Question for users of a digital temp controller

So after fermenting a British Bitter at 76 degrees during these scorching summer days in Arkansas, and having the A/C go out after priming the same batch, I decided to get one of these:



My question is basically: how do I use it?? The instructions are kind of cryptic. For example, the Set Point is the temperature at which you want the thing to turn on your fridge. But what does the Differential, the Anti-short Cycle Delay, and the Temperature Offset do?

I've set the Set Point to 55 degrees F, and I've noticed that it kicks on when it gets to 56 degrees F. The problem is it keeps cooling and the temperature sometimes gets to 49 degrees F.

I want to have this figured out by tomorrow. I'm brewing a Nut Brown Ale, and I'd like to let it ferment at around 65 degrees (as measured by the wort, not ambient). Any suggestions on how I should configure this doo-hicky?

I'm a computer programmer for a living, so it makes this post that much more humiliating.

Hi,

I am not entirely familiar with the Johnson controller but:

Differential -or- Temperature Offset(not sure which one) will control how much fluctuation there is in the temperature, so say you set 55 with a differential/offset of 2 your cooling will kick on at 57 and off at 53

For the Anti-short cycle delay, I would assume this is why the colling keeps going. I have a feeling this keeps the compressor from going on and off repeatedly or on and off in a set period of time.

ExpertBrewers said:

Hi,

I am not entirely familiar with the Johnson controller but:

Differential -or- Temperature Offset(not sure which one) will control how much fluctuation there is in the temperature, so say you set 55 with a differential/offset of 2 your cooling will kick on at 57 and off at 53

For the Anti-short cycle delay, I would assume this is why the colling keeps going. I have a feeling this keeps the compressor from going on and off repeatedly or on and off in a set period of time.

Click to expand...

If it didn't have a couple degree offset then your compressor would burn up trying to keep the freezer at the same temperature. With several degrees of play, the compressor won't kick on as much which minimizes damage.

You basically set the SP to the temp. you are shooting for, and it will keep it within that range. It will have a certain set degrees of deviance, like said above, this will prevent your compressor from killing itself. When I have mine outside, even a 4 degree swing will turn it on just opening it on hot days.

I basically ended up just playing with it a bit, I still don't know exactly how or why it works but it seems to be keeping the beer at a constant 64 degrees. And man the yeast seem to LOVE it. Woke up this morning with a nice 3-inch healthy krausen less than 24 hours after pitching.

I'm never looking back to the days of hot summer ferments again! I just wish I had a bigger fridge or freezer.

Man, thanks for posting this, I was looking at the exact same controller, and had the exact same questions!

DutchK9 said:

If it didn't have a couple degree offset then your compressor would burn up trying to keep the freezer at the same temperature. With several degrees of play, the compressor won't kick on as much which minimizes damage.

Click to expand...

I just got the Ranco digital today. What's a good setting for the differential to minimize compressor damage while not having the temp swing too much for the beer?

I have mine set to 4

I thought differential was the +- from the set temperature, and the offset was how different from actual the controller registered, meaning if it's really 75, and the controller showed 73, the offset was 2.
-keith

I have the Ranco and it does not have a temperature offset feature. I assume this may be a calibration setting but could be wrong. For example, if compared to a calibrated lab thermometer the controller reads a difference of 2 degree's then this would allow you to "offset" from the reading to get a more accurate controll. Of course this is speculation on my part.

What has already been said about the differential and setpoint is correct however, you may want to try an experiment with a calibrated themometer.

It's a well known fact that the wort temp can rise up to 10*F during fermentation due to exothermic heat generated by the yeast. I suggest you try to measure that actual temperature of fermentation and utilize a setpoint around that.

For example, I generally set my controller 5 to 8 degree's lower than my desired ferm temp to compensate for the generated heat.

Some brewers simply tape the probe to the side of the fermenter with success and others buy a fermentation thermowell (available from B3).

GilaMinumBeer said:

I have the Ranco and it does not have a temperature offset feature. I assume this may be a calibration setting but could be wrong. For example, if compared to a calibrated lab thermometer the controller reads a difference of 2 degree's then this would allow you to "offset" from the reading to get a more accurate controll. Of course this is speculation on my part.

Click to expand...

Here is what the booklet that came with mine says about the Temperature Offset feature:

Temperature Offset (OFS) establishes a set secondary Setpoint and Differential values that may be invoked to control an application when a circuit is closed between the binary input (BIN) and common (COM) terminals (and BIN appears on the display). See Figure 6. Offset range is 0 to 50F or C (in 1-degree increments). A typical application might use a switching time clock to invoke night-setback temperature settings.

Click to expand...

Anyone get that?

damrass said:

Anyone get that?

Click to expand...

Sure - you use an outside control device to change the set points - not something we would probably do as homebrewers. I think you can safely ignore that setting, as it won't get invoked without hooking another control device up to the temp controller.

damrass said:

Here is what the booklet that came with mine says about the Temperature Offset feature:



Anyone get that?

Click to expand...

Hmmm. I am not sure how it would be implemented for brewing but I can see the commercial application. IIUC, these controolers are originally designed to operate HVAC systems. Some buildings conserve energy by raising the building temperature in the evenings so, this may be the application atht the controller was designed for. Again, pure speculation on my part.

I have the Johnson controller pictured in the original post.

The SP is the temperature at which the controller turns on. Depending on whether it is set on cooling mode or warming mode it will turn on when the temperature rises above or falls below that temp, respectively.

The differential is the number of degree below (or above) that set point at which the controller turns off.

The offset is only used if, for instance, you know your fermenter is always 2 degrees warmer, colder, etc than the temperature measured by the probe. It is very unlikely that this value will stay the same, so I just set it to zero.


My current settings are:
SP=69F
Diff=2F
Off=0
Short cycle=10 min

This keeps the carboy temp between 67 and 69 (My target temp is 68 for WLP001).


As another trick...
Use a cold pack that comes from Norther Brewer with yeast or one that you can buy at the grocery store and let it warm to ambient temperature. Sandwich the controller temp probe in between the "cold" pack and your carboy with some tape. You'll get an fairly accurate measurement of the actual carboy temperature (not your fridge air temp) and it won't fluctuate every time you open the door.

dlauver said:

I have the Johnson controller pictured in the original post.

The SP is the temperature at which the controller turns on. Depending on whether it is set on cooling mode or warming mode it will turn on when the temperature rises above or falls below that temp, respectively.

The differential is the number of degree below (or above) that set point at which the controller turns off.

The offset is only used if, for instance, you know your fermenter is always 2 degrees warmer, colder, etc than the temperature measured by the probe. It is very unlikely that this value will stay the same, so I just set it to zero.


My current settings are:
SP=69F
Diff=2F
Off=0
Short cycle=10 min

This keeps the carboy temp between 67 and 69 (My target temp is 68 for WLP001).

Click to expand...

That makes perfect sense. Thanks! Explains the temperatures I've been seeing with my configuration.

As another trick...
Use a cold pack that comes from Norther Brewer with yeast or one that you can buy at the grocery store and let it warm to ambient temperature. Sandwich the controller temp probe in between the "cold" pack and your carboy with some tape. You'll get an fairly accurate measurement of the actual carboy temperature (not your fridge air temp) and it won't fluctuate every time you open the door.

Click to expand...

My carboy has a carboy hauler on, and I've just stuck the probe in between one of the straps and the carboy wall. Fits snuggly there, and it seems to be reading at what the stick on thermometer reads. Opening the door doesn't seem to have any affect on it either.

I read this somewhere...

I wrapped the probe in a paper towel (folded a couple of times, then cling wrap and then some packing tape to hold it together. Then I left it just hanging about halfway down in my chest freezer.

Anyone see a problem with this??

Thanks,
Stuart

stuartm said:

I read this somewhere...

I wrapped the probe in a paper towel (folded a couple of times, then cling wrap and then some packing tape to hold it together. Then I left it just hanging about halfway down in my chest freezer.

Anyone see a problem with this??

Thanks,
Stuart

Click to expand...

That would work to prevent the temperature swings from opening the fridge door (and the unnecessary wear on the freezer compressor), but if you have an extra vigorous fermentation the carboy could actually be a degree or two warmer the the air temperature that the probe is measuring.

Thats kinda anal though, I'm sure the temps you're measuring are basically the same as the carboy.