My new car lift motor is listed as 18 amps. do I use a 20 amp breaker or go up to 30. 18 amps is pretty close to 20
Edited 8/31/2006 11:01 pm by brownbagg
My new car lift motor is listed as 18 amps. do I use a 20 amp breaker or go up to 30. 18 amps is pretty close to 20
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Replies
Use the 20.
If this is a dedicated circuit and if the motor (or motor starter) has overload protection (which I suspect that it does) then you can go up in breaker size.
Does the motor also have a HP rating on it?
Use 20 amp, its not a commercial garge door opener
The instructions for the opener should specify which breaker to use. Dont forget that the breaker is there to protect the wiring. You cant just change the breaker without upgrading the wire also. "Typically" a 15 amp breaker is for #14 wire, 20 amp for #12 and 30 amp for #10 wire.
Bill Koustenis
Advanced Automotive Machine
Waldorf Md
"Dont forget that the breaker is there to protect the wiring. You cant just change the breaker without upgrading the wire also. "Typically" a 15 amp breaker is for #14 wire, 20 amp for #12 and 30 amp for #10 wire."Not true for dedicated motor and air conditioning circuits.On general purpose circuits that is true because you never know what combination of loads might be plugged in at any one time.But for dedicated circuits you know exactly the loads. The motors (or motor starter) have overload protection builtin based on the motor and application.Thus the wire is speced based on the motor load.The circuit breaker is only needed to protect against faults in the wiring.There are different multipliers based on the whether it is protected by a CB, adjustable breaker, and several types of fuses. I think for ordinary breakers it is 225%.
Bill,'
Not knowing bb's experience level, my point was that you cannot just "upsize" the breaker without also increasing the wire size. I have had people tell me that they had to put in a "bigger" breaker because they kept blowing the old one ! That was what I was trying to avoid happening here. Also why I had "typically" in quotes in my answer :)Bill Koustenis
Advanced Automotive Machine
Waldorf Md
I,m pretty good with elecrtical. I wired my house and shop with no problem. i plan on 30 amp wire(10 ga) with a 20 amp breaker.My question was about the 18 amp motor and the 20 amp breaker. I dont know if the motor will have peaks on startup
What kind of door are you lifting? Properly adjusted door will lift with one hand. What is the specific language on the rating? That must be LRA or something like that. It seems pretty high for running amps if that is the right term. I cannot imagine a normal garage door opener popping a CB that will spin up my table saw and keep it going through some pretty serious wood.
If you do the 10ga and 20 amp then you certainly have enough plus an abundance of overkill IMHO however if that opener is rated at 18 you would not pop a 20 on 12 ga. If you mentioned the length of the run I missed it. Do not think 10ga will do much unless a long run.
Disclaimer: not an electrician either
Bob
Edited 8/31/2006 10:27 pm ET by rasconc
Who said anything about lifting a garage door.Not BB.I believe that this is for his CAR lift.
remember its a hydrulic pump lift, so all the motor is doing is pressurize the pump for the clyinders.(I had a mispelled word in the first post)
Edited 8/31/2006 11:11 pm by brownbagg
For some reason I was thinking that it was direct drive. Some kind of winch type of system.Don't know enough about hydraulic systems, but it it starts against pressure then again it is a hard starting situation.I would still not use anything less than 30 amp (or at least 25 amp, but you need to go to an electrical suply house to get 25 amp).
Duh on me, I read gar, not car, thought something was funny. Couple of posts later there was a mention of commerical door opener.
http://forums.taunton.com/tp-breaktime/messages?msg=78090.
The motor has a large starting current. For something like the lift it is proably very large.But the common breaker is time inverse. That is it will hold on a very large overload for a very shrot time period. On a moderate overload it will hold for a longer time period and for about 20% overload it will hold forever.Thus is will take ordinary motor starting. But you are already near the breaker rating.By code you can go to 2.5 times the CODE BOOK CURRENT RATINGS, which are based on horsepower and usualy even higher than the label ratings.But based on the label ratings I could go upto 45 amps on the breaker.But I would not use less than a 30 amp breaker.
The startup current on the motor will take it above 20 amps for a very short period. You might get by with it, but you may have nuisance trips. You'd be better off with the 30 amp circuit.
Can it be rewired for 220V? That would heve several benefits.
it is 220v.
It is 220? Well, that make a difference... First difference being... this is almost certainly on its' own circuit. If you plan on adding it to an existing 220 circuit... stop right there and ask an electrician. There are some judgement calls only a pro should make. If you're running a new circuit... wire is cheap. Might as well use #10- and run a neutral for possible future use. If you've already run the wire, using #12, and with only two insulated wires, plus ground.... well, don't lose any sleep. It'll work. I'd run it on the 20 amp breaker, and see if a problem develops. If one does, this is one of the "exceptions" in the code, where you could go up to the next standard size.... which is 25 amp, not 30. Two "hot" legs, pulling 18 amps each.... that just seems a bit high. I submit that you will not be lifting anything near the maximum capacity of the lift, and that your actual draw will be quite a bit less.
I don't see any problem with using a 20 amp breaker at all. Using a higher rated breaker could cause a problem in the event of an equipment failure. A 20 amp breaker will hold a 25 amp load for quite a while before tripping anyway, and this is an intermittent application.
"I don't see any problem with using a 20 amp breaker at all. Using a higher rated breaker could cause a problem in the event of an equipment failure. A 20 amp breaker will hold a 25 amp load for quite a while before tripping anyway, and this is an intermittent application. "A circuit breaker is never designed to the loads, just the wiring.For general purpose circuits it has to be sized based on the wire as you never know what size load will be plugged in.But on a dedicated more circuit things are completely different and covered by a different section of the code.The motor is protected by internal motor protected. The motor can't draw more than it rated current for any length of time or the internal motor protection will trip.The circuit breaker is only to protect the wiring from wiring faults, IE shorts.Thus code allows you to go up to 250% of motor rating." A 20 amp breaker will hold a 25 amp load for quite a while before tripping anyway, and this is an intermittent application. "But this motor probably draws over 100 amps when starting. And while intermittent it is the type of applicantion where it might be run several times in a very short period of time. Perfect recipe for circuit breaker to be tripping when it is undersized for a motor application.
Ok, put a 30a on it.
Edited 9/1/2006 11:04 pm ET by MarkH
Wire is NOT cheap any more...
do they even make a 20 amp 220v breaker????
I vote for 30a on 10 ga wire
unless you have some bigger stuff laying around.
How far to the panel??
"The truth, when told does nothing but bolster a mans character."
Yes, they make 20 amp 240 breakers.
Is the motor plug-and-cord connected, or direct-wired?
What is the nameplate HP?
What does in the installation instructions specify?
Article 430 (Motor Circuits) is the longest one in the NEC (you probably didn't want to hear that). This type of circuit can be very different than general-purpose ones.