FWIW, I can appreciate both, or all sides of what this discussion turned into. Looking at it from what may be some of SK's perspective, using a 1.25 factor may be first off, safe(r), more practical and less calc. work, but I'd probably still do the calcs anyway if anyone asked for them, particularly if design temps. went below -40, but otherwise, still use wire sizes/components based on the voltage a 1.25 factor gave me. Having a license and potential liability can make one conservative in design philosophy.
As a practical consideration, and in a vendor "do as much the same every time as possible" standardization, any relative $ savings in materials from cutting things close every time can be quickly lost by calc time and engineering charges, not to mention added inventory costs and a somewhat hidden cost of more opportunity for mistakes by using the wrong stuff. All this may seem like overkill, but practical reality (and safety) trumps theory most times.
On the other side, I'd suggest that doing the design calcs is never a bad idea, provided they are understood, as well as the reasons behind them, their necessity and their limitations. One doesn't need to have a P.E. license to understand what's required. Just a brain.
Reading all this got me thinking. If one goal of codes is safety, and that goal has Voltage as f(operating temp) as a parameter, as one example only, one temp. consideration that neither codes (at least not explicitly to my knowledge) nor anyone here has mentioned, is the idea that a PV array can, particularly in the type of climate that may use design temps of -40, have an operating temp. less than -40 due to nocturnal, or more likely, early morning radiative sky cooling. I note that, as a comment to the informational note added to 690.7 (A), that the ASHRAE temp. mentioned as an informational note does not take such radiative cooling into account. Such cooling can depress equipment temps. a few to maybe 10 C. below the ambient temp. Just an example of situational awareness that good engineering requires that codes may miss. There are many others.
Around most situations and in this case about what Voltage to use for design, relying on the most conservative code direction will probably get you by and may even be the most cost effective and common sense approach. But, throwing a code at a situation by using code calcs, or worst case, or not, without understanding what the whole situation can entail, and in so doing getting hung up on what may be written in a code while not looking at what the situation really calls for, maybe even beyond code is, to me anyway, poor engineering.
As a practical consideration, and in a vendor "do as much the same every time as possible" standardization, any relative $ savings in materials from cutting things close every time can be quickly lost by calc time and engineering charges, not to mention added inventory costs and a somewhat hidden cost of more opportunity for mistakes by using the wrong stuff. All this may seem like overkill, but practical reality (and safety) trumps theory most times.
On the other side, I'd suggest that doing the design calcs is never a bad idea, provided they are understood, as well as the reasons behind them, their necessity and their limitations. One doesn't need to have a P.E. license to understand what's required. Just a brain.
Reading all this got me thinking. If one goal of codes is safety, and that goal has Voltage as f(operating temp) as a parameter, as one example only, one temp. consideration that neither codes (at least not explicitly to my knowledge) nor anyone here has mentioned, is the idea that a PV array can, particularly in the type of climate that may use design temps of -40, have an operating temp. less than -40 due to nocturnal, or more likely, early morning radiative sky cooling. I note that, as a comment to the informational note added to 690.7 (A), that the ASHRAE temp. mentioned as an informational note does not take such radiative cooling into account. Such cooling can depress equipment temps. a few to maybe 10 C. below the ambient temp. Just an example of situational awareness that good engineering requires that codes may miss. There are many others.
Around most situations and in this case about what Voltage to use for design, relying on the most conservative code direction will probably get you by and may even be the most cost effective and common sense approach. But, throwing a code at a situation by using code calcs, or worst case, or not, without understanding what the whole situation can entail, and in so doing getting hung up on what may be written in a code while not looking at what the situation really calls for, maybe even beyond code is, to me anyway, poor engineering.
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