lurker18

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Just used my two stage Ranco temp controller for the first time a week or so back, and ran into a few snags. I was just trying to drop yeast out after fermentation so there was no problems caused, but I wanted to clear things up for next time.
I put the glass carboy in the garage, the temperature never got above freezing, but there was fluctuation on how cold it was. All I had the temperature controller set to do was keep the beer from freezing. Had low set at 4C and high set to 6C, but whenever I looked at the readout, the temperature would be somewhere between 8 and 13C. The heat belt was comming on, it was warm, so the temperature was certainly getting cold enough. I assume that the high going so far over the set temperature was due to warmth moving from the outside of the glass to the middle of the wort where the probe was.
How do you avoid such big swings in temperature if I ever wanted to use this as a true temperature controller and keep the wort withing a degree or two?

GilaMinumBeer

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You have to employ heating and cooling control to mitigate swings. There will still be some variation tho'.

samc

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Where was the probe placed? That could greatly effect what you are reading.

lurker18

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Would the cooling not be taken care of by the outside temperature that was below freezing. I was trying to keep the wort just above freezing (4-6 C). I was surprised by how warm the wort got after a heating cycle.

lurker18

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Probe was in a termocel in the center of the wort, with a heat belt around the carboy.

samc

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setpoints & differentials - are they in the Ranco instructions?

not familiar with the Ranco (I use Love & Johnson controllers), but your settings might not be doing what you think they are doing. You should read up on those.

lurker18

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I read the instructions and set as what they said. Could the problem be the heat belt not heating the wort fast enough. By the time the heat has gone from the outside of the wort to where the probe is, the thermal mass on the outer part of the carboy near the heat belt has gone up so high that it continues to heat far past the shutoff points.

GilaMinumBeer

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Yes, In contrast the cooling abilities of the ambient air is insufficient to drive the temps down quickly once they have crept up. For example;

I use a chest freezer and a space heater to control wort temp within a 4 degree range. On the heating cycles the chest gets up to 80+*F. In cooling mode the freezer can drop well into the single digits.

Sort of like chilling to pitch temp. The larger the differential between the two thermal environments the more efficient the balancing act becomes.

Incorportating a fan may provide some increase to the efficiency but, having a huge differential between wort/beer and ambient is still needed. the belt is more efficient because it has a more direct transfer of heat into the liquid. The ambient air does not.