Morberis

I think that's over complicating it. You shouldn't be designing your heat exchange so close to the margin that you're going to rely on radiated and conducted heat exchange. But you should definitely do a calculation to find out how much heat you are generating and how much airflow you need to have going through at the max ambient temperatures, or above, that the box will experience. Then add in whatever margin you're comfortable with. For the conditions that my boxes experience I always assume that it's 33C.   If your box is going to be outside. Make sure it's either shaded or calculate how much heating it will get from the sunlight. It will mess everything right up. I spent 1 summer going around doing changes to all of my predecessors irrigation control boxes. I added shade structures and up-sized the fans for 33C. The existing fans would only be able to handle... 26C.   I also always positively pressurize my boxes because I have seen negatively pressurized boxes collect fine dust. But I work in ag where small particles and corrosive gases abound.  Again I don't think top or bottom really matters as long as you have cross flow of air. It's that direct contact with recently exchanged air that is going to keep your devices cool. Not sitting in it's own pool of stagnant air and heat because there is a natural eddy of air like you get in a truck bed. Maybe that means don't go with a large fan, go with 2 smaller ones and 2 smaller exhausts if the box is large enough.   

Yeah. Like NevergoldMel says heat shouldn't be an issue as long as you have airflow past drives. In fact I would say you'd be worse off putting the drive at the top if it doesn't have airflow because the heat won't be exhausted as easily. Doesn't matter much if you have the intake in the bottom or the top with the exhaust at the other side etc if you have large flow fans. If you are only exhausting small amounts of air put the exhaust on the top to take advantage of the small gains from natural convection. Just make sure the airflow crosses the drives. If you want good info on stuff like this look at all the work computer enthusiasts have put in testing airflow with large heat generating components.  I have found that if I have a large diameter intake and exhaust I can get away with no fans even in ambient 32C weather. That's 2x 12" intake/exhaust ports with 12hp worth of 208v drives running full out. Customer wanted to try that rather than paying for a fan. The PLC has been counting any overheat faults and in 2 years he hasn't had 1.  Personally I always put my drives in a separate box from the logic components. I found that often the price of the larger box was very similar to the cost of the 2 smaller boxes. Just join them up with some large diameter pipe. That way I have good separation from the VFD's noise and it's higher voltages. Usually I'm dealing with 480v drives or large numbers of small 3hp 208v drives though.  The few times that I have been concerned about objects falling into the drive I have just bent up a piece of metal on a small metal break we made and bolted it above the drive. Paying attention to make sure that I'm not going to have airflow issues.

I personally use painters tape to guard against this. Never get a scratch.   But I use a combination of the greenlee m22 punch, die grinder, and jigsaw. For stainless I use the die grinder. Stainless rated jigsaw blades still burn out too quick for my liking. For fiberglass I use whatever I want.   If you have punches that are starting to wear out you can take them to get sharpened. Great way to get extra life out of a $500 punch.

Hmmm.    I decided to double check since I remembered something about this years ago from school. In the CSA 14-016 it does say that "Devices required by this Section shall not be connected in any grounded conductors except where..." (not relevant a and b sub-rules)   However motor overloads are not required by Section 14. They are required by Section 28. In that section only 28-506 seems to apply. In that if the overload is wired on the load side of the coil if the wire becomes accidently grounded between the coil and the overload the overload would no longer prevent the motor from starting or stop it. Here is the text. 28-506 - When Power for a control circuit for a motor controller is obtained conductively from a grounded system, the control circuit shall be arranged so that an accidental ground in the wiring from the controller to any remote or signal device will not a) start the motor; or b) prevent the stopping of the motor  by the normal operation of any control or safety device in the control circuit   So my read on that is if you're using an floating/ungrounded dc system or a system where both wires are live like in 208v  this rule would not prevent you from wiring in your overload on the load (A2) side of the coil.    28-200 to 28-206 are about branch and feeder conductor over current protection so the rule in 14-016 would not apply.    Let me know if I'm missing a relevant rule.     

I've seen alot of electricians wire the OL contact before the coil rather than after. I'm not sure what US code requires vs Canadian CSA though. 

I use heatshrink labels for single conductors. There's not really a trick other than what @NevergoldMel said about clean dry hands. And using a tiny flat blade screw driver to help with insertion.