Room temp

Hi,
My yeast has a optimum temp of 67-74, my room temp has been holding at 70 the last 2 days (first 2 of primary) with good airlock activity. Last night the room got to 63. I turned the heater on to warm the place up. Did this dip in temp screw my brew up?, does the internal temp of the fermented increase when their is active fermentation?, if so how much?, also what might happen if I brew at a couple degrees below suggest temp?, using wl400 Belgium wit yeast.

Thanks for the info!

Shouldn't be a problem. The optimum temperatures are for fermentation temp which will vary from ambient room temperature quite a bit. Fermentation creates heat. For example, I fermented my last brew at around 65F which meant I kept my fermentation chamber at 60F. One thing that is useful is to put stick-on thermometer on your carboy or bucket. They aren't the most accurate but they're pretty good.

I haven't used WL400 but my guess is you don't have to worry. Now, when you are going for a cleaner style of ale you might want to let it ferment at a lower temp (eg, 63F) Higher fermentation temps will give rise to certain characteristics that might be fine in a wit, some belgians, saison, etc. but you don't want your stout to taste too fruity. It's why a lot of brewers are seasonal (lagers in winter, etc.)

Cheers

I doubt it dropped much in temperature since it was during active fermentation and you caught it quickly.

70 ambient is a little high. Ambient temperature tells you nothing about fermenting temperature. You're probably going to get some esters/phenols with that temp, as active fermentation can easily raise the temp inside by 5-10. From what I hear getting fermentation temp under control is the next step to making better beer.

You'll be fine. It takes quite a while to get your beer temp way down if your ambient temperature drops over night. Try and get your temperatures steady at least during active fermentation. You might get a slightly more fruity flavor from higher temps but the beer will be terrific regardless.