Fermentation Chamber build

Building off of this thread...

After waiting on a tax return, dealing with a family issue and several other delays, I am ready to begin construction.

I have decided to move my box to a different wall in the garage to deal with the placement of my attic stairs. So the box will be the same in concept, just the higher temp ale chamber will be on the left instead of the right.

I have acquired a 6000 BTU window unit, and have all of my lumber. I purchased some 1" bead foam board and will buy the 3-1/2" R-13 batt rolls this week. Instead of PC fans, I have elected to use bathroom exhaust fans (LINK). 50 CFM for $14 with an in-line baffle and a 3-1/2" port. I'll use 3-1/2" bath exhaust vent for the little ducting I need. I received two of the aquarium temp controllers, and a friend gave me an analog controller that I intend to use on the coldest box.

So all I have left to buy for my parts list is the ducting, 1 fan, the batts, outlets/boxes, and some zip cord to run the electrics.

Here's the space I'll be building in:



Updates to follow...soon, hopefully!

Looks like you have a nice space to work with. How big of a chamber are you planning?

The footprint will be 4' x 8'. Half of it will be 4' tall (the ale chamber), and half will be 8' tall - two 4' chambers stacked on top of each other (lager chamber in the bottom, cold beer storage/conditioning in the top).

Walls and top will be 2x4 with insulation and 1" foam board interior surface, with OSB exterior.

Here's what I'm cooling with:



Question: will I have to by-pass the internal thermostat on the A/C/ unit to get it down to ~35*, or will just turning the knob down let me cool it as much as I want?

Here is the build so far:



The left box is for ales, the right-bottom is for lagers, and the top is for cold beer storage. All of the parts are in-hand, now I just need more than an hour at a time to finish the dayum thing!!

First brew will be 10g AG Kolsch...alongside a 5g ext Amber. I hope 15 gallons will get me through July...

That unit will not get down to 35 without you modifying the thermostat. Some people have claimed you can just 'trick' the thermostat by either relocating the probe to the outside of the box, or putting a small heat source near the probe so it thinks it is warmer than what it really needs to be.

My AC unit does not let me do that. I put a 45W halogen lamp right near the probe and it still only goes down to 55 or so. I think there is some sort of internal safety that will not let it drop lower. I havent gotten around to gutting and bypassing the thermostat, mostly because I dont intend to bring my temps down further than that.

If you don't like the idea of bypassing the thermostat, I would give the probe trick a try first. You might get lucky.

The other thing you need to worry about is when the temperature drops that low, you will have freezing on the evap coils, especially when the condenser cycle is off. People have gotten past this by either wiring the fan on the unit to run constantly, or installing separate PC fans that blow towards the coils constantly. This allows the ice to thaw by blowing above freezing air over the coils. I would suspect that this is going to be a pretty big issue in that coldest chamber when you are trying to approach 35. Making sure the box is absolutely airtight, and not opening it very often will keep the moisture level down and will help.

Sorry for the long winded post. If I would spend some time actually working on my ferm closet instead of talking about others', I would be done with it!

kpr121 said:

That unit will not get down to 35 without you modifying the thermostat. Some people have claimed you can just 'trick' the thermostat by either relocating the probe to the outside of the box, or putting a small heat source near the probe so it thinks it is warmer than what it really needs to be.

My AC unit does not let me do that. I put a 45W halogen lamp right near the probe and it still only goes down to 55 or so. I think there is some sort of internal safety that will not let it drop lower. I havent gotten around to gutting and bypassing the thermostat, mostly because I dont intend to bring my temps down further than that.

If you don't like the idea of bypassing the thermostat, I would give the probe trick a try first. You might get lucky.

Click to expand...

Thanks for the tip...I'm not sure if I'll try the probe thing or just jump straight to bypass.

The other thing you need to worry about is when the temperature drops that low, you will have freezing on the evap coils, especially when the condenser cycle is off. People have gotten past this by either wiring the fan on the unit to run constantly, or installing separate PC fans that blow towards the coils constantly. This allows the ice to thaw by blowing above freezing air over the coils. I would suspect that this is going to be a pretty big issue in that coldest chamber when you are trying to approach 35. Making sure the box is absolutely airtight, and not opening it very often will keep the moisture level down and will help.

Sorry for the long winded post. If I would spend some time actually working on my ferm closet instead of talking about others', I would be done with it!

Click to expand...

Something that you don't see is that in the top (coldest) box, I plan to install a return baffle. The cold air will blow into the chamber, and the return air to the coils will flow through the un-cooled return air path. There will be a single 3-1/2" inlet from each of the 3 boxes into the return air path. Hopefully, this will prevent freezing since I don't plan on insulating the baffle.

Time for some updating...

I finally have been able to squeeze in some build time. Let's start with a pic from right after the last one:



In this pic you can clearly see the 2-1/2" gap between the box and the wall, due to some moulding and electrical conduit. If you look in the A/C opening, you can see the 3 layers of blue-foam used to seal around the window. Same view, backed up a bit:

Today, I was able to mount the A/C unit in the opening. Sounds easy, and wasn't TOO difficult. Just had to put on my thinking cap a bit. Since the A/C unit isn't really deep, and the box is away from the wall, the AC unit only sticks out the window opening about an inch:



So, after framing in the front (that goes inside the box), I had to deal with the exterior. If I had left it as-was, the insulation and wall inside the window would be open to the elements. So I did some southern-engineered framing on either side of the A/C unit and tacked in some 1/4" luan panels on a diagonal so that the AC unit's side vents were unobstructed:



All sealed with metal/aluminum duct tape.

I then set about sealing the inside as tightly as possible, using OSB, 1/4" blue foam, and the all-important metal/aluminum duct tape:



I also by-passed the thermostat on the unit, so now as long as the switch is turned on, the fan and compressor are running.

Next step: adding the return-air baffle to the rear of the box...

EDIT:
BTW...I'll throttle my camera down to a smaller rez next time...

IT'S...ALIIIIIVE!!!!

Finally...after many far-too-separated days of sweat and insulation rash, splinters and re-works...it's alive and running.

First, after installing the baffle on the back of the top (cold) box, I realized that I didn't have hardly any room in it. Sooooo...out it came, and in went a smaller air return baffle. Here you can see part of it with one of the bath exhaust fans in place:



This one is back a little further, and you can kind of see the door construction as well. It's OSB with 1 x 2-1/2 framing. R-13 batts in the framing skinned with 1" R-7 foam board. As with the entire unit, it's all sealed and edge-wrapped with metal tape.



Here is the completed unit all buttoned up. Top box is cold crashing/storage, to be kept at ~ 38-40*. Bottom right box is lagering, to be kept at ~ 55*. Bottom left is ale, to be kept at ~ 65-68*.



I finished hooking up the controllers at about 11 p.m., and after 30 minutes of a shower and getting ready for work the temp in the cold box was at 44*.

The lager box was at 73* and the ale box was at 72*.



I'm letting them run tonight while I'm at work to see how the temps stabilize. Hopefully, the fermentation boxes will eventually get down to the temps I want.

WOO-HOO!!! Brewday Saturday, assuming everything works as envisioned!

kpr121 said:

The other thing you need to worry about is when the temperature drops that low, you will have freezing on the evap coils, especially when the condenser cycle is off. People have gotten past this by either wiring the fan on the unit to run constantly, or installing separate PC fans that blow towards the coils constantly. This allows the ice to thaw by blowing above freezing air over the coils. I would suspect that this is going to be a pretty big issue in that coldest chamber when you are trying to approach 35. Making sure the box is absolutely airtight, and not opening it very often will keep the moisture level down and will help.

Click to expand...

Well, you nailed it there unfortunately. I got home from work and the temp in the top box was ~ 80* and the evap coils were frozen solid. I just hope the compressor didn't get damaged. The box is as airtight as I'm going to get it, but I live in Knoxville where the RH rarely drops below 50%, and is usually in the high 60 to low 70% range.

It's looking like I might need to mount a fan on the exterior of the box, and duct it into the baffle to pull in warm air from the outside. Hopefully that won't kill my return draw from the lower boxes. Or I guess I could mount a light fixture inside the baffle and put a heat source in there?

Dammitall!

Maybe put some computer fans on the coils and have them blow over the coils so that they do not freeze up.

AJC16 said:

Maybe put some computer fans on the coils and have them blow over the coils so that they do not freeze up.

Click to expand...

You need a 9v adapter to do that, right?

Yes radio shack has them

or use an old cell phone charger

Found a 120 ac 3" fan @ Radio Shack. Used lamp cord and installed. We'll see how the temps do now.

Might need one of these: http://www.storeitcold.com/

Wish they weren't so pricey.

Awesome set up, mine goes in a couple weeks! The joys of control and plus the addition of my 2nd bath tub not being filled with carboys.

Coils are still freezing up, even with the PC fan blowing directly on them. Do I need to duct in warm air from the outside? Need some help, here.

Here are the nuts & bolts of the beast I've built...

Here is the inside of the upper (cold) box. The return duct is 22"w X 6"d. BUT the holes cut for return air flow are only 2" in diameter. That's restricting airflow, hence the PC fan blowing across the coils.





Here is the bottom right box, showing the ducting:





The hole in the first pic is the return from the bottom right box. The hose in front is the supply to the bottom left box, and the rear hose is the return. THe hole in the second pic is the supply to the bottom right box. The third pic shows the supply/return in the bottom right box.

The temps have been in the upper 90s with RH in the mid to high 60s. The coldest I have gotten the cold box is 39* before the coils freeze. The bottom right box (the lager box) won't get below 70, and the bottom left box (ale) will get down to about 60. Not sure why the ale box gets cooler than the lager box. Seems to me that the lager box would get cooler just by being positioned directly under the cold box.

Other than ducting warm outside air into the return baffle, I'm at a loss as to how to fix this. I need some help!!

I'm not 100% sure on this but look at how the pressure changes effect the due point. The point of adding the PC fan to the coils is not only to increase the air flow over the coils but also to lower the pressure drop across the cooling coils and therefore reduce condensation. All the ducting for the return air is probably causing a choke point and therefore more of a pressure drop more condensation etc etc. You might have to have a larger opening on the return ducting or put a fan on the opening as well as a fan on the coils.

I'm an Elec Eng not an Mech Eng so this is not gospel just and opinion... hopefully a HVAC Engineer out there can give you a better opinion. If you went to your local Engineering College with free beer and dropped by the Mech Eng Dept chances are you will have 20 Eng students over at your house and you will be freezing carboys before you can say more beer.

Clem

Warm (wet) air ducted in is the last thing you want. Maybe get the fan blowing closer on the coils. Cool it slowly, stepping down the temp as you go. Plug any air leaks. Insulate more.

RDWHAHB said:

Warm (wet) air ducted in is the last thing you want. Maybe get the fan blowing closer on the coils. Cool it slowly, stepping down the temp as you go. Plug any air leaks. Insulate more.

Click to expand...

+1M All of the above and maybe use a much larger fan or multiple fans. Elimination of air leaks, even very small ones, is very important. The advice to step the temperature down very gradually is also spot on. I'm thinking the unit may be underpowered for this use. I don't know, just guessing. Maybe a forced defrost cycle would help. I suppose you could do it with a cheap timer. Some trial and error would be needed to see what works. Compressor off for a period with the fans running continuously might do it.

The PC fan is already ~ 5" from the coils. I am in the process of stepping down the temp, it's currently at 45*. I'm going to leave it there for a bit and see what happens.

I'm thinking the unit may be underpowered for this use.

Click to expand...

You think 6000 BTUs isn't big enough? The space in the cold box is less than 35 cu ft., and the space in each cool box is not much more than that. Also, my windows are a strange dimension, and I can't get a bigger unit in there. What I got is what I got so I have to go with it and make it work.

I'm thinking I'll cut at least one more, probably two more holes in the baffle to try and get more air circulation. I'm hoping I don't have to cut through insulation and decking to make more holes into the bottom boxes. That = BIG P.I.T.A.

Yeah, 6,000 BTU's is on the small side IMO, but I have no idea if it's too small or not. My understanding is that bigger is better for a cold room. I would think that if the unit is running continuously and not cycling normally, icing might be unavoidable.

Any progress?

Catt22 said:

Maybe a forced defrost cycle would help. I suppose you could do it with a cheap timer.

Click to expand...

Maybe you could run a second temp controller with the probe between the evap. coils. If it gets too cold (meaning they are iced up) you lock out the compressor until it defrosts.

RDWHAHB said:

Any progress?

Click to expand...

Good progress...

Stepping down the temp slowly got me down to 39* without freezing.

Next step is to open up the duct holes from 2" up to 3.5" where possible. I think enlarging the airflow channels will put me right where I want to be.

But for now, I'm brewing a kolsch tomorrow and I'm going to ferment it in the top cold box. It'll hold at 60 or so degrees without breaking a sweat. So further mods are going to wait until the kolsch is in the bottles.