Electrical terminal clearances
Electrical terminal clearances
(OP)
I have received some heating elements that have been constructed out of the norm for this vendor.
The concern at this point is that proper clearances have not been maintained phase to phase.
575V 3Ph
Anyone have any information or a source that will outline these clearances....NEMA website not a lot of help.
Thanks
The concern at this point is that proper clearances have not been maintained phase to phase.
575V 3Ph
Anyone have any information or a source that will outline these clearances....NEMA website not a lot of help.
Thanks






RE: Electrical terminal clearances
RE: Electrical terminal clearances
RE: Electrical terminal clearances
basically is a NEMA requirement.........
UL standards also apply...
RE: Electrical terminal clearances
I'm sure there are UL standards that are more or less equivalent to CSAs. There's probably a standard for heaters that will give you the answer you need.
RE: Electrical terminal clearances
Powell Electrical Manufacturing Technical Brief PTB #59 mentions that ANSI switchgear standards do not list such clearances but goes onto say they (Powell) use 1 inch between bare conductors up to 635V.
RE: Electrical terminal clearances
For the voltage referenced, this is a typical requirement given the considerations concerning potential for loose strands from the supply wiring and potential for overly long stripped insulation during the installation, creating the potential for bridging the two circuits.
In the IEC, assuming an overvoltage withstand rating of 6 kV, based on the supply voltage and the likely installation category, in standard 664-1, Insulation Coordination, the required through-air spacing [clearance] would be 5.5 mm and the over-surface [creepage distance] would be 9 or 10 mm depending on the material. There may be other considerations but your posting does not provide any other details.
RE: Electrical terminal clearances
good info...
received response from manufacturer via vendor today stating that their UL approved clearance for these elements 6KW @ 575V is a minimum of 1/4" phase to phase......
Thanx for your time.
RE: Electrical terminal clearances
(99 NEC) Table 384-36. Minimum Spacings… would probably apply, and could be reduced by overpotential type testing and labeling through a standard like UL508, at the discretion of the AHJ.