hazardous location motor thermostat leads 1

[nmark]

A customer had a 5hp 480v 3 phase motor in a class 1 division 1 area that was being relocated.It is controlled by a
xp manual starter.While disconnecting from original location I found 2 wires for thermostat in motor junction box that were wirenutted together.The question is do I need to use them?The motor is rated for hazardous location and has overload protection in the manual starter.

 

[aolalde]

Nmark:

Yes you must connect them in series with the overload circuit. If the motor is overheated for watever reason, the temperature rise shall be limited by the thermostats before ignition temperatures for the Class and Group are reached.

 

[Mendit]

It is in the Canadian Electical code that all TEXP motors have as temperature limiting device. Klixon or Thermister. If you do not connect them and there is a failure you have no insurance and all claims against you are valid. An electical contractor could lose his licence for not connecting protective devices. RTDs don't not qualify unless they are set with a warning and trip at less than maximum rated temperatures. Class 1 Div 1 Groups C-D have maximum surface temperatures of T3B or 150C Many motors are class F and rated 155C howver the temperature sensor should be derated to reflect that you may not see the highest recorded temperature. We install 130C Klixons and 130C thermistors, note Thermisters have color coded leads, these lead should be brought out in the correct color for connection Blue-Blue is PTC color for 130C.

 

[GordS]

Where in the CEC does it say TEXP motors must have temperature limiting devices?

Repair shops, I believe, need to install these devices on motors they repair. In Alberta, there used to be a standata that required us to connect these devices if they were present; this requirement no longer exists in Alberta's standata as of about 2 years ago.

 

[petronila]

Hello nmark,

The answer is YES,


The Explosion proof motors have one or more thermostats in order to trip(BY DESIGN) before the frame reaches the maximum allowable temperature for the specific class and group. The normally closed contacts of the thermostat must be connected in the motor control circuit so that power to the motor is removed immediately when the thermostat trips.

Regards

Petronila

 

[Mendit]

CEC 22.2, 77-95 section 4.1.1
CEC 22.2, 145-1972 section 6.3.4
Read also Hazardous Locations by Bossert chapter 19 Repair Facilities. Chapter 19
Repair and contstruction of motors and generators is contolled and audited by CSA at qualified facilities all across Canada not by Alberta Standata.

 

[rbalex]

In the US, where provided, an inherent thermal protective device is part of the Class I motor's listing. Not all motors have them; but, for those that do, connecting them is required under Section 110.3(B) of the NEC.

 

[GordS]

CEC 22.2 77 is for motors with inherent thermal protection which must be labelled "Thermally protected". This labelling indicates you need to connect the thermal device into a control circuit.

Where exactly in CEC 22.2 145 is it required that explosion proof motors NEED a thermostat ( or similar device )? They are allowed to have them. And if they have them, they must be operable when the motor is tested on the over temperature test. But a motor does not seem to need to have a thermostat ( or similar) device to pass a CSA temperature test. Refer to 7.3.1 of the standard.

By the way, my copy of the document by Bossert ( 1986) doesn't have 19 chapters.

Repair of motors is definitely defined by CSA standards and requires a thermally sensitive device installation in the motor at repair; however, the connection of thermal devices in the field has nothing to do with motor construction - it is motor installation. It is installation that is impacted by Standata.