Fermentation won't start

Ingredients
1

Brewed the recipe for Belgian Wit from Brewing Classic Styles 2 days ago.  I usually do an ample yeast starter, but was in a hurry so I pitched 2 vials of WLP400 instead.  Carboy was cleaned with PBW, rinsed and sanitized with Starsan.  I hit all of my numbers for the step mash and hit my target OG.  I oxygenated for 2 minutes.  It has been over 48 hours now and I see no signs of fermentation.  The only difference from the 100s of other brews I have done is the use of flaked wheat, no starter, and my oxygen tank ran out right at the end of my 2 minute innoculation.  I cooled the wort to about 65 and have had my fermentation chamber set to 68.  The use by dates on both vials of yeast is 7/4/15.  I would think the odds of having 2 bad vials of yeast would be pretty slim.  I have tried shaking the carboy a bit to rouse the yeast.

Has anyone experienced this before?  Should I hit it with oxygen again?  Any ideas?  Thank you for any ideas you want to throw at me.

2

Have you taken a gravity reading?  It could be that it’s just a slow starter with no visible kraussen yet.

3

I haven’t taken a reading yet.  I will do that this evening.  Finally this morning I have a light krausen.  Still barely getting any bubbles from my blow off tube.  Seems to be a very weak fermentation.  This is my first time with this yeast.  I read some posts from people that said it stalled on them.  Maybe I was just being impatient.  I am used to seeing a much more vigorous fermentation.

4

I just had the same experience with pitching 2 vials of WLP400.  No time for starter.  It took longer than I am accustomed to get going.  I don’t know how common that is with this yeast.  It did finally “start” on about the third day, was finished out on day 10.

5

Sounds like simply a slow start.  You should be fine since krausen is forming.

6

Thank you all for your replies.  Sounds like we had the same experience Factory.  Mine took about 3 days to start.  It seems ok now.  I have just never had that issue before.

7

I would guess with the age of the vials that you most definitely under pitched somewhat.  That yeast can be a slow starter as well and will even take some extra time finishing up as it is a pretty hefty “top-cropping” strain and will sit on top of your wort for days.  A gentle swirl here and there will help knock it back into your wort and keep the fermentation rolling along.