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Discussion Starter #1
I just bought an old but still good 7000# 2-post lift and got it bolted down in my new shop floor. I am ready to wire it but have a question about something called an "amp-adjust knob" that is located in the main electrical junction box. It appears to be between the main power supply and the motor and the instructions that I got from the manufacturer say to adjust the knob to 8 amps for a 2.2kw motor or 7 amps for a 1.5kw motor. The device itself appears to be broken and the previous owner appears to have bypassed it and applied 220 single phase power directly to the motor, just breaking the supply of power with a household light switch. Therefore, one leg going to the motor is always hot and the other is only hot when the switch is on.

I've spokent o a buddy who has a few lifts and he says none of them have anything like an amp-adjust knob. It obviously my lift isn't essential to my lift either as it has obviously been bypassed by the previous owner. But I want to wire this thing up right and know that I've done a good job as it is the first lift that I've owned and I just can't live knowing that I did it half-assed.

Anyone got any advice? I'd be willing to bet that buying a new amp-adjust knob is expensive. Should I buy it, keep bypassing it, or replace it with something else? My buddy says a starter would work well but I dont' know what that is, either.

J. J.
 

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Sounds like a potentiometer, can you get a picture of the broken piece? front and back, maybe i can find something or somewhere for you to get one.
(i am an electrical distributor)
 

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Discussion Starter #3 (Edited)
I think you are right about it being a potentiometer. No way to get pics for a few days at least. It is just a little knob on the front of a black plastic junction block though. Smaller than a dime. What is its purpose given that the lift works fine without it and modern lifts do not have them?

J. J.
 

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The pot would typically be used to control motor speed. The only reason I could think you would need it is if it is to control the speed of the motor for hydraulics or maybe the gearbox/transmision. Depending on the motor that is in the lift you could adjust the rpm to work best for the weight of the vehicle etc...
Other than that I don't see a reason for it.
 

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Here are the wiring instructions for the lift:

J. J.
Scratch that, i just saw the diagram, the amp adjust is the motor overload setting.

Such as, 5 hp motor will pull appx 15amps at full load, you adjust the "amp adjuster" to trip the overloads at the setting to keep from burning the motor up.

So yes, you need it to protect the electric motor.

Also, from the factory this lift was 3 phase, did the owner switch the motor out to a single phase motor? It sounds like he did but i am guessing here. To break both hot legs going to the motor you will need to put in a Double pole Single throw switch. It may be fine but if the motor ever rotor locks it could cause some damage to the wiring etc... It would be safer to have some sort of overload on it.

Take a pic of the starter/contactor, motor, and pushbuttons, If i can see what you have i could probably tell you if the single phase contactor has built in overload protection.



Tony
 

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Discussion Starter #7 (Edited)
Oops, I'm sorry. The instructions say that the motor can run on 3-phase or single-phase. I posted the wrong diagram above. Here is the 230V single-phase diagram:

J. J.

PS: The knob is not meant to be adjusted real-time as the panel it is attached to is about 10-feet up the side post and behind a screwed on metal cover.
 

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If you can get me a picture of the magnetic contactor, I would say that the knob is adjusted to max seeing as how it is broke off.
If you get me that I can hunt down the manufacturer and then see if i can find a replacement or at the very least get a picture of a new one so you will know where in the range of that knob needs to be to keep the motor protected.

As it is now he has bypassed the contactor and is running the motor off a switch. The only protection you have is the breaker in your panel. It will work fine as is but if you want to protect the motor etc... you will need to put a new starter in it and wire up the switch to control the coil in the starter.
 

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Discussion Starter #9
The adjuster is not broken off. The knob is still there and spins. The plastic panel that it is attached to is busted off the metal backing plate and some wires to it have been cut. It is hanging just by some wires at this time.

The way the previous owner had it is as you explained. So from you are saying, I gather that the adjuster was just to adjust the trip setting in case the motor locks up or something? The breaker at the panel should also protect against that if I am not mistaken, so the adjuster is just redundant, correct?

What exactly is a starter. I have a buddy who is good with electric who said I could also wire one of those in to replace the adjuster. Where could I get one on short notice? I'm wanting to get this thing up and running this Sat. (My days off of work are few and far between.)

My shop is 30 mins away over a toll bridge from where I live. I can't just run over there for pics. I can snap some pics while I'm there this weekend but that will be too late.

J. J.
 

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Like it was said, thats you overload protection so you don't slowly cook the motor by running it to hard. Its not to protect against shorts or anything like that.

For your own home use its going to cost you a fair bit of money to replace it and honestly if it was mine I'd just run it as is.

Just the opinion of a ticketed Industrial Electrician :beer:
 

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The breaker in your panel is sized for the complete circuit, say 20amps, the overload on the starter/contactor is to protect the motor. The overload would be set at say 15 amps to trip. If there is no overload the breaker in the panel would eventually trip depending on what it is but it may be too late thus burning the motor up.

See if there is a CED, Rexel, or Graybar electrical distributor in your area. They should have a Manual motor starter. Ask them for a 2 pole manual starter, then you will need to find out the full load amp on the motor unless you know the horsepower. (the dist. should be able to size the overloads based on HP and voltage)

As pook said, you are probably fine, but at the least change that switch out to a Double pole single throw so that you are turning off both hot leads to the motor. This will get you by until you have more time to go back and install a starter.

A starter is nothing more than a contactor with an overload built in or bolted onto the load side of the contactor. Some are manual and require no control circuit others are magnetic and require a control circuit to energize a coil that magnetically pulls the contacts together.

The easiest for your app would be a manual starter.

If it is a small motor, pulling no more than 15 amps. see if you can find a GE or equal. (i sell ge, so i have the part numbers)
GE Part# CR101H1
this is a 2 pole manual starter

You will need a heater/overload as well
Depending on the load, Say 14.8amp the part # would be
CR123H171B this is just an example since i don't know exactly what motor you have.
Total cost should be no more than $60 to $70

This is as cheap as you can go but still protect the motor.
Tony
 

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x2 on a proper 2 pole switch. You need to tell the store the HP of the motor, typically up here I can find them rated from 1-3hp off the shelf of any bigger electrical wholesaler.

Another option may be a momentary 2 pole switch rated for the right HP and voltage (needs to be rated for motor load). But only if its one of those hoists the motor just runs to bring it up. Could get rid of all the crap in the box and clean up the wiring. Still no overload current protection but will work and I wouldn't hesitate to do it this way at my own house. Just size the wire and breaker properly.
 

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Discussion Starter #16
Well after spending a few minutes at the electric supplier I came home with a new contactor and switch. But after looking in the electric box of the lift more I realized there was a switch built in that in contact by a lever when you push a certain direction on the release lever at the bottom of the lift. So I just replaced the busted contactor and rewired it all back to factory form minus the amp adjuster and it all works great now! Looks like it should, too instead of stringing a shitty switch down the side of the post. I knwo the motor does not have its own protection now but I dont' think I'll be working it to death anyway. I may use this thing once or twice a week, not up and down all day like it would see in the shop it came out of and was sold for.

It is rated at 7000# but it is WAY beefier than any 10000# lift I've seen made these days. (Not that I own anything that would tax the 7000# limit anyway.) Cappy cell phone pic, but thanks for the help ya'll.

J. J.
 

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As a side-note, does anyone know where to buy cheap replacement lift pads?

J. J.
Are they rubber or plastic? A local plastics supplier may have some teflon or delrin sheet sheet you could make them out of, or a rubber, gasket or hose supplier may have some hard rubber sheet you could make them out of. Might not be cheap tough. McMaster/Carr has it all, but minimum qty and shipping???

You could check the local gyms or schools. They use thick, tough rubber mats that lock together to protect the floors from weights, usually about 24" x 24" or 30" x 30". They would make good material to cut pads from if you found someone who was ready to discard one.
 
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