Single phase motor wired to 3 phase overload

I typically do it like this diagram shows:
https://ckm-content.se.com/ckmConte...ver?id=0151H0000088Z2aQAE&oid=00DA0000000abSm

Certainly for a Thermal Overload it makes no difference electrically, thermal overloads have heaters inside that try to mimic the heating going on inside the motor. Heaters don't care which way electricity is moving.

But from a logical wiring point of view it is more doubtful, cabling goes in to Ls and out of Ts. Personally, as an old school engineer, I would consider it a lazy way of doing it. If all the rest of the wiring runs in at the top and out at the bottom, logic says to do the same. Someone fault finding in the future and without the drawings, won't thank you.

But but, from an environmental position, it saves on copper, so it is a good thing, though I would add labels to the Overload exchanging an L and a T.

BryanG said:

Certainly for a Thermal Overload it makes no difference electrically, thermal overloads have heaters inside that try to mimic the heating going on inside the motor. Heaters don't care which way electricity is moving.

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Actually it makes a difference for the overload relay.
The thermal overloads are constructed in such a way that the tripping point is different if the current is equal in all phases or different in some of the phases.
Gil47 explained it in post #15 (http://www.plctalk.net/qanda/showpost.php?p=288933&postcount=15).
It is called "differential tripping".
Because of that, for single-phase or 2-phase motors, it is customary to loop one phase twice through the overload.

Btw. the thread is from 2008 !

The original thread was 2008, Jeff23spl revived it yesterday with a different question, my answer is to his question. I stand by my answer sir, and challenge you to a duel

BryanG said:

I stand by my answer sir, and challenge you to a duel

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I yield to your fine argumentation (not because I am a chicken).

What a laugh, as a nearly dead sales rep and sparky, just ask the manufacture which way to wire it, it is pretty basic and you don't need to be an engineer or any duelling (or l could answer correctly). On top of that use common sense which seems to be getting hard to find even in this forum. Or ask Drbits, even with out practical experience he can tell you the correct answer, go DrB.
In all honesty this forum is becoming a laugh. Its an answers for lazy students, or a show off between Drb and Peter which Dr is winning, but Peter of course actually knows what he is talking about, Drb is purely academic but of course very brainy ( how about l acknowledge it, he is easiest the brainiest PLC person here, if not the world, all this is in a very short time, doubley makes us all feel stupid) has nothing better to do apart from show how intelligent he is, which of course he is big time.
I believe has been challenged by his brother the plc expert " and has proven he is within minutes has the handle of PLC's, which of course he has, because he makes everyone here, particularly the long timers ( polite term for the legends) make them look stupid and argumentative and don't even answer here very often and normally to only disagree with Drb.
So Drbit, you have proved your intellect to your brother and if he knows more than you, he must be very proud but he isn't on this site answering school questions, between you and parky all the answer to question for inept too be engineers.
Of course l have to own up to not having your IQ and have learnt it the hard way (but lm not at your level, at least not in the typing) and am not willing to pass it on to someone on the internet.

It saddens me that between you and Parky, you can't even wait for the complete questions before you are giving your complete codes for the F%^^&* wits, you dont even know which PLC's it maybe, so you give different options.
I apologise if l am the only one that thinks this, but look at the posts, you are giving answers with out the OP's putting in any effort.
Stop racing to supply the complete answer and go back to how/why this forum started'
Show your work and then help.
STOP trying to show how smart you are, we all know you are super intelligent, but what you aren't doing is helping the OP's to learn. Between you and Parky, trying to beat each other to the post, let the OP's post something!
Ok l could be totally wrong, l imagine l will find out shortly.
You both have the ery high competences in PLC's, how about letting the Ops have some time between posts to think, think, rethink, write some code then give them some help, not try and beat each other with the answer.
Cheers Kevin

PLCnovice61 said:

What a laugh, ...
Cheers Kevin

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Wow, good point. Thanks for the advice.

And @Peter and @parky especially, along with many many others, here know far more and are far smarter than me; I only know how to code, count, and challenge (my) assumptions.

PLCnovice61, I don't know if you are having a bad day, or if you have been getting worked up over this for a while, I do know that your way of expressing yourself does you and the rest of the forum no favours. Anger just causes anger, look around the world and see what effect that has by polarising societies. Discussions can only work if you have respect for the other side, be prepared to listen, be prepared to learn and be prepared to change you thoughts and ideas.

So, take a breath, and maybe start a thread about how you would like things to be on the forum.
Don't post angry.

Marc said:

Thanks for the replies,


What about the addage that you should never break the neutral? I only ask because someone else mentioned this as a no no and that the line should loop through all three and the neutral should be unswitched.

Not trying to be a pain, just looking for a better understanding.

Marc

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Wiring a neutral through an overload relay heater coil does not "break the neutral". When an overload relay trips, it doesn't open the heater coil circuits. Instead it drops out the upstream contactor via operation of an auxiliary contact.

In a typical 3 phase motor starter, the contactor is dropped out by breaking the starter coil's neutral through the OL relay's auxiliary contact. So, "breaking the neutral" is the norm for OL relay operation, although it is the control power neutral that is broken. The heater coils themselves never open due to an overload condition.

Bit Bucket has it correct. The idea that the overload heaters open on an overload condition seems to be a common error in thinking. This is a drawing that I use in my classes to show the relationship of the heaters to the coil circuit.

jaden said:

Bit Bucket has it correct. The idea that the overload heaters open on an overload condition seems to be a common error in thinking. This is a drawing that I use in my classes to show the relationship of the heaters to the coil circuit.

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Yes, had to deal with this recently on a few pumping station control panels. The panel builder was under the impression that the O/L heater elements actually opened like contacts and broke the power to the pumps, but they don't so we had to modify the wiring to put the N.C. O/L relay contacts in series with the coil.

i think in the past there was some old heater one time use that was opening like a fuse.
But these days overload i did see wasn't opening the power line but give a contact to get the contactor coil to open.
I remember 20 years ago that i had to bring an overload to an old thrusted teacher because he wasn't believing me about the fact it is not opening the power lines. And later i went to troobleshoot an old softstarter that was using a separated overload but the SST shorted and everything melted instead of tripping because there was just the short circuit protection remaining to open the circuit...

Some can get confused by manual starters that combine overload and supplementary short circuit protection and these ones will open the power line in case of ol or short...

PLCnovice61 said:

What a laugh, as a nearly dead sales rep and sparky, just ask the manufacture which way to wire it, it is pretty basic and you don't need to be an engineer or any duelling (or l could answer correctly)....

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ok...well i wasn,t looking to make an emotional debate....and i'm not either a lazzy student lookng for a single projet answer. i was looking to get other user opinions in general regarding a larger quantity of brand of components and especially, ''why'' they would choose a way of wiring it over another...

Maybe some may feel ok with just getting an answer from a person they thrust without any reason behind. (Do it this way because i said so) but like probably many on here, i need to understand.

And Maybe not all salesman are the same but the ones i work with aren't very technically oriented to answer and it doesn,t seem to be unusual...Yes there is service support that should go deeper but with lack of workers, sometimes we reach out someone that cannot help much....



Comming back to my question, i appreciate feedback like BryanG. It gives an opinion and the reason behind....

Bit_Bucket_07 said:

Wiring a neutral through an overload relay heater coil does not "break the neutral". When an overload relay trips, it doesn't open the heater coil circuits. Instead it drops out the upstream contactor via operation of an auxiliary contact.

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letitmotif, Ahhh the terminology gets us again

I'd read this entire thread without realizing that when everyone said overload I was picturing what we call a "manual motor starter" and I'm not even sure that's the right words.