Water cooler repair / heat pump learning exercise

[Daox]

Last night I was at my church, and I saw a couple water coolers in the back hall. I asked why there were there and got the reply that they don't work. I asked if I could take them and try to fix them and I got a big happy 'sure'.

I believe one of them has an issue with the hot water which seems like it should be an easy fix. Its just an electric water heater, so I basically just need to find where the electricity stops flowing and fix it.

The other cooler I believe has an issue with the refrigeration side of things. So, I'll be getting to tinker with it. However, I'm really not sure where to even start. I don't know much about heat pumps, let alone trying to fix a broken one. This is why I want to try my hand at it with this hopefully simple system. I'm pretty sure when you plug it in, the compressor motor just runs and runs and nothing happens.

Help me out fellas, where do I start?

[pinballlooking]

Sorry I can’t help but I subscribed. Interesting stuff.

[NiHaoMike]

Most likely a leak somewhere. Probably not worth fixing.

[Daox]

How would I go about trying to find this theoretical leak?

This isn't just about fixing it, its about learning about it too.

[NiHaoMike]

Pressurize it with nitrogen (plus a trace of refrigerant) and use a leak detector. Air duster also works, but might not find really small leaks due to its lower pressure. You can even use air duster (R152a) to charge it. You might be able to rent a vacuum pump (maybe for no charge) at a local auto parts store.

[jeff5may]

what kind of tools do you have at hand? this will most likely dictate the approach.

If the unit has a leak, you can usually find it in a quiet room without any tools. First, look for oil on the plumbing and/or condenser. If it was run with a leak, some oil would have leaked out. The evaporators in these coolers are double-wall, so if the evap coil leaks, the oil runs out the bottom. A light dusting with baby powder will reveal any stray oil.

No luck? No problem. Plug it in, turn it on, let it run for a minute or so. Again, look for oil leaks or foaming. If the unit is quiet enough, you can hear the leak for a few seconds or so when it first starts running, sucking or blowing gas trying to find equilibrium. Unplug the unit and quickly listen for leaks. Same thing here: the leak will suck or blow for a few seconds when the compressor shuts off while the pressures equalize.

After this quick diagnosis, tools will be required if repairs need to be done.

I like charging things with camping propane. If you have a leak, you can smell it. Your nose makes a really good leak detector for free. Caution, Will Robinson.

[Ryland]

replace the heating and cooling guts with a peltier junction.

[Daox]

Last night I just had a few minutes, but I was able to get some pictures and do some real quick checking on things.



Here are the coolers. The one on the left is a Crystal Mountain brand.






The other one is a Primo brand.








Here is a picture of the info tags on the two coolers.






And here is a business end shot of both of them. The Primo is on the right side, and Crystal Mountain on the left.


So, I did take some time to do some very quick diagnostics.

The Primo went first. I plugged it into a kill a watt to see what was happening. It has switches for everything, a main power switch, a switch for the cooler, and a switch for the heater. This made things very easy. I threw the main switch and then the cooler switch and I could hear the compressor motor kick in. The kill a watt showed a quick 500W draw, and then it backed down to about 75W. I only let it run a few seconds, and then turned it off. There is no water in these coolers and I didn't want to wreck anything. Next, I flipped the switch for the heater. The kill a watt indicated no power draw. So, I at least know the heater is bad on the Primo cooler.

Next up was the Crystal Mountain cooler. It has one switch, and its just for the heater. When I plugged it in, the compressor motor immediately kicked in and started running. It did very similar to the Primo cooler, ~500W initial draw, then it backed down to 85ish watts. I then flicked the switch on the unit and the power consumption shot up to around 600W. So, I know the heater is good on the Crystal Mountain cooler.

I guess the next thing on the list is to try to put some water in the coolers and see which one's cooler actually works. Then, I'll try jeff5may's advise and see if there are any leaks.

I have a question about the pressure ratings. The Crystal Mountain unit has significantly higher pressures listed for the high and low side. Why is this? The Primo is an energy star cooler while the Crystal Mountain isn't (as far as I can tell). Does this have anything to do with that?

As for tools... I don't even know what tools you guys use on this kind of stuff. I don't have a vacuum pump, but I do know I can 'rent' one from the automotive store. I have a map gas torch if I need to braze anything (though I've never actually brazed anything before). I do have a manifold gauge set from harbor freight I got years back when I thought I might need it for something and then never used it. I have no idea how to use it. I'm not sure what else I'd need.

[jeff5may]

The pressure ratings on the nameplates are maximum design pressures, not typical running pressures. In operation, these should be much lower.

Both of these units have refrigeration units in them that are very similar to a mini-fridge. The best part is that they use R134a, which you can easily procure from your local auto parts store (I like NAPA). Heck, you may have some laying around from a previous auto a/c recharge! They don't seem to need or have cooling fans in them, so finding a leak should be simple enough.

Since you have a gauge set, you can get a can tap for the R134a (if you don't have one already) or a can with a hose and fitting attached (like fix-a-flat). You can buy an old-school R12 adapter from NAPA that will fit the gauge set. Then you can do purges and recharges easily. All you would need is a service valve in the unit to connect to. If not already equipped, they are easy to fit.

Before you poke around too much in the refrigeration circuit, I would get a good idea of how the one that works acts. It will definitely help you with the one that doesn't.

[AC_Hacker]

Daox,

Jeff's advice is pretty good.

Some of this effort has to do with your objective.

Your header said, "Water cooler repair / heat pump learning exercise".

Are you just trying to fix the unit(s), or are you trying to establish a basis of success that can lead on to more adventurous hacks?

At your stage, you're bound to learn something, no matter what you do.

I bought one of those little water coolers like you have have there. I tried mucking about with it, and I found the experience frustrating, and this was after I had successfully hacked a de-humidifier into a working heat pump, which was very much simpler. These little water cooler thingies are not built to be repaired, but rather thrown away when they fail, which is usually quickly.

Trying to salvage the parts from one and making something else more interesting is really tempting... Like making a tiny solar panel powered hot water pre-heater, or something similar and very cool.

The problem is that the cap tubes on these units are about the thickness of a bacteria's eyelash, and if that were not bad enough, they are integrated into the evaporator, so you can't get your hands on the most critical part which is the pre-sized length of cap tube. Don't even ask if it is possible to get a TXV valve that tiny... you can't. And going through the whole exercise of calculating the appropriate sized cap tube, and then finding it, is not so likely to succeed, either (ask me how I know).

So, what I'm saying is that if you're trying to build a basis of success, you have unfortunately picked the most challenging candidate, that is more likely to confound you than lead to confidence.

So, if your attempts on this effort go bad, don't be set back by it... instead keep you eyes open for an air conditioner or a de-humidifier (which at this time of the year should be extremely easy to find), and give it another go. Then you will have a better than even chance for success.

Daox, I'm not at all trying to be discouraging... I'm trying to point you in a direction that can lead you to a win.

Very important in the beginning.

Best,

-AC