Temperature Controller

[ZacMac]

Just got my Johnson Temp Controller. Having a little trouble with balancing the desired temp. Is there any trick to where the thermostat on the fridge should be set. Set to run it's coldest so that when the controller kicks in, it is sure to run. Or will this damage the compressor somehow? Thanks.

 

[BlindLemonLars]

Is there any trick to where the thermostat on the fridge should be set. Set to run it's coldest so that when the controller kicks in, it is sure to run. Or will this damage the compressor somehow? Thanks.

You got it right, just crank it all the way up. You're essentially bypassing the controller in the fridge, and letting the Johnson manage the temperature. Most external controllers allow a few degrees of swing (which is adjustable on some) to make sure the compressor isn't chat-tering on and off.

 

[ZacMac]

You got it right, just crank it all the way up. You're essentially bypassing the controller in the fridge, and letting the Johnson manage the temperature. Most external controllers allow a few degrees of swing (which is adjustable on some) to make sure the compressor isn't chat-tering on and off.

That's great, thanks for your input Lars.
Any suggestions on whether or not to keep the temp probe in water or wrap in a wet towel?

 

[BlindLemonLars]

Any suggestions on whether or not to keep the temp probe in water or wrap in a wet towel?

Technically, I suppose keeping the probe in a container of liquid is the correct thing to do. Personally, I dangle the probe between the carboys/kegs, and it seems to work out fine.

I don't like the wet towel idea, as I think it would be inviting mold and mildew to develop. You want to keep the inside as dry as possible, I even keep a container of Damp-Rid in there towards that end.

 

[mnadamn]

First off, sorry for the long post.

Well... I would not with the controller you have. Correct me if I am wong but it should have about a 4degree temp swing +or- 2 degrees. If you have this set for your air temp (no water or towel) the thermal mass of the beer will protect it from the swings and will maintain a pretty constant av between the 2 extremes and hold at your set point. If you have water in the equation The more water you have the more thermal mass has to be efected before the probe switches on the compressor. This means that the ambient temp will have changed far more significantly then the 2 degrees that you would have without either method and that will allow the beer to have more temp swings/less consistancy. This is even a bigger concern if you are using it to ferment in. This is because for the temp probe to recieve the heat, the heat first leaves the carboy/bucket/whatever then changes the ambient air temp which then changes the temp of the probe water. this time delay allows the fermenation to heat more then desired and when the compressor does kick in the fermentation will not be cooled as much due to the amient air temp changing faster in cooling mode.

So, to sum it up... I would not use water or a towel personally. And if you are fermenting in there, I would tape the temp probe to the bucket or w/e so that it senses the slightest swings as soon as possible and adjusts the themp accordingly. An even better meathod is to get something along the lines of a temp probe sleeve so that you get even better readings.

 

[lamarguy]

mnadamn is correct - do not place the temperature probe in liquid (carboy, glass of water, etc.). If you do, you'll severely overshoot your lower target (due to the much lower ambient air temperature) and there will be a wider swing on the upper end of your target (due to the thermal change delay of the mass).

People have actually published on temperature control for homebrewing in the past. The best method is to affix a temperature probe to the outside of the fermentation container. Depending on what material the fermentation container is made of, you may need to insulate the probe from the ambient air.

Your two goals should be:

1.) Maintain an accurate target temperature with a narrow (+-2F) temperature differential in the liquid mass.

2.) Avoid starting/stopping the compressor too often.