L5KEdit
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- Chicagoland
Hi All,
I'm trying to find a rule in the NFPA, NEC, etc. that talks about safety with respect to power cycling a control panel. Guys, I've been designing industrial control panels for over 15 years but never had to find this rule because I've always designed panel power on/off circuits using 'good practice' putting safety first. I now work for an unusual company that has inexperienced Mechanical Engineers in 'higher positions' than EEs making controls decisions on products to save a few bucks.
For industrial control panel power I usually use a power on and power off pushbutton, which seals an Master Control Relay; the power off button breaks the seal and powers down the panel. We do this because 'it has always been done' and also we don't want the panel to power up live on a power cycle or initiate any motion without pushing a 'safety reset' or 'power on' first. Similar philosophy to clearing a hardwired E-stop condition with 'machine safety reset' using a safety relay.
We have this simple panel which plugs into 120VAC being sold into the Industrial market. It controls a Fluid spray process and I was just assigned to add features to the product and 'add to the base design'. Well, the base design was not put through a peer review process and it has one "power" button which is maintained (push on, push off). Therefore this panel could start a liquid spray process on power cycle or when powering up WITHOUT pressing any sort of buttons. Because this is the only hardwired button; it has a simple HMI but WILL come up 'barking' (spraying) under certain conditions on power up if the power button is left pressed in.
So I'm asking for help to find a standard, rule, or code that states this is unacceptable. I've been beaten down by the fact that Marketing and Mechanical Engineers "know best" in terms of product design and I'm not interested in an argument so I'd really like to find a rule...
Thank you so much for any input....
-Beaten down and discouraged Controls Engineer
I'm trying to find a rule in the NFPA, NEC, etc. that talks about safety with respect to power cycling a control panel. Guys, I've been designing industrial control panels for over 15 years but never had to find this rule because I've always designed panel power on/off circuits using 'good practice' putting safety first. I now work for an unusual company that has inexperienced Mechanical Engineers in 'higher positions' than EEs making controls decisions on products to save a few bucks.
For industrial control panel power I usually use a power on and power off pushbutton, which seals an Master Control Relay; the power off button breaks the seal and powers down the panel. We do this because 'it has always been done' and also we don't want the panel to power up live on a power cycle or initiate any motion without pushing a 'safety reset' or 'power on' first. Similar philosophy to clearing a hardwired E-stop condition with 'machine safety reset' using a safety relay.
We have this simple panel which plugs into 120VAC being sold into the Industrial market. It controls a Fluid spray process and I was just assigned to add features to the product and 'add to the base design'. Well, the base design was not put through a peer review process and it has one "power" button which is maintained (push on, push off). Therefore this panel could start a liquid spray process on power cycle or when powering up WITHOUT pressing any sort of buttons. Because this is the only hardwired button; it has a simple HMI but WILL come up 'barking' (spraying) under certain conditions on power up if the power button is left pressed in.
So I'm asking for help to find a standard, rule, or code that states this is unacceptable. I've been beaten down by the fact that Marketing and Mechanical Engineers "know best" in terms of product design and I'm not interested in an argument so I'd really like to find a rule...
Thank you so much for any input....
-Beaten down and discouraged Controls Engineer