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I'm a compliance Engineer and have

I'm a compliance Engineer and have

I'm a compliance Engineer and have

(OP)
I'm a compliance Engineer and have a detailed question regarding electrical enclosures. When I have a customer that has a very large system and requires several connected enclosures (e.g. Hoffman enclosure with a master door,)I seem to always run into an issue that is not easily solved.
In EN 60204-1, clause 6.2.2 b) "Protection for Enclosues" the requirement states that the doors can only be opened when the Disconnect device is opened. "so far no problem"
The Disconnector can only be closed when the door is closed. Then a little further down it states, that upon closing the door the interlock must be restored. When more than one door can provide access to live parts, care should be taken to implement this intent. " this is the problem"
The master door meets this requirement but the other two or more doors can be left opened. When I come into the picture at a customer site the electrical panel has already been laid out. Most electrical engineers would not even consider electrically interlocking the doors because most large machinery has a large current draw, it requires a huge contactor and there is not enough real estate in the panel.
Mechanically, Hoffman or anyone else we've been able to find makes a mechanical interlock that guarantees that the Disconnector can only be closed after all the doors are closed.
Has anyone found a solution to this clause besides "service persons are trained to enter the enclosure". Please keep in mind this does not guarantee that the interlock will be restored on all the doors the same as the master door. As an ispector this is a real pain, I understand the issue for the machine manufacture and most of the time I end up giving in to some form of training and documentation because I don't have a solution. I try to be as reasonable as I can and still meet the standards requirements for my customers. I think this is an important problem that shouild not be ignored. Sorry for the long thread but it's driving me nuts.

Christopher Caserta
ccaserta@enorthhampton.com
Ph:904-225-0360

RE: I'm a compliance Engineer and have

So the interlocks are not in the control circuit?
I am no inspector but have quite a bit of experience with low voltage standards and such. Based on what your posting, when the outer door is closed everything is fine. If the outer door is opened the disconnect is 'disconnected'. Shouldn't this cut off all power to the entire panel? If it does, then I see no problem. It sounds as though they are referring to more than one main door into the enclosure and not 'internal access' doors. This would be like having a large panel with access on the front side and access on the rear side. I think if your external doors follow this rule then your customer will be in compliance. UL508 defines appartus as open or closed devices. Open devices have no enclosure requirements (designed to be used with another enclosure).

RE: I'm a compliance Engineer and have

(OP)
Yes my question refers to a large floor standing enclosure with only an outer access door. Once the door is open you can have direct access to hazardous live circuits.
Yes when the master door (the door with the Disconnect device) is open the disconnect is off "no problem" when the master door is closed the disconnect is turned on "no proble".
Some of the machines I work on have 4 to 8 doors and more for an electrical enclosure. They contain PLCs several servo drives, open power supplies and transformers, lots of circuit breakers, fuses, DIN terminals, safety relay circuits, etc. all are required to be in an IP 54 or Nema 12 enclosure.
The problem is for machinery that has more than one door for its' electrical enclosure is when the master door is closed by a service/maintenance person the disconnect can be turned on. It's possible to leave the additional doors open with hazardous live voltage available to the operator.
I agree UL508 only states that the doors can only open when the disconnect device is turned off that requirement can be met mechanically for all the doors. EN 60204-1 has additional requirements, when it's time to close the doors there is no guarantee the additional doors were also closed.

Christopher Caserta
ccaserta@enorthhampton.com
Ph:904-225-0360

RE: I'm a compliance Engineer and have

Why don't you simply series up all the disconnects to prevent power from being applied if ANY of the doors are open?  I understand that this will require running wires to each enclosure, but this is a fairly simple way of guarenteeing that all doors must be closed before attempting to operate the machinery.

RE: I'm a compliance Engineer and have

Melone has a good point.
Thanks for your clarification on this ccascerta. The internal doors are not the problem its because you have so many 'external' doors. I think Melone found the solution.

RE: I'm a compliance Engineer and have

(OP)
There is only one disconnect and that is all that is required by the standard. The first door will have the disconnect device for the incoming power, the second, third, fourth doors and so on are just mechanically interlocked to the first disconnect device. None can be opened woithout the disconnect being shut off, once the disconnect is off all doors will open. Again unfortunately, the disconnect guarantees the first door to be closed before it is turned on but so far I haven't been able to find any mechanical linkage that guarantees all the doors must be closed first then the single disconnect be turned on.
I'm not trying to be difficult this is the problem I keep running into. If any one has EN 60204-1 read clause 6.2.2, you'll see the requiremnt I'm trying to work with.

Christopher Caserta
ccaserta@enorthhampton.com
Ph:904-225-0360

RE: I'm a compliance Engineer and have

Hi, you can get isolators with an auxillary electrical interlock for use with microswithes on the doors.Or you have amechanical interlock which only allows the doors to be opened if the door with the isolator is open.Or you have the doors locked from the inside except the door with the isolator.  

RE: I'm a compliance Engineer and have

(OP)
So what would be the working voltage for the Isolator, is this a DC device or are you saying use 400 Vac or 230 Vac. How do I drop out the 3PH circuit to kill AC power to those panels when the switch is open or closed. Please clarify

Christopher Caserta
ccaserta@enorthhampton.com
Ph:904-225-0360

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