MakingAComeback
Electrical
- Aug 22, 2005
- 23
Recently at one of our sister plants an employee was burned when an arc occurred as he was inserting the fuses for a DC motor operated valve. What caused the arc is still under investigation.
However one of the persons who is involved with the investigation issued a proclamation which blamed the employee for putting his other hand in harm's way by depressing the reset button on the thermal overload device while he was inserting the fuses. This practice is widespread and has been followed for decades at our plant and evidently at other plants as well. The philosphy is that pushing the TO reset prevents an inadvertent start of the equipment while its power fuses are being inserted.
The investigator proclaimed that pushing the reset button was a totally wasted effort because the "49" contact on eutectic TOs does absolutely nothing when the reset is pushed unless there has been an actual overload event beforehand.
Well, well. We double checked the equivalent equipment at our plant and found that the "49" contact does indeed open when the reset button is pushed, so obviously the blanket statement that was issued is not quite on the mark. By the way it should be noted that the TO in question is vintage to put it kindly (once made by Cutler Hammer but no longer).
For those of you out there who have experience with the various thermal overloads that have been manufactured over the years how many of them do nothing at all when the reset is pushed, and how many of them behave like ours? Does it matter if the TO is eutectic or bimetal? Is there any consistency amongst the many makers of these things?
However one of the persons who is involved with the investigation issued a proclamation which blamed the employee for putting his other hand in harm's way by depressing the reset button on the thermal overload device while he was inserting the fuses. This practice is widespread and has been followed for decades at our plant and evidently at other plants as well. The philosphy is that pushing the TO reset prevents an inadvertent start of the equipment while its power fuses are being inserted.
The investigator proclaimed that pushing the reset button was a totally wasted effort because the "49" contact on eutectic TOs does absolutely nothing when the reset is pushed unless there has been an actual overload event beforehand.
Well, well. We double checked the equivalent equipment at our plant and found that the "49" contact does indeed open when the reset button is pushed, so obviously the blanket statement that was issued is not quite on the mark. By the way it should be noted that the TO in question is vintage to put it kindly (once made by Cutler Hammer but no longer).
For those of you out there who have experience with the various thermal overloads that have been manufactured over the years how many of them do nothing at all when the reset is pushed, and how many of them behave like ours? Does it matter if the TO is eutectic or bimetal? Is there any consistency amongst the many makers of these things?
