Johnson A419 for RIMS?

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sweetcell

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i'm in the planning stages for my single-tier brew stand. i will be using propane burners for the HLT and BK, but want to use RIMS to maintain temps in the MLT. my plan is to use a low-density 120V element.

is there any reason why i couldn't use a Johnson A419 controller (or something similar) to control the heating element? my thought is to constantly recirculate the mash, stick the A419's probe at the output of the RIMS tube and plug the heating element into the A419 which has been set to mash temps. seems to me the A419 has enough flexibility to maintain temps (http://cgproducts.johnsoncontrols.com/MET_PDF/125188.PDF). is there something better than a A419?

i might get around to building myself a proper PID controller at some point, but seems to me that the A419 has everything needed and will get me going faster. just getting the brew stand built and piping in the propane will be a pain. if/when i get a PID controller built, i can re-purpose the A419 for fermentation control.

again, pardon my ignorance and thanks for your help!

Digital-Temeperature-Controller-web.jpg
 
It looks like it would probably work ok to start out with. The relay is rated for 16a so you would be limited to a 1500w element. But that should be fine for the RIMS tube.
 
The probe is not waterproof so you will need to come up with some type of thermowell for it. I just used this type of setup to run an e-BIAB test batch two nights ago. I snaked the probe into the mash through my barbed fitting on the lid and put it in thermoplastic tubing with a brass butt end barbed fitting on the other end. It worked well and kept temps within 2+/- degrees once it ramped up. I recirculated the mash and it only had to kick on a few times during the hour. It can handle a 1500 watt element just fine, but you have to change the jumpers inside to handle heat vs cooling.

That all being said, a PID controlled RIMS or HERMS is really the way to go for an end game solution. A PID can turn on and off in split seconds. The Johnson only cycles on and off with a 2 degree swing, even set at its narrowest offset setting.
 
Have the specs on the Johnson a419 changed? Happened upon this thread and the manual I have for my A419 states states the following specs:

Wide Temperature Differential Adjustment
Range (1 to 30F° or C°)

If I remember correctly, the temp differential is 1 degree (F let's say). That means once it gets below your temp by 1 degree, it turns on. It turns off at 1 degree above your set temp, so really like a 3 degree span.

I forget how it works, but you can set the way it cuts in or cuts out, maybe getting you to 2 degree accuracy.
 
As far as I know the Johnson has a mechanical relay though which isnt ideal for constant quick changes in state... This is normally why an SSR is used for such things because there are no relay contacts to heat up and burn up or fuse closed... My rims element turns on and off multiple times a second sometimes to maintain temps... Not the ideal task for a Johnson controllers mechanical relay.

That said I know of at least on person using one to control his HLT temps which I believe would require less frequent switching..
 
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