JLD614/612 Questions - Homebrewing Fermentation Setup

[Luckbad]

I recently purchased a JLD614 temperature controller (AC) and I'm using it for homebrewing. I'd like to control a freezer and heating tape at the same time to maintain accurate control of the temperature of my fermentation vessel. Note that I brew 5 gallons of beer at a time, so the thermal mass is not insignificant, and the temperature of the liquid takes a while to change.

I'll give details on how I have things configured and I'm asking a few questions at the bottom.

Here's my current setup:

• 5 cubic foot chest freezer. (Link)
• 2 feet of 11" heat tape (Link)
• JLD 614 controller (Link)

My JLD614 controller set up is as follows:

• I have a 2 outlet receptacle, the JLD614 controller, and the SSR (with heatsink) mounted inside a project box from radio shack.
• One of the outlets is connected to the SSR (terminals 11 and 12)
• The other outlet is connected to J1 (terminals 6 and 7)
• The outlet connected to the SSR has the chest freezer plugged into it
• The outlet connected to J1 (terminals 6 and 7) is connected to the heat tape
• I have a thermocouple connected and it seems to be working fine

My current settings for the parameters within 0089:

• IntY: K Thermocouple
• outY: 2
• HY: 2
• P56: 0
• rd: 1
• CorF: 1

Example: I'd like to set the temperature to 52 degrees F and make it so the chest freezer turns on if the temperature probe reads 54 degrees (then the freezer turns off if the temperature probe reads 52 degrees or lower). And, I want the heat tape (hooked up to J1) to turn on if the probe reads 50 degrees (so the temperature goes back up to 52, then the heat tape turns back off).

Questions:

• Should I set the Control Period (ot) to a high number (such as 199 seconds) to make sure the compressor on the freezer does not get damaged? It seems like it is turning on for a few seconds sometimes, and that will probably wear out my freezer's compressor.
• What is Step-Type Feedback (HY) and what should I set it to? It seems like this might be the temperature differential.
• Is it possible to use a +/- 2 degree F differential that controls both the chest freezer and the heat tape?
• Do I have to set AH1 and AL1 to specific numbers, or can these be differentials from the set point?
• Does it matter what values I set for AH2 and AL2 since I have nothing connected to J2?
• What should the parameters within 0001 look like for the Example I provide above?
• Should I actually be using outY 3 instead of outY 2? (3. J1, J2 alarm output; differential control by SSR.)
• Do you have any other recommendations for how I should change this setup to accomplish my Example?

Thanks a lot! Hopefully I can get this set up so I have accurate control over the temperature of fermentation and I can show other homebrewers how to use the JLd614!

[richiem]

Sorry -- can't comment right now. Let me have a day or two.

[Luckbad]

Thanks for letting me know you'll take a look.

I did a bit of testing with just water in my carboy (~5 gallons of it) using both outY 2 and outY 3. I'm not sure what the difference was between them, to be honest.

I was able to keep the temperature within a few degrees of my target, but it was fluctuating pretty constantly. The cooling brings the temperature down fairly slowly, so the ambient temperature inside the freezer gets pretty low before the temperature of the liquid is at the target, and it ends up overshooting... then the heat tape comes on because it is connected to the alarm, then that gets to too high of a temperature and the freezer has to come back on.

Example:
I try to hold the temperature at 60. The water starts at 65 so it has to be cooled initially. By the time the liquid gets to 60, the ambient temperature of the chamber is around 20 (and the chamber is insulated, so it takes a while to warm up), so the water gets down to 58. Then the heat tape turns on because it's set to turn on at 58. By the time the water is back to 60, the ambient temperature of the chamber is around 90, so the water ends up getting up to 62 and the freezer has to kick back on.

This is less stable than I'm after. I'm fine with minor fluctuations, but it just keeps overshooting in both directions and never quite remains stable.

[richiem]

I haven't yet been able to do a thorough review of your plan, but I do have a couple of comments --
I think you'll be better off to let the freezer to run with its own thermostat at a constant low temp of say 50 degrees or maybe 40, then use the PID function of the controller with an SSR to control the heat tape (I think you'll need more heat tape -- 20W per foot is not a lot of heat). The SSR can handle the variable cycling much better than the relays in the controller can, and doesn't care about the extra current load of more heat tape.

This does a couple of things -- it prevents short-cycling of the freezer's compressor, and also lets the controller system converge on the temp you want and then hold it. Given the thermal masses involved, the 2 degree or so variation in the freezer temp via its own thermostat won't have a material affect on control stability. This configuration should pretty much eliminate the overshoots.