Jimmie_Ohio
Member
I built control panels from the time I was 13 (1970) until I went into consulting (1992). Then I reverted to just designing, testing, and programming them.marksji said:25% free space goes away quickly... I'd say in 25% free space in a panel lasts from 1-24 months most of the time.
Everyone is always hung up on "spare panel space". Automotive companies paved the way with specifications that spelled out 10%, 20%, or whatever. Murphy's Law now enters in. If you have 20% spare, your need 25%. If you have 25%, you need 30%.
Now I work for a company that deals in power plant equipment. The panels for this equipment are usually mounted on "Unistrut" in buildings that you can fly an airplane in. MCCs control the motors. If I need spare anything, it's I/O. For this I simply furnish extra chassis space or cards with wired spares. Never had a problem yet.
Plus, against what everyone with a bad back has said, I put terminals horizontal along the bottom. This is for good reason. In plants that may have a lot of condensation, water cannot run uphill in the conduits, so they are bottom entry. If the conduits originate overhead and don't dip below the botom of the panel (like a trap in a drain), the panel will fill with water.
The people who mount the panels in my business are the same guys who land the wires, so they mount the panel at a decent level, so they can work on it. I also help by specifying 4"-6" of empty panel space below the terminal strips. Other ways are to put the mounting information on a drawing or locate the pushbuttons at a level that will dictate where the panel is located (eye level).
BOTTOM LINE:
We are all in different industries. These industries have different needs. You, as the designer, must know what your specific needs are. If somebody mounts your panel under a table or so high that you need to be Frankenstein to operate the disconnect, that is just plain stupid (not to mention potential code and safety issues.)