bonding liquidtight
- Thread starter dompell
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- Location
- Mission Viejo, CA
- Occupation
- Professional Electrical Engineer
Re: bonding liquidtight
It could be; the primary distinction is whether it supplies an actual load such as a transmitter, or it is simply a instrument actuated switch.
It could be; the primary distinction is whether it supplies an actual load such as a transmitter, or it is simply a instrument actuated switch.
- Location
- Illinois
- Occupation
- retired electrician
Re: bonding liquidtight
I know the code says this, but how does the type of load at the end of the liquidtight change how it performs as an EGC? We use this exception for all of our loop powered instruments. Most are on 125mA fuses and operate at about 28 volts DC. The 4-20mA loop provides the power that lets the instrument do its work.
Don
I know the code says this, but how does the type of load at the end of the liquidtight change how it performs as an EGC? We use this exception for all of our loop powered instruments. Most are on 125mA fuses and operate at about 28 volts DC. The 4-20mA loop provides the power that lets the instrument do its work.
Don
- Location
- Mission Viejo, CA
- Occupation
- Professional Electrical Engineer
Re: bonding liquidtight
I can?t dig deep enough into my available Proposal/Comment documentation to determine why Subpart (c) of the Exception wasn?t simply limited to loads subject to overloading (such as clock or stepper motors) rather than the more general class of ?power utilization equipment;? especially since the Exception only applies to Division 2. Frankly, I don?t know why Subpart (c) exists at all.
The original purpose for auxiliary bonding on flexible metal conduit or liquidtight flexible metal conduit was that short-circuit currents can be shown to ?jump? the gaps between the turns of the metal tape (even with an integral auxiliary bonding tape) and they are capable of igniting a standard test lab atmosphere.
In Division 2, short-circuit conditions are generally ignored beyond their ?usual? effects; in other words, they are rarely used to justify ?enhancing? an installation. In the case of motors, overloads are not generally considered either. [See 500.8(A)(5)]
So, in this case, I can only state ?what? the Code says, not why it says it.
This may be a good opportunity for a Proposal Don
As an aside, I recall the Forum had a rather lengthy discussion about what ?utilization? equipment was in the first place. I believe the case could be made that equipment that only ?modulates? a 4-20mA signal was not ?utilization? equipment; however, if it generates the signal, it is.
I can?t dig deep enough into my available Proposal/Comment documentation to determine why Subpart (c) of the Exception wasn?t simply limited to loads subject to overloading (such as clock or stepper motors) rather than the more general class of ?power utilization equipment;? especially since the Exception only applies to Division 2. Frankly, I don?t know why Subpart (c) exists at all.
The original purpose for auxiliary bonding on flexible metal conduit or liquidtight flexible metal conduit was that short-circuit currents can be shown to ?jump? the gaps between the turns of the metal tape (even with an integral auxiliary bonding tape) and they are capable of igniting a standard test lab atmosphere.
In Division 2, short-circuit conditions are generally ignored beyond their ?usual? effects; in other words, they are rarely used to justify ?enhancing? an installation. In the case of motors, overloads are not generally considered either. [See 500.8(A)(5)]
So, in this case, I can only state ?what? the Code says, not why it says it.
This may be a good opportunity for a Proposal Don
As an aside, I recall the Forum had a rather lengthy discussion about what ?utilization? equipment was in the first place. I believe the case could be made that equipment that only ?modulates? a 4-20mA signal was not ?utilization? equipment; however, if it generates the signal, it is.
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