Two cord connected motors

[realolman]

Two conveyors, one conveys materials to the other, both 110v single phase fractional HP motors... 11 amps total... would like to plug one into a receptacle on a 20 amp fuse, run the circuit along the conveyor to a switch on the other end, which would switch both conveyors on and off, and plug the second conveyor into the discharge end of the first.

Neither motor is thermally or impedance protected. The conveyors are just placed there and are not permanently installed, ( I'm not sure what constitutes being permanently installed ) but are too big to be carried around, and although they get moved around somewhat, stay in the same place most of the time.

Do they need any overload protection?

Do they have to have overload protection on each motor?
It seems to me that having a manual starter with OL large enough for the combined load of both motors would be better than nothing.

If I put overload protection for the second cord connected motor ahead of the plug, can I use a regular 110v 15 a. straight blade receptacle and plug to hook it up, or should I use some other configuration to make it less compatible with other common plug in equipment?


The thing I would feel the best about is to put a manual starter and overloads on each motor, but it will make more of a conglomeration on the conveyors, a little harder to start/stop both conveyors at once, and none of the previous ones are like that. If I put a magnetic starter on them, I will still have to run some plug in conductors ,between the two.


The reason this all seems to be troubling to me is that it is an insignificant little application, and I don't want to make a mountain out of a mole hill, but I do like to try to do things correctly if I can. I was looking in the 2005 NEC today, and I can't decide what is correct.

thanks

 

[LarryFine]

It seems to me that, since the units come with cords and plugs, they contain all the control that the manufacturer intends.

 

[RUWired]

The case of not having O.L. protection with 1 hp or less is about having the operator of the motors right there (in site) of the equipment running in case of failure.The motors are connected to a switch and mounted to the frame ( permanently installed ). If you turn this on ,can you go take a leak or have a smoke or do you have to stand there the whole time.I think that would be a deciding factor.
Rick

 

[realolman]

I was afraid that my post was already too long. I guess I didn't explain it enough.

These are not manufactured units. I'm building them. There are several of them already here over the years, that I did not make. They have a cord plugged into a 20 a recpt. that runs along the conveyor to the other end to a manual starter that has an OL that is sized for the combined load of both motors. From the manual starter, the motor of the first conveyor is wired direct, and the second is plugged into a receptacle mounted on the the first, fed from that same starter and OL.

The conveyors are often running unattended.

That doesn't seem quite kosher to me, but I can see why it was done that way, and electrically it doesn't seem particularly unsafe, but I would like to know if it is code compliant. After going around in a few circles ( I believe it was Art. 430 ) I am not sure.

 

[Snorks]

I agree with you realolman.

Regardless of any other opinions on this thread, I would add an overload (up to 125% of FLA) to the circuit supporting both motors. With this you will have some protection for the motors and more important, some protection in case of a short circuit.

 

[RUWired]

Article 430.53(A) allows two or motors on the same branch circuit, but you will need O.L. protection for each motor seperately.Having one O.L. for two motors does not protect the motors.

430.53 Several Motors or Loads on One Branch Circuit
Two or more motors or one or more motors and other loads shall be permitted to be connected to the same branch circuit under conditions specified in 430.53(D) and in 430.53(A), (B), or (C).
(A) Not Over 1 Horsepower Several motors, each not exceeding 1 hp in rating, shall be permitted on a nominal 120-volt branch circuit protected at not over 20 amperes or a branch circuit of 600 volts, nominal, or less, protected at not over 15 amperes, if all of the following conditions are met:
(1) The full-load rating of each motor does not exceed 6 amperes.
(2) The rating of the branch-circuit short-circuit and ground-fault protective device marked on any of the controllers is not exceeded.
(3) Individual overload protection conforms to 430.32.
Rick