hxdbzxy/iStock/Thinkstock
Ecmweb 6944 Floorfan
Ecmweb 6944 Floorfan
Ecmweb 6944 Floorfan
Ecmweb 6944 Floorfan
Ecmweb 6944 Floorfan

Electrical Troubleshooting Quiz - Dec. 23, 2014

Dec. 23, 2014
Why are the overloads blowing?

The plant engineer asked you to walk out to the small MCC near the plant’s paper making machine. There, he pointed to an open cubicle with a floor fan blowing into it.

“That’s the motor starter for the main drive motor under the machine. The operators put that fan there to keep the overloads from blowing. I want you to put a lock on that door and figure out why the overloads blow.”

 Where do you start?

After you put a lock on that door, you need to find out why the motor is drawing enough additional current to open the heater strips. The application (paper, which means particulates) and location (under the machine) are two big clues.

If it’s an open drip proof (OPP) case motor, replacing it with the correct Totally Enclosed Fan Cooled (TEFC) motor may solve the problem.  But is there a washdown procedure with this machine? If so, specify a Totally Enclosed Washdown (TEW) motor.

If the motor is already a TEFC or TEW, maybe accumulated paper is insulating it (a hotter motor draws more current). Or maybe particles accumulating in the machine have increased the effective load; the plant engineer needs to investigate that issue.

Voice your opinion!

To join the conversation, and become an exclusive member of EC&M, create an account today!

Sponsored Recommendations

Fiberglass Electrical Conduit Chemical Resistance Chart

This information is provided solely as a guide since it is impossible to anticipate all individual site conditions. For specific applications which are not covered in this guide...

Champion Strut Catalog

Champion Fiberglass is the most advanced manufacturing facility of fiberglass conduit, fiberglass bridge drain and fiberglass strut systems in the world. Its well-trained and ...

Considerations for Direct Burial Conduit

Installation type plays a key role in the type of conduit selected for electrical systems in industrial construction projects. Above ground, below ground, direct buried, encased...

How to Calculate Labor Costs

Most important to accurately estimating labor costs is knowing the approximate hours required for project completion. Learn how to calculate electrical labor cost.