I quoted a job for a new 3 phase sub panel which has no ground wire in the conduit. The existing wire is underground and the panel is in the end of a prep table. the prep table is stainless.. the customer did not accept my quote and said another electrical company said the could ground the existing panel to the stainless prep table. this Has danger all over it if you ask me. is this legal? thanks
Grounding
- Thread starter Enterdawg
- Start date
- Status
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
What they described is legal, if I correctly understand what you said that they said. But it is not complete, and therefore will not give the owner a legal installation. We need to connect the external metal parts of electrical equipment to each other, and (somehow, somewhere, eventually) to planet Earth. Presuming that table already has a connection that (somehow, somewhere, eventually) makes its way to planet Earth, then that is an option. I am guessing (and hoping) that the other electrical company was describing the use of the table as a point to which the new subpanel's external enclosure will be bonded.
But do not confuse that concept with the requirement for an Equipment Grounding Conductor to run from the Ground Bus inside the sub-panel (somehow, somewhere, eventually) to the N-G bond point in the main panel. What you described as the other electrical company's plan does not appear to deal with the requirements for an EGC. But even worse, if the other company is suggesting that they can achieve the required fault path that an EGC provides by simply connecting the Ground Bus in the sub-panel to the table, then they are dangerously wrong.
But do not confuse that concept with the requirement for an Equipment Grounding Conductor to run from the Ground Bus inside the sub-panel (somehow, somewhere, eventually) to the N-G bond point in the main panel. What you described as the other electrical company's plan does not appear to deal with the requirements for an EGC. But even worse, if the other company is suggesting that they can achieve the required fault path that an EGC provides by simply connecting the Ground Bus in the sub-panel to the table, then they are dangerously wrong.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Is the feeder run in a suitable metal conduit that could be used as a ground, ie EMT or rigid, etc. IN this case no EGC is needed.
BryanMD
Senior Member
Enterdawg said:
When I built custom foodservice equipment (chef counters,etc) we provided a mounted panel with all branch circuits wired (and often tested) but never got into the particulars of how the EC on that site would do his final connections.
It was hard enough getting and answer from the site EC on what voltage was being supplied but we (I) would always recommend a ground wire be installed because of the abuse the emt or flex would endure... not because the steel frame (stainless and otherwise) wasn't suitable as code *minimum*.
Anyone who has worked in a restaurant kitchen will attest that having that ground wire is better than not having it.
Pierre C Belarge
Senior Member
- Location
- Westchester County, New York
Roger posted the section of Art 250 you will need to show for reference in regards to NEC requirements.
I think this picture is similar to your described installation...
If this picture is similar, the table does not "ground" the panel, you may need to bond the table to the panel equipment ground - which may be effected by virtue of the manner in which you have mounted the panel within the table.
I think this picture is similar to your described installation...
If this picture is similar, the table does not "ground" the panel, you may need to bond the table to the panel equipment ground - which may be effected by virtue of the manner in which you have mounted the panel within the table.
BryanMD
Senior Member
Pierre C Belarge said:
Every fab shop will do things differently of course but "typically" there will be a steel frame (angle iron or formed channel) contiguously welded throughout the entirety. Welded and or bolted to the frame will be the various s/s veneer items (like doors,shelves, etc) and of course the s/s countertop.
The electrical panel will in turn be welded directly to that frame or bolted to other steel item which is welded to that frame.
In all instances the ground bar and the panel housing (and the frame/top/etc) should be one contiguous whole (electrically). If you come across one that has the panel isolated from the steel (for some bizarre reason) then yes you need to defeat that isolation with some bonding.
Pierre C Belarge
Senior Member
- Location
- Westchester County, New York
250.136(A) Equipment Secured to Grounded Metal Supports.
Electrical equipment secured to and in electrical contact with a metal rack or structure provided for its support and grounded by one fo the means indicated in 250.134. The structural metal frame of a building shall not be used as the required equipment grounding conductor for ac equipment.
Electrical equipment secured to and in electrical contact with a metal rack or structure provided for its support and grounded by one fo the means indicated in 250.134. The structural metal frame of a building shall not be used as the required equipment grounding conductor for ac equipment.
- Status