Do I need a disconnect for compressor?

[kingchevy]

I have a 5hp Baldor motor on my compressor that draws 23A. It doesn't have a starter just a Square D 9013FHG34S155J39 pressure switch. Someone put an oddball 3 pole dial type switch on it that doesn't even have an enclosure.

My question is: Do I even need a disconnect? I have the compressor in my garage on a 30 amp dedicated circuit and it is controlled by a 2 pole contactor with a 120v coil that I control with 3 way switches in my garage and in my shop. Switches are pilot lit so I know if the compressor is on.

I found a 2 pole Cooper switch that is motor rated at 5hp and 30 amps and I'm thinking of just mounting this on the compressor before the pressure switch, good idea or not?

 

[rsnip988]

Couldn't hurt anything... If it is hardwired I think it is supposed to have a disconnect of some sort per "code", mine has a plug and I still installed a disconnect switch.

 

[nadogail]

Your compressor should have a way to disconnect it for service. An accessible circuit breaker in sight of the compressor is sufficient.

 

[kingchevy]

Your compressor should have a way to disconnect it for service. An accessible circuit breaker in sight of the compressor is sufficient.

One of the 3 way switches is within a few feet and line of sight.

 

[landyacht]

Yes but if the other 3way is out of sight someone could turn it back on without realizing you're working on it.

 

[kingchevy]

Yes but if the other 3way is out of sight someone could turn it back on without realizing you're working on it.

Yeah, I'm looking at this switch.

http://www.westwayelectricsupply.co...-q9y6_QCFosuYKYSbg98ACGtOpChkMYRNIaAs1e8P8HAQ

 

[rsnip988]

Seems pretty expensive for what it is... (essentially a 30A lightswitch) it could also easily be switched back on by accident...

http://www.homedepot.com/p/GE-30-Amp-240-Volt-Non-Fuse-Indoor-Safety-Switch-TGN3321CP/100674081

Also has a safety lockout to ensure no one cuts it back on... It's what I used.

 

[rlitman]

I used an air conditioner disconnect. I want to say it ran me $15.

 

[Norcal]

I used an air conditioner disconnect. I want to say it ran me $15.

Or they can cost a bit less less. Some people want to spend as much of their money as they can based on a number of threads that have been posted here.

 

[matt_i]

I would do as you already have done and buy a motor starter (IEC or NEMA) and control the unit by inhibiting (or not) the coil circuit. Let the contactor/motor starter do the heavy amp lifting.

 

[wyliesdiesels]

I have a 5hp Baldor motor on my compressor that draws 23A. It doesn't have a starter just a Square D 9013FHG34S155J39 pressure switch. Someone put an oddball 3 pole dial type switch on it that doesn't even have an enclosure.

My question is: Do I even need a disconnect? I have the compressor in my garage on a 30 amp dedicated circuit and it is controlled by a 2 pole contactor with a 120v coil that I control with 3 way switches in my garage and in my shop. Switches are pilot lit so I know if the compressor is on.

I found a 2 pole Cooper switch that is motor rated at 5hp and 30 amps and I'm thinking of just mounting this on the compressor before the pressure switch, good idea or not?

Wow what a hodge podge.

How does the PS control the motor? Is it inline with the motor or does it control the contactor?

Second, does the motor have built in overload protection?

Third, u say u have it on a 30 circuit. Is it hardwired to this circuit or connected via cord and plug?

Fourth, is the 30a the breaker rating and what size wire did u use?

Fifth, how far away is the breaker panel and is it within sight of the compressor?

One of the 3 way switches is within a few feet and line of sight.

That doesnt qualify as a DC because it controls the contactor. U need a positive disconnect such as an AC disconnect.

Light switches are not motor grade switches.

Hes using the switches to control a contactor coil. They arent wired directly to the motor.

 

[kingchevy]

It's on a 30 amp breaker with 10 gauge romex going to an enclosure in the wall by the compressor housing the contactor. From there it goes to a junction box next to compressor where I will hardwire to the compressor. There is no overload protection on the motor, so are you suggesting a mag starter as well as a disco?

 

[wyliesdiesels]

No overload protection? Definitely hodge podge!

How is the PS wired in? Its only rated for 15a and 2HP...

Yes U definitely need a motor starter and a disconnect IF the breaker panel is NOT within site of the compressor and more than 50' away. How else do u plan on providing overload protection for the motor?

Also, #10 NM is too small to be code compliant. U need 35a rated wire. Wire for motors is sized @ 125% of NEC FLC table current.

A 5HP motor is 28a FLC

BTW Unless u can find a plug rated for 5HP or more(standard NEMA plugs are rated for max 3HP) then it needs to be hardwired.

 

[kingchevy]

Here is the ps.

 

[kingchevy]

Looks like my Baldor L1410T specs at 23 fla so the #10 is good, no?

 

[Moose364]

Here is the one I used on my compressor 30 Amp 240-Volt 2-Pole Indoor Light Duty Safety Switch
from Home depot for 29.99 you can even lock it out if needed

 

[md21722]

Looks like my Baldor L1410T specs at 23 fla so the #10 is good, no?

The NEC basically says to take the HP rating of the motor and then reference their tables for Full Load Current (FLC) ... For wire size use 125% of FLC. Breaker size can be a maximum of 250% of FLC. So, 5HP 230V single phase = 28A FLC by the table. 28A FLC x 125% = 35A. That's #8 Romex / NM or #10 THHN if running in conduit. 28A FLC x 250% = 70A maximum breaker size.

I suspect a good many people run #10 thinking its like an electric drier. It may work, but its not up to code.

 

[wyliesdiesels]

Here is the ps.

Strange.

Various sites online list that as a 600VAC 12A PS 2 HP max.

http://zainabsupplies.com/products/square-d-part-9013fhg34s155j39

Looks like my Baldor L1410T specs at 23 fla so the #10 is good, no?

As said above, the wire is sized @ 125% of NEC table FLC NOT the FLA on the motor.

So no #10 NM-b is too small because #10 NM-b is max 30a. NM-b is sized on the 60* c column.

I would get a motor starter, an AC disconnect and change the wire. Wire the 3-way switches inline with the overload relay. PS goes to other side of coil.

 

[kingchevy]

Thanks for you help Wylie, I will install a mag starter and disco. But doesn't NEC 430.6 (A)(1)exception 3 allow me to size conductors per the nameplate fla?

 

[md21722]

I believe that exception applies to what the code considers appliances, like an air conditioning unit that has a compressor motor. I don't think you'll find a way out of wiring your compressor with less that the wire stated above if you want it to meet code. Rather than go with "just because the book says to" consider that motors have inrush current when they start. They're not quite the same as a resistive load like a baseboard heater or electric drier. There is also the potential that a motor could be replaced with one that uses more power than the one you started with. And the code only specifies the minimum. You can always go bigger if you want...