eBIAB and Temp Drop - How much is too much?

I've done two batches now in my newly completed electric kettle. On the first batch the temp drop pretty quickly and so I added 3 layers of Reflectix on the sides and 2 on the top before the second batch. I brew indoors (71F).

Here are the readings from my temp probe on the second batch (target was 152F):
10:42 - Strike water 158
10:44 - 156
10:52 - 155
10:57 - 153
11:09 - stirred and the temp rose to 151
11:20 - 147
11:32 - 142
11:32 - stirred and temp rose to 148
11:39 - 143

Is my temp fluctuating too much? Is this costing me efficiency? Is it worth recirculating so I can use my element during the mash to hold temp?

dfborn said:

Is my temp fluctuating too much? Is this costing me efficiency?

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It's not so much a question of costing you efficiency as it is changing the character of your beer. Without going into great detail about the chemistry involved, some styles (like many Belgians) mash in the upper 140's for a drier result vs. other maltier/sweeter beers which may mash up around 156*F. A 6-8*F difference in mash temp can have a significant influence.

dfborn said:

Is it worth recirculating so I can use my element during the mash to hold temp?

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Absolutely. I recirculate gently via a DIY stainless sparge arm during the entire mash. My keggle isn't insulated, but maintains a consistent mash temp throughout.

That's one of the best things about eBIAB. The ability to set a precise mash temp on the PID and keep it there.

dfborn said:

I've done two batches now in my newly completed electric kettle. On the first batch the temp drop pretty quickly and so I added 3 layers of Reflectix on the sides and 2 on the top before the second batch. I brew indoors (71F).

Here are the readings from my temp probe on the second batch (target was 152F):
10:42 - Strike water 158
10:44 - 156
10:52 - 155
10:57 - 153
11:09 - stirred and the temp rose to 151
11:20 - 147
11:32 - 142
11:32 - stirred and temp rose to 148
11:39 - 143

Is my temp fluctuating too much? Is this costing me efficiency? Is it worth recirculating so I can use my element during the mash to hold temp?

Click to expand...

Where are you taking your temp readings? At the kettles edge? In the middle of the grain? Everywhere?

To get a good idea of what your temp is doing I would only pay attention to what your "post stir" temp readings are doing, and I would also ignore any temperature readings early on in the mash as it takes a while for the temp to settle down after adding grains. Lastly, you need to take the reading close to the same spot in the kettle every time to get a good approximation of the rate of temp loss. If you take one reading at the kettle wall before stirring it's going to be a lot lower than a reading in the middle of the grain bed.

To me, it looks like you hit your mash temp spot on at 151F (11:09 reading) and you only lost about 3 degrees during the entire mash to 148F (11:32 reading).

But yes, your temperature will vary across the kettle if you're not somehow circulating or continuously stirring. My own concerns with temperature variances and the impact on repeatability was one of the reasons for me to go circulating eBIAB. But you don't have to go this route. Lots of folks make excellent beer and simply don't fuss about this temp stratification issue. I would bet that Mark Schoppe doesn't worry about this on his award winning 1 to 2 gallon batches.

TexasWine said:

Where are you taking your temp readings? At the kettles edge? In the middle of the grain? Everywhere?

Click to expand...

The temp readings are from my RTD probe for my PID. It's in the kettle wall a few inches to the right of where the ball valve is.

And you're right that only including the post-stir reading changes the picture quite a bit.

Thanks.

dfborn said:

The temp readings are from my RTD probe for my PID. It's in the kettle wall a few inches to the right of where the ball valve is.

And you're right that only including the post-stir reading changes the picture quite a bit.

Thanks.

Click to expand...

Ah so this leads to more questions. Why do you have a PID controller? Most people use them to control mash temp. But they're almost always used in conjunction with a pump.

Insulating will help with heat loss and stratification but the only way to keep everything one solid temp and allow the element to correct for it is to recirculate.

TexasWine said:

Ah so this leads to more questions. Why do you have a PID controller? Most people use them to control mash temp. But they're almost always used in conjunction with a pump.

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I started with a PID that could do both auto and manual planning to move to recirculating at some point, and I already had it.

For you guys that do recirculate how do you return the water at the top of the mash. e.g. Spray head, simple hose, from the side of the kettle, etc

dfborn said:

For you guys that do recirculate how do you return the water at the top of the mash. e.g. Spray head, simple hose, from the side of the kettle, etc

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Through the lid. I have a tee in the lid which also holds my temp probe. On the underside a simple silicon hose connects to a barb which is attached to an elbow connected to the tee.

I'd go ahead and spring for circulating capabilities if I were you. Sounds like you've key much got everything you need except for a pump. Save some coin and get one of those 24v DC pumps for about $50. I've got one and it works great.

http://brausupply.com/collections/plumbing/products/brew-pump-24v