Calling electricians - 220v inline switch question on a lift

[BuickMike]

Hey all. I'm installing a 2 post lift and can't wrap my head around something electrical.

So I have a 220VAC motor that requires a 20A single phase circuit. So I run 12-3 to it and go to wire up the box on the lift. Straight forward accept for one thing. There is an overhead safety switch that will break the circuit if the car hits the padded bar it is connected to. They say to wire that inline with the hot that goes to the main power button, but the wires to the overhead switch are 18ga. There is no way in hell that will work, right? Seems like I would want to get a relay to run that. I can't believe this is code, especially coming from an ALI certified lift. Anyone here run into this?

 

[PaulieB]

I’m a licensed sparky, so let me see if I can help ya. First off, if it’s straight 230v, you don’t need 12/3. 12/2 is all you need (2 hots and an equipment ground). In trade parlance 12/3 contains 3 insulated and one bare.. only need two insulated for your installation. As for the 18 gauge wiring to the switch, I’ve seen some weird stuff like that over the years. Since it’s not a continuous load, that is probably why the manufacturer went with a small conductor. You’d be surprised how much current a small conductor can handle for short time use. “Short time” being the thing to remember... What is the nameplate current of that motor? That’s what they use to size the conductors....

 

[BuickMike]

Thanks!! I'll take a look a little later and let you know.

 

[BuickMike]

What do you need off the nameplate? The motor says GHS PT# FA7389 PH = 1 Duty = INT INS = F HP = 2 KW = 1.5 amps is 12-16.

 

[PaulieB]

What do you need off the nameplate? The motor says GHS PT# FA7389 PH = 1 Duty = INT INS = F HP = 2 KW = 1.5 amps is 12-16.

The Amps are what I was looking for. I would say that you are ok, based on the fact that it is a factory assembly. I would wire it up the way the instructions show. Are you positive it’s 18 ga? It’s probably 16 ga, which is a bit bigger. Again, factory wiring is sometimes on the small side..

 

[BuickMike]

Cool. Thanks!

 

[1986 Buick GX1]

The Amps are what I was looking for. I would say that you are ok, based on the fact that it is a factory assembly. I would wire it up the way the instructions show. Are you positive it’s 18 ga? It’s probably 16 ga, which is a bit bigger. Again, factory wiring is sometimes on the small side..

^^^ X2
I've been a commercial/ industrial electrician for 18yrs. and in motor applications the wire size and over current protection device (circuit breaker) size are based off of the motor HP chart in the code book. You are allowed to oversize an instantaneous trip circuit breaker or fuse 800% of the name plate rating (amps) due to the start up (in rush) current.
If they recommend/ require a 20 amp circuit (probably mean 20A breaker) the motor draw (name plate full load amps [FLA]) could be as low as 2.5 amps. 2.5A X 800% = 20A
The 18ga. or 16ga. wire is more than capable of 2.5 amps and as PaulieB said, they can handle considerably more for the 2-3 seconds it takes during start up.
The 12-16 amps listed may be locked rotor current which is a lot more than the running current.
And keep in mind this is not a continuous load.
Cheers,
George

 

[dynoman]

Are you sure that there is no contactor inside the box where the power up button is located ?? I just went out and checked mine and the over travel switch is in series ( inline ) with the power button . From the power button it goes to a motor contactor coil ( relay ) to power the motor through it's heavy contacts , just like our hot wire set ups for the fuel pumps .
Also if you only put cars on it , it will never even come close to making that over travel switch . A truck or van yes , car no . Sam

 

[gnxtc2]

Could you post the nameplate on the motor? There is no way that the 2 post lift motor is 2.5A, even at 240v.

Another thing, the common household breaker is not an instantaneous trip breaker. A household breaker is a thermal, magnetic breaker also known as an inverse time circuit breaker. An instantaneous trip breaker is known as a magnetic only circuit breaker. Yes, the instantaneous trip breakers are great for motor circuits but I never saw one for a residential panel board.

Oh yea, been doing electrical work for close to 30 years in the residential, commercial and industrial sectors. And also a license holder.

My Bendpak 10k 2 post lift in my shop was fed with #10 THHN and needed a 2 pole 30A breaker to satisfy the NEC.

Billy T.
gnxtc2@aol.com

 

[No disintegrations]

I think dynoman may be right. I think there is a contactor that is tripped open by the small 18ga wires when the roof switch is bumped. Meaning those are control wires and carry minimal current.

 

[dynoman]

Correct , the roof switch breaks the circuit to the contactor coil , thus opening the contactor shutting the pump motor off . That part of the circuit probably has barely 1amp on it with the only load being the contactor coil .
My lift pump is 12.5 FLA @ 230vac........ Been at this 44 yrs