>From a practical standpoint, some designs use an EPO/EMO in series with a
motor or other high current device potentially creating a hazard (laser,
linear actuator, etc).  I can see why you would not want to use an EPO in
this manner (breaking significant current on a regular basis could cause
damage to the switch terminals).  However, if your EPO goes to a
logic-level or low power control input to a relay, perhaps that is OK.  The
standard I work with does not prohibit you from doing this.  You would need
to show that the relay is designed appropriately to function as an on/off
switch.  You might also want to consider the effect of 'training' users to
use the EPO switch during service- that might lead to some learned behavior
that is not appropriate for other pieces of equipment.

-Ken A

On Tue, May 31, 2022 at 9:20 AM Brian Kunde <bkundew...@gmail.com> wrote:

> Greetings  to All!!
>
> I have an industrial machine with blades that has to be changed out by the
> User/Operator.  The blade is behind a door with a positive mechanical
> action switch that when opened puts the motor's VFD into a Safe Stop
> Function Mode (this is a certified Safety Function).  In addition, power is
> removed from the Start Button circuit so the motor cannot unexpectedly
> start.
>
> When the E-Stop button is pressed, it does the same as the Door Switch
> above, but in addition, it also opens the Motor Enable Relay which removes
> the 3-phase power from the VFD.  Now the motor really really cannot
> unexpectedly start.  I think this circuit arrangement is typical.
>
> We noticed that many of our Customers instruct their Employees (Operators)
> to PRESS the E-STOP Button before changing out the Blade taking advantage
> of the extra layers of protection.
>
> So here is my question.  Is it OK to instruct the Operator in OUR MANUALS
> to Press the E-Stop when changing the blades?  We have always been told
> that the E-Stop function should ONLY be used for Emergency and not for
> routine tasks.  Is there any additional liability on  our company if we
> give these instructions? In doing so, are we admitting that our product is
> unsafe or not as safe and may unexpectedly start unless you press the
> E-Stop?
>
> What is your opinion of this topic?
>
> Thanks to all.
> The Other Brian
>
>
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