Electrolytic Cells

[mic]

I am designing the electrical connections for a electrolytic cell.

I have questions relating to the following sections of the NEC:

250.22 (3) states that electrolytic cells shall not be grounded.
Is this refering to grounding one leg of the power system (as in automotive)?

668.3 states that equipment associated with the cell line dc power circuits shall not be required to comply with 250.
Does this include bonding of the non-current carrying metal parts?

668.11 (B) states that all metal enclosures of power supply apparatus for the dc cell line process over 50V shall be grounded.
Sounds like bonding, but what about the rest of the metal parts on the system?

The system I am working on is completely closed and the metal frame is completely isolated from the chemical process (i.e. there is no chance of leakage current except under fault).

I would think that if a fault occurs that inadvertantly energizes the frame that it should be bonded to ensure the breaker trips.

Let me know if I am way off on this one.
c

 

[mic]

Guessing by the huge response, I am not the only one with little experience in this area.

Since this system is different than those described in 668 (closed and electrically isolated) I am going to bond the frame.

If anyone sees any safety issues with this speak now or forever hold your piece. O.k. you can answer whenever you want but please don't tell me what I should have done after I toast the maintenance guy. :roll:

c

 

[weressl]

Guessing by the huge response, I am not the only one with little experience in this area.

Since this system is different than those described in 668 (closed and electrically isolated) I am going to bond the frame.

If anyone sees any safety issues with this speak now or forever hold your piece. O.k. you can answer whenever you want but please don't tell me what I should have done after I toast the maintenance guy. :roll:

c

I agree that you can leave the electrical system floating for operational purpose and I would bond all metallic parts and connect them to ground.

Sometimes it takes a while to get some response. There ARE still some people who are busy........

 

[mic]

Thanks Laszlo.

By the way, I like your signature quote. I think I will have it put on a billboard and installed above the entrance to our shop. :smile:

Chris

 

[mic]

I originally posted this at the end of last year and subsequently reccommended bonding of all non-current carrying metal parts.

They have since constructed the system and included FR4 insulation between the steel frame of the cells and the steel rack that holds the bank of cells.

I have been told that for electrolytic cells they do not "ground" the frame. This does not sit well with me but my experience in this area is limited.

Does anyone see a safety concern with this setup?

Thanks

 

[benaround]

II have been told that for electrolytic cells they do not "ground" the frame. This does not sit well with me but my experience in this area is limited.

Does anyone see a safety concern with this setup?

Thanks

Mic,

Short answer, No.

The cell itself uses only DC power, bonding the metal parts of the cell to the AC supply

grounding conductor will not help trip the DC protection, IMO.

It sounds like they insulate the pos. side from the neg. side really good to prevent such

a fault ( DC) from happening.

 

[mic]

Thanks Frank,

A few more details on the system:

The power supply is +/- 90VDC
The configuration is series/parallel (series connected banks of parallel cells)
The anode and cathode connections are fully exposed

I don't think I understand why the DC protection would not trip. I know that the PS is not a grounded system but wouldn't shorting it to ground still cause the current to spike and eventually trip the breaker?

C

 

[Cold Fusion]

I don't think I understand why the DC protection would not trip. I know that the PS is not a grounded system but wouldn't shorting it to ground still cause the current to spike and eventually trip the breaker?

Draw out your circuit. Follow the current path.. Remember, the curent has to return to the source - it is not necessarily seeking a path to ground.

From your description: connecting one side of the DC source to earth does not provide a path back to the source - it is not a fault.

cf

 

[mic]

Drew it ... Got it ... Thanks