al hildenbrand
Senior Member
- Location
- Minnesota
- Occupation
- Electrical Contractor, Electrical Consultant, Electrical Engineer
The rule of 2014 NEC 314.43 doesn't make an exception for the type of screw.
Plastic timer box grommet/bushing
- Thread starter Joseph6044
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FionaZuppa
Senior Member
- Location
- AZ
- Occupation
- Part Time Electrician (semi retired, old) - EE retired.
314.43 suggests that no mounting screws should be in the box. the box as-is is not constructed to protect screws on the inside. a screw head cover would protect, but NEC verbiage does not address that.
if the box is UL listed and provides a mounting hole inside the box, then 314.43 needs to be re-done? or perhaps the provides holes inside the box simply not used?
if the box is UL listed and provides a mounting hole inside the box, then 314.43 needs to be re-done? or perhaps the provides holes inside the box simply not used?
al hildenbrand
Senior Member
- Location
- Minnesota
- Occupation
- Electrical Contractor, Electrical Consultant, Electrical Engineer
There is no "should" in the rule.
The "or" opens the clause about screws inside a box.
We can't see but a small portion of the box, so we can't assume how the manufacturer instructs mounting. Suffice it to say, the manufacturer's instructions should be consistent with 314.43 for the box to have a UL stamp.
FionaZuppa
Senior Member
- Location
- AZ
- Occupation
- Part Time Electrician (semi retired, old) - EE retired.
there's enough in the pic to say the box is not constructed to protect mounting screws from wires, it was said the rock screw we see is in a hole that was there for mounting, and there is no protections provided by the box, etc. maybe if you bond the screw to the egc it makes it all good?
al hildenbrand
Senior Member
- Location
- Minnesota
- Occupation
- Electrical Contractor, Electrical Consultant, Electrical Engineer
I can't leap to that conclusion, not without more information. It seems the box is also reported as 3R.
Joseph6044
Member
- Location
- Jacksonville, florida
It's a t103p. I can't find any specific instructions for mounting the box but why would they have holes in the back of the box if they aren't for mounting? And since code says not to screw from inside the box where conductors are, how else would you mount it?
FionaZuppa
Senior Member
- Location
- AZ
- Occupation
- Part Time Electrician (semi retired, old) - EE retired.
t103p is in a nema 3r according to the rip sheet on it. when the guts of t103p are installed are the screw holes (screws) covered in some way?
all of the plastic 3R's i see (basically a blank box) have outside mounting provisions.
does nec allow the installed guts to provide the protection? thus far i am only seeing a drill hole for mounting screws, and nothing of the box itself provides protection, etc.
all of the plastic 3R's i see (basically a blank box) have outside mounting provisions.
does nec allow the installed guts to provide the protection? thus far i am only seeing a drill hole for mounting screws, and nothing of the box itself provides protection, etc.
al hildenbrand
Senior Member
- Location
- Minnesota
- Occupation
- Electrical Contractor, Electrical Consultant, Electrical Engineer
Sure you can find specific instructions. Read the second bullet point under "WARNING Risk of Fire or Electric Shock". It says: "Installation and/or wiring must be in accordance with national and local electrical code requirements."
That's the argument that screws can't be used inside the box, which is not what the NEC rule says:
FionaZuppa rightly points to the area of the box behind the timer movement.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Can't recall ever using a T100 series timer in the plastic enclosure, but from pictures looks like the plastic enclosure is nearly identical in construction (other then material type) to the steel enclosures, with lower mounting holes through the back of the enclosure - also in same area where field wiring will be present. Only instructions I can find online are about the timer itself and contain nothing specific the the enclosure.
At same time I have never lost any sleep over a metal screw through a non metallic enclosure into wood or other non conductive material, especially with voltage to ground being under 300 volts.
Sierrasparky
Senior Member
- Location
- USA
- Occupation
- Electrician ,contractor
I have a Intermatic timer here in the office and it is a non-metallic enclosure similar to their outdoor units. There is no provision in the mounting holes for screw protection the only thing is there is a reinforced boss for strength. I can believe the timer is not UL listed. I don't think the 314 section cited does not include such boxes.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
My guess is the timer is listed, it is the same thing that fits their other enclosures, the plastic enclosure might not be listed though. I don't think the metal enclosures are required to be listed, so they probably aren't listed either.
FionaZuppa
Senior Member
- Location
- AZ
- Occupation
- Part Time Electrician (semi retired, old) - EE retired.
wll, here's my thoughts
what is this at red arrow? looks like the bottom edge of a metal receptacle box. thats a no-no as wires can chafe there, move the plastic box up some so that metal edge is not in the plastic punchout.
also, i would use a std pan head screw, not a rock screw, only because the taper on rock screw can cause the box to crack over time.
then, if the guts move the wires and the guts keep wires from getting near screw, then ok, otherwise use a screw head cover.
what is this at red arrow? looks like the bottom edge of a metal receptacle box. thats a no-no as wires can chafe there, move the plastic box up some so that metal edge is not in the plastic punchout.
also, i would use a std pan head screw, not a rock screw, only because the taper on rock screw can cause the box to crack over time.
then, if the guts move the wires and the guts keep wires from getting near screw, then ok, otherwise use a screw head cover.
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