Solid State Devices in Haz Loc.

[chardos5471]

When is it unacceptable to use a solid state device in hazardous location without the use of an explosion proof enclosure? Since there are no arcing or sparking components, I would presume they would all be acceptable or is there something I'm missing?

 

[rbalex]

When is it unacceptable to use a solid state device in hazardous location without the use of an explosion proof enclosure? Since there are no arcing or sparking components, I would presume they would all be acceptable or is there something I'm missing?

Surface temperature.

 

[sgunsel]

What makes you think solid state devices cannot arc or spark?

 

[chardos5471]

I'm sure then this is an assuption then, but under its normal working conditions, within the components capacity, and without moving parts a solid-state device shouldn't spark, correct?

 

[jdsmith]

As Bob mentioned, surface temperature is an issue and many solid state devices will be tested and marked for Class 1 Div 2, Groups A, B, C, and D, and they will have a temperature code listed, typically a low one like T5 or T4.

There are a number of solid state devices that have been tested and are marked with Class 1 Div 2, Group, and T code. Phoenix Contact makes size 1 solid state FVNR and FVR motor starters, and many manufacturers offer HMI displays and PLCs or programmable relays marked for Class 1 Div 2. Many PLC cards are suitable for Class 1 Div 2, but digital output cards, relay output cards, and power supplies can be a problem. LED pilot lights are another example of a solid state device that can be used in hazardous locations.

 

[kwired]

I'm sure then this is an assuption then, but under its normal working conditions, within the components capacity, and without moving parts a solid-state device shouldn't spark, correct?

If that device is overloaded or otherwise fails what is to keep it from arcing or becoming extremely hot?

Conductors in raceway or other non arcing/heating equipment is no different. Under normal circumstances they do not arc or generate very much heat but if there is a failure they sure can so we must still install them in a proper raceway or enclosure for the application.

 

[chardos5471]

That's true I wasn't really thinking WORST case scenario, but what about capacitors? I've seen them unprotected in class 1 div 2 areas and I've seen them explode. It probably was suppose to be in an enclosure!

 

[rbalex]

That's true I wasn't really thinking WORST case scenario, but what about capacitors? I've seen them unprotected in class 1 div 2 areas and I've seen them explode. It probably was suppose to be in an enclosure!

It?s difficult to address all the underlying philosophies of Classified locations in a single post. (If it could be, Articles 500 to 516 could be considerably shorter)

As a most general statement: Within the context of the fire triangle components (oxygen, fuel, ignition source), once a location is properly classified, Division 2 only attempts to address ?normal? ignition sources, Division 1 attempts to address all possible ignition sources.

Assuming an appropriate ?T-Class,? capacitors are not ?normally? an ignition source; therefore they would not require a Section 500.7 protection technique in Division 2. This would apply to the solid state devices mentioned in the OP too; but you asked if there was anything beyond arcing or sparking to consider. See 500.8(B)(3) and 501.100(B).