Brewzilla temperature calibration

[Hop_it]

I imagine that this topic has been covered before, but I could not be bothered to look back through 546 pages of topics to find out. So, here we go again . . . . .

I brewed a couple of days ago, and suffice it to say it was not one of my best days. The beer was a rye pale ale, using ~20% of malted rye . . . . . it's a long story Anyway, whilst struggling to get my mash up to temperature after the beta-glucanase rest I realised that it was not going to get up to the set point (in this case 66 degC). I had previously trusted the BZ readout to be reasonably accurate, and had not paid too much attention to checking it. Several hours later when I eventually got to the boil phase, I noticed that the readout was showing 102 degC. Now, I understand that a sugar solution boils at a higher temperature than water, but after doing a bit of research I found data that suggested that the change to the boiling point of a typical wort with an OG of ~1.060 is only +0.2 degC. This confirmed my growing suspicion that the temperature calibration might be wrong . . . . despite the manual suggesting that this is very unlikely.
The following day I put ~10l of water in the BZ, and heated it up to 45 degC, and set the pump going. I checked the temperature with 2 digital thermometers, and conventional mercury thermometer, and a jam making thermometer. In all cases except for the jam making thermometer I was achieving measured temperatures between 1.5 and 2.0 degC below the set level and the digital display. I then ramped up the temperature in 5 degree steps, and repeated the measurements. I got the same results all the way up to 75 degC.
So, the lesson is . . . . . Do not assume that the calibration is correct. I've now adjusted it by -2 degC to compensate for the error. Hopefully it will behave better in future

 

[AnimatedGIF]

Good to know
I wondered if it would need calibration before using. I just bought one of these and am itching to get a brew going on it.

 

[stripeyjoe]

On my BIAB system I tend to recalibrate my PID on the fly during mash after taking a few measurements of the grain bed temp and the wort coming out of the recirculation hose. I also do a check just before strike. I’m not sure anything is going to be bang on as, generally, you are measuring the temperature at the base of the boiler, right next to the element.

 

[Hop_it]

Good to know
I wondered if it would need calibration before using. I just bought one of these and am itching to get a brew going on it.

Using the BZ can be a long, and at times frustrating learning curve. . . . . . But with a little bit of time and effort I have at least managed to eliminate one source of error.
However, I'm still not convinced that the BZ is best suited to step mashing. You need a really good flow through the grain bed to have any chance of bringing the temperature up at a reasonable pace. Just heating up the wort in contact with the heater is not good enough. I tried adding a couple of kettles full of very hot water to bring the temperature up a bit quicker. However, this has to be taken away from your sparge volume, otherwise it messes up your total volume calculations. So, I will keep on experimenting until I find a better solution