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-   -   thoughts on circuit for car hoist (http://www.diychatroom.com/f18/thoughts-circuit-car-hoist-170265/)

grizzzlle 01-27-2013 12:59 PM

thoughts on circuit for car hoist
 
Getting ready to run wire for a hydralic motor on a car hoist. Plate on the motor says 16.4 amps at 220. There is a plate on the motor that says the motor is not protected from overloads. Normally I would run number 10 wire off a 30 amp breaker but for this install I was thinking of running a 12 guage wire off a 20 amp breaker. My thought was the motor is not on for more then 60 seconds (that is the amount of time it takes to raise a vehicle to its highest point). If there is a overload situation I was thinking the 20 amp breaker will pop faster protecting the motor sooner. Ive talked and read several sites and sounds like 20 amp breakers people are not having trouble. The total run length is under 50 ft. The wire will be run in metal flex not behind a wall but in open air so I also think the wire should be able to dissipate any heat easier. Thoughts from anyone? Am I over looking something?

Thanks in advance.

joed 01-27-2013 01:09 PM

What does the lift manufacturer recommend?

grizzzlle 01-27-2013 01:27 PM

They get vague in that area wanting to refer to local code. Even the company that installed the lift said they were no help since they are not licensed to do electrical work. Most they would say is they know of lifts that are wired of 30 amp breakers and 20. To test the lift the installing company wired the motor for 110 and ran the pump off a 15 amp circuit using a extension cord to plug it in. After all the testing was done the 110 volt setup was removed and I dont plan on wiring it that way.

brric 01-27-2013 03:27 PM

Are you sure it is 16 amps @ 240 volts?

joed 01-27-2013 03:39 PM

Post link or make and model number for the lift or the motor.
Sounds like the 20 amp circuit would be enough since it will use half the current of the 120 setup used in the test. It will use more current with an actual load on the lift however.

micromind 01-27-2013 05:21 PM

I wouldn't be too worried about an overload, since you'll be right there during the whole time the lift is in operation. Most electric motors can take a pretty serious overload for 60 seconds, especially if they're cold to begin with.

I would have no problem with a 30 amp breaker and either #10 or #12 wire. Yes, #12 is perfectly code compliant to use with this motor and a 30 amp breaker. The rules are different with motors.

A lot of these motors are built special for their purpose, and many of them have a higher starting surge than a normal motor of the same size. A 20 amp breaker might not hold during starting, a 30 almost certainly will.

If you want the code references, post back and I'll look them up.

Rob

grizzzlle 01-27-2013 06:08 PM

Joed

John S. Barnes Corp
Model PR610771BD94B
HP 2.8
VOLTS 208-230
AMPS 16.4-16.5
DUTY 5 MIN
MADE BY EMERSON ELECTRONICS Z41285738000
2190427

Micromind

Would this fall under an exeption like welders or heat pumps have for wire size? What is strange is im looking at the SEOOW cord used to come off the motor that is ment to be plugged into a receptical it was wired using 14 awg for about 2 ft with a 30 amp twist lock plug placed on it. This is a used lift that was removed from a Honda dealership.

Im still getting this site figured out so my responses might take a few. Sorry. Realized my email was calling this site junk mail. Think I got that figured out.

micromind 01-27-2013 07:57 PM

Motors, HVAC equipment and welders are not governed by the normal overcurrent/wire sizes in the code. They're pretty much stand-alone articles in the code.

The 14/3 cord is pretty normal for a factory installation, though to be code compliant, it'd need to be #12. Factory installations are not covered by the code.

Rob

mpoulton 01-27-2013 09:07 PM

What controls the motor? Since the motor says it does not have internal overload protection, your controller needs to provide overload protection. Make sure it does. Assuming your controller includes overload protection, you can wire this with #12 wire. The breaker can be 20 or 30A. If 20A works without tripping on startup, then that's fine. Otherwise a 30A breaker may be needed.

micromind 01-27-2013 10:06 PM

Now that we know what the motor is, here's the code stuff.

According to 430.22(E), for a 5 minute motor, the conductors need to be rated at 110% of the motor nameplate amps. Not the table amps we usually use, actual nameplate amps. 16.4 X 110% = 18.04. 220.5 (B) says that we are allowed to drop fractions that are less than 0.5, so the conductors need to be rated at 18 amps or more. Table 400.5(A) lists #14 cord as good for 18 amps. That would be the minimum. 240.4(D) says that unless permitted in 240.4(G) (240.4(G) covers motors), #14 wire needs to be protected at not more than 15 amps. But that 15 amp rule doesn't apply here. So according to the 75șC column of table 310.16, #14 is good for 20 amps. 110.14(C)(1)(a)(4) says that motors use the 75șC column. So #14 is the smallest wire allowed.

But wait!! There's more!! 334.80 states that NM cable (Romex) is to be calculated using the 60șC column. There are no exceptions for motors. The 60șC column lists #14 at 20 amps, as does the 75șC column. So it doesn't matter if NM is used, but most of the time it does.

430.33 allows an intermittent duty motor to be protected by the branch circuit short circuit and ground fault device (in this case, the breaker in the panel). According to table 430.52, the maximum circuit breaker size would be 250% of the full-load amps of the motor. Since this is an intermittent duty motor, the nameplate amps is used, not the amps found in table 430.248. 16.4 X 250% = 41. You could use up to a 40 amp breaker on this motor.

Confusing.....Yep!!! Code is like that......

Rob

P.S. To sum up, the breaker can be any size up to 40 amp. There is no minimum. The wire and cord can be #14 or larger. Yes, you can indeed put a #14 under a 40 amp breaker.

I'd use #12 and a 30.

mpoulton 01-27-2013 11:58 PM

Micromind: Don't those rules only apply to motors with overload protection?

frenchelectrican 01-28-2013 12:28 AM

Quote:

Originally Posted by mpoulton (Post 1103783)
Micromind: Don't those rules only apply to motors with overload protection?

Oui they do., with or pas overload protection however read one part with Micromind's comment there is addtional part that have to be addressed and for the motour rating we useally go by NEC ( in USA side ) to get the correct OCPD sizing.

Merci,
Marc

grizzzlle 01-28-2013 08:17 AM

Quote:

Originally Posted by mpoulton (Post 1103685)
What controls the motor? Since the motor says it does not have internal overload protection, your controller needs to provide overload protection. Make sure it does. Assuming your controller includes overload protection, you can wire this with #12 wire. The breaker can be 20 or 30A. If 20A works without tripping on startup, then that's fine. Otherwise a 30A breaker may be needed.

When you say controles are you refering to the switch? If so bolted to th motor is a push button on switch that has to be manually held on. Inside the box that houses the on button the safety shut offs for the liftt are housed. I will look today to see if there might be some sort of overload protection in there. If there is none would installing a relay or fuses that trip both power legs be considered over load protection and allow me to get away with 12 wire?

All great responses. Thanks im learning alot.

grizzzlle 01-28-2013 08:29 AM

Just thought of this. Could the actual manual on switch have a thermal overload device in it? Is there a way to tell?

micromind 01-28-2013 08:44 AM

Quote:

Originally Posted by mpoulton (Post 1103783)
Micromind: Don't those rules only apply to motors with overload protection?

In a nutshell, 430.32 covers continuous duty motors, and it states that all motors need O/L protection sized to the specific motor.

430.33 covers intermittent duty motors, and it states that O/L protection can be the feeder breaker. No requirement for specific O/L protection.

Rob


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