in front of my breaker so access to the breaker can be a journey at best....
 
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easlers

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well quite the read on the thread. OK. Getting all info from Northern tool where I ordered the compressor . It will require 70 amp breaker, #8 wire. Looking at disconnects they are running from 60 amp to 100 amp. can't find an 80 amp disconnect. I will propably go with interupting the pressure switch circuit and get a on off cheap switch. The compressor will have its own room already built.
It draws 32 amp full load so at start up possibly 90 amps for 3-5 seconds this is what a staff member said. I will have to run 75 feet of wire but compressor is 40 feet away. I know by code u should have a disconnect but the only option I see if a disconnect is used I would have to get 100amp. That ***** and relly overkill.

Now # 8 wire they say you dont need ground wire is that right? And what kind of wire nm ?
Do I need the run to be in conduit or flexible line like armor. clue me in guys. Ive got a wwek before compressor is delivered. It would be nice to have the wire ran ahead of time.
 

wyliesdiesels

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nope...and I know apples/oranges...just thought I'd post an option. sometimes you throw a bunch of ideas out there and it drives other creative solutions...

The 6HP rating is probably inflated. Pretty rare to have a pressure switch rated for 6HP...

whats the FLA on the nameplate?

and your compressor is probably rated for more than 1.5hp so yes the disconnect u used is not the right one...

well quite the read on the thread. OK. Getting all info from Northern tool where I ordered the compressor. It will require 70 amp breaker, #8 wire. Looking at disconnects they are running from 60 amp to 100 amp. can't find an 80 amp disconnect. I will probably go with interrupting the pressure switch circuit and get a on off cheap switch. The compressor will have its own room already built.
It draws 32 amp full load so at start up possibly 90 amps for 3-5 seconds this is what a staff member said. I will have to run 75 feet of wire but compressor is 40 feet away. I know by code u should have a disconnect but the only option I see if a disconnect is used I would have to get 100amp. That ***** and relly overkill.

Now # 8 wire they say you dont need ground wire is that right? And what kind of wire nm ?

Do I need the run to be in conduit or flexible line like armor. clue me in guys. Ive got a week before compressor is delivered. It would be nice to have the wire ran ahead of time.

Wire for motor circuits is sized by the HP rating.

SO 7.5hp motor requires 60a rated wire.

8/2 NM-b is too small. Northern tool gave u the wrong wire size.

U need 6/2 NM-b or #6 THHN in pipe...

the breaker can be sized max 250% of NEC FLC table current. 40a breaker may work.

Have u contacted your PoCo to find out if they allow this size motor? And if your end of the grid can handle it?

yes u do need a ground wire. who said u didnt need one?

In-rush doesnt last for 3-5 secs. Its more in the 100 millisecond range...

The disconnect needs to be rated for at least the same HP as the motor. The amp rating is inconsequential here.

Since the compressor is out of sight of the panel, u WILL need a disconnect.

From the disconnect to the compressor u SHOULD use THHN stranded wire. U can put this in FMC- flexible metal conduit.
 
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easlers

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wellThanks for all the input guys. KEVS 78 and Wyliesdiesels I'm going with the cheap 8.00 pull out 60 amp but I looked at it and it does say for up to 10HP . At first my concerne was the 60 amp level with a 70 amp breaker but I think it will be fine. #6/2 with ground wire ,a 70 amp breaker and that pullout disconect will be installed Thanks
 
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