Are conduit seals needed on EX motors?
Are conduit seals needed on EX motors?
(OP)
All UL listed Explosion Proof Motors have factory seals for the wires leaving the motor housing and entering the motor conduit box.
For a Class I, Div 1, Group D enviroment installation a UL listed motor for the area, is it necessary to also install conduit seals (ie Crouse Hinds EYS fittings) at the motor conduit box?
I believe it is not necessary because inside the box is only wire splices, not arcing contacts or hot components.
However, NEC 501.15(A)(1)(2) says seals are required for trade size 2" or larger and the enclosure contains terminals, splices, or taps.
Are you putting seals on all EX motor conduit boxes, only those 2" or larger, or never on any regardless of size.
For a Class I, Div 1, Group D enviroment installation a UL listed motor for the area, is it necessary to also install conduit seals (ie Crouse Hinds EYS fittings) at the motor conduit box?
I believe it is not necessary because inside the box is only wire splices, not arcing contacts or hot components.
However, NEC 501.15(A)(1)(2) says seals are required for trade size 2" or larger and the enclosure contains terminals, splices, or taps.
Are you putting seals on all EX motor conduit boxes, only those 2" or larger, or never on any regardless of size.





RE: Are conduit seals needed on EX motors?
RE: Are conduit seals needed on EX motors?
The code is not always practical even though it attempts to be.
The code says that in my 12x12 wireway I need to derate the 31st conductor. What if they are all number 14 awg? Do we all go back and rework existing wiring in the wireway when we add the 31st conductor?
RE: Are conduit seals needed on EX motors?
Good on ya,
Goober Dave
RE: Are conduit seals needed on EX motors?
Most people would consider 30-#14 in a 12x12 wireway impractical - and not too likely a design choice either. But, if you did make such a choice, then yes you would have to derate if you added the 31st conductor.
RE: Are conduit seals needed on EX motors?
The reason you need a seal when leaving the terminal box is thus: If a termination gets hot or loose (arcing) while a combustible mixture is in the box, the explosion's pressure will vent down the conduit (since the entry from the motor is sealed). The more distance it goes, the higher the pressure-piling effect will be -- possibly (probably) enough to blow the conduit apart at the next seal or enclosure -- resulting in the explosive mixture outside the electrical system being ignited. Hence, the need to seal near the termination box.
Good on ya,
Goober Dave