Author Topic: Got the refrigerator thermostate, now 3 (quickish) questions  (Read 1295 times)

Offline cowardm

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I'm about as unhandy as they come so I had a couple of questions.

1) Ok, got this thing in and I know that somehow this copper wire goes into the fridge to take a reading on the temperature.  So, do I just uncoil it and wind it around through the door and let it just sit anywhere in there? Or is there a back way I need to put it in, or does it go in the freezer, or what?  Anyone have pics of their own?


2) If the optimal fermenting temperature of a yeast is say 68-73F do I need to keep the fridge at like 70F or will the internal temp of the fermenter (carboy) be warmer than the temp of the fridge?

3) Last.  So, even though this is a 6.5gal I've needed a blow off hose for every batch (just for the first 2 or 3 days).  Could it be because I haven't been regulating temperature before this, or do I just need to have one anyway?
Michael

Offline brewbeard

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Re: Got the refrigerator thermostate, now 3 (quickish) questions
« Reply #1 on: May 19, 2010, 02:11:03 PM »
1) With an analog controller, which usually has a large differential of 3 degrees Celsius, I would let it hang in the air in the refrigerator with the wire simply running through the door of the refrigerator.

2) Since fermentation produces heat, the fermenter will be warmer than the ambient air. Therefore, you need to set the controller a few degrees below your desired fermentation temperature. I set mine about 4-6 degrees lower, depending on how vigorous I know the yeast is. However, you always want to measure the temperature of the fermenter. Those cheap stick-on fermometers are surprisingly accurate. This way, you can adjust the controller if the fermenter is warmer or cooler than you want it to be.

After a few brews, you'll get a pretty good idea of how much lower you need to set the controller to get it to your desired fermentation temperature.

3) In general, you won't get as much blow-off after you start fermenting cooler. The only exceptions are for particularly crazy yeast, i..e hefeweizen, Belgian, etc. In my opinion, fermentation temperature control is one of the most important things you can do to improve the quality of your beer. After controlling temperatures, my beers stopped tasting "off" and started tasting a lot more like commercial craft beer.

Offline a10t2

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Re: Got the refrigerator thermostate, now 3 (quickish) questions
« Reply #2 on: May 19, 2010, 03:15:32 PM »
Make sure you calibrate that controller too. Mine is off by 6°F.
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Offline dak0415

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Re: Got the refrigerator thermostate, now 3 (quickish) questions
« Reply #3 on: May 19, 2010, 03:44:21 PM »
I have a digital controller but I put a 5 inch muffin fan in my fermreezer and blow air onto the carboy.  Much less temp deviation.
Dave Koenig
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Offline micsager

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Re: Got the refrigerator thermostate, now 3 (quickish) questions
« Reply #4 on: May 19, 2010, 07:33:05 PM »
I would let it hang in the air in the refrigerator with the wire simply running through the door of the refrigerator.

I look at things a bit different.  I duct tape the probe as tight as possible with some insulation to one of my buckets/carboys.  It's the temp of the beer that's critical, not the temp of the air surrounding it.

But at the end of the day, it's all beer.  And how can that be a bad thing?

Offline dak0415

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Re: Got the refrigerator thermostate, now 3 (quickish) questions
« Reply #5 on: May 19, 2010, 08:28:28 PM »
I would hesitate manipulating the bulb on that controller.  That copper coil is hollow and if you kink or break it the controller is useless.
Dave Koenig
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Offline richardt

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Re: Got the refrigerator thermostate, now 3 (quickish) questions
« Reply #6 on: May 20, 2010, 04:41:09 AM »
I'm researching the controller issue, as well.  I definitely want to improve my control over fermentation temps.
I find it frustrating that we can't just swap out a controller module on the fridge and use the existing thermometer.

Online, I've found that the analog controllers are around 50-60 bucks and the digital ones run around 70-90 bucks.

Are the digital ones (Johnson or Ranco) any better? 
Is there still an issue with the hollow copper coil linking the probe to the digital controller or is it a different type of probe?
I'm also curious--If half of the copper coil was outside the fridge, wouldn't it "warm up" the air within the probe by the time it got to the controller and give a falsely higher reading?  Or is the temperature of the probe tip all that matters?  Why is the copper coil hollow, anyway?  Opening and closing the refrigerator door is bound to compress or kink the tube, anyway.  I'd rather use a probe that can stand up to some abuse.

Anybody figure this out yet? 

Offline dean

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Re: Got the refrigerator thermostate, now 3 (quickish) questions
« Reply #7 on: May 20, 2010, 05:09:24 AM »
If the fridge is specifically for brewing and not going to be used in the house as a normal fridge, I would and do drill a hole in the side of the fridge just large enough for the bulb to be inserted.  You'll need to uncoil the capillary tubing just long enough for the bulb to reach the point you want to mount the bulb... strap the bulb down (hardware stores generally have small clips available) inside where the cold air duct doesn't blow on it and somewhere preferrably on the wall.  Don't worry about kinking the capillary tube, just don't put a sharp bend in it or get rough and hasty with it... its meant to be unrolled so you can position the bulb away from the control.  I use them all the time, they are reliable, they aren't sensitive to voltage and or moisture issues like some digital controllers.  Usually commercial refrigeration controllers are sensitive to within plus or minus 2 degrees F not C.  You can calibrate it by filling a small bucket with 50% "small or shaved" ice and 50% water... the temperature of the slush will be close to or at 32 F.  But if its new, its a good bet that its already calibrated.... check it and see if you feel the need.

Don't forget to pick up some silicone and fill the hole you drilled after you've inserted your temperature probe.  There are more things you can do and get quite accurate control with an analog controller but thats another day and I'm only allowed to give out one or two secrets a week.   ;)

Offline dean

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Re: Got the refrigerator thermostate, now 3 (quickish) questions
« Reply #8 on: May 20, 2010, 05:19:54 AM »

Is there still an issue with the hollow copper coil linking the probe to the digital controller or is it a different type of probe?
I'm also curious--If half of the copper coil was outside the fridge, wouldn't it "warm up" the air within the probe by the time it got to the controller and give a falsely higher reading?  Or is the temperature of the probe tip all that matters?  Why is the copper coil hollow, anyway?  Opening and closing the refrigerator door is bound to compress or kink the tube, anyway.  I'd rather use a probe that can stand up to some abuse.

Anybody figure this out yet?  

The capillary tube is hollow to allow the expanding gas inside the bulb to effect the position of the bellows diaphram inside the control to move... remember, temperature is pressure and pressure is temperature.  So the gas in the bulb which is inside the fridge reacts to the temperature IN the fridge, as the temperature goes up the gas inside the bulb expands exerting pressure on the bellows which moves the position of the electrical contacts inside the controller... which can be mounted anywhere within the length of the capillary tube.  Mounting the contol outside the fridge is the best option imo... less moisture issues generally.   The bulb is about as rugged as you can get and gas laws are more constant than any digital programming that can hiccup at any time or could be effected by someone having a bad day on an assembly line.   ;)
« Last Edit: May 20, 2010, 05:24:28 AM by dean »

Offline richardt

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Re: Got the refrigerator thermostate, now 3 (quickish) questions
« Reply #9 on: May 20, 2010, 10:37:03 AM »
Would having the majority (or all) of the copper tubing within the fridge be the best way to go?  In other words, even though the bulb is inside the fridge, should I minimize/eliminate the amount of copper capillary tubing outside the fridge (where it is warmer)so that the gas doesn't warm up by the time it gets to the controller?  Or am I forgetting some impt physics here?

Offline a10t2

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Re: Got the refrigerator thermostate, now 3 (quickish) questions
« Reply #10 on: May 20, 2010, 12:26:13 PM »
In other words, even though the bulb is inside the fridge, should I minimize/eliminate the amount of copper capillary tubing outside the fridge (where it is warmer)so that the gas doesn't warm up by the time it gets to the controller?

It won't make a significant difference. The volume of the tube is tiny compared to the bulb.
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Offline dak0415

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Re: Got the refrigerator thermostate, now 3 (quickish) questions
« Reply #11 on: May 20, 2010, 02:37:58 PM »
I think you guys are missing the point.  The analog controllers measure pressure, not temperature.  I don't know if there is a gas or liquid in the bulb, but there is a sensor in the controller detects the change in pressure of the substance, and makes/breaks a relay in the thermostat.  That is why, if you kink the coil, it seals off the bulb from the sensor.
Dave Koenig
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Offline richardt

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Re: Got the refrigerator thermostate, now 3 (quickish) questions
« Reply #12 on: May 20, 2010, 06:37:26 PM »
I'm guessing gas, since liquids are practically non-compressible.
But, now that you've got me curious, I'm gonna have to look up all these various sensors and thermistors and figure out how they work.

Offline dean

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Re: Got the refrigerator thermostate, now 3 (quickish) questions
« Reply #13 on: May 21, 2010, 03:55:58 AM »
I think you guys are missing the point.  The analog controllers measure pressure, not temperature. 

 :D  Okay, one more time... specifically in this case, pressure and temperature are both effected and predictable if you know either one you can know the other.  Which gas is used in the bulb doesn't really matter as long as the manufacturer calibrated the control to that gas.  Pressure is temperature, as the fridge warms up the gas in the bulb expands forcing the contacts in the controller to close which provides power to the cooling circuits and once again cools the fridge causing the gas in the bulb to contract opening the contacts removing power from those circuits. 

As far as the tube being mostly in or out, its your choice, doesn't matter.  I've put many controls in like yours and actually kinking them so they won't work is much harder than you think so don't sweat it.   That control is likely to outlive you, see if a digital lasts so long.   ;)  The control will generally have a minimum 2 degree differential built in to avoid short cycling the compressor... on and off, on and off, etc.  You can adjust that wider if you want, generally you don't have to but in some situations it may be desirable.

If you want to go digital, spend the money and get one that has all the bells and whistles otherwise dollar for dollar the cheaper ones probably aren't worth it in the long run.  jmo.