hazardous area motors

[steveomalley1956]

on site we have 4 motors (siemens) with the following statement stamped on them,
"motor meets during normal operation the definition in the national electric code (2005)-501-125 (B) for motors to be installed in Class 1 Div 2 areas"

these motors are equipped with Thermistor protection, my question is, does the thermistor protection have to be hooked up to the switchgear to trip, for the motors to comply with code requirements ?

 

[jdsmith]

on site we have 4 motors (siemens) with the following statement stamped on them,
"motor meets during normal operation the definition in the national electric code (2005)-501-125 (B) for motors to be installed in Class 1 Div 2 areas"

these motors are equipped with Thermistor protection, my question is, does the thermistor protection have to be hooked up to the switchgear to trip, for the motors to comply with code requirements ?

Are you thinking about the T rating and having the motor trip off if it gets near the temperature limits of your area? One of our newer hydrotreaters has all Siemens motors with the same plate on them that you have. The medium voltage motors have RTDs in the stator and on each bearing, but I don't think the 480v motors have any thermal sensors on them. I know we don't have the RTD's tied to the relays right now, but I don't have a conclusive answer to your question.

From a design perspective, I've always been told that temperature is too slow of a variable to use in realtime. Temperature monitoring of a motor is for preventative maintenance planning only and trended over months and years just like vibration measurements and motor megger readings.

 

[Mule]

Same here I dont have a conclusive answer to your question. But I can offer some info.....It's my understanding that TEFC motors are allowed Class1 Div 2 areas, but I have to agree I have not seen installations where RTD's or thermistors have been used in these types of area classifications.

I have seen some larger scale synchonrous motors or MV 3ph motors that were open type that had these type of embeded sensors installed in questionable locations. Although the relays were always installed in MCC's in GP areas or they were purged.

 

[weressl]

on site we have 4 motors (siemens) with the following statement stamped on them,
"motor meets during normal operation the definition in the national electric code (2005)-501-125 (B) for motors to be installed in Class 1 Div 2 areas"

these motors are equipped with Thermistor protection, my question is, does the thermistor protection have to be hooked up to the switchgear to trip, for the motors to comply with code requirements ?

Siemens should state the answer in the installation instructions.

Does the motor have any otehr hazardous area stamp, such as ATEX? The thermistor may be for that or ASD application in hazardous locations.

 

[weressl]

Are you thinking about the T rating and having the motor trip off if it gets near the temperature limits of your area? One of our newer hydrotreaters has all Siemens motors with the same plate on them that you have. The medium voltage motors have RTDs in the stator and on each bearing, but I don't think the 480v motors have any thermal sensors on them. I know we don't have the RTD's tied to the relays right now, but I don't have a conclusive answer to your question.

From a design perspective, I've always been told that temperature is too slow of a variable to use in realtime. Temperature monitoring of a motor is for preventative maintenance planning only and trended over months and years just like vibration measurements and motor megger readings.

RTD's are real-time integrated motor thermal protection to aid in modeling the thermal profile of the motor. They allow tighter protection curve for the motor allowing wider utilization profile and faster tripping than current data alone. It also aids in calculating restart time without thermally damaging the motor. They long term predictive value is non-consequential. Bearing temperature monitors ARE predictive tools.

 

[Zstroken]

The RTD should be used to help the motor maintain its classification rating.

 

[jdsmith]

RTD's are real-time integrated motor thermal protection to aid in modeling the thermal profile of the motor. They allow tighter protection curve for the motor allowing wider utilization profile and faster tripping than current data alone. It also aids in calculating restart time without thermally damaging the motor. They long term predictive value is non-consequential. Bearing temperature monitors ARE predictive tools.

So it sounds like I need to get prices to connect my RTDs back to the substations then while there's extra money floating around:smile:

 

[bobgorno]

I have seen similar Siemens labels on TEFC motors. They have also been placed on motors without thermal protection in the past. It is not a certification that the motor is good for Div. 2. Just their interpretation that the motor is good for Div. 2 It may not take into consideraiton your actual operating environment. For example, is the motor installed outdoors? What is your minimum ambient temperature? What is the insulaiton type of the motor? What are the flammables that are potentially in the atmosphere? Do the have a low AIT. Temperature rise and mechanical clearances are important to consider. Refer to IEEE-1349 as noted in the FPN of 501.125

 

[weressl]

The RTD should be used to help the motor maintain its classification rating.

Nope, unless the motor instructions say so in order to manitain the listing of the motor.

Ex. the Clixons are required to be wired into the control circuit on some Cl.I Div. 1 motors.