# Mag Starter Standard Control Wiring Question



## EE1 (Nov 17, 2009)

We are always taught not to switch the nuetral or grounded condutor as it poses a potential shock hazard to persons working on an electrical system. Here is my question.
On a standard mag starter using a two or three wire control, 120v control circuit and coil you always see the nuetral series through the overload block then up to the coil. Why do we not just run our 120v ungrounded control circuit through the overload contacts and then up to the coil instead. It seems that when the overloads open we are "switching our nuetral" so to speak. I know there must be a good explanation for this I just don't know the answer.


----------



## CTshockhazard (Aug 28, 2009)

I believe it's ok because it's listed that way.

Also, the coil voltages vary, and except for 120 and 277, you wouldn't be switching the grounded conductor.


----------



## smeric28 (Nov 16, 2009)

EE1 said:


> We are always taught not to switch the nuetral or grounded condutor as it poses a potential shock hazard to persons working on an electrical system. Here is my question.
> On a standard mag starter using a two or three wire control, 120v control circuit and coil you always see the nuetral series through the overload block then up to the coil. Why do we not just run our 120v ungrounded control circuit through the overload contacts and then up to the coil instead. It seems that when the overloads open we are "switching our nuetral" so to speak. I know there must be a good explanation for this I just don't know the answer.



The reason this is done it to prevent automatic restart of and overloaded device. If you like to run it to the aux contacts first go ahead there's no reason not to.


----------



## John Valdes (May 17, 2007)

Regardless, the motor stops and that is what an overload relay is supposed to do. Once the OLR has tripped and the starter is out, the only way to restart is to reset the OLR and restart the motor. It cannot come back on (coil) by itself if either the neutral or hot is open.


----------



## EE1 (Nov 17, 2009)

Exactly, when the OL trips there is no way for it to accidentally restart you have to manually push it in. Why not just series the 120v two or three wire control circuit through the OL block, instead they always come wired with the nuetral in the OL block.

This is just really bugging me because I was told (about 10 years ago) a logical reason by a long time MC/PLC guy. It made sense to me then when he told me but for the life of me I cannot remember what he said or what the reasoning was. I guess thats why I joined this Forum. Thanks for your input guys!!:thumbup:


----------



## John Valdes (May 17, 2007)

EE1 said:


> Exactly, when the OL trips there is no way for it to accidentally restart you have to manually push it in. Why not just series the 120v two or three wire control circuit through the OL block, instead they always come wired with the nuetral in the OL block.
> 
> This is just really bugging me because I was told (about 10 years ago) a logical reason by a long time MC/PLC guy. It made sense to me then when he told me but for the life of me I cannot remember what he said or what the reasoning was. I guess thats why I joined this Forum. Thanks for your input guys!!:thumbup:


In control work the term neutral is insignificant. In some instances the white wire is not even grounded on the XFMR secondary. (I ground mine for troubleshooting purposes) It is considered no different than any other wire in the panel. Many good control people purposely do not use white for this conductor. We all know that the white wire carries current too. Notice, I am not saying neutral. I am saying white instead, and only for the purpose of this post.
I personally use white, but some use a color no different than the other conductors in the control panel.
The wire is marked with a number, as are all the other wires. To complete the circuit the current must return to the XFMR. This just happens to be a wire with a number or the color white.
Opening the white, black, yellow or the red wire opens the circuit to the coil. So no, it does not matter because every wire in the panel is no different than the others.
Now if you want to call wire #2 the "return wire" as it completes the circuit, that would make perfect sense.


----------



## smeric28 (Nov 16, 2009)

John Valdes said:


> Regardless, the motor stops and that is what an overload relay is supposed to do. Once the OLR has tripped and the starter is out, the only way to restart is to reset the OLR and restart the motor. It cannot come back on (coil) by itself if either the neutral or hot is open.


The contactor and the OL are different devices usually hooked together. the coil closes the contactor the OL "heaters" are attached. what the purpose is to open the contactor if the OL's trip.

EDIT: most OL can be set to reset automatically. the way you really want to wire these things is so that when the OL trips you break the seal holding on the contactor


----------



## TheRick (Apr 13, 2008)

I always use the ungrounded conductor of a grounded 120V control circuit for the OL contacts, then take the status of the OL contact to a PLC input. When the control room operator can "see" the OL is tripped it can greatly reduce downtime. The input can also be used as a permisive in the PLC logic.


----------



## cdnelectrician (Mar 14, 2008)

I was taught to use the grounded lead for my O/L contacts, but now we use the ungrounded lead for O/L's, I see a lot of control panels wired like this now.
Not exactly sure what the reasoning behind that is. But apparently that is the new standard. The CEC also says that X2 of any control transformer must be grounded.


----------



## 5volts (Jan 11, 2008)

Since the discussions about mags/OL I went to the 'Rockwell Automation' Fair 2009 last Thursday. I was impressed when I saw this OL relay for a mag starter. It was a electronic solid state OL that had a Ethernet port. From your network you have the ability to control, monitor current etc.. 

Pretty impressive although where I work almost everything is on a VFD and is controlled using AB (CIP) Ethernet/IP comm module.

Has anyone seen one like this in the field?


----------



## TheRick (Apr 13, 2008)

p_logix said:


> Since the discussions about mags/OL I went to the 'Rockwell Automation' Fair 2009 last Thursday. I was impressed when I saw this OL relay for a mag starter. It was a electronic solid state OL that had a Ethernet port. From your network you have the ability to control, monitor current etc..
> 
> Pretty impressive although where I work almost everything is on a VFD and is controlled using AB (CIP) Ethernet/IP comm module.
> 
> Has anyone seen one like this in the field?


Never seen it actually in use, but we had a Rockwell sales whore come to our plant about a year and a half ago with a mobile demonstration unit of their "Smart MCC" that included those OL blocks among other cool automation/safety features.


----------



## John Valdes (May 17, 2007)

smeric28 said:


> The contactor and the OL are different devices usually hooked together. the coil closes the contactor the OL "heaters" are attached. what the purpose is to open the contactor if the OL's trip.
> 
> *Okay.*
> 
> EDIT: most OL can be set to reset automatically. the way you really want to wire these things is so that when the OL trips you break the seal holding on the contactor


*Okay.*


----------



## smeric28 (Nov 16, 2009)

TheRick said:


> Never seen it actually in use, but we had a Rockwell sales whore come to our plant about a year and a half ago with a mobile demonstration unit of their "Smart MCC" that included those OL blocks among other cool automation/safety features.


I had an application where i tired to use the smart mcc's (siemens makes them too) .... They are freaking expensive. i had to pick my jaw up off the floor after they told me the price. It would be cheaper to buy a remote I/O block for the comm type your using and wire it up. they were like 300 bucks apiece for small 1HP IEC style disconnects. I shudder to think what they would cost for a NEMA motor disconnect version.


----------



## John Valdes (May 17, 2007)

While we are discussing contactors. Why use them at all. Check this http://www.weg.net/files/products/WEG-ssw-05-soft-starter-usassw05-brochure-english.pdf The price is competitive with any NEMA starter on the market, and it does so much more. Exception is IEC starters. They are less inexpensive.


----------



## smeric28 (Nov 16, 2009)

John Valdes said:


> While we are discussing contactors. Why use them at all. Check this http://www.weg.net/files/products/WEG-ssw-05-soft-starter-usassw05-brochure-english.pdf The price is competitive with any NEMA starter on the market, and it does so much more. Exception is IEC starters. They are less inexpensive.


Every time i've had the opportunity to put a soft start in a panel they turned out to be the same price or more than a vfd. Vfd's inherently soft start so i always end up using them instead. how much do these run i bet ~$250 for a 1-2HP sized one. Plus there are some heating drawbacks/wiring complications to soft starters. Many of them should be bypassed once the motor is at full speed. sometimes this built in sometimes it's not.

Nobody i know uses NEMA starters anymore, due to the cost. I always use the IEC style and i've never had any complaints. Although my pickest customers are the Europeans and they invented IEC style starters :laughing:

Keep in mind the IEC ones don't live as long. NEMA starters are built like a brick $hit house and will live forever unless you really try to break them.


----------



## micromind (Aug 11, 2007)

I do a lot of work in rock-crushing plants, mines, concrete plants, and other 'high abuse' environments. 

Almost everyone uses NEMA starters. Once in a while I'll see an IEC one, but it doesn't last very long. 

IEC stuff certainly has its place, but not where it'll be abused.

Rob


----------



## subelect (Nov 25, 2007)

We are putting IEC starters in grain bin ventilation fans. The motor terminal boxes on those old fans are too small to use a NEMA contactor and overload. 
So far, they seem to stand up pretty well. 

I do have a dumb question regarding IEC starters.
Most of them have terminal screws with multi-heads; Phillips and some other type of driver. I can not even describe it accurately, but I would like to buy the correct type of tool to tighten them with.
What type of driver do you use, or do you just use a standard phillips?

Rick


----------



## John (Jan 22, 2007)

EE1 said:


> We are always taught not to switch the nuetral or grounded condutor as it poses a potential shock hazard to persons working on an electrical system. Here is my question.
> On a standard mag starter using a two or three wire control, 120v control circuit and coil you always see the nuetral series through the overload block then up to the coil. Why do we not just run our 120v ungrounded control circuit through the overload contacts and then up to the coil instead. It seems that when the overloads open we are "switching our nuetral" so to speak. I know there must be a good explanation for this I just don't know the answer.


The reason for the OL‘s to be wired on the grounded conductor side of the starter coil is for safety. If the is a short circuit or short to ground on the ungrounded side of the contactor coil and the OL’s are tripped the contactor will not energize. There are control circuits that do not have any fuse protection or have oversized fuse protection out there and you have to try to stupid proof stuff just in case some idiot comes along after you.


----------



## John Valdes (May 17, 2007)

smeric28 said:


> Every time i've had the opportunity to put a soft start in a panel they turned out to be the same price or more than a vfd. Vfd's inherently soft start so i always end up using them instead. how much do these run i bet ~$250 for a 1-2HP sized one. Plus there are some heating drawbacks/wiring complications to soft starters. Many of them should be bypassed once the motor is at full speed. sometimes this built in sometimes it's not.
> 
> Nobody i know uses NEMA starters anymore, due to the cost. I always use the IEC style and i've never had any complaints. Although my pickest customers are the Europeans and they invented IEC style starters :laughing:
> 
> Keep in mind the IEC ones don't live as long. NEMA starters are built like a brick $hit house and will live forever unless you really try to break them.


You are right on the price. Around $250-$300 for a 3 Hp soft start with built in bypass, IEC. However, you get so much more than just a starter.
I used to be of the opinion that IEC was crap and NEMA was better. Not anymore. What do you pay for a Square D NEMA 5 starter? Replacement contacts? I can get one for half that price, get equal quality and they are totally rebuildable. Most everything comes in today with IEC, so you cannot replace with NEMA due to space limitations. 
I agree with Rob regarding the aggregate plants. NEMA would be my choice here.


----------



## Bob Badger (Apr 19, 2009)

I am one of those that believe IEC stuff is throw away junk. Yes it's great when building equipment, it's small and cheap. But having to maintain it stinks, the stuff seems very prone to falling apart.

I think this sums it up very well.



Jraef said:


> LOL, the age old DP debate.
> 
> *NEMA = "Find it, Fix it and Forget it!"*
> Overbuilt for the US auto industry to take the worst possible thing a 'Lectrician could throw at it without having to talk to the overpaid engineering staff about the application. Probably more than most people need, but cheaper in the long run if down time costs $1000 / minute and it takes 10 minutes to get an Engineer on the phone.
> ...


----------



## amptech (Sep 21, 2007)

I couldn't agree more. I have to deal with a lot of IEC equipment in a soybean seed processing plant and it is all Bic lighter throw away grade. Plus it is mounted in enclosures so tightly that you need the hands of the 12 year-old Indonesian kid who assembled it to work on it. Telemecanique is probably correctly translated in to english as "tell them to make it cheap".


----------



## John Valdes (May 17, 2007)

amptech said:


> I couldn't agree more. I have to deal with a lot of IEC equipment in a soybean seed processing plant and it is all Bic lighter throw away grade. Plus it is mounted in enclosures so tightly that you need the hands of the 12 year-old Indonesian kid who assembled it to work on it. Telemecanique is probably correctly translated in to english as "tell them to make it cheap".


Telemecanique owns Square D. And they are the least desirable of the IEC brands including, PB's, relays and contactors IMO.
Siemens, Weg and Benshaw seem to give more bang for the buck. I like Weg as they are truly rebuild able. I believe they are rated 2 million cycles mechanically and 1 million electrically. So it is cost effective to rebuild them.

I would get used to them if you are not already. The cost is what drives the market. They cost less and do the same thing. We (electricians and control) said the same things about PLC's and AC inverters when they first came out.
Note: When building your own control panels, you can choose panel size. This enables you to eliminate crowding.


----------

