Need schematic

[stickelec]

Up to this point there are a few areas that I have failed to see mentioned.

IMO without a Risk Assessment and proper Engineering design there are too many points of potential failure. A few of which relate to:
1. Contactor specifications.
2. OCP specifications ie: An improperly designed OCP could result in welded contacts in the Contactor.
3. The Contactor Aux-Contact is very much subject to failure and not a substitute for a Safety Rated Relay.
4. A failed ESD Pushbutton contact.
5. A failed Reset Keyswitch.
6. Lack of circuit condition monitoring and/or status indication.
7. Although not part of the original question, a lack of protocol for testing and/or preventing unintended restart of machines during Reset.

Maybe the regs are "just less stringent" then I would have imagined. Without such design issues being addressed, I would not want to "defend the performance of the circuit".

Did NATEF analyze the design or just watch the result of a RED button being pushed? I think "approval" and "reliable performance" may not be the same thing and would only come to light in the event of a failure involving an injury.

 

[rkrieger]

Thanks for the comments

Thanks for the comments

All of your points are valuable and to be considered. In my experience with training institutions and the jurisdiction involved (NATEF) & (OHSA), the system design as stated has been said to be compliant. Is it as safe as you have questioned?? Perhaps no....., but if the school owner/responsible party is interested in compliance and the system is "passed", are they required to go farther?? Do not mis-understand my position. I fully understand your comments and do not dis-agree with them. The problem with installations has always been to answer the question...."How far do we go with quality, design and installation?". I have deliberately stayed away from the "cost" factor, because that is another topic for heated discussion.

I include copies from the facility evaluation manual just for information.

Standard 8.2 - Safety
The facilities should meet all applicable safety standards and an emergency plan should be in place and posted in all classrooms and lab/shop areas.

(Copied from EVALUATION FORM completed by NATEF evaluators and inspectorsJ

8.2.C ?Rate the availability of an electrical disconnect power system or posted procedure to shut down all outlets in case of emergency?


Thanks for your input..........

RLK

 

[stickelec]

All of your points are valuable and to be considered. In my experience with training institutions and the jurisdiction involved (NATEF) & (OHSA), the system design as stated has been said to be compliant. Is it as safe as you have questioned?? Perhaps no....., but if the school owner/responsible party is interested in compliance and the system is "passed", are they required to go farther?? Do not mis-understand my position. I fully understand your comments and do not dis-agree with them. The problem with installations has always been to answer the question...."How far do we go with quality, design and installation?". I have deliberately stayed away from the "cost" factor, because that is another topic for heated discussion.

I include copies from the facility evaluation manual just for information.

Standard 8.2 - Safety
The facilities should meet all applicable safety standards and an emergency plan should be in place and posted in all classrooms and lab/shop areas.

(Copied from EVALUATION FORM completed by NATEF evaluators and inspectorsJ

8.2.C ?Rate the availability of an electrical disconnect power system or posted procedure to shut down all outlets in case of emergency?


Thanks for your input..........

RLK

I would ask the following question, "How does an Emergency Stop circuit differ from a simple (and basic) Start/Stop circuit?" With all respect, I would say the circuits illustrated thus far are no different than a basic control circuit for a Yard Light.

Why is this ES system any different than one protecting a worker in an industrial setting? Respectfully stated, my concern is you will never know if the circuit will function when the kid is...

RK, per the NATEF 8.2.C standard you provided, it appears that an ES system is not even required if a "posted procedure" offered another method of disconnecting power. Therefore I suppose all this is a mute point, but its been fun. Regards

 

[rkrieger]

Indeed, is has been fun........

Indeed, is has been fun........

The fact that the standard allows a "written" procedure in lieu of an actual system, gives schools and NATEF the mindset that if as you said, they install a simple "stop/start" circuit, then they feel that they have been prudent and gone "the extra mile".

FYI- I once asked a NATEF evaluator is he felt that Light Curtains would ever be required in the automotive shop setting? His answer? "What are light curtains?" Enough said !!!! So. as this post draws to a close...........thanks for all the help, comments, drawings and such. There really are a great bunch of folks here with many great ideas.

Happy Holidays.

RLK