Ferm temp got too high over night

[PSB-Roger]

So about 36hrs into Fermentation the Solenoid valve for my Glycol failed to fire and thus temp rose. on my last check before leaving for the night temp was at 66 @ about 10:30 pm. When i came back in around 9:30 am temp was at 76 and at some point the krausen had made its way out the blowoff and into my bucket. I fixed the solenoid(and have since tested it and it is working fine, but have ordered another anyways) and got temp back down to 66 by about 1-2pm. Now however fermentation has slowed to the point where i have to move the blowoff tube to even prove that CO2 is still bubbling. late last night I checked Gravity and it was in the 1.024 range and this morning around 1.020. This was a porter with an OG of 1.065. Batch Size 3BBL.
Question's are what kind of damage was probably caused in the 12 or so hours that the temp got out of control, and why has ferm slowed like this now?

Sorry for rambling but any help or advice would be great.

[jebzter]

76 degrees isn't too bad, you will want to taste it for more esters and off flavors. In a porter, you probably wont notice. Had a tank do something similar, got to 95 degrees though and it was a phenolic, and dead yeast tasting nightmare, which was only deserving of the drain. As for the slow down, two possibilities, one is that the time to get from 76 to 66 was very quick and you shocked the yeast and some have gone dormant, or you are just approaching your terminal gravity already because at 76 degrees, the yeast did the work much faster.

[soia1138]

You did more damage by dropping the temp down to 66 from 76 than you would have if you left it. 36 hours in is normally when I will start letting the temp free rise to 75F on ferments using US05. Yeast does not appreciate a temp shock like you gave it. Most of the ester production happens very early on but dropping the temp will cause them to go into a protection mode and most likely struggle to fully ferment. That being said, it seems like you might be close to terminal at 1020 on a porter.