Thermostat Seems Inaccurate

[cheetrowe]

Hi all,

So I picked up an old chest freezer on Craig's List and a new Johnson Controls A419 temp controller from BrewInternational.

I have my set temp at 65° and the differential at 1°, but temp on the controller has stayed around 50° today (won't go up to 65).

I have had a lab thermometer in a flask of water in the freezer for a few hours and it also reads around 50.

I'm just dangling the probe in and closing the lid on the freezer (probe is in the air, not touching the sides or anything), so there is a small space created by the wire. I'm wondering if this space, combined with the fact that my freezer is on my apartment balcony, is the problem (it's been about 45-50° today so maybe that's why--there is an overhang and it doesn't get direct sun or rain).

Anyone have ideas of what might be the problem and how to fix it? I was thinking maybe some electrical tape over the space where the wire passes through, or maybe I can do some sort of pass-through shank, but I was hoping not to drill into the freezer if not necessary.

The temp controller came prewired and is new, so unless something went wrong in the fabrication, it was supposed to just be plug and play. Any ideas would be welcome!

 

[Gavin C]

If the freezer is sitting in an ambient air temperature of 50 degrees and there is no heat source how will it gain heat and rise to 65f. It will stabilize at the ambient temp assuming it is below your set point which in this case it is.

The energy has to be added for the heat to increase and the temperarure to rise.

 

[cheetrowe]

If the freezer is sitting in an ambient air temperature of 50 degrees and there is no heat source how will it gain heat and rise to 65f. It will stabilize at the ambient temp assuming it is below your set point which in this case it is.

The energy has to be added for the heat to increase and the temperarure to rise.

Good point. Not sure why I was thinking it would do that. So basically I can only use the fermenter to lager when the ambient temperature is higher than what I want inside the freezer... (Or unless I convince the wife to put the freezer inside the apt haha).

Also I realized that I misnamed the thread...the temp control works fine of course.

 

[Gavin C]

Add a simple heat source to your setup like this one


or an incandessent lightbulb in a paint can. You can do any temperature profile you want this way.

You want to monitor the temperature of the contents of the fermenter not the ambient temp of the air in the freezer or a jar of water. Fermentation is exothermic and will give your fermenting wort a higher temp than ambient is.

Tape the probe to the side of the FV and insulate it or use a thermowell

Once fermentation is over everything reaches equilibrium. If you use the freezer as a keezer or for lagering you would likely monitor the air temps as you may have multiple vessels to control. Not so during active ferment. Apologies if this is all old info. Just thought I'd share my process

 

[Gavin C]

So basically I can only use the fermenter to lager when the ambient temperature is higher than what I want inside the freezer....

If your ambient is very cool that would be suitable for lagering. Not an option here in Texas. A temperature controlled freezer is a must have in my view. $25 for an STC 1000 and project box is a great solution.

Edit you can lager in the freezer without a heat source unless your ambient goes below a desired lagering temperature. Freezing

 

[cheetrowe]

Hmm but I thought the Johnson Controls a419 could do the same thing as the STC 1000? I'm reading online that you can change the jumpers of the a419 to control heat...so if I add the heat source I should still be able to use the one I have right? (just changing the jumpers in winter and summer I guess...

 

[cheetrowe]

ps thanks for the info...very helpful!

 

[Gavin C]

Hmm but I thought the Johnson Controls a419 could do the same thing as the STC 1000? I'm reading online that you can change the jumpers of the a419 to control heat?

It can do one or the other but not both. The STC1000 does control both. Controls heat and cool. Its much cheaper too. An even better option is the black box which has a flashed STC 1000. A little pricier but a great product.

Freezer and (DIY)controller

STC 1000

 

[Gavin C]

ps thanks for the info...very helpful!

Happy to help out in any small way.

 

[cheetrowe]

argg lol guess I should have researched more before buying the johnson controls. ah well will have to make do for now! I guess I'll pick up an STC and heater for next winter though.