# overload requirement for multiple motors



## ctown (Nov 27, 2018)

good morning all, first time posting. I have a job coming up wiring a dairy barn that is 500ft x 250 ft. There are multiple fans through this building and a lot of them will start at the same time. The fans that where ordered do not have overload protection built into them and are 1/2 hp. Some are up to 1.5 hp. Voltage is 3-phase 480 volt. My questions is, can I use the circuit breaker as the only means of protection as long as the wire amp rating does not exceed the breaker?
If not, is there anything I can put directly on the fan that acts as the overload protection?


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## frenchelectrican (Mar 15, 2007)

ctown said:


> good morning all, first time posting. I have a job coming up wiring a dairy barn that is 500ft x 250 ft. There are multiple fans through this building and a lot of them will start at the same time. The fans that where ordered do not have overload protection built into them and are 1/2 hp. Some are up to 1.5 hp. Voltage is 3-phase 480 volt. My questions is, can I use the circuit breaker as the only means of protection as long as the wire amp rating does not exceed the breaker?
> If not, is there anything I can put directly on the fan that acts as the overload protection?


very simple just order a small IEC contractor and sized the OL to match the motor rating.,,

You can use a circuit breaker to handle multi motors but you will need a manual motor starter or manual OL to handle the overload on indidual motors


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## ctown (Nov 27, 2018)

There are many motors spread through this very large building. My concern is the amount of wire required for each fan is going to increase substantialy if I have to run a home run shot back to the main control panel for each fan.


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## frenchelectrican (Mar 15, 2007)

ctown said:


> There are many motors spread through this very large building. My concern is the amount of wire required for each fan is going to increase substantialy if I have to run a home run shot back to the main control panel for each fan.


Maybe I have other solution is just get IEC or small NEMA starter and run the control conductors as need to be and you mention most will start at the same time so put a contractor in the main control panel and put in a indiduval ol blocks at each motors so if it do trip it will kick that motor off line. 

Just hang on one of our member dealt a lot of barns so he will know a answer or two.,,


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## JRaef (Mar 23, 2009)

I would use these type of devices, they are IEC versions of "Manual Motor Starters" and don't require a contactor or control circuit. You can mount one near each motor in an appropriate enclosure.












Enclosed version:








This they also gives you a local disconnect and Lock-Out / tag-Out point.


There are some brands with smaller cheaper enclosed versions, but I HATE having to terminate in the tiny little plastic boxes they give you. Most were designed for metric conduit fittings, so by the time you buy adapters and screw them onto your conduit, then futz with trying to pull wires in the tight quarters they leave you with, you would have been done had you used the steel box type.


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## telsa (May 22, 2015)

Overloads, per se, HAVE to be dedicated to one motor.

Overloads protect motors from trauma. 

The conductors are protected back up the line -- perhaps by circuit breakers, perhaps by fuses -- sometimes by both. That's a separate design issue.

In your setting, it's common for this or that fan to suffer environmental abuse. (loaded down with dust and gunk) Small motors usually have internal thermal protection -- but this is not usually the case with 480 VAC 3-phase motors. For them some sort of 'heater' (thermal overload) is the norm. 

Such heaters can be found in plain vanilla manual motor starters, too. ( NEMA and IEC, both )

The only hang-up with IEC is that they don't have fantastic distribution in farm country. You're most likely going to have to perform your own engineering and have them shipped in. NEMA gear is much more forgiving. ( over-engineered )

You get to pick your poison.


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## Cow (Jan 16, 2008)

A good majority of our work is for dairies.

I think what you're leaning towards, and what we've done in the past is to run one properly sized circuit through a contactor to each bank of fans. Install a 140M manual motor protector (the type that qualifies as an OCPD and overload in one) in a rotary disconnect enclosure at each fan for maintenance purposes. 

Then one fan won't take out the whole bank when it fails.

We've used a ton of those 140M's for this.

Almost all dairies run fans in banks, most of the time they aren't interested in individual fan control, so there is no reason to run separate circuits to each one.

That is a waste of material and time, in my opinion.


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## micromind (Aug 11, 2007)

Cow said:


> A good majority of our work is for dairies.
> 
> I think what you're leaning towards, and what we've done in the past is to run one properly sized circuit through a contactor to each bank of fans. Install a 140M manual motor protector (the type that qualifies as an OCPD and overload in one) in a rotary disconnect enclosure at each fan for maintenance purposes.
> 
> ...


The 140Ms referenced here are the ones that JReaf has pictured in his post above. Made by Allen Bradley. 

I've also installed tons of them. 

You'll need to know the full-load current of each motor before you buy them, each one has a fairly small range of current settings and there's no overlap. You have to get the right one for each motor. 

They are not like a magnetic starter in that they will stay closed when power is removed. Think of them as a switch that has built-in overloads. 

If you want to get really fancy, contact blocks are available that can be installed on the 140Ms that will change state upon overload tripping. It's an extra wire for each one, plus a common to all of them but you could hook them up to an annunciator panel and you'd know in an instant if any fans have tripped.


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