armoire-kegerator build hiccup. Thoughts?

So, after almost a year of planning, several months of half-assed material collection, and two weekends of cutting, screwing, painting, and assembling, my thorough conversion of a plain old armoire to a kegerator is complete!

I will enthusiastically post photos, when my "hiccup" is cured.

I took the guts from a mini-fridge (coils and compressor on the outside of the body; old style), and transplanted them into the insulated cooling chamber (the cooling plate, anyways; the rest is set up in the back). I have that hooked up to a Johnson Controls A419ABG-3C digital temp controller.

Everything hooks up, starts up, and starts cooling. The problem is, the "cooling tube" (I think its called a suction tube) running from the compressor to the cooling plate begins to develop a layer within 3 minutes of running.

The fridge I gutted to get the cooling guts is about 10 years old, but hasn't been used at all in about 7 (sitting in my parents' basement). I fired it up for a party about 6 weeks ago to make sure it was working just fine. It ran for a week with zero frosting and efficient cooling.

Either it has started having problems in 6 weeks of disuse, or I missed something at install, or both.

SO, I'm at a loss. I ran the unit for 3 hours and it dropped the chamber from 75 to 68 and it will go no further. Plus, I know it can't be good to run with 1/2 layer of frost around any tube.

Anybody have any ideas?

Have you considered adding a computer case fan? Some folks wire them to an AC/DC transformer for a cell phone or some such thing. Having one of those blowing across the cooling plate might decrease the condensation and frost. Wire it to kick on with the mini fridge guts.

The frost issue isn't inside of the cooling chamber on the cooling plate - it's outside in the back of the unit on the line leading from the compressor TO the cooling plate inside.

And actually, I was just researching case fans to put inside!

Would a fan across the line outside have any effect, you think? I mean, if it works inside, it could work outside, too, right? Food for thought.

Why not just insulate the cold side plumbing from the compressor to the expansion coil? That's not an uncommon practice anyway...

Cheers!

6 weeks ago, there was no frost build up at use. Now, after transplant, there is. So, despite similar working conditions (open back, cooled chamber), something is fundamentally different about how this is operating.

I thank you for the suggestion of insulation. I'll get to Lowe's and get some. It does raise a question, though. If I'm right and something is different, won't insulating it simply mask the issue?

PLUS, will insulating the cold side plumbing increase my cooling in the chamber (and how would it do so)? As I said, it took 3 hours to go 6 degrees.

I know it may seem I'm being difficult, and I'm sorry for that. I approach problems from a "asking endless questions" approach. This is not a subject that I'm fluent in and I figure if I can understand the "what's" of what's going on, the "why's" should be easier to determine. I really do appreciate any suggestion I get!

Reposition so more of the cold side lines are in the cold section as well as insulating anything outside the cold side is what I'd try.

-cheers

brewingmeister said:

Reposition so more of the cold side lines are in the cold section as well as insulating anything outside the cold side is what I'd try.

-cheers

Click to expand...

Based on day_trippr's comments (and now yours), I am insulating the outside cold lines as we speak.

Could you (or somebody else) explain to me why this will make a difference? Mechanically, what does the insulation do that helps me cool inside better? Again, I'm just trying to understand what's going one in my head, I'm not challenging your suggestions.

And again, why, would you guess, wasn't this icing up present a few weeks ago?

If it's icing outside of the designated cold area it is not as efficient as it could be. The unit is going to have to work harder to do what you want it to. How much mangling did you do to get the guts out? Was this mini fridge the kind with lines in the shell? If there are any restrictive bends or leaks in the system that could be causing problems.

-cheers

I'm not an HVAC guy, but from what I remember reading from some of the experts is that what you have described my be an indication that the unit may be low on refrigerant. You can probably re-charge it, but doing so is beyond my expertise, so someone with more knowledge on the subject will have to take it from there. I don't think it's a big deal if you know what you are doing and have the right equipment. The problem is that if you have a professional do it, it will likely cost more than the fridge is worth. Insulating the coolant line going to the evaporator is a good idea, but it likely will not solve the problem. That cold line is essentially not very different from the evaporator coils inside the unit. The refrigerant passing through it has begun it's expansion phase and it's absorbing heat. Condensation is forming on the exterior of the tube and eventually freezing. Insulating the tube will reduce it's heat gain conserving the cooling capacity of the refrigerant a bit. The insulation will also reduce the condensation accumulation. I say try recharging the unit. It's worth a shot after all the work you put into the armoire. It may be difficult to find a replacement unit in the same configuration.

Brewingmeister- the coils of the unit were (luckily) the ones on the outside of the unit so it was less of a PITA. The mangling was kept at a relative minimum. It wasn't difficult at all, just extremely time consuming.

Catt- I haven't discounted the need to recharge the compressor. I am surprised, though that when I used the fridge just a few weeks ago, there was no frosting of the lines. Your take on that?

cimirie said:

Brewingmeister- the coils of the unit were (luckily) the ones on the outside of the unit so it was less of a PITA. The mangling was kept at a relative minimum. It wasn't difficult at all, just extremely time consuming.

Catt- I haven't discounted the need to recharge the compressor. I am surprised, though that when I used the fridge just a few weeks ago, there was no frosting of the lines. Your take on that?

Click to expand...

The unit may have lost some of the refrigerant in that few weeks time. The frozen condensation rate of accumulation will vary substantially with the ambient relative humidity. That could account for some of the difference. I did read that icing problems can be a result of low refrigerant, but I can't explain why that would be the case.

FYI, the coils on the back of the unit are condenser coils which radiate the heat extracted from the interior. The "plate" inside is the evaporator. The plate encloses refrigerant tubes or channels and functions much the same as coils. Very basically, a refrigeration unit is a condenser, an evaporator and a compressor. Mechanically, they are fairly simple systems with only a few moving parts. Maintaining the integrity of the sealed system over the very long term is the biggest challenge. I am amazed that most units hold up as long as they do. Even an extremely tiny refrigerant leak would spell trouble in a very short time I would think.

Catt22 said:

. Even an extremely tiny refrigerant leak would spell trouble in a very short time I would think.

Click to expand...

If this were a refrigerant leak, how long before all refrigerant were gone? I ask only to use as a troubleshooting barometer.

If there is a leak, would the "soapy bubbles" technique (as used on leaky co2 tank seals) work here?

Could I wrap the evap coils in some sort of tape if there is a leak?

Finding a fridge with the condenser coils on the back really saved you some work. I thought I had mentioned low refridgerant as a possible cause but I must have just been thinking it. I agree with Catt22, being low on gas is definitely a possible cause of the icing. Fridges and freezers are strange birds. I've seen them last lifetimes without any problems, they get moved and then they quit. Did you give the compressor adequate time to sit upright so it's oil settled back to the bottom before turning it on?

Soappy bubbles may lead you to a leak, refridgerant leaks are usually found through ultraviolet dye. As far as fixing a leak if you find one tape isn't going to cut it. Soldering would be the way to go. I can't remember what thread it was but someone on the board managed to sand the paint off around the leak and put JB weld on it. Apparently it worked, I have never used the product though so I can't really comment on it.

-cheers

1. IMO, this cannot be reliably predicted. It can happen very quickly or very, very slowly.

2. I seriously doubt it unless the leak large. You might have to pressurize the system to find the leak then again after you repair it. A pro may have some tricks to make this much easier. I know that they often use special dyes and a black light to detect refrigeration leaks on cars. It's probably the same for refridgerators.

3. There may be some type of special epoxy tape available for this type of repair, but I don't know where to point you to get it. Maybe J-B Weld would work. I don't know, but first you need to find the leak which may or may not be in the tubing. It could be internal to the compressor or just about anywhere in the system.

It would be very good if you could find a buddy who is familiar with this stuff to take a look at it. A shot of refrigerant may be all that it needs.

UPDATE:

First, thank you for all your help and suggestions. They all helped me putz through this.

I pulled out the evaporator coil, rearranged the insulation on the coil, and covered the rest of the coil with insulation. Re-installed the coils properly.

Then, I installed an AC fan on the inside of the cooling chamber to help with air flow.

Amazingly, both of these things, one of these things, or neither of these things has performed magic!

Yesterday, if you remember, it took 3 hours to drop from 74 to 69 degrees. On top of that, the evaporator coil was covered in ice.

Tonight, it took 1 hour to drop the chamber from 68 to 51 and the evaporator coils are warm! It's so strange how much difference 1 day and some insulation makes.

Thanks again for all your suggestions!

Pictures/ build notes?

I've posted my entire photo-journal build notes here:

https://www.homebrewtalk.com/f51/my-finally-finished-keezer-267412/

Let me know what you think!