Can't Reset Motor Overload Relay/Starter

We have a large 20HP grinder motor (3 ph, 480V). Has run flawlessly for last year or so, after changing out 2 of 3 heater elements. Yesterday, while running, the overload unit tripped out. We changed out the one heater element we didn't change out last year, and the motor started up and ran fine. This morning, the motor wouldn't start. Reset the overload unit (AB 509-COD -- Allen Bradley 59 Cod 12V AC 25HP 45A Amp Size 2 Motor Starter D521332 | eBay -- best I could do -- can't get photo to upload), tried to start, and tripped off again. Now, we can't even get the overload unit to reset (when pushing the white button).

Looked at the ratchets on the heaters, and they look fine.

Any ideas?

When you push the reset button, can you see the dogs engaging the ratchet teeth and holding? If they are holding then I would suspect the relay contacts. In fact, with that style of OL, you should be able to push in the reset button and hold it...the contacts should close. On the other hand, I don't know if AB has one that closes the contacts only after releasing the reset button.

Tom

Remove and examine all three heaters.

Thanks for replies.

Tom, when the heaters are installed, we can't see behind them at all. I will retry with the one heater we have that doesn't have a plastic case on it, and see if we can see anything re: engagement.

Ron, am attaching picture of the heaters. Have tried various combinations, but can't get reset to "stick", which I assume would be all three of the brass contacts engaging with the heater ratchets. I tried turning each of the ratchets by hand (to see if eutectic material has failed), but can't turn any of them using hard hand/finger pressure.

I have three more heaters in the mail, and will try those when they come.

The other picture I have attached is of the overload element, with the white reset button. When we push the reset button, it clears the white/yellowish "tripped" indicator, but then when we release the reset, the spring just pushes the button back and the tripped indicator is "lit", indicating that the spring contacts have not stayed engaged with the heater.

Sounds like the ratchet arms are not engaging the ratchet wheels. When you push the reset button down, do the contacts close?

Tom

Tom,

Thanks for your analysis. I went back and tried a few configurations of the heaters, and yes, with both styles (plastic case and plain metal), you can see whether the contacts contact the ratchets. I have isolated the T2/middle contact as being the issue, as when you press the reset button, the other two contacts/ratchets engage.

There appears to be some damage to the contact area of T2 (see photo). Not completely sure, but it appears that we may have been running the grinder with the heater put in the wrong way on T2. There was the metal heater in that slot (no plastic case, and it may have been inserted the wrong way. I guess that is one benefit of the plastic type of heater -- totally idiot proof.

The damage to the back of T2 seems to be incidental (when I move the contacts with the reset button, it appears to move the same as T1 and T2, and the contact shape and surface appear to be substantially similar. Nevertheless, it is not engaging. So, I am getting a used relay sent to me, and will swap it out. I hope this solves the issue.

I am, with some fiddling, able to get the middle contact to engage. Can we temporarily run the motor this way, or are we risking any damage by doing so (assuming it runs without immediately tripping again.)?

Two additional questions, as long as I have the ear of a few experts:

1. There is a button on the right side of the relay (to the right of the heaters) that says "To Test Circuit / Press". What does this do? How does one utilize this to test the circuit?

2. One of the main stranded hot wires coming into the starter has scoring on the outside copper strands, where someone was stripping the outer sheath and cut through a portion of the copper strands. Is this a situation that could be affecting the current through this leg? Should I cut this back, or leave it be, as motor has been operating for 5+ years this way?

The "test circuit" button temporarily closes the OL contacts. Pushing that should start the machine, but will stop when you release it. The nicking of the wire will not affect anything, so long as it doesn't mechanically effect the strength of the wire. If you can get the middle heater to engage the ratchet, go ahead and use it.

Tom

TDegenhart said:

Sounds like the ratchet arms are not engaging the ratchet wheels. When you push the reset button down, do the contacts close?

Tom

Click to expand...

Just FYI, it has been ILLEGAL for anyone to manufacture an OL relay that will do this for at least 25 years. ALL overload relays must be what is called "trip-free" meaning you CANNOT hold down the Reset button to override the trip function.

Heater elements don't "wear out", they do their job. Those heater elements are a eutectic melting alloy type, noted for being the MOST reliable type available (before Solid State came into being), because you literally cannot change the chemical composition of the metals inside.

Palak,
There is no "forward or backward" in installing a heater element. Here's what has happened to you though. There are not two TYPES of OL heater element that work for that 509 series of starter, there is only ONE, the type W heaters. There was an OLDER version of that starter, the 709 Series, that used a DIFFERENT type of heater element, the Type N. You CANNOT use a Type N heater in a 509 starter and vice versa.

In the Type W, the heater element, solder pot and pawl of the ratchet is part of the replaceable unit, only the moving part of the ratchet mechanism and contacts are in the relay. In the old type N version, the solder pot was in the RELAY, only the heater element that goes around it was replaced. So if you put a Type N heater into a 592 OL relay for a 509 starter, it would not have the solder pot or pawl of the mechanism and would NEVER have anything to close against.

Replacing OL heater elements is NEVER the problem with a motor starter that is tripping, they are NOT like fuses, they are SENSORS and as I said, they do NOT wear out or burn (unless everything else burns too). If the OL relay is tripping, it is DOING ITS JOB because the motor is overloading. Changing the elements never fixes the problem. Some people "fix" it by putting in larger heater elements, but if they were properly sized to begin with, all you are doing is accelerating the motor winding insulation failure.

As I mentioned in my reply, I didn't know if this particular relay was made before or after the "trip free" requirements. I worked at GE and only had a little information on the variations that AB, SqD and CH had. One of the requirements that was instituted in the GE 300 line was a trip free OL. That was about 1980. And yes, I have seen defective solder pots, ones that were damaged, not made right or whatever. Some of them wouldn't reset, some that wouldn't trip. So please do not use the word NEVER. If its made by man, it can and will fail.

"Heater elements don't "wear out", they do their job. Those heater elements are a eutectic melting alloy type, noted for being the MOST reliable type available (before Solid State came into being), because you literally cannot change the chemical composition of the metals inside."

Can I guess that you either work for or sell companies that only have solder pot relays? If they are the most reliable, why has the world gone to bimetal?

Tom

One thing I do not think I saw..... Has anyone looked at the motor to see if it has a problem? Measured resistance? Checked wiring? Checked for something that might overload the motor itself?

I totally agree, if the overload unit says its overloading, then its nearly certain to be overloading.... they are pretty reliable that way.

That said, if the overload will no longer reset, and nothing is connected to it, then it would seem to be defective.

Overloads are not like fuses, they react like the motor, to shorter term larger overloads, or to longer term low level overloading, and have a delayed response to a sudden overload or short circuit. That's what fuses etc are for.

Then also, "will not reset" could be mechanical, or electrical. Sounds mechanical, as if some physical thing in the overload itself is not working, that it will not mechanically reset. But the overload is often in series with a contactor coil power, so if it fails to "make" that connection, the contactor would not close, and the overload could be said to "not reset".


As for bimetal vs pot types....

Many things are done for cost reasons.....the solder pot type may be significantly more expensive, while the cheaper bimetal still meet the technical letter of the requirements.

The solder WILL melt at the temp it is set up to melt at. It's a physical property that can be easily checked for an entire batch, subject only to any variation due to the degree of mixing.

The bimetal probably will operate at the temp it is supposed to. They can be sample tested, but each one is an individual part with variations. Even in a controlled process, there can be outliers.

TDegenhart said:

I have seen defective solder pots, ones that were damaged, not made right or whatever. Some of them wouldn't reset, some that wouldn't trip. So please do not use the word NEVER. If its made by man, it can and will fail.

"Heater elements don't "wear out", they do their job. Those heater elements are a eutectic melting alloy type, noted for being the MOST reliable type available (before Solid State came into being), because you literally cannot change the chemical composition of the metals inside."

Can I guess that you either work for or sell companies that only have solder pot relays? If they are the most reliable, why has the world gone to bimetal?

Tom

Click to expand...

Bi-Metal is the norm because of cost, not necessarily because it's better, that's why we like em made in China and other low wage countries right?. GE adopted this early on because of cost.

Disclaimer; I used them all, and never worked for an OEM

I've seen eutectic alloy heaters that were bad from AB and SqD, most were damaged from repeated overcurrent and some were defective from OEM. Doesn't mean their inferior. There are plenty of damaged bi-metal relays out there too, also usually do to repeated abuse.

Most users just replace the fuses and push the reset button, until that no longer works, which is where I think the OP is now. This repeated abuse usually ends up on the motor re-winder's bench, only to go home and repeat the cycle. When the cost and downtime becomes significant enough, then the customer is willing to investigate the real issue at fault, seen it many times before.

SAF Ω

Palak said:

1. There is a button on the right side of the relay (to the right of the heaters) that says "To Test Circuit / Press". What does this do? How does one utilize this to test the circuit?

2. One of the main stranded hot wires coming into the starter has scoring on the outside copper strands, where someone was stripping the outer sheath and cut through a portion of the copper strands. Is this a situation that could be affecting the current through this leg? Should I cut this back, or leave it be, as motorView attachment 167064 has been operating for 5+ years this way?

Click to expand...

Testing the overload by pressing the "Test" causes the overload to trip out. It confirms that the NC overload contact is working, and that it can disengage the starter.

Re terminating the nicked supply lead couldn't hurt. Nicked wire never helps.

SAF Ω

TDegenhart said:

As I mentioned in my reply, I didn't know if this particular relay was made before or after the "trip free" requirements. I worked at GE and only had a little information on the variations that AB, SqD and CH had. One of the requirements that was instituted in the GE 300 line was a trip free OL. That was about 1980. And yes, I have seen defective solder pots, ones that were damaged, not made right or whatever. Some of them wouldn't reset, some that wouldn't trip. So please do not use the word NEVER. If its made by man, it can and will fail.

"Heater elements don't "wear out", they do their job. Those heater elements are a eutectic melting alloy type, noted for being the MOST reliable type available (before Solid State came into being), because you literally cannot change the chemical composition of the metals inside."

Can I guess that you either work for or sell companies that only have solder pot relays? If they are the most reliable, why has the world gone to bimetal?

Tom

Click to expand...

The "world" is going to solid state actually, much more reliable and repeatable now, plus it offers real single phasing protection.

Bimetal has always been used because it is cheaper, not better. But basic bimetal OLs cannot be used behind VFDs, they are calibrated to 50/60Hz only. Only eutectic alloy OL heaters are insensitive to frequency variations, up to 400Hz. But upcoming changes are forcing mfrs to scramble to come up with a reasonable alternative for use behind VFDs.

Melting alloy overloads will be obsolete by this time next year if you didn't know. The solder has lead and other heavy metals in it, including trace amounts of mercury to attain that specific melting temperature. There are new international rules called "RoHS" (Reduction of Hazardous Substances, unaffectionately pronounced "Rohas") that are requiring that all mfrs of eutectic alloy OL heaters cease shipping them by Jan 1, 2017.

RoHS by the way is going to cause a lot of unpopular changes in the electrical industry from here on out. We (North America) were given 20 years to adapt to the coming changes, which went largely ignored by American mfrs until the bitter end, which is this coming July to stop manufacturing them and Jan. 1 to cease shipments. You will see numerous products redesigned or phased out and no longer available (except as surplus) because of it. No more FRP (Fiberglass Reinforced Plastic) for example will be forcing the obsolescence of most non-residential circuit breakers and other devices that use it, contacts can no longer contain any heavy metals in their alloys, ie cadmium used to make siver more durable, etc. etc. Every part of every electrical product must now be 100% recyclable from here on out.

Anyone who has been shipping product into CE countries has long ago adapted to RoHS. Should not be an issue for the majority, although there are always holdouts. So long ago that I had to think about when that was adopted and became law in the EU.

The biggest issue has always been the poor quality and 3 year life of any consumer product that has no-lead solder in it. Solders have been improved, but I have personally seen the early failure of solder take out very expensive devices.

Apropos of that, there are RoHS compliant solders of nearly any melting point you can imagine, so the issue of solder pot overloads SHOULD not BE an issue for anyone with a metallurgy lab or a decent alloy vendor. Other reasons may be in play, but that one should not be.

yes, but the final nail in the coffin is that they are not 100% recyclable.

I wasn't able to see those photos before because they were blocked by whatever server I was on at the time. Now that I see them, the "metal" one is just the same Type W heater that has had the plastic broken off, they are not sold that way and are not supposed to be used without the plastic cover, because it affects the heat rise inside of them. That is the solder pot and pawl that you are looking at and from the discoloration, it appears to me that it got extremely hot, possibly hot enough to have melted out the solder into the relay itself and that might be what is interfering with the operation. Put one of the other two heater elements into that slot and see if it resets and holds. If not, you will have to replace the entire relay.

What do you mean by 100% recycleable? Thermoset materials cannot be recycled.

Tom

I just mean recyclable as defined in the RoHS rules, I have no idea what the details are about it. I originally got into this when a lot of older circuit breaker designs started disappearing and the replacements were built completely differently from what I was used to. That's when I discovered this rule change and the myriad ways it was going to affect us all (in the electrical equipment industry anyway).

It's not me, it's them!

If, in fact melting alloy OL's are going away, this is just an academic question. Why do you say that solder pots are usable to 400Hz and bimetals are not? They are both essentially straight resistances. Second, bimetals offer adjustability, ambient compensation, quick trip, automatic reset and differential trip for phase unbalance. Solder pots have none of these. Solder pots are not immune to change in alloy and therefore melting point due to solid state diffusion of the elements (copper, zinc, tin) and what else is in the stem of the solder pot. Bimetals will do this too, due to aging and shrinking of the ol body.

When it is all said and done, neither is a perfect replica of the motor thermal characteristics, nor is any other ol.

Tom