Boil Time is not Preserved During Recipe Scale

I found the following issue.

1) Start with a recipe that uses a 90 minute boil, say a 5 gallon batch size.  Make a copy of it to use for scaling.
2) Scale the recipe up to a larger batch size, say 8 gallon for reference.

After doing this, the resulting Boil Time is reduced to 60 minute instead of the intended 90 minute.  However, I think that despite the Boil time being not as intended that the water volumes may actually be correct for a 90 minute boil.  The problem being that if you then adjust the Boil Time to the intended 90 minutes your water volumes will be too high which may result in lower than intended Post Boil OG.

If my assumptions are incorrect about the end result of this then perhaps I just had terrible efficiency yesterday.  I noticed the boil time difference during the mash and after adjusting Boil time in BeerSmith I was prompted to add ~1 gallon to my sparge.

Regardless, the reported Boil Time is not preserved post scale so I'd like to understand the expected results.

My Details:
Platform = Windows 8 (x64)
BeerSmith 2 Version = 2.1.02
Expected Result:  The Boil Time used in the base recipe would be the same in the scaled up target

Hi,
  Is it possible that when you scaled it the recipe you actually changed the equipment profile (such as from a 5 gal profile to a 8 gallon profile)?  The reason I ask is that the equipment profile also has a boil time associated with it so if your new equipment profile has a different boil time then it will change the recipe also.

  I just tried it leaving the equipment profile the same (90 minutes) and just changing the batch size, and the boil time did not change.  The only time I could get the boil time to change was moving to a different equipment profile with a different boil time embedded in it.

Brad

Thanks for the reply.  Yes, it seems that is exactly what happened.  I created a new equipment profile with a 90 minute boil time and the scaled recipe now shows 90 minute.

I guess that isn't what you (I) think should happen in that scenario but at least I now understand what happened.  It seems to me that the recipe I'm scaling should scale in every way.  I wouldn't expect that using a larger MT and Kettle would change my boil time for the recipe I created.

As it turns out, me simply adjusting the boil time after the fact was "the right thing to do" after all. Doing that did increase water volumes closer (not exact) to that of the recipe scaled to a 90 minute boil equipment profile.  So it seems that I just had terrible efficiency...  :-[

What do you suggest is the best path?  Creating unique equipment profiles for all my recipe scenarios or simply being diligent about checking all adjustable fields in the future?