Underwriter Laboratory issued their final report

Late last year I reported to Underwriters Laboratory a problem we had with three heaters.  I’ve have received several phone calls from them and exchanged email a few times since then.  Today I received the final report:

Hello Mr. Huffman,

I have completed my investigation on the subject product and have the following items to report to you.

  • The product was found to operate within in is rated load (1500 W).  Based on this it does not appear that the product was drawing excessive current or overloading the plug.
  • We conducted a temperature test while the unit operated at the maximum setting.  The highest measured temperate on the plug was under 52 degrees C, the unit was operated until thermal stabilization (approximately 1.5 hours).  
  • I measured the plug blades for compliance with applicable requirement, the blades were found to be within permitted tolerance.


  • I dissected the plug and found that the charring does not appear to originate at point where the conductor is crimped to the blade.  The plastic near crimp on the conductor side is lightly discolored but not charred, the plastic on the blade sided of the conductor showed slight signs of charring.  Base on this observation it is not likely that the crimp or electrical connection between the blade or and the crimp is the heat source.  A majority of the charring was near the plug face and reduced as it approaches the crimp.

Base on the information collected through the course of my investigation it appears the heat source is external to the plug.  With this being the case I ask that you examine the receptacle this product was plugged into, do plugs appear to be secure when inserted, or is there some degree of slack or loose connection.  If the receptacle in question is UL Listed let me know and I will opened an investigation on this product.

Please be informed that the investigation has been pursued to completion. However, due to the needs of UL to protect the proprietary nature of the companies it represents, the information released to you may be limited in nature.

I want to thank you for bringing this matter to our attention. I would encourage you to bring to our attention any other situations you may come across in the future, which involve products bearing references to Underwriters Laboratories Inc. Reports from sources outside of Underwriters Laboratories Inc. is a valuable resource utilized to promote public safety and maintain the integrity of our Marks.


John Boyles
Engineering Project Handler
Field Report Department
Phone 360-817-XXXX
Fax 360-817-XXXX

UL now has customer service professionals on hand to handle all your nontechnical matters and deliver fast and efficient service to meet your needs.  They can be reached in the U.S. @ 1-877-ULHELPS (1-877-854-3577) or World-Wide at CustomerService.CAM@us.ul.com.

-- For more information about UL, its Marks, and its services for
EMC, quality registrations and product certifications for global
markets, please access our web sites at http://www.ul.com and
http://www.ulc.ca, or contact your local sales representative. --

********* Internet E-mail Confidentiality Disclaimer **********

This e-mail message may contain privileged or confidential
information. If you are not the intended recipient, you may not
disclose, use, disseminate, distribute, copy or rely upon this
message or attachment in any way. If you received this e-mail
message in error, please return by forwarding the message and
its attachments to the sender.

UL and its affiliates do notaccept liability for any errors,
omissions, corruption or virus in the contents of this message
for any attachments .

I will check the outlets to see if there is any problem with them and if they have been UL approved I will send the information to Mr. Boyles.