# Contactors / coil voltage



## BBQ (Nov 16, 2010)

Typically you can change the coil in a contactor like that, usually you can get 24 volt through 480 volt in AC or DC.


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## erics37 (May 7, 2009)

guitarboyled said:


> Hi folks
> A few questions concerning contactors...
> 
> Is the coil integrated in such a device (see picture below)?
> ...


BBQ nailed it.

It's typical to transform 480V down to a lower voltage, usually 120 or 24, because it's cheaper and easier to find controls for those lower levels. But if you have controls rated for 480V already in place, plus a contactor coil rated at 480, then you're pretty much good to go.

And if you're going to step the control voltage down, you'll just have to get a control transformer. They're pretty cheap.


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## guitarboyled (Jun 22, 2009)

I noticed that different coil options are available...

Therefore, if I select a 24V coil for instance with the contactor I also have to install (separately) a transformer.


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## erics37 (May 7, 2009)

guitarboyled said:


> I noticed that different coil options are available...
> 
> Therefore, if I select a 24V coil for instance with the contactor I also have to install (separately) a transformer.


Yeah. If you have 480 volts available, and you need 24 volts to run your coil, you need a transformer.


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## erics37 (May 7, 2009)

Wait a sec. You're a self-proclaimed first year HVAC dude.

Maybe you shouldn't be working with 480 volt 3-phase stuff at this point


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## Bulldog1 (Oct 21, 2011)

BBQ said:


> Typically you can change the coil in a contactor like that, usually you can get 24 volt through 480 volt in AC or DC.



My inside salesman swaps coils at his desk if they don't have the correct contactor in stock.


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## wildleg (Apr 12, 2009)

guitarboyled said:


> I noticed that different coil options are available...
> 
> Therefore, if I select a 24V coil for instance with the contactor I also have to install (separately) a transformer.


I think what everyone is saying is - it's easiest to get a contactor that uses the control voltage you have, and is rated for the amps/voltage that your load has, rather than do a bunch of unnecessary horse$hit that just may cost more as well as give more things to break or go wrong.


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## varmit (Apr 19, 2009)

The IEC contactors, like the one that you posted, have replaceable coils. Usually, the contactor frame for DC coils is physically larger that the same amp rated AC contactor. Any AC coil that the mfr. makes for this contactor series will fit the AC coil version. The DC coils will, on any brand that I use, only fit the contactors for DC coils. 

Most major plants, in the US that enforce safety rules, are going to 24 VDC controls for safety reasons. The most common control voltage for the last 40 years or so has been 120 VAC. Some really old equipment has 480 controls. I do not know how this correlates to Canadian standards.


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## A Little Short (Nov 11, 2010)

I've used a ton of the Telemecanique contactors. Mine were mostly 48V coils. The coil mounts, usually on a Din rail, then the contactor mounts to it. You should have two terminals marked A1 & A2, these are for the coil. As has been mentioned, the coils come in various voltages. Also, as has been said, if you're starting from scratch, get something that is similar to your control voltage.


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## ilikepez (Mar 24, 2011)

What do you need this for anyway? Timers for the pot grow?


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## guitarboyled (Jun 22, 2009)

I'm not doing any work, just trying to further my electrical facts. You're not much of a hvac guy if you have limited electrical knowledge.


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## guitarboyled (Jun 22, 2009)

I found this wiring schematic that gives me a pretty good idea of a circuit with a transformer... 

Probably a stupid question but control side is always 1 phase or DC right? 

If no stepdowns are required the coil feeds off two legs or one leg and the neutral?


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## erics37 (May 7, 2009)

guitarboyled said:


> Probably a stupid question but control side is always 1 phase or DC right?
> 
> If no stepdowns are required the coil feeds off two legs or one leg and the neutral?


If control power is DC usually it comes from a DC power supply. Otherwise it's usually always a single-phase AC circuit. If you have a transformer stepping 480 down to 120 then all your controls, including the coil, will probably be 120. Sometimes on a lower voltage circuit, like 208 or 240, the controls will be directly tapped with no transformer. In those ones, the control circuit is at 208 or 240 also.


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## guitarboyled (Jun 22, 2009)

The control power supply is always external from what I can understand.

We don't just connect a switch to A1 and A2 but actual voltage must be supplied to complete the circuit.

In the following diagram would one just run a wire between the Neutral and A2 terminals?

Are the over current protections usually incorporated in the contactor? Is it a seperate module? It as to be between L1,2,3... and T1,2,3


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## varmit (Apr 19, 2009)

The control power supply is always external from what I can understand.
*YES*

We don't just connect a switch to A1 and A2 but actual voltage must be supplied to complete the circuit.
*YES*

In the following diagram would one just run a wire between the Neutral and A2 terminals?
*NOT DIRECTLY, THE NEUTRAL WOULD USUALLY RUN THROUGH THE NC CONTACT ON THE OVERLOAD BLOCK THAT WOULD BE CONNECTED DOWN STREAM OF THE CONTACTOR.*

Are the over current protections usually incorporated in the contactor? Is it a seperate module? It as to be between L1,2,3... and T1,2,3
*IT WOULD BE A SEPARATE MODULE, EITHER AN OVERLOAD BLOCK DOWNSTREAM OF THE CONTACTOR OR A "MOTOR PROTECTOR"/ MANUAL STARTER UPSTREAM OF THE CONTACTOR.*


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## guitarboyled (Jun 22, 2009)

I see some overload protections direct mount on the contactors.











I'm presuming the copper pins plug in the contactor and the load connects to the lower T1, T2, T3 terminals of the OCP and not the original terminals of the contactor.

In such a case where would one physicaly tap in to power up the coil? Would a junction box be required?


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## jmsmith (Sep 10, 2011)

guitarboyled said:


> I see some overload protections direct mount on the contactors.
> 
> 
> 
> ...


In this case, you would wire one NC terminal to neutral, and the other NC terminal to the A2 terminal on your contactor. This will drop the neutral to the contactor in the event of an overload. We used to use the NO terminal to provide a remote trip indication for troubleshooting purposes.


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## sparky105 (Sep 29, 2009)

at the A1 and A2 on the starter the ol relay u have shown gets wired into the control circuit on nc set of contacts on the relay when the load exceeds the amp draw the bi metal in the relay opens the relay and shut the load down.


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## Spannerz (Aug 13, 2011)

guitarboyled said:


> I see some overload protections direct mount on the contactors.
> 
> 
> 
> ...


Yep, they certainly are a bastard.

You have to route, 1 of the coil supplies, back through terminals 95+96 of the overload. These are normally closed, so if you have an O/L situation these go open, and the coil drops out.

Use the N/O contacts for a indication light, or something useful.


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## JRaef (Mar 23, 2009)

guitarboyled said:


> The control power supply is always external from what I can understand.
> 
> We don't just connect a switch to A1 and A2 but actual voltage must be supplied to complete the circuit.
> 
> ...


Just so you are clear on this specific concept in the above drawing, this is taken from an IEC (European / Asian) wiring diagram. In those parts of the world, 3 phase power systems are ALWAYS 4 wire, typically nominal 400/230V where is it 380-415V line-to-line and 220-240V line-to-neutral. Because it is so universally the same, they traditionally used 230V control as shown in the above diagram. In the last 10 years though they have been switching to 24VDC as noted previously.

Here in the US we are no so monolithic in our power distribution systems. We have 480V 3 wire and 480/277V 4 wire, 240V 3 wire and 120/240V "red leg" 4 wire and 208/120V 4 wire systems. Although it is possible to use a 277V coil on a 480/277V 4 wire system, it's fairly uncommon and if you try to go that way you will have grief on getting replacement coils readily. Only 208/120V 4 wire systems will be able to be connected this way. 

Local control distributors are going to stock 120VAC or 24VDC coils on the shelf. Most other voltages are likely going to take some looking or shipping. So my advice is that is that if you want your control system to be easily repairable, stick to 120VAC or 24VDC coils. Use a CPT for 120V and a 24VDC power supply if you want to go for lower safer voltages.


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## jmsmith (Sep 10, 2011)

JRaef said:


> Just so you are clear on this specific concept in the above drawing, this is taken from an IEC (European / Asian) wiring diagram. In those parts of the world, 3 phase power systems are ALWAYS 4 wire, typically nominal 400/230V where is it 380-415V line-to-line and 220-240V line-to-neutral. Because it is so universally the same, they traditionally used 230V control as shown in the above diagram. In the last 10 years though they have been switching to 24VDC as noted previously.
> 
> Here in the US we are no so monolithic in our power distribution systems. We have 480V 3 wire and 480/277V 4 wire, 240V 3 wire and 120/240V "red leg" 4 wire and 208/120V 4 wire systems. Although it is possible to use a 277V coil on a 480/277V 4 wire system, it's fairly uncommon and if you try to go that way you will have grief on getting replacement coils readily. Only 208/120V 4 wire systems will be able to be connected this way.
> 
> Local control distributors are going to stock 120VAC or 24VDC coils on the shelf. Most other voltages are likely going to take some looking or shipping. So my advice is that is that if you want your control system to be easily repairable, stick to 120VAC or 24VDC coils. Use a CPT for 120V and a 24VDC power supply if you want to go for lower safer voltages.


Good point.... The info I gave him was going by using the above devices as a REPLACEMENT for existing... In that case, control voltage is supplied via a control xfrmr in the bucket or separate 120VAC or 24VDC supply. But outside this, all other internal wiring remains the same. Thanks, JRaef, missed that important point...
-Jim


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## sparky105 (Sep 29, 2009)

JRaef said:


> Just so you are clear on this specific concept in the above drawing, this is taken from an IEC (European / Asian) wiring diagram. In those parts of the world, 3 phase power systems are ALWAYS 4 wire, typically nominal 400/230V where is it 380-415V line-to-line and 220-240V line-to-neutral. Because it is so universally the same, they traditionally used 230V control as shown in the above diagram. In the last 10 years though they have been switching to 24VDC as noted previously.
> 
> Here in the US we are no so monolithic in our power distribution systems. We have 480V 3 wire and 480/277V 4 wire, 240V 3 wire and 120/240V "red leg" 4 wire and 208/120V 4 wire systems. Although it is possible to use a 277V coil on a 480/277V 4 wire system, it's fairly uncommon and if you try to go that way you will have grief on getting replacement coils readily. Only 208/120V 4 wire systems will be able to be connected this way.
> 
> Local control distributors are going to stock 120VAC or 24VDC coils on the shelf. Most other voltages are likely going to take some looking or shipping. So my advice is that is that if you want your control system to be easily repairable, stick to 120VAC or 24VDC coils. Use a CPT for 120V and a 24VDC power supply if you want to go for lower safer voltages.


And being Canadian The OP should remember that we use more 600 /347 4 wire, 208 /120 4 wire, 600 3 wire, 240 /120 3 wire and that our control voltages are easily any one of these or as well 24 and 12 volt ac all easily sourced with again the 120 and 24 v being the dominate usage.


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## nolabama (Oct 3, 2007)

Answers
Yes
Either xformer or change the coil.
No
Whatever the engineer specs.

Somwhere you asked about a jbox. I would recommend putting all of this in some sort of box or cabinet.


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## guitarboyled (Jun 22, 2009)

jmsmith said:


> Good point.... The info I gave him was going by using the above devices as a REPLACEMENT for existing... In that case, control voltage is supplied via a *control xfrmr in the bucket* or separate 120VAC or 24VDC supply. But outside this, all other internal wiring remains the same. Thanks, JRaef, missed that important point...
> -Jim


 
What's *the bucket?*


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## jmsmith (Sep 10, 2011)

guitarboyled said:


> What's a the bucket?


Sorry 'bout that... We used to refer to the draw-out units in motor control centers as "buckets". Usually it was the disconnect, contactor, and control transformer (if used) as a complete unit that could be inserted or withdrawn out of the MCC without disturbing the main wiring. If you are dealing with one unit, though, I would recommend a Hoffman box with the bolt-in back panel to mount the units you need in.

Sent from my iPhone using ET Forum


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## guitarboyled (Jun 22, 2009)

Spannerz said:


> Yep, they certainly are a bastard.
> 
> You have to route, 1 of the coil supplies, back through terminals 95+96 of the overload. These are normally closed, so if you have an O/L situation these go open, and the coil drops out.
> 
> Use the N/O contacts for a indication light, or something useful.


Is the NC 95-96 route mandatory by code or simply a good practice?


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## erics37 (May 7, 2009)

guitarboyled said:


> Is the NC 95-96 route mandatory by code or simply a good practice?


Code mandates that all the ungrounded conductors in the circuit be opened if overload conditions exist... easiest way to do that is to run the coil control circuit through an NC contact that opens when one or more of the overload elements trip. Then the coil loses power and opens all of the main circuit conductors.

Why we run L2 through that contact is beyond me, but it's been done that way forever and there's no real reason to change it in my opinion.


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## jmsmith (Sep 10, 2011)

erics37 said:


> Code mandates that all the ungrounded conductors in the circuit be opened if overload conditions exist... easiest way to do that is to run the coil control circuit through an NC contact that opens when one or more of the overload elements trip. Then the coil loses power and opens all of the main circuit conductors.
> 
> Why we run L2 through that contact is beyond me, but it's been done that way forever and there's no real reason to change it in my opinion.


Whether there is any truth to it or not, I was taught they originally thought it was safer to break the neutral side of the coil in the case of any contacts on the high-side of the coil stayed in or was just a manual on off switch. Neutral to coil breaks, contactor got turned-off solid. (?) kinda old-school, but still done this way today. It also made it harder to bypass the overload than the normal interlocks to make a piece of equipment run.

Sent from my iPhone using ET Forum


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## erics37 (May 7, 2009)

jmsmith said:


> Whether there is any truth to it or not, I was taught they originally thought it was safer to break the neutral side of the coil in the case of any contacts on the high-side of the coil stayed in or was just a manual on off switch. Neutral to coil breaks, contactor got turned-off solid. (?) kinda old-school, but still done this way today. It also made it harder to bypass the overload than the normal interlocks to make a piece of equipment run.
> 
> Sent from my iPhone using ET Forum


It's not always a neutral on that side of the coil.

But it makes sense to dedicate one portion of the circuit to overload protection, considering how vital it is. Only putting one single contact on the L2 side of the coil would eliminate a lot of potential failure points.


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## jmsmith (Sep 10, 2011)

erics37 said:


> It's not always a neutral on that side of the coil.
> 
> But it makes sense to dedicate one portion of the circuit to overload protection, considering how vital it is. Only putting one single contact on the L2 side of the coil would eliminate a lot of potential failure points.


You're right there! Just have been used to everything I worked on was always speced for either 120VAC or 24VDC... Other than a couple of jobs where everything was DC, everyone else held control voltage down for operator safety. Thanks for the correction... L2 side of coil...
: thumbsup:

Sent from my iPhone using ET Forum


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## kf5aeo (Dec 4, 2011)

when we must use a 480v coil we always use a 480 to 120v control transformer for control circuits and istead of going through the starter (contactor) coil, we go to a coil on a 2 pole open face relay and pass the 480 through its contacts then to the contactor's coil. so instead of everything being 480, you have very little 480.


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