building a walk-in cooler -- the details

[thedrake]

I am starting to design a walk-in cooler. Approx. 4' x 8' x 6'. I live in a place where the space will need to be heated in the winter and cooled in the summer. I am planning to use a Ranco Digital Two-Stage Temperature Controller with a window AC unit and a space heater. Before I start, are there any common pitfalls of lessons learned that any of you walk-in coller owners could share? I would really like to get this right the first time.

One specific question - do I need to mess with the electronics of the AC unit to get a small walk-in down to 40-45 F or is that within its normal range?

[TimC]

You will need to bypass the thermostat controls in the A/C with the Ranco to get that cold.

I haven't built my walk-in yet but it is on the short list. Keep us informed as to your progress!

[Bugeater]

When investigating this idea of a walk-in cooler last year, I came across this gadget that seems just the thing for what you want to do.
http://storeitcold.com/index.php

Wayne

[Dubba_Brew]

Bug... that is a killer find! Thanks for sharing.

[hotrod38]

Yea, along with a killer price tag too.

[bcmaui]

I have purchased Bug's controller and have been watching the prices of AC units - especially the LG units that are suggested to work well with this controller. Trying to best work out the size of cold room I want to build and location of the AC unit in the brew area. I figure if you oversize the AC unit it is easier on the compressor (longer life) and less chance of freezing up (although this controller has an additional sensor for that which makes it a bit more expensive than the Ranco.

Are there less issues with condensation inside a cold room since the AC is pumping out moisture and pumping in de-humidified air, or should I also address the issue of condensation inside the cold room similar to what I am experiencing with my chest freezer set at 39F?

I can mount the AC almost anywhere - was thinking to mount it close to the ceiling since hot air rises.

What is target temp for typical cold rooms out there? If 55F is good I can also store wine in there and may slightly adjust the size to reflect that.

[foomench]

How much do those standard AC units cost? I ask because I've been looking to build a walk-in and was going to use a wine cellar cooling unit, which comes with the necessary controller. I thought I saw one a while back as cheap as $200, but my googling at the moment is only coming up with $400. The ideal wine storage temperature is 55 F, but the units I was looking at would go to 32 below ambient, which for my basement puts me below 40. Actually, my plan is two-stage room, beer walk-in and wine cellar, with the cooler in the beer side at about 45 F and a separate controlled fan to pump air in to the wine side to keep it at 55 F.

If you look at some of the wine cellar web sites you can find a lot of information useful for walk-in beer cooler construction too, e.g. http://www.rosehillwinecellars.com/3rsV ... .php?id=26

-Eric

[BrewTa2]

Here's mine:























What I did:
The space is 4X8X8. I installed a 15,000 BTU LG unit that I got on clearance last fall. I ripped out all the control boards and wired it to a contactor I had laying around. A relay would work too. I added a 24vac transformer and ran that to a RiteTemp thermostat. All the RiteTemps I've seen go down to 35F, not all thermostats do. If you need to heat it in the winter, you'd have to switch it to heat.
I used a pre-hung insulated exterior door.
I kept the room at 40F all winter long, but I had a couple of problems. The first problem was frost. I cured this with 4 containers of Damp-Rid. The second problem was when the outside temperature dropped way down, the compressor wouldn't work. I cured that by attaching a length of pipe thaw to the bottom of the unit and boxing it in with insulation board.

Everything was great until spring and the humidity started to rise. No amount of Damp-Rid helped. I had a dehumidifier collecting dust so I put that in. I haven't had any freeze ups since, but I'm afraid to go below 50F since a little ice forms at the bottom of the evaporator as it is and the humidifier is rated to work only to 45F.

What I would do differently:
I didn't use any vapor barrier and I should have, especially on the concrete floor. The interior has every joint taped and any little gaps around the a/c filled with foam, but the extra insurance from a vapor barrier would help.
I would have added an electrical outlet for a fan. The unit blows so hard that cold air circulation isn't a problem, but I need an outlet for the dehumidifier. I also want to put in a small fan that will blow on the evaporator. Hopefully, that will eliminate any frost when the unit isn't running. I have my fingers crossed that the frost will stay away. The temperature has been at 50F for a month now, and the humidity has been at about 50%. If the problem comes back, the next step is to rig up a small strip heater to the evaporator that will come on when a sensor in the fins gets to 32F. I'll use an extra PID I have so an alarm signal will shut off the a/c.
I thought about using 2X6s for the two walls I had to build since the outside wall and ceiling are 2X6, but one existing wall was 2X4, so I didn't see where 2X6s would help. The R value of the 2X4 walls is about R-16. R-13 fiberglass and R-3 for the foam board. I thought about using foam board on the outside as well, but I just used bead board paneling.

As it is now, the unit runs for about a minute every 15 or 20 minutes. This has been a cool summer so far so I don't have any idea how it would run if the outside temperature was over 100F like normal. In the winter, it ran maybe a minute every 30 or 45 minutes. Of course, pack it full of beer and the thermal mass helps with efficiency! Except for the frost, it's been great.