The difference between wort and ambient temps

I'll be brewing my first batch tomorrow since having a dedicated fridge for fermentation. I have a Johnson analog temp controller and will be using WLP007. Any suggestions on what temp to set the controller to maintain 67 degrees or so? I've read there can be a 10 degree difference and I've read that it can be 5-6 and I've also read that it can be less. I'm sure this has been discussed before and I searched 'temp controller' and the first 15 threads or so didn't seem to address it. Any help is appreciated, thanks.

It's very dependent on the material, size and shape of the fermenter as well as the volume of liquid, stage of fermentation, level of activity, ambient temp range, size of chamber used for fermentation.

Having said that, I find the temp of the wort is about 5F higher for lower ambiet temps (55-62ish) and about 7 for higher temps. I use plastic buckets mainly for primary fermentation in an upright freezer with temp controller. This is for ales. Lagers are not my forte, so I cannot speak for them.

Tape the probe to the side of the fermentor, and cover it with some sort of insulating material. This will give you a pretty accurate wort temperature.

The problem with using ambient temperature is that, depending on the level of activity of the yeast, it could be anywhere from ambient, to more than 10° over ambient. Obviously, this makes it absolutely impossible to dial in a precise differential, because there isn't one.

Ah man... Well i've spent the last couple days playing around with my johnson control and my chest freezer and heres what i was able to accomplish

emjay is right..tape a probe to the side of your fermenter with some insulation covering it. I use a different thermometer than my johnson controllers because I can adjust the controller depending on the temperature of the fermementer.

Ive got my SP at 67, my SF 0 , OFs to 0, ASd to 8 and dIF is set to 4.

My chest freezers ambient temp would vary from 61 to 67... cutting in at 67 and cooling for a few minutes before cutting out and hitting a low of 61 degrees F.

With those settings my ferm temp from the insulated probe was pretty stable at 64 degrees..

Also remember you might want your SP a little lower for the first few days of fermentation because your wort could warm up a bit due to the activity.

Not sure if this will help but i hope it does, good luck

Thanks for the responses. I'll try taping the probe directly to the plastic fermenter and insulating it. In doing this should I set the temp to 67 if that's what I'm shooting for or should I try lower 63-64?

When I brew, my wort is usually about 5-6 degrees above the ambient temperature at first. I would set your temp control to about 63 and so should be right in the middle of the ideal temp. range. After the vigorous part of fermentation, I would raise the temp to about 67 or 68 since the wort won't be producing so much heat of its own. Maybe raise the temp a couple degrees each day after the initial fermentation is complete?

ErkenneDichSelbst said:

Thanks for the responses. I'll try taping the probe directly to the plastic fermenter and insulating it. In doing this should I set the temp to 67 if that's what I'm shooting for or should I try lower 63-64?

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If you tape the probe and insulate it decently, set it to exactly what you're shooting for.

I wouldn't use the controllers probe taped to the fermenter for this reason.. It takes a large body of liquid (your wort) a long time to change a degree in temp whether cooling or warming. If your fermenter eventually warms enough to trigger the freezer to cut in, its going to be on for a long time before the fermenter cools and your controller cuts out again. your freezer could get 30-40 degrees in that time or lower! Just my 2 cents..

Thehopguy said:

I wouldn't use the controllers probe taped to the fermenter for this reason.. It takes a large body of liquid (your wort) a long time to change a degree in temp whether cooling or warming. If your fermenter eventually warms enough to trigger the freezer to cut in, its going to be on for a long time before the fermenter cools and your controller cuts out again. your freezer could get 30-40 degrees in that time or lower! Just my 2 cents..

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Freezer temp doesn't matter, the wort temp does...

Do y'all usually let it ferment at room temp for 24 hours until visible signs of fermentation appear or as soon as I put the blow off on should I put it in the fridge and attach the probe?

Begin at fermentation temps immediately. If you can't chill it down that low, go as low as you can, pitch yeast, then put it in

Many experts actually recommend pitching slightly lower than fermentation temps, and letting it rise to fermentation temps naturally, which I totally agree with.

This will happen even if you set it up with the temp controller immediately (unless you have it set up to heat as well), because cooling won't kick in until it gets just above your set-point anyways. Although even if you also have a heater, the quicker rise in heat really isn't such a big deal...

I live in Texas and it's about a steady 100 degrees every day. I set the probe to 67.5 taped it to the side of the plastic primary and insulated with bubble wrap folded four times over. Getting a dedicated fridge was the only way I can brew from March to November. No matter how it turns out it will be better than the temp swings in my office where I have been leaving the fermenters prior to getting the fridge.

ErkenneDichSelbst said:

I live in Texas and it's about a steady 100 degrees every day. I set the probe to 67.5 taped it to the side of the plastic primary and insulated with bubble wrap folded four times over. Getting a dedicated fridge was the only way I can brew from March to November. No matter how it turns out it will be better than the temp swings in my office where I have been leaving the fermenters prior to getting the fridge.

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Nice... you should definitely see a huge improvement in your beers!

So most of the bubbling has stopped and from what I've read this can be normal for the strain. Is there anything I can do help ensure the yeast is cleaning up after itself?

http://www.facebook.com/photo.php?pid=31577852&l=ae6c912923&id=1271262504

ErkenneDichSelbst said:

Do y'all usually let it ferment at room temp for 24 hours until visible signs of fermentation appear or as soon as I put the blow off on should I put it in the fridge and attach the probe?

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Ideally, you would first cool your wort to the desired pitching temperature (I prefer the low end of the recommended range and sometimes a few degrees below that). The problem with letting the fermenter warm until visible activity is evident is that you may not be able to cool the fermeter fast enough to keep it under control at that point and if that happens, it may be substantially over with before you can cool it down to the desired target temp. Typically the yeast are very active for the first few days and can generate considerable heat. After that initial burst of enthusiasm, they then slow down considerably and the wort temp will drop off. There are more than a few variables involved as others have mentioned, so these comments are meant in a general sense. Your specific system may behave somewhat differently. The size and type of the refrigeration equipment, how full it is, fan/no fan, probe placement and method of monitoring the actual wort temperature all come into play among other things.