Johnson A419 Differential

[AnOldUR]

I'm using a Johnson A419 for mash temperature control. I have the differential set at 1 and the temperature set at 151. Heat stays on until it hits 151 then shuts off. It stays off until reaching 149. You could say that it allowed a one degree drop and kicked in after it got below that, but to me that's a 2 degree difference in temperature. Or could I have some other setting wrong?

 

[tyzippers]

I was under the impression that if the set point was at 151 with a 1 degree differential, then the controller would kick off at 152 and kick on at 150. One degree above and below.

 

[AnOldUR]

No. That's controlled by cut-in, cut-out. It controls either turning on or off at the set point, so it will vary only above or below that temperature depending on which you use. My question is where it should be turning back on? Right at 1 degree, or allowing one degree and than changing after that?

Pretty sure my Ranco only allows one degree.

 

[LKHA]

Off at set allows 1 on at 2 so it is correct allowing 1deg off set

 

[tyzippers]

No. That's controlled by cut-in, cut-out. It controls either turning on or off at the set point, so it will vary only above or below that temperature depending on which you use. My question is where it should be turning back on? Right at 1 degree, or allowing one degree and than changing after that?

Pretty sure my Ranco only allows one degree.

Ok. I got ya. I just took a look at the Johnson instructions. It operates a bit differently than my Ranco. At any rate, is it possible that the Anti-Short Cycle Delay is set so that it is preventing the unit from operating before the PV drops more than one degree below the SP?

Just spitballing here...

 

[DSmith]

I saw the A419 1F differential to be more like 2F in reality vs. the screen setting, datalogging in both heating and cooling mode. Multiple data sets with the A419 led me to buy a Love TSS2 and now use it with 0.3F differential. The 0.1F resolution is really nice if you start caring about 1-2F differences. That's a feature unique to the Love TSS2.

 

[AnOldUR]

The 0.1F resolution is really nice if you start caring about 1-2F differences. That's a feature unique to the Love TSS2.

The OCD in me may have me make that switch somewhere down the road (unless the lazy part wins out.) Although I doubt that it will make too much difference in the beer. Now, if I want 150 degrees, I set it at 151. At the extremes it'll hit 151 and 149, but still spends most of the time at 150 and works fine for stepping temperatures.