# I think I have a burned out relay



## Eremius (Jul 20, 2021)

I am duplicating this post as I believe this is the proper place for it rather than the original post.

Unfortunately I have run into an issue with the controls.  When the start button is pushed the motor will start, run for a few seconds and turn back off.  This running period has been getting shorter and shorter.

It is a momentary button push start system with the start button being NO and the stop button being NC.

I *believe* the cause may be a failing relay (M relay on the diagram)







but I have no idea where this little gem is located.

The control circuit is 120v and the power is 220v 3ph.














I know the orange wires go to the start/stop switches.  The red/white/black are line 1,2,3.

I am willing and able to provide any additional information as requested.

I am also willing to replace for newer components.  This isn't a resto.


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## den-den (Jul 20, 2021)

It looks like you have a 4 pole contactor with the far right pole (lowest picture) most likely being the "M" contact (blue wires).


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## markba633csi (Jul 20, 2021)

The coil is probably going open circuit as it heats- OR one of the other connections is flaky and doing the same. I would first go around and clean/tighten as many of the screw connections as possible and replace any crimps that look iffy- with power off of course
Use an ac voltmeter and check for voltage at the coil when it fails- that would tell you everything.  If the voltage is steady then the coil is failing- if not then it's something other than the coil- like the transformer or connections to
-Mark
ps looking closer I do see something funny on the coil like a overheated area or fishpaper coming loose- check that out.


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## benmychree (Jul 20, 2021)

Surely not the overload relays tripping, since they have been jumped with a piece of bare wire ---


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## Eremius (Jul 20, 2021)

The red box or the green box?


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## Eremius (Jul 20, 2021)

markba633csi said:


> The coil is probably going open circuit as it heats- OR one of the other connections is flaky and doing the same. I would first go around and clean/tighten as many of the screw connections as possible and replace any crimps that look iffy- with power off of course
> Use an ac voltmeter and check for voltage at the coil when it fails- that would tell you everything.  If the voltage is steady then the coil is failing- if not then it's something other than the coil- like the transformer or connections to
> -Mark
> ps looking closer I do see something funny on the coil like a overheated area or fishpaper coming loose- check that out.


That was my thought as well but I have taken this out, hooked 110 directly to the coil and it locks up.

I greatly appreciate the brainstorming!


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## Eremius (Jul 20, 2021)

markba633csi said:


> Use an ac voltmeter and check for voltage at the coil when it fails- that would tell you everything.  If the voltage is steady then the coil is failing- if not then it's something other than the coil- like the transformer or connections to
> -Mark


I put my meter on it hit the start button and it started up.  The voltage to the coil was jumping all over the place and the coil was dropping out/coming on quickly for a few seconds (15-30 ish) then the voltage straightened up at 127v and no more coil chatter.

Next stop, metering out the transformer?


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## sdelivery (Jul 20, 2021)

Where were your meter leads?
You can put meter leads in many places and achieve many readings.
 Looking at this picture I am reminded that there is a color code for wiring for a reason.
If the coil is not maintained when releasing the PB then it's the latch circuit. Poor connections are usually the cause of chattering.


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## Eremius (Jul 20, 2021)

sdelivery said:


> Where were your meter leads?
> You can put meter leads in many places and achieve many readings.
> Looking at this picture I am reminded that there is a color code for wiring for a reason.
> If the coil is not maintained when releasing the PB then it's the latch circuit. Poor connections are usually the cause of chattering.


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## talvare (Jul 20, 2021)

benmychree said:


> Surely not the overload relays tripping, since they have been jumped with a piece of bare wire ---


I'm sure those are precisely engineered fuseable links 

Ted


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## markba633csi (Jul 20, 2021)

Yes you have a bad connection somewhere in there, some of those terminals look positively nasty with corrosion and dirt
You can start by probing the transformer but I suspect the fault is somewhere else
See if you can locate any loose wires or screw terminals first- you may find a wire that pulls right out of it's lug
A voltmeter could be used to go point by point and track down the failure, but I've often located faults like this by just wiggling wires (with an insulated stick, and gloves)

-M


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## talvare (Jul 21, 2021)

Eremius said:


> I put my meter on it hit the start button and it started up.  The voltage to the coil was jumping all over the place and the coil was dropping out/coming on quickly for a few seconds (15-30 ish) then the voltage straightened up at 127v and no more coil chatter.
> 
> Next stop, metering out the transformer?


Based on this comment, I would highly suspect either a bad connection or bad auxiliary contacts in the holding circuit.

Ted


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## Eremius (Jul 21, 2021)

talvare said:


> Based on this comment, I would highly suspect either a bad connection or bad auxiliary contacts in the holding circuit.
> 
> Ted


I have filed the contacts on the stop button.  I am unsure what relay I should be checking out for the holding circuit.


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## talvare (Jul 21, 2021)

Eremius said:


> I have filed the contacts on the stop button.  I am unsure what relay I should be checking out for the holding circuit.



The holding circuit contacts are represented as the "M" contact in your schematic. Very likely that those are the contact at the top right hand side of your mag starter.

Ted


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## Bi11Hudson (Jul 21, 2021)

The "M" coil on the starter looks *B-A-D* in the photo. It has been severely overheared at some point in the past. So I would venture to guess that there is something external that has caused the overheating. There is also the possibility that something (rust?) is causing the armature (moving contact carrier) to drag. That will generate high heat and coil failure. The coil is rated for 120 volts, check the control power is within 10% of that value and hang a 120 volt lamp in parallel with the coil. That should give an indication when (if) the coil is dropping out. Many cases troubleshooting controls, a lamp is as good as or better than a meter.

It is bad practice to run a machine with the overloads bypassed. It is often done short term for troubleshooting. I did such at age 17 at the CG school in 1968, blew out power for the whole end of the building. Memory digression there. . . The overloads are there to protect the much more expensive motor. They should be kept functional. Heaters are sized to motor full load amps.(FLA)

Attempt to (unplugged) lift the contacts into place, the armature will be tight but must be smooth. If there is dirt in the magnetics, it will cause severe heat in the coil if it doesn't seat properly.

I didn't see any signs of burnt wires in the photos, except around the starter coil. I would concentrate there, but don't wear blinders. Also, there is nothing in the photos to cause much heat. Watch/check for something warm. But change that "M" coil right away. If it isn't causing the trouble, it certainly is interfering with operation.

.


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## markba633csi (Jul 21, 2021)

In post #7 the coil voltage was found to be jumping around so even though the coil may look suspicious, it's apparently OK
The voltage to the coil is intermittent due to a bad connection or crimp lug, we think. Could even be a faulty transformer. The OP was going to monitor it when the fault occurs but we haven't heard the result of that test yet.  Tracking intermittents can be very time consuming-ask any mechanic or tech
-M


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## sdelivery (Jul 21, 2021)

What kind of machine are we dealing with here?
Post a picture of the tag on your motor.
I see your in Michigan. I probably have a good used contactor with overloads.......if you pay for shipping


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## projectnut (Jul 21, 2021)

Do you know the history of the machine?  If it's a 3 phase machine it's likely it could be wired either 220V or 440V.  If it was originally wired 440 and is now running on 220 it's likely the overloads (heaters) are too small.  I had a similar problem with a Bridgeport.  It was originally run on 440 and later changed over to 220.  It would run a few minutes, or sometimes only a few seconds then quit.  A little investigation found whoever changed over the wiring hadn't replaced the overloads.  At 220V the overloads were undersized and  couldn't handle the current.

I would also check the coils for the contactors.  If they're 440 coils they likely won't pull in or hold the contactors when run on 220 volts.


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## Papa Charlie (Jul 21, 2021)

It is wired for 220V single phase. Take a look at the first image.

There are three things that I think could cause this coil to not stay engaged, but I hate trying to diagnose electrical issues without being there and without specifics about the components.

1) Bad connection between the power source and the coil. Test the voltage at each of these points. Also all the connections between the coil and the switch. 
2) The coil is worn out. They only have so many cycles in them and every time it is activated, make or break, those contacts spark and weaken the connection.
3) I don't know if the motor starter has heaters or some other type of overload protection. But those again have a limited life to them. If that is the case, they are relatively inexpensive to replace. For a reference the reset button there is most likely tied to them.

You can do a little research using the Manufacturer and the part number and learn a great deal about the motor starter that could help you here. Most likely there is a manual online, possibly from the manufacturer or other users, that could also have a trouble shooting guide that could help


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## sdelivery (Jul 21, 2021)

Take the wires off the coil. Wire in a pigtail that you can plug into a wall to energize the coil with the coil energized use your meter to check the far right set of contacts on the motor starter.  These appear to be the latch circuit. A latch circuit is what holds the contactor on when the on push button is not depressed.


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## Eremius (Jul 22, 2021)

sdelivery said:


> What kind of machine are we dealing with here?
> Post a picture of the tag on your motor.
> I see your in Michigan. I probably have a good used contactor with overloads.......if you pay for shipping


Cincinnati 2ML

Main motor



Overarm motor




projectnut said:


> Do you know the history of the machine?  If it's a 3 phase machine it's likely it could be wired either 220V or 440V.  If it was originally wired 440 and is now running on 220 it's likely the overloads (heaters) are too small.  I had a similar problem with a Bridgeport.  It was originally run on 440 and later changed over to 220.  It would run a few minutes, or sometimes only a few seconds then quit.  A little investigation found whoever changed over the wiring hadn't replaced the overloads.  At 220V the overloads were undersized and  couldn't handle the current.
> 
> I would also check the coils for the contactors.  If they're 440 coils they likely won't pull in or hold the contactors when run on 220 volts.


It was originally wired for 440.  I rewired for 220.  I am unsure if the machine even has heaters as it looks like they have all been jumped.  I believe this is the case with the overarm.



sdelivery said:


> Take the wires off the coil. Wire in a pigtail that you can plug into a wall to energize the coil with the coil energized use your meter to check the far right set of contacts on the motor starter.  These appear to be the latch circuit. A latch circuit is what holds the contactor on when the on push button is not depressed.


I have already done this and the coil seems to lock up solidly.


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## Eremius (Jul 22, 2021)

I will be unable to make it back out to the shop until Friday so it's going to be a couple of days.

As I said before, I am not adverse to updating the circuits to something a bit more modern.  At this point would that be a good option?


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## tq60 (Jul 22, 2021)

Stop this!

Wrong things being suggested, rather wrong process.

Do NO corrective action as it is intermittent and you need to measure things to determine fault.

When working or not working measure major points or if not sure print a few copies of photos and with your voltmeter measure voltage on every terminal.

Circuit is very simple.

Power routed through a normal open push button (start) to the coil of the contactor.

Other side to return or neutral.

Power also to contactor line connections and an extra for latching.

This output is usually routed back to the coil via the heaters (circuit breaker like devices) and a normally closed push button (Stop switch), when normal this line holds the contactor closed, if any of them open then coil releases.

Measure and confirm voltages along these lines, does holding the start button stop the chatter?

Yes then latch line

No then contactor 

Make corrective action only when you find an issue then treasure to confirm your repair was correct.

This is really easy if you take your time.

Sent from my SAMSUNG-SM-G930A using Tapatalk


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## sdelivery (Jul 22, 2021)

It is not intermittent as he has the same result everytime he tries to start the machine.
If someone doesn't have a good understanding of electricity and how to troubleshoot with a meter then suggesting that they work on a live circuit with an unknown meter and leads and without them knowing exactly where they are going to be probing with those leads doesn't sound good or like it will achieve quick or accurate results.
Instead deenergize the panel and start using an ohm meter with your drawing in hand.
You will START to learn and understand the circuits and will probably find the issue without possibly being shocked.


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## Bi11Hudson (Jul 22, 2021)

I have looked over the posts from the git-go, I couldn't find for sure where I got the impression. So I ask point blank if the machine is being run from single phase power. I see the photos of the motor, three phase. If so, it is quite possible that control power is being drawn from the "synthetic" third phase. Whether using a Rotary Phase Converter, a capacitor bank, or a VFD really doesn't matter. If one side of the control power is coming from that synthetic third phase, it will be, at best, unstable at the start. It will smooth out some as the motor comes up to speed, but still not as it should be. Follow that through and make sure that control power is from the two leads where power is solid under all circumstances.
The coil of the starter is in *bad* shape. It should be replaced, whatever the circumstances. If I were at work (been a while) the entire starter would be changed out. Having only two overload heaters dates the starter from long ago. They have had three for as long as I can remember. For machine tools, the third is superflous but is the norm today. It might be more cost effective to find a Chinese made starter rather than trying for a coil and two heaters.

The "insight" came from sleeping on the problem. Having been out of the electrical field for ten years plus, my mind is not what it once was. But look into where control power comes from, make sure it is from the line, not the third, synthetic line.

.


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## Eremius (Jul 22, 2021)

sdelivery said:


> It is not intermittent as he has the same result everytime he tries to start the machine.
> If someone doesn't have a good understanding of electricity and how to troubleshoot with a meter then suggesting that they work on a live circuit with an unknown meter and leads and without them knowing exactly where they are going to be probing with those leads doesn't sound good or like it will achieve quick or accurate results.
> Instead deenergize the panel and start using an ohm meter with your drawing in hand.
> You will START to learn and understand the circuits and will probably find the issue without possibly being shocked.


No, it is intermittent and seems (seat of the pants) to follow load.

In reply to sd, I am fairly familiar with circuits and am "comfortable" working with live circuits.  I am just not all that familiar with control circuits.


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## Eremius (Jul 22, 2021)

Bi11Hudson said:


> I have looked over the posts from the git-go, I couldn't find for sure where I got the impression. So I ask point blank if the machine is being run from single phase power. I see the photos of the motor, three phase. If so, it is quite possible that control power is being drawn from the "synthetic" third phase. Whether using a Rotary Phase Converter, a capacitor bank, or a VFD really doesn't matter. If one side of the control power is coming from that synthetic third phase, it will be, at best, unstable at the start. It will smooth out some as the motor comes up to speed, but still not as it should be. Follow that through and make sure that control power is from the two leads where power is solid under all circumstances.
> The coil of the starter is in *bad* shape. It should be replaced, whatever the circumstances. If I were at work (been a while) the entire starter would be changed out. Having only two overload heaters dates the starter from long ago. They have had three for as long as I can remember. For machine tools, the third is superflous but is the norm today. It might be more cost effective to find a Chinese made starter rather than trying for a coil and two heaters.
> 
> The "insight" came from sleeping on the problem. Having been out of the electrical field for ten years plus, my mind is not what it once was. But look into where control power comes from, make sure it is from the line, not the third, synthetic line.
> ...


I have an RPC.  The transformer is not connected to the generated leg.


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## projectnut (Jul 22, 2021)

The controls, or at least the coil looks to be Allen Bradley.  Hopefully you have a complete circuit diagram with a parts list.  If not you can download them from the Allen Bradley website.  Heaters and coils of this vintage are plentiful and cheap on eBay.  Depending on the model coil you have they are available in the $10.00 to $20.00 range.  There are also several contactors available in the same price range. Heaters (overloads)  are in the $3.00 to $.500 range.  

I have several machines with similar controls.  It's far cheaper and far less labor to replace the faulty parts than convert to newer style controls.  If you're considering repairing the current controls this is an excellent time to buy the needed parts, and maybe even a few spares.  My machines with AB controls date from 1955 to 1982.  They all have the original components except for the coils and heaters that had to be changed on the machines originally wired for 440V.

I have one lathe with Furnas controls.  They are far more expensive than Allen Bradley.  The contactors on this machine are getting worn.  Rather than try to find replacement parts for this system I purchased a complete NOS panel with reversing starters, coils, heaters, etc., etc. for less than $100.00.  When/if the time comes to make the change I should be able to replace the entire unit in an afternoon.  The best part is I'll be able to use the original controls, including the gear motor that allows infinite changes of spindle speed.


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## sdelivery (Jul 23, 2021)

Eremius said:


> No, it is intermittent and seems (seat of the pants) to follow load.
> 
> In reply to sd, I am fairly familiar with circuits and am "comfortable" working with live circuits.  I am just not all that familiar with control circuits.


So the intention isn't to offend anyone but, OSHA pretty much made virtually all working on live circuits a violation about 15 years ago and that was in a trained professional environment.
Do people still do it? Sure, that doesn't make it a good idea.
Not having worked with a person I don't know their skill level, I rarely advise working on live circuits.
When the OSHA rulings came about I worked on  virtually every thing live but the company would not allow that so I realized I could do alot of troubleshooting with the circuits deenergized. 
No disrespect to the poster but after 30 years of working with people who said they knew or understood your post shows you don't.  Again I mean no disrespect this is from decades of experience that I say this.
I  believe you can and will learn this and more but I would prefer it would be without incident.
Obviously the latch circuit is you issue just for the fun of it deenergize the panel and use your ohm meter after some basic test with the ohm meter use a pigtail to energize just the contactor with the wires that were on the coil removed try that ohm meter between the off PB and the latch circuit intersection to the coil through the contacts on the motor starter. 
A test of the motor starter coil will give you a value in ohms.
the circuit if good should be very close to that ohm reading if not you can safely touch, wiggle , remove and reattach the wires in the latch circuit until you find the issues.


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## rabler (Jul 23, 2021)

If it was me I'd just replace the contactor, overload heater, switches, and transformer.   Rewire the whole thing in the process.  You have old heat damaged components, corroded terminals, and jumpered heaters.  It'll cost you a bit of money, but if you have some feel for electronics it is relatively easy.

So the only question is with two motors ... do both motors run at the same time?  Or is the photos shown of only one motor's control circuitry?   *Ideally* the two motors would each have their own overload heater, set for their Full Load Amps (FLA) rating.   If both motors run at the same time, you can use one 4 pole contactor rated at combined load, then split the power after the contactor through separate overloads to each motor.  The control circuit becomes  x----Stop----Run-----OL1-----OL2-----contactor coil-------x
Where x is the two 120v outputs of the transformer,
Stop is just the stop switch
OL1 is the switch contacts on the overload heater to motor 1
OL2 is the switch contacts on the overload heater to motor 2
Run is a little trickier, it is

   --RS--
   |         |
--|         |----
   |         |
   --C4--


Basically the run switch (RS) in parallel with the 4th set of contacts on the contactor (C4).

Hopefully in this case C4 doesn't correspond to explosives  

Ah well, the html processor eats my spaces on the RS/C4 diagram.  Apparently the [PRE] tag doesn't work here. Grr.


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## Eremius (Jul 31, 2021)

rabler said:


> If it was me I'd just replace the contactor, overload heater, switches, and transformer.   Rewire the whole thing in the process.  You have old heat damaged components, corroded terminals, and jumpered heaters.  It'll cost you a bit of money, but if you have some feel for electronics it is relatively easy.
> 
> So the only question is with two motors ... do both motors run at the same time?  Or is the photos shown of only one motor's control circuitry?   *Ideally* the two motors would each have their own overload heater, set for their Full Load Amps (FLA) rating.   If both motors run at the same time, you can use one 4 pole contactor rated at combined load, then split the power after the contactor through separate overloads to each motor.  The control circuit becomes  x----Stop----Run-----OL1-----OL2-----contactor coil-------x
> Where x is the two 120v outputs of the transformer,
> ...


I am leaning toward just replacing everything as it has been hacked on for who knows how long and I believe all the protections have been taken out.

I will probably salvage the transformer as I *just* put it in.

Yes, both motors usually run at the same time.  The upper motor should be powered from the main circuit as it shouldn't ever be able to run without the whole mill being powered on.  It runs only the vertical spindle.  The main motor powers the hydraulics of the mill (travel, lubrication, etc).   The photos are only showing the primary control circuitry.

The secondary motor has it's own switching and contactor but, like the primary, it has been jumpered out.  It uses a 2P2T switch to control forward and reverse on the spindle.


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## Eremius (Aug 10, 2021)

Whee.  So it's been a fun couple of weeks.  I've been busy changing jobs so, yeah, I've been distracted.

In any case...

So here is what I *think* I will need:

1x main contactor
1x auxiliary contactor
1x three pole breaker (15A)

I am planning on going all DIN rail stuff.

I will be reusing the transformer I have as it was replaced less than a year ago.

The motors are both 3HP (images in another post).

What am I not thinking about?


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## Eremius (Aug 10, 2021)

Ok, so doing a little more reading, I will want that contactor to have an auxiliary contactor that will be for the motor control circuit.

I *think* this list covers everything except possibly an overload relay. Suggestions?

Am I missing anything here on the lower controls?


If I am getting close on this I should probably start talking about the upper controls.  The upper motor controller uses a 2P2T switch for forward and reverse.  I don't have any clue what I need for a controller here.


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## rabler (Aug 11, 2021)

Generally, you use a 4 pole contactor.  The 4th pole is connected in parallel with a momentary contact normally open "run" switch.  This acts as a safety feature, if the power dies, the contactor opens and turns it off.    There are other ways to wire it but that is how your original was done.  This should allow you to keep your front end switches and wire things up very close to one-for-one.  Your stop switch is a momentary contact normally closed.

You don't need a breaker, that is covered by your wall panel.   You do need the overload, and probably want to order them at the same time as the contactor since the overload is typically an accessory, so you need to match brands.


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## rabler (Aug 11, 2021)

Eremius said:


> Ok, so doing a little more reading, I will want that contactor to have an auxiliary contactor that will be for the motor control circuit.


My post of a few minutes ago was looking at your schematic and post #32. You have got the right idea.  Typically vendors will just sell that as a 4 pole contactor.  There are such things as 3 pole contactors with (accessory) auxiliary contacts, but l believe the 4 pole contactor will be cheaper.

I may miss your posts depending on how busy I am in any given time period.  Don't be afraid to message me directly if you need help.


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## sdelivery (Aug 11, 2021)

The above post are pretty accurate except for install a main breaker in your panel.
The circuit breaker in your house or garage is meant for the wiring not for any attached load.
Additional breaker for control voltage from the transformer secondary output is highly recommended. 
I typically buy all the above components from either Automation Direct, marshall Wolf, 
Circuit breakers are inexpensive and can be a life saver.


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## Eremius (Aug 12, 2021)

sdelivery said:


> The above post are pretty accurate except for install a main breaker in your panel.
> The circuit breaker in your house or garage is meant for the wiring not for any attached load.
> Additional breaker for control voltage from the transformer secondary output is highly recommended.
> I typically buy all the above components from either Automation Direct, marshall Wolf,
> Circuit breakers are inexpensive and can be a life saver.


There is a 20A 3-pole breaker specified on that list for just that purpose.


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## rabler (Aug 12, 2021)

sdelivery said:


> The above post are pretty accurate except for install a main breaker in your panel.
> The circuit breaker in your house or garage is meant for the wiring not for any attached load.
> Additional breaker for control voltage from the transformer secondary output is highly recommended.
> I typically buy all the above components from either Automation Direct, marshall Wolf,
> Circuit breakers are inexpensive and can be a life saver.


I don't think they are required even by modern safety standards, such as UL.   Since the wiring is in a metal cabinet is it really even a safety issue?   (honest question, what safety issue does it address) 

It can't hurt other than a very small cost.  My understanding is you put fuses/breakers in an appliance when you're trying to protect internal components from damage.  Which for example is what overload/heaters do for the motor.  But when the cost of the components (such as a transformer) are on par with the cost of the breaker, it seems like diminishing returns.

That said, do whatever makes you feel safe.  I certainly don't want any liability!!!


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## Papa Charlie (Aug 12, 2021)

Regardless of the location, the breaker is to protect you from shock should the wire, switch or system short out. Once it hits that panel, everything that has continuity to the box is subject to voltage.


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## sdelivery (Aug 12, 2021)

UL isn't involved with machine tool certification. UL certification requires a manufacturer to provide a sample product for testing.
Circuit breakers in homes and businesses are sized based on the conductors ampacity.  They are there to protect the wiring during an over current situation. This is per the National Electric Code.
Circuit breakers in machine tools are there for that purpose as well.
An overcurrent condition can melt wires (perhaps energizing the machine cabinet or more) but primarily to protect from a melt down that could start a fire.
I have seen and repaired the first condition and I have seen the result of the second. They scrapped the machine.
An average single pole Circuit breaker for a control Circuit up to 10 amps is between 7.00 and 15.00 dollars, depending on the size of the control transformer I would guess a small one to be about 75.00 to 100.00.
The cost of a fire?


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## sdelivery (Aug 12, 2021)

Oh and as far as modern conditions, open the panel up on any industrial machine tool and you will find circuit breakers and on many of the I/O cards you can find micro fuses.
When a company produces an inexpensive machine tool or any thing else they reduce the number of circuit breakers they also reduce the wire size and quality.
The only way to bring the price down to the level consumers are willing to pay and still make the profit their investors want is to reduce costs. In a perfect world we wouldn't even need circuit protection.......


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