Starters and Disconnets and misc

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mikoal

Member
Hello everyone, first time poster, long time reader.

I have some questions for y'all

1) First of all what are the differences between motor starter and disconnect

2) Can someone give me an example of a starter that is not considered as a disconnect? And how can one distinguish the difference.


Ok so.......I'm developing the electrical drawings for a motor that will have the option to rotate something 12" to the left and 12" to the right.
The motor rating is 3/4HP, 208-240/460V, 3 ph, 1200 rpm TEFC motor with end of travel limits. The motor is ~50m away from the control room.
So my questions are:


3) The voltage rated are they all 3 ph voltages? from 208-240 and 460?

4) Where to place disconnects and/or starters? The CEC states that a means of disconnect should be 9m away from the motor (28-604).
There will also be a controller sending signals to the motor to go left or right and this will be in the control room 50m away from the motor. I think that a starter and/or disconnect should be placed near the motor with the controllers in the control room and it is breakered with a15A breaker in the LP.

5)What type of disconnects?
I'm thinking the one near the motor be Across the line and disconnect in one? Or can the across the line behave like a disc?
The one in the control room would not be a disconnect but a push button (left + right) to control the across the line starter

6) How is this shown on the SLD and elect layout?
- The motor should be circuited to the panel
- the starter and disconnect should be near the motor
- But not sure how the control buttons should be shown on the SLD, layout and how the wiring should be shown. Where would the push button's wires go?

Thanks!
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
Hello everyone, first time poster, long time reader.

I have some questions for y'all

1) First of all what are the differences between motor starter and disconnect
!
Disconnects are just that... a means to disconnect power to the motor.. common ones range from a wall switch (hp rated) to fusible and non-fusible safety switches. (Some manual starters also serve as a disconnect)
2) Can someone give me an example of a starter that is not considered as a disconnect? And how can one distinguish the difference.!
A magnetic motor starter such as one on larger air compressors is an example.
The starter provides overload protection and is operated by the pressure switch (example)
Ok so.......I'm developing the electrical drawings for a motor that will have the option to rotate something 12" to the left and 12" to the right.
The motor rating is 3/4HP, 208-240/460V, 3 ph, 1200 rpm TEFC motor with end of travel limits. The motor is ~50m away from the control room.
So my questions are:


3) The voltage rated are they all 3 ph voltages? from 208-240 and 460? !
Motors and starters and disconects can be single pahse or 3 pahse and the ratings differ by phase, and voltage
4) Where to place disconnects and/or starters? The CEC states that a means of disconnect should be 9m away from the motor (28-604).
There will also be a controller sending signals to the motor to go left or right and this will be in the control room 50m away from the motor. I think that a starter and/or disconnect should be placed near the motor with the controllers in the control room and it is breakered with a15A breaker in the LP. !

NEC requires a dsocnnect within sight of the motor and the controller (with some exceptions) NEWC 430.102
5)What type of disconnects? !
I'm thinking the one near the motor be Across the line and disconnect in one? Or can the across the line behave like a disc?
The one in the control room would not be a disconnect but a push button (left + right) to control the across the line starter

The disconnect must be motor rated and must actually open the power conductors to the motor... a "stop" button that opens the control circuit will not suffice as a 430.102 disconnect.
6) How is this shown on the SLD and elect layout?
- The motor should be circuited to the panel
- the starter and disconnect should be near the motor
- But not sure how the control buttons should be shown on the SLD, layout and how the wiring should be shown. Where would the push button's wires go?

Thanks!
can't help you on #6
 

mikoal

Member
Disconnects are just that... a means to disconnect power to the motor.. common ones range from a wall switch (hp rated) to fusible and non-fusible safety switches. (Some manual starters also serve as a disconnect)

Thanks for the quick reply!

But can't a starter disconnect power to the motors?
What starters can be considered as disconnect (i know you listed some manual starters, but what else?)


A magnetic motor starter such as one on larger air compressors is an example.
The starter provides overload protection and is operated by the pressure switch (example)
Can that same magnetic motor starter be operated by a switch and be considered as a disconnect?
Can you list other examples of starters not being disconnects?

Motors and starters and disconects can be single pahse or 3 pahse and the ratings differ by phase, and voltage
I meant to say, if a motor's rating was 208-240/460, what voltage source is required? 208-240 3 phase and 460 3 phase?


NEC requires a dsocnnect within sight of the motor and the controller (with some exceptions) NEWC 430.102
Will a disconnect in sight of motor (9m in the CEC) and being supplied power from a breaker from a panel be sufficient?

The disconnect must be motor rated and must actually open the power conductors to the motor... a "stop" button that opens the control circuit will not suffice as a 430.102 disconnect.
can't help you on #6

What is considered as "motor rated"
a stop button that opens the circuit which in turns open the power to conductor....would that work? I dont have the NEC with me, only CEC.
 

skeshesh

Senior Member
Location
Los Angeles, Ca
Disconnects are just that... a means to disconnect power to the motor.. common ones range from a wall switch (hp rated) to fusible and non-fusible safety switches. (Some manual starters also serve as a disconnect)

A magnetic motor starter such as one on larger air compressors is an example.
The starter provides overload protection and is operated by the pressure switch (example)

Motors and starters and disconects can be single pahse or 3 pahse and the ratings differ by phase, and voltage


NEC requires a dsocnnect within sight of the motor and the controller (with some exceptions) NEWC 430.102

I'm thinking the one near the motor be Across the line and disconnect in one? Or can the across the line behave like a disc?
The one in the control room would not be a disconnect but a push button (left + right) to control the across the line starter

The disconnect must be motor rated and must actually open the power conductors to the motor... a "stop" button that opens the control circuit will not suffice as a 430.102 disconnect.

can't help you on #6

#6 If I'm using starter with something like a start stop pushbutton I show that as a symbol (box or box with diagonal cross, etc. just Google electrical symbols and check out some of the conventions). The SLD normally shows the source (panel, MCC, what have you) the OCPD, conductor from OCPD to the starter (or disconnect) and of course the load. Depending on the scope of the project, I may not show the wiring of the starter and the controls. If we are to show that wiring I like to toss that wiring diagram towards the end of the drawing set as a detail and reference that detail on the SLD and/or floor plans. Rest of the stuff is pretty standard as Gus covered it and I'm sure others will jump in to. I would highly recommend that you do some extra reading since I think that disconnects and starters would be considered some of the more common concepts and an electrical designer working with motors should be at least fairly familiar with that equipment.
 
Last edited:
Hello everyone, first time poster, long time reader.


6) How is this shown on the SLD and elect layout?
- The motor should be circuited to the panel
- the starter and disconnect should be near the motor
- But not sure how the control buttons should be shown on the SLD, layout and how the wiring should be shown. Where would the push button's wires go?

Thanks!
`

Typically the installation in formation would be shown on 4 different type documents:
  • Layout drawing shows the location of components and power/control cable routing with appropriate tags for each.
  • Single Line diagram would show the power components and their designations and sizes. Does not represent any physical layout, attempt to do so will get you into trouble.
  • Schematic/connection drawing would show the control logic, wire and terminal tags. Does not represent any physical layout, attempt to do so will get you into trouble.
  • Cable and conduit schedule will show you sizes, designations, routing path if in tray or multuiple designated wireways, lengths etc.
Following basic drawing rules:
  • Minimize the duplication of the same information on multiple drawings. Preferably either end of the circuit - equipment tag or the controller/starter tag - should appear on all drawings to tie all together. If you stay consistent, when revising the drawing you don't have to hunt for changes on all different type drawings.
  • Drawing is a picture, not a strorybook, minimize verbiage.
  • Use scale on physical drawings.
  • In the case of a small, single item installation, you may use one drawing to represent all the information listed above, but make sure you keep each portion of the drawing functionally separate.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
Thanks for the quick reply!

But can't a starter disconnect power to the motors?.

Starters do disconnect (operational) power to the motor, but (other than manual starters) but they do not meet the 430.102/109 requirements for the required disconnect (servicing/safety)
What starters can be considered as disconnect (i know you listed some manual starters, but what else?).
The manual starters and wall type switches come to mind. See 430.109 for acceptable disconnecting means.
Can that same magnetic motor starter be operated by a switch and be considered as a disconnect? .
No... See 430 Part IX

Can you list other examples of starters not being disconnects?
.
For practical purposes, only manual starters are so if you use magnetic, they are not (exception would be combination starters)..
I meant to say, if a motor's rating was 208-240/460, what voltage source is required? 208-240 3 phase and 460 3 phase?
.
Normally, but they could be single phase.. The voltage/phase source must match the motor. The one you listed could operate on 208, 240, or 460 (with matching phase-single or three)


Will a disconnect in sight of motor (9m in the CEC) and being supplied power from a breaker from a panel be sufficient?.

You must meet 430 Part IX for disconnect and 430. Part III for overload protection
What is considered as "motor rated"
.
Disconnects are rated in HP
a stop button that opens the circuit which in turns open the power to conductor....would that work? I dont have the NEC with me, only CEC.
Not as the required safety disconnect...the stop button only serves as operational (start-stop) disconnecting.
 
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mikoal

Member
Thanks everyone for the replies!

`

Typically the installation in formation would be shown on 4 different type documents:
  • Layout drawing shows the location of components and power/control cable routing with appropriate tags for each.
  • Schematic/connection drawing would show the control logic, wire and terminal tags. Does not represent any physical layout, attempt to do so will get you into trouble.

For your first point, in an example of a panel to a motor. You will see power routing from panel to disconnect then motor. Also from starter (push buttons) to motor?

As for schematic/connection drawings, is there somewhere I can easily pick up the basics of learning to draw these schematics?
`
Following basic drawing rules:
  • Drawing is a picture, not a strorybook, minimize verbiage.

Re: Verbiage
How would I word something like a push button controller (left or right) to the contractor?


Starters do disconnect (operational) power to the motor, but (other than manual starters) but they do not meet the 430.102/109 requirements for the required disconnect (servicing/safety)

The manual starters and wall type switches come to mind. See 430.109 for acceptable disconnecting means.
No... See 430 Part IX

For practical purposes, only manual starters are so if you use magnetic, they are not (exception would be combination starters)..

Why can't mag starters be considered a disconnect?
Does anyone have some pictures showing the different from a manual starter, mag starter, and a combination starter?

Normally, but they could be single phase.. The voltage/phase source must match the motor. The one you listed could operate on 208, 240, or 460 (with matching phase-single or three)
So this motor can be ran only single or three but not both?
Like 120/208 is 120 single and 208 3.
this motor states 208-240/460 3 phase. Does that mean its 208,240,460 3phase?
Reason why i ask is because, isn't 240/460 240 single and 460 three phase generally speaking?
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
Thanks everyone for the replies!



..........................



Why can't mag starters be considered a disconnect?
?
smart answer :grin: because they aren't listed in 430.109..
and this wording in 430.103 also:
The disconnecting means shall be designed so that it cannot be closed automatically.

Does anyone have some pictures showing the different from a manual starter, mag starter, and a combination starter??

Any motor control catalog (GE, Square D, A-B) has pages full

You might find browing thru any of the above catalogs most infromative.

So this motor can be ran only single or three but not both?
Like 120/208 is 120 single and 208 3. ?

A motor will be designed for single phase or 3 phase (+ other possibilities)
this motor states 208-240/460 3 phase. Does that mean its 208,240,460 3phase? ?
Yes , it can operate on any one of the three options.,

Reason why i ask is because, isn't 240/460 240 single and 460 three phase generally speaking?

460 is most often 3 phase, 240 can be either...
a single phase motor can be operated off a 3 phase system, but not the other way around (without added equipment)
 
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maghazadeh

Senior Member
Location
Campbell CA
Originally Posted by mikoal
Reason why i ask is because, isn't 240/460 240 single and 460 three phase generally speaking?

No, 240 does not mean it is single phase in regards to 3 ph motors. It only means that the motor you have has two voltage rating (high and low). There is a diagram comes with the motor showing how to connect the motor winding leads to your 3 ph power source desired or available.
Also when you say motor will change direction, then that requires to have Minimum of two (2) 3 pole motor contactors in order to control the direction of motor (clockwise or counter clockwise).
As the earlier posts mentioned you can have a combination motor starter and disconnect all in one enclosure. I believe you could have them all (starter + reversing + disconnect) in one enclosure. I think if all that are near the motor would be cost effective, since for stop, start, reverse push botton switches in the control system smaller wire sizes needed than wires powering the motor.
 

mikoal

Member
smart answer :grin: because they aren't listed in 430.109..
and this wording in 430.103 also:
The disconnecting means shall be designed so that it cannot be closed automatically.

I see, that makes sense. i think i actually have the NEC somewhere, i'll cross ref with my CEC.
Since i'll need the motor to move left and right. My guess is a combination reversing manual starter and disconnect would work?


A motor will be designed for single phase or 3 phase (+ other possibilities)

Yes , it can operate on any one of the three options.,

460 is most often 3 phase, 240 can be either...
a single phase motor can be operated off a 3 phase system, but not the other way around (without added equipment)

Originally Posted by mikoal
Reason why i ask is because, isn't 240/460 240 single and 460 three phase generally speaking?

No, 240 does not mean it is single phase in regards to 3 ph motors. It only means that the motor you have has two voltage rating (high and low). There is a diagram comes with the motor showing how to connect the motor winding leads to your 3 ph power source desired or available.
Also when you say motor will change direction, then that requires to have Minimum of two (2) 3 pole motor contactors in order to control the direction of motor (clockwise or counter clockwise).
As the earlier posts mentioned you can have a combination motor starter and disconnect all in one enclosure. I believe you could have them all (starter + reversing + disconnect) in one enclosure. I think if all that are near the motor would be cost effective, since for stop, start, reverse push botton switches in the control system smaller wire sizes needed than wires powering the motor.

so a 120/208 motor doesnt that mean single phase 120 and three pahse 208? So wouldnt a 230/460 represent the same thing if the notation is consistent?

Finally a really stupid question.
When you see the main disconnect rated at 100A, and the voltage to the buidling is 120/240 single phase. What is the max assumed power that the buildng draws(assuming they are not overloaded)? I ask because we are not certain of the loads, no consumption/demand data.
Is it 100*240*.8=19.2kW?
 
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maghazadeh

Senior Member
Location
Campbell CA
so a 120/208 motor doesnt that mean single phase 120 and three pahse 208? So wouldnt a 230/460 represent the same thing if the notation is consistent?

Finally a really stupid question.
When you see the main disconnect rated at 100A, and the voltage to the buidling is 120/240 single phase. What is the max assumed power that the buildng draws(assuming they are not overloaded)? I ask because we are not certain of the loads, no consumption/demand data.
Is it 100*240*.8=19.2kW?
Last edited by mikoal; Today at 08:15 AM.

When describing a circuit system 120/208V means 120V L-to-N or G is single phase, 208V means L-to-L. But when describing a motor 120/208V means Motor is a single phase dual voltage ( Low Voltage 120V L-to-N) and (High Voltage 208 or 230 L-to-L).
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
"Since i'll need the motor to move left and right. My guess is a combination reversing manual starter and disconnect would work?"

Be a rather unusual circumstance..... fairly rare. If its truly a manual operation you would probably end up with a "drum switch" (see catalogs). Keep in mind a manual starter would preclude limit switches
(except in small motor applications)
 

mikoal

Member
"Since i'll need the motor to move left and right. My guess is a combination reversing manual starter and disconnect would work?"

Be a rather unusual circumstance..... fairly rare. If its truly a manual operation you would probably end up with a "drum switch" (see catalogs). Keep in mind a manual starter would preclude limit switches
(except in small motor applications)

Wait I'm confused. THere will be product being dropped on a conveyor.....and when it gets to a certain point the operator switches it and moves the other direction and the product gets shifted and dropped into a truck.

So here is my thought process.
1) since motor is moving left and right, a reversing starter is required
2) since the operator is manually controlling it, a manual starter is required
I picture an operator pushing reverse and then forward.

Why would it prevent the limits from working?
It is a 3/4HP motor.

When describing a circuit system 120/208V means 120V L-to-N or G is single phase, 208V means L-to-L. But when describing a motor 120/208V means Motor is a single phase dual voltage ( Low Voltage 120V L-to-N) and (High Voltage 208 or 230 L-to-L).

I did not know that 120/208 motor represented only 1 type of phase (single or three)

So it can be 120/208 single phase? meaning 208 single phase? How would this work?
and 120/208 three phase? meaning 120 three phase? Once again how does this work.
 

skeshesh

Senior Member
Location
Los Angeles, Ca
I did not know that 120/208 motor represented only 1 type of phase (single or three)

So it can be 120/208 single phase? meaning 208 single phase? How would this work?
and 120/208 three phase? meaning 120 three phase? Once again how does this work.

The motor will always be either single phase or three phase but may be rated for various voltages.

Yes a single phase unit can be dual rated for 120V and 208V single phase, that is to receive power from either 120V line-to-Neutral or 208V line-to-line voltages of a 208Y/120V system.

Look, and again I'm saying this in a positive way because you seem interested to learn, I really think you should take some time over the weekend to really read up on these subjects. We all start somewhere, but if you're an electrical designer as your profile states and you are actually specifying starters for reversible motors in a manufacturing setting, I think you really should at least be easily able to distinguish between the voltages. We'll try to help as much as possible of course, but I would strongly recommend beefing up your theory a bit.
 

mikoal

Member
The motor will always be either single phase or three phase but may be rated for various voltages.

Yes a single phase unit can be dual rated for 120V and 208V single phase, that is to receive power from either 120V line-to-Neutral or 208V line-to-line voltages of a 208Y/120V system.

Look, and again I'm saying this in a positive way because you seem interested to learn, I really think you should take some time over the weekend to really read up on these subjects. We all start somewhere, but if you're an electrical designer as your profile states and you are actually specifying starters for reversible motors in a manufacturing setting, I think you really should at least be easily able to distinguish between the voltages. We'll try to help as much as possible of course, but I would strongly recommend beefing up your theory a bit.

Thanks for feedback, anywhere you recomend to look for reading materials?

I was going to say
"This is the part that confuses me, a 120/208 system produces 120 single phase L to N voltage, and 208 L to L 3 phase ".....

Then I thought, maybe you are referring to 2 of the 3 legs.
I'm so used to blindly looking at 208 as 3 phase i didnt even consider using 2 legs for a single phase 208.

I'm learning through senior engineers as well as forums.
hope to get from both sides.

As for the starters I'm picking out. What would you recommend? thanks!
 

skeshesh

Senior Member
Location
Los Angeles, Ca
Assuming you already took machine theory and power system courses, I'd brush over the books or google specific subjects.

Browsing manufacturer websites is a good approach too because you can often find quality white papers and application papers as well as be exposed to what products are available, what they can do, and what is their proper application.

Finally, my personal mode of operation is when I see something new or something I'm unsure of, I research it pretty deep. Sometimes you can be in a hurry to finish your work so what ends up happening is you find the answer to your specific question on a site or forum but fail to actually understand what's going on. I find it worth my time to understand that part of the subject deeply and get it over with instead of coming back over and over and never establishing a decent understanding.
 

mikoal

Member
Assuming you already took machine theory and power system courses, I'd brush over the books or google specific subjects.

Browsing manufacturer websites is a good approach too because you can often find quality white papers and application papers as well as be exposed to what products are available, what they can do, and what is their proper application.

Finally, my personal mode of operation is when I see something new or something I'm unsure of, I research it pretty deep. Sometimes you can be in a hurry to finish your work so what ends up happening is you find the answer to your specific question on a site or forum but fail to actually understand what's going on. I find it worth my time to understand that part of the subject deeply and get it over with instead of coming back over and over and never establishing a decent understanding.

Do you know if that motor starter is correct for this application?
 
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