Heaters for 10hp motor keep tripping 1

[VOLTZNAMPZ]

The starter relay for a 3 phase 230v/23.4FLA /10 hp motor continues to trip.The heaters are type W61.The starter relay is a Allen-Bradley model 509 COA. The heaters trip while under load and with the load uncoupled. What could bring about this condition ?

 

[dpc]

Check the motor amps with a clamp-on. Verify the heater amp rating.

If the motor amps are OK and heaters are sized correctly, check for loose connection or other heat source around the overload relay in the starter.

Are you sure it is the overload relay tripping and not the breaker?

If tripping continues and no cause can be found, replace the overload relay.

David Castor

http://www.cvoes.com

 

[VOLTZNAMPZ]

It's the starter relay for sure. With the load uncoupled I got readins of 0.1a/0.3a/0.1a on all 3 phases. That's normal but, the starter still tripped.

 

[dpc]

I'd replace the overload relay.

David Castor

http://www.cvoes.com

 

[jraef]

The A-B type W heater elements are eutectic melting alloy type and the solder pot is built into the replaceable element. If it has tripped over and over and over, the case holding the solder can get damaged and some of the solder can leak out, rendering the heater unable to hold in. Did you try just replacing the heater elements?


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
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[ccjersey]

Maybe I'm wrong, but I believe there's something wrong with your ammeter. No load amperage should be higher than 0.1, 0.3, 0.1! I would check again with another instrument or at a different point on the motor leads.

 

[jraef]

Good point, shouldn't be any less than 20% FLC, so around 5A or more.


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> faq731-376

 

[waross]

I agree with jraef and ccjersey. Replace the heaters and check your meter.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[lectricwes]

look... I'm just a maintenance electrician.... it's been my experience that 80% of all breakdowns are caused and cured by the simplest fixes.

Change the overload block and the heaters.

If you are a jobber or an independent, and this is prohibitively expensive, then jumper the NO on the OL blockjust long enough to see if it will run.

The OL relays do sometimes wear out, especially if you have production workers who know how to reset and rerun.

 

[lectricwes]

In my previous post I said to jumper the NO contacts on the MOLs. Everyone knows that MOL contacts are NC. My mistake, My first post. Sorry.
Sincerely,
lectricwes

 

[waross]

A slight correction. Replace your melting alloy units. In Square D units these are part of the heaters. With Allen Bradley you may keep the heaters but must change the overload relay to replace the alloy units.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[jraef]

Bill,
That was true with the old "N type" heater elements, but when they (A-B) went to the W type they moved the solder pot onto the element so that you are replacing it when you replace the element.

lectricwes,
I'd be careful about suggesting that anyone "jumper out" a protective element like that. I assume you meant it to be a temporary situation of course, but a lot of people read things like that and take it to mean it must not be a big deal. it is.


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> faq731-376

 

[waross]

Thanks for the info, Jeff.
Yours
Bill

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[lectricwes]

jraef,

I should have added that jumping motor overloads is never a fix, and should be used only as a troubleshooting tool.