AC Unit Fermentor Chamber Questions

[Redwiggler]

I just built a 48" X 30" X 26" ferm chamber w/ a 6000 BTU window unit. I just ordered a digital Johnson temp control for it. I rewired the ac unit so that the temp sensor is on the out side of the chamber. I still have a little insulating to do around the unit it self but over all it's extremely well insulated and air tight. So I turn it on high. close the door and plug it in. The temp inside went from 70 to 30 degrees in just under 4 mins. I unplugged it so it would not freeze up and repeated the process a few times. I determined that I was losing 1 degree every 3 to 4 mins when unplugged.

At first I thought this was great but now I'm second guessing my self.
So my Questions are:

How do you keep the temp controller from turning the system off as soon as it comes on?

The temp controller will have a lag time of 3 degrees, so after 12 mins of being off it will turn back on. Will this hurt the unit?

The unit it self is leting some of the cold out(conducting cold), how much should I insulate it w/o covering any of the vents and will this help?

Will having a few full carboy in the chamber help w/ temp control?

Thanks to every one on this site! I've been reading and learning a lot in the last few months!!

I took lots of pics and will post them when finished.
Thanks!

 

[rcrabb22]

Mount the temp probe in the lid of 1 pint mason jar filled with water. The temperature of the water will change much slower then ambient air. It will take a little longer to warm up and cool down the water vs the air temp. You might need to use a thermowell if the tip of the probe isn't waterproof. Having thermal mass from filled cornys will help too. If you if have empty cornys, fill them with water and store them in the chamber as well. You can always dump out the water to use as needed.

 

[strat_thru_marshall]

it's ALL about the temperature and thermal mass of the full carboy, not the airspace in the chamber. Strap your temp probe to the side of your carboy and insulate it so it only is measuring the carboy temp, not air temp. i tape the probe to the glass then cover it with two folded hand towels and a piece of foam, and tape that in place so the probe is totally covered (or use a thermowell stopper). The thermal mass is so great that even if your airspace loses a degree every 4 minutes, the carboy will likely hold steady for an hour or more.

Once the carboy is at your target temp, the ac will cycle on when it goes 1 degree over your setpoint (with a 1 deg differential setting) and will only cycle once an hour or two for just a few minutes to drop the carboy 1 degree.

I have this same setup in my garage and it works like a champ, barely cycling the ac unit. Just remember...control the temp of the liquid, not the air.

Also, if you need to use this unit to drop the temp significantly (more than 2-3 degrees at a time) you have to step it down a degree or two an hour. if your wort is at 80 and you set the controller to 68, the unit will run too long and ice up.

 

[hamiltont]

it's ALL about the temperature and thermal mass of the full carboy, not the airspace in the chamber. Strap your temp probe to the side of your carboy and insulate it so it only is measuring the carboy temp, not air temp. i tape the probe to the glass then cover it with two folded hand towels and a piece of foam, and tape that in place so the probe is totally covered (or use a thermowell stopper). The thermal mass is so great that even if your airspace loses a degree every 4 minutes, the carboy will likely hold steady for an hour or more.

Once the carboy is at your target temp, the ac will cycle on when it goes 1 degree over your setpoint (with a 1 deg differential setting) and will only cycle once an hour or two for just a few minutes to drop the carboy 1 degree.

I have this same setup in my garage and it works like a champ, barely cycling the ac unit. Just remember...control the temp of the liquid, not the air.

Also, if you need to use this unit to drop the temp significantly (more than 2-3 degrees at a time) you have to step it down a degree or two an hour. if your wort is at 80 and you set the controller to 68, the unit will run too long and ice up.

That's how I have mine set up as well except I use a 2 degree differential & it's in my basement. Here are a couple pics. Cheers!!!

Since this pic I added a little more insulation by the side of the fermenter to hold the temp probe up against it.

 

[Redwiggler]

Ah ha, that makes since! once the wort gets chilled the the temp probe want fluctuate as much. Can you tell that there is an increase in you power bill? SWMBO pays the bill and asked a few times if this was going to cost a lot with me replying quickly, No Mam.

 

[hamiltont]

Ah ha, that makes sense! Once the wort gets chilled the the temp probe won't fluctuate as much. Can you tell that there is an increase in you power bill? SWMBO pays the bill and asked a few times if this was going to cost a lot with me replying quickly, No Mam.

Really doesn't run that often. Maybe once every couple hours for a few minutes during the initial fermentation due to the heat production but after that it rarely runs. Part of that is due to it being in the basement. If it were in the garage in the summer that would be a different story... Cheers!!!