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The Difference Between Contactors And Relays - ELECTROMAGNETIC SWITCHES electricians use
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- Опубліковано 8 сер 2024
- A lot of people get really confused by contactors and relays and tend to treat them like some kind of mystical magic device without understanding what exactly they do. They have some similarities but still have very distinct differences.
00:00 Intro
00:27 How Are They Similar?
01:33 How Do They Differ?
04:22 Outro
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Contactors and relays are simply switches. They differ from a standard switch, however, by being able to be controlled with electrical current rather than your finger. Both operate with a coil on the inside that, when energized, sucks contacts closed or snaps them open. It would be as if you were able to zap a normal light switch with a bolt of lightning to get it to change states....kind of.
Both relays and contactors are also multi-pole switches. This means that they can control several circuits, rather than just one like a normal single-pole switch would do. A typical 8-pin cube relay can control 2 circuits, while an 11-pin can control 3. General-use contactors can control anywhere from 2-4 whereas lighting contactors can control from 6-12 circuits/loads. All with the flip of a single action (bump of current).
What makes them different are a few things. First off, relays are typically lower voltage applications as well as lower-current applications. Relays you may come across could have coil voltages of anywhere between 12v and 240v on average, and can control loads in the 5-15amp range. Contactors tend to be more stout and can handle higher amperage through the coils and contacts. You could see coil voltage ratings between 120v-480v, and contacts around 30-50amps on average.
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#contactors #relays #electrical
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Relays "tend" to be for logic switching. Contactors for power switching.
Most of the time you're right, but the fact you put "tends" to in there lets me know you're experienced in the field lol
Relays are used to switch solenoids frequently.
Yes, relays are durable and inexpensive in "low power" switching applications.
@@Stones_Throw Right, not gonna see much over 120vac thru them. I haven't anyways.
40 amps ssr
Wow. I went through a 5 year IBEW apprenticeship here in Florida and you explained relays and contactors much better than the so-called instructor I had. Thanks.
Feel sorry for you, hope you found someone better to work with.
What local brother.
Local 18, Los Angeles, sorry that you had that experience.
Orlando?
Wow, why I find better instructors on you tube than school.
Latching and unlatching relays are fairly common. Some also have manual over-rides to latch or unlatch. Not to mention the myriad specialty relays, multiple types of timing relays, alternating relays, current sensing, voltage sensing, etc. I started working in switchboard shops before PLC's came out and worked a lot with relay logic; panels with as many as 300 control relays of various functions. Troubleshooting? Oh, joy!
My classmate created his own "stoplight" using timing relay cubes. They're fun and can be implemented into a bunch of different things once you understand how the N.O./N.C. functions work
Zach Nicastro yeah right
The contactor you were holding in your hand will accept auxiliary contacts as well. Auxiliaries are used regularly for latch circuits and/or if there needs to be a sequence during a matching start up, switching a indicator light, sending a signal to a plc, etc. I'm an industrial tech, it's rare to see a contactor without auxiliaries attached.
Can I use contactor ..auxiliary /hold circuit for power cut off function in my device ? when the device send a trigger relay break input to the holding auxiliary circuit of the contactor?
Basically I need this in my plc project to cut off supply whenever any emergency/error occurs.
You are very knowledgeable. Very good explanation about the coil operation. I too am an electrician and constantly seeking knowledge from people like you. Learn one and teach one will make you a master. Thank You
Can I use contactor ..auxiliary /hold circuit for power cut off function in my device ? when the device send a trigger relay break input to the holding auxiliary circuit of the contactor?
Basically I need this in my plc project to cut off supply whenever any emergency/error occurs.
This is a great channel with a wealthy info. Have you ever done any thermal imaging videos showing heating issues with electrical components.
Electrician for 22yrs, good video and much respect for the old school Nintendo controller hat
very good explaination of the two. I have a HVAC unit where the contactor is failing and had no idea what it was. Once I looked it up I said that's just a posh relay. But you have expanded my understanding of these, thank you.
I'm an HV AC controls electrician. But I'm in my second year of doing it. I keep calling contactors relays. thank you for making it so easy to search this topic.
Wow I loved your explanation- very precise and easy to understand. Thanks👍
No problem my dude!
Wow clear explanations. Thanks bro.
That was super satisfying, and I'm thankful for your help! I'm looking to turn on and off a 30amp motor with a smart plug and a contactors seems like the right path.
A relay is a device where there is no emphasis on the closing and opening mechanical forces for making and breaking a circuit, meaning that current can be switched on via energizing the coil or it could be switched on via releasing the coil and relying on the spring to make a contact. A contractor is actually different as its intended to only ever close a circuit when energized, and slam down with considerable force hence the name "to make contact" Yes some units can be configured to break a normally closed circuit too. The aux contacts that piggy back on the contractor mechanism are an optional extra and are for low power use only. The reason why contractor are used to slam down and make contact hence the name in high power applications is because a large amount of force is required when switching high energy equipment.
Great video Dustin thanks a lot!
Great info, explained well!
If you take video requests I wouldn't mind hearing your perspective on why with low volt LED lights why or how it works that you need both the magnetically switch trans and a special dimmable switch as well.
Hi! Greetings from Finland. Your videos are awesome. I'm an electrician and now studying to come a ship electrician.
Thank you for the video it is very helpful!
great video. Thanks, Dustin!
Thank you! This was helpful
You should do a video on pulling wire in conduit and laying out what Neural wire goes with what color and circuit number. also on what numbers are associated with wich colors. lots of apprentices have problems with this and they like to mix up the neutral wires with the wrong circuits. Thanks
You cant fix stupid.
Was reviewing stuff for a 50 year old machine at work, and you may have just saved us a few hundreds of usd lol, thanks man
Excellent video. Thank you.
What a great video. Well done.
If i have a 50A breaker (which is probably too big) servicing an old Lennox (armstrong air) condensing unit, and my contactor craps out, can I use a 40A contactor? The condensing unit is 30 years old snd has no markings on it at all. No idea how many tons, or what contactor is in there now.
Obvously, just looking for an opinion, from someone who knows more than I do. Everything is working, I just like to understand how the stuff inter relates.
Thanks.
Thanks for the awesome explanation my man .
Excellent explanation many thanks from the UK👍
Very useful video.
Can I request a video decyphering the contact ratings on the side of these contactors? ac 1, 2,... 20, iec, ul. Ac vs Dc etc. Thanks for your incredible channel.
We’ll said. Thanks for the information.
nice video , is it possible to have contactor which is 6 NC and 4 NO and they switch the NC to NO and vise versa ? if yes can you please give me a info where i can find such a device thanks a lot
Thanks for the info and educational place to chrckout
Thanks cleared up my confusion
Thanks for this video brother...👊
Great Info :)
That was relay interesting !
Haww... HAWWWW...! UB2 fun E!
Contactors also are able to have extra contacts easily installed on the top either n/o or n/c to provide additional circuits to be added as required.
(Auxiliary contacts)
Can I use contactor ..auxiliary /hold circuit for power cut off function in my device ? when the device send a trigger relay break input to the holding auxiliary circuit of the contactor?
Basically I need this in my plc project to cut off supply whenever any emergency/error occurs.
Sorry to say I don't know.
You can get relays that also have latching. The ones I am familiar with use a magnet to hold the contact closed.
Yep- the very early AMF bowling pinspotters used several latching relays for control.
@@NipkowDisk
So did old traffic light controllers
On Relays the Nickel Cadmium on the Contacts is rated for Less than 20amps used typically for lower voltages single phase.
Contactors are typically 20amp or greater and up to 3phase with auxiliaries
Let's get that onto a tray. Nice.
I love the next video ideas.
Hey Dustin, Do you have a video on how to wire relays and contactors? Fire alarm, door mags
3:12 what type of relay would allow me to open the N/C switch while closing the N/O switch with only one control voltage source?
Excellent video.
Thank you
You forgot to mention price. I looked at a few contactors and saw that generally they're more expensive than relays. Even surprisingly so, for some!
4:10 But there IS an animal called a "latching relay" which preserves its state even when the input is gone. They toggle given pulses from a momentary switch.
Did you discuss the activation Voltage on the coil ? AC versus DC?
When did "[v]oltage" become a brand of some sort, to you?
You're asking if he discussed that because... you didn't watch the video, or...?
Putting out information that apprentices might not get on the field (or in school evidently), Awesome.
Just some viewer feedback...
Not sure if anyone else feels this way but I almost miss your garage studio. I mean, the wall frame and tar paper in your garage was a cool theme in my opinion. I realize you might be going for a more professional and organized look for Electrician U, but it would be cool if you got a little creative with the background in your studio to add some style and a new texture to the videos. The current background is neat and clean, but not as interesting to me. Other than that, The content is very interesting!
So I'm looking at a relay/contactor it's for my vehicle there's a 9-32vdc switched leads for closing the the normally open coil that handles up to 500amps of current it's completely sealed with an epoxy with 2 bolts for heavy gauged wire I'm wondering if this is a relay or connector? My alternator currently puts out 15.5vdc internally regulated and clamps 430amps to charge up my (LTO) lithium titanate oxide battery I've built for car audio it's a massive bank capable of putting out 3200amps constant and 6400amps for a 60second clamp holding . The goal is to protect my alt but just wondering what it would technically be called whether it's a relay or a contactor? Thank dude love the channel
I would love the comparison had been a bit more technical instead of generalities. I appreciate the video though.
Any Relay\Contactor can be configured for NO\NC.. Using either Grounding\Neutral\Power signal switching. Also relays can be rated up to 100 amps. But cost more then a Contactor of same rating. You can also change the coil line side control voltage for Contactors. In many configurations from 12 volt to 120 to control 277\480 volt line\loads... Some relays have timers. That reset after so many minutes. And relays are the best thing since running water for PLC systems.
To add:
Relays are available with coil ratings of nearly every standard system voltage, from 3 volts up to 277 volts, AC or DC.
Can I use contactor ..auxiliary /hold circuit for power cut off function in my device ? when the plc device send a trigger relay break input to the holding auxiliary circuit of the contactor?
Basically I need this in my plc project to cut off supply whenever any emergency/error occurs.
Cant find a video of yours wiring up contractors?
Really like your videos too!
Contactors not contractors lol
Thank you so must dude !
Which one is used in split ac..i have 1.5, 2 and 2.5 ton a/cs ?
great video
Thank you!
So, if I have a pump that is 230v w/ max draw of 6.1A, a relay could work for it? (I've seen relays that look like the one you've been holding in the video that do up to 250v and 10A). All I want is something to make a float lever tell the 230v pump to turn on when the float is down and turn it off when the float is back up to a certain point (to fill a cistern). Would the relay work for that?
Any idea how to wire that? The float has 3 wires (with only 2 being used depending on what you want it to do-- in the one I'm looking at getting, the brown wire would be excluded if I want the pump to turn on when float is down). I keep trying go find diagrams but they say it is specific to the application.
4:22 what's this
How would I control one to four items 120 volts 15 amps heaters sequentially choosing to use one to four items on time per second or so each item sequentially ???? Can you help guide me Sir ??? Thanks
That’s great information...I’m 1000% smarter about relays and contactors now !!!
Very useful.
I need a dpdt contactor or relay, 24 or 110 ac coil, to power a Grunfos ac/dc well pump powered by solar during the day and utility power at night. Can’t find one to handle the load of the dc without burning the contacts. Need 110 ac 15 amp on the normally closed side and 100 vdc 20 amp on the normally closed side. Can you refer me to a product.
There's a tonne of class ntactors out there that will handle that load with no issue at all. I controlled 480v 50A loads with 120/20 for cranes on a regular basis. Any electrical contract supply house should be able to help you out with specific units, they won't be cheap...
I am still waiting for your video of the conductor and relay wiring.
There are Many different configurations available especially when you factor in Add-On NO / NC Contact Blocks.
What you said isn’t Wrong, but the Easiest Way to distinguish each of the Three Types is:
Relays = Control (Very Low Draw)
Contactors = Control Power (High Draw and AIC)
Starters = Contactors with Overload Protection (High Draw and AIC)
I usually think of them about the same, contactor usually I think large loads or motors, 3 phase things. I think a contactor for a motor though is a bit different with fuse links, etc I think that is called a starter to me it is a contactor.
So how are these spec'd? I mean if I want a contactor that will pass 220v through it but is switched (coil) by 110v, how would that be identified? I want to turn on a 220v motor with a 110v switch...if that makes sense?Thank you for the video. I have subscribed so I can learn even more.
I have asked many electricians and those in electrical field what their difference are but none explained it satisfactorily. Until now.
Looking forward to explaination of the application of contactors and relays in circuits.
Glad you gained something from the episode, thanks for watching my friend!
I was hoping you were going to explain how one is mechanical and one is solid state. Explaining the pros and cons.
little late to the game here but question..... wiring a trailer dealing with shore power 120v, and battery 12v, switching from shore power to inverter power, could you technically use a 30 amp relay as oppose to a 30 amp contactor?
Do know you much about auto/manual/off bms systems would be a good video as they often involve relays and contactors
I'm actually trying to work something out where i can film a NOVAR (or similar) system and talk about all of the different components as well as do a bird's eye view to explain it all...without actually talking about specific branding or specific stores. Kind of a challenging thing to film because I need to show it, not just talk about it. So gaining access to stores with BMS's is in the works. May just take some finesse and time.
Does the contactor isolation provides safety in lightning??
Can you please make a video on Motor Control?
Please make more content !!!!!!
Can you Please Please PLEASE DO A VIDEO EXPLAINING THREE PHASE POWER
Contractors are equipped to wider gap in case of opening circuit so they have capacity under induction loads and limiting arc.
Relays has no ability to extinguishing arcs, the open contact gap in relays are smaller than contactors.
For switching off a 16A electromotor or induction loads such as transformers, you need a contractor not a relay, calculated in correct rating which not necessarily that 16A. The opening speed of contacts in a contractor is faster than a relay.
The main difference is braking current capacity.
I have a question. Let's say I wanted to have 4 landscape lighting circuits. Could I use 4 GFI Breakers then go into a lighting contactor to feed each individual contactor and or landscape out., could you also show me how you would do it if possible thank you
GFCIs might not like the contactors per say.
As it is looking for any sort of short from A to B.
But it is possible to do something like this yes.
@@ElectricianU thank you for responding I enjoy all your videos
YOU HAVE EXCEEDED YOUR "SO" QUOTA FOR THE DAY!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
I replaced a Type 91 Two Pole relay with an Eaton C25BNB230T. Didn't see a rating on how long it would last but I don't much care as the price is better.
So relays can handle more than a couple of separate loads, since you included 3. Maybe some can do 4, even.
my understanding of relays is that a lower amperage signal/circuit controls a higher amperage circuit such as in a car for the starter relay where the key switch sends power to the relay which controls higher amperage out to the starter .. because you would never send all the amps for the starter through the key switch. in a relay the two circuits are independent and the lower voltage or amperage one controls the higher voltage/amperage circuit
That is definitely the case in automotive as well as some lighting and building control systems. But that's not always true in electrical in general. Many times I've used relays at higher voltages for controlling circuits of that same voltage. For example a 208v control circuit, switching several 120/208 circuits on/off at the same time.
Nice job. Beefy
Simple explanation for a relay is a switch that uses a lower power load to operate to switch a higher power load.
Saying a relay is only for small low power uses is simply false. Go look at an older car with a starter relay separate from the starter. You have the small wires which control the coil operation in the relay. The heavy gauge battery cable and cable to the starter are connected to the contact points for the relay.
I stumbled on this video and watched all the way through in case I was missing something but it was just in accurate.
Contactors typically have an auxiliary so that you can change from N/O to N/C, you just have to do it with the low voltage signal lines.
Any books you recommend?
yes lots actually. www.electricianu.com/books has some recommendations depending on what direction you're heading down
Bro how to contact u
please can you help a noob, can somebody tell me if i can wire a 3 pole
relay as a single pole, i think thats what i want/need?, i needed a
relay to turn on and off from - 24vac,on the coil side-, 240v 35a on the
main load , and with out spending silly money i could only find a 3
pole one cheap, thats 35 amps , all i need it to do is when activated by
the 24v ac , allow the current of my 240v ac to pass to make the
circuit, and that can be just the live or the live and neutral, etc etc
if
it can be done?, would wiring it so my live splits and goes in to all 3
poles and then out all 3 poles(when activated), to give more current,
as its for my mig welder ,(24v trigger), so more amps the better, thank
you
What's with the picture 4.22 ?
Interesting video. Thanks.
I have a variable speed controller for a 130 VDC treadmill motor. I have a dpdt switch for forward and reverse. I’d like to have a green led light come on when it’s in forward (+-) and a yellow led light when it’s in reverse. But the LED’s are low voltage and current.
So I need a switch that allows low dc voltage to flow to a led when the polarity is +- and when the polarity to the TM motor changes, it closes that gate and opens another.
I’m doing a poor job of explaining it, but I hope you understand.
Any suggestions? Space is limited.
Thanks for your attention.
Paul
One can run two sets of LEDs connected to the appropriate resistor and a blocking diode in series, one green and one yellow, and then connect them in parallel with the power wires running to the motor. With them being connected in different polarities and the motor is moving one way, the polarity will only allow current to flow through the diode and the resistor to supply the proper voltage to light the appropriate color LED. Green LEDs have a different resistance than yellow ones, so each resistor will need to be sized accordingly. This will work as long as the speed controller is pulse width modulated (with some possible flickering of the LEDs) and not voltage modulated. If the voltage is modulated, then you will only have a narrow window of voltage that the LEDs will function in.
@@GoCoyote Thanks. I’ll try it. I’ll have to lay it out to understand first. Thanks for taking the time to answer.
It’s a shame that I can’t find a nice DPDT rotator selector switch that can handle 130 VDC and 20+ amps. I ended up with a monstrous 3PDT changeover switch that’s yellow and red. 3” deep. I wanted something a bit sexier in stainless. But even the 20 amp DPDT toggle switches don’t hold up to a 4.25 hp treadmill motor.
May I ask you more questions about wiring? Do you have a website where I can send you pictures? I’m desperate here so I’m reaching out.
Thanks,
Paul
Decent vid hoss
Please note the fact that a contactor is typically bigger and heaver, high power etc than a relay is missing the point of why a contactor is called a contactor. A relay is a device where there is no emphasis on the closing and opening mechanical forces for making and breaking a circuit, where with a contactor there is emphasis hence the name to slam down with considerable force and make contact.
This is how a real teacher looks.
good
how about a video on wiring these to......
So is it true that if I have a relay that the coil usually stays energized then the normally open contact is normally closed. :/ Wut?
The term 'normally', in this case refers to the "at rest" or unenergized position of the contacts. The same terminology is uses to designate the contact configuration in momentary type switches.
Eeh...you are generally correct...if explaining to someone who knows nothing about anything electricity.
If you couldn't tell...that's exactly what this whole channel is about.
And it is widely appreciated dustin I have learned a ton from both this and the journey to master channel's over the past 2 years and look forward to eventually getting my foot through the door in my area thank you
you are awesomwe
My suggestion add subtitles at the bottom videos.
I would love to do this but it takes a lot of time so I need help from the community. Do you know you can contribute subtitles and translations in the “contribute” tab? If it’s something you’re interested in helping with please feel free to do so. If not that’s ok too, thanks for watching my friend!
So in other words a contactor is a heavy duty relay.
yes
Not exactly. Contactors are like super-duty on/off switches that are controlled by another circuit. Relays have leads/terminals that are normally open and normally closed, so they can be used for more complex operations.
@@RB-xv4si That is exactly what a relay is. One circuit energises a coil to flip a switch. A lower power circuit can switch a higher power circuit.
Dave B I don’t think you’re processing a significant difference. Yes, it is operated by a circuit sending/cutting off voltage to its coil, like a contactor. But relays also have NO and NC terminals or leads. That allow them to send voltage and cut voltage to multiple devices at the same time.
@@RB-xv4si Back when I posed the observation I was an electronics engineer that had been asked to learn electrical switching so I researched what I could to get up to speed with terminology, things like contactors were a new entity until I striped one down to find that it is just a type of relay. To do the job I had been asked to do I needed to know exactly what components were irrespective of their name so that I could design circuits using existing equipment. A contactor is a cheap one trick pony version of a relay, hence why they are used so often. Its not the only electronics definition that has been changed for the electrical trade, LED is another one.
OK as far as it went but you missed some very important features of relays. Relays operate far faster than contactors, they also can handle much higher current than you said also they can have far more coil voltages and switch elements than any contactor. I would definitely want a relay at the end of an emergency stop switch for the speed of disconnection And most important you did not mention latching Relays sometimes called bistable relays , these relays only require voltage applied to the coil to move the armature one way and the contacts will stay open or closed without further supply current or voltage. Its state can be changed by applying an other voltage current pulse to change its state. Some of these type of relays have two coils to change state and others can have one. This type of relay is used in machinery switching using momentary action switches doing away with mechanical interlacing switch linkage far increasing reliability and speed of operation. I was taught that a relay is a fast precise electromagnetic component where a contactor uses slow brute force, one is a donkey the other a thurourbred race horse.