Had to get a new AC unit for my ferm cabinet

[limulus]

Now that is getting warm, I noticed that my fermentation cabinet was not staying on 68F. The AC was working, but I don't think the compressor was working. I think it must have burnt out. I bought it new last year. It was an inexpensive GE 5,050 BTU unit controlled with an STC 1000. So, I have gone out and bought another new AC unit. This time, I bought an Emerson 5000 BTU model with analog controls like the GE but this one has two AC speeds, two fan only speeds and an adjustable coolness knob. The GE was simply off and on. The probe on this new one seems to be a little more delicate, so I'm going to be extra careful when I bend it. The last one was bent so that it ran down the outside of the AC and was outside the cabinet in the ambient garage temps. Around here, my garage gets over 80F in summer.

Has anyone else had any issues with the $99 GE AC units or the $99 Emerson units?

 

[cjgenever]

No idea between the two. I do know that refrigerant compressors like some down time between cycles. If the system cuts power, only to startup again a few minutes later, it will kill the compressor. It is optimal to have a min of 15-20 minutes break between. This can be controlled a few different ways depending on the controller.

Could this be the culprit here?

Sent from my SCH-R970 using Home Brew mobile app

 

[limulus]

No idea between the two. I do know that refrigerant compressors like some down time between cycles. If the system cuts power, only to startup again a few minutes later, it will kill the compressor. It is optimal to have a min of 15-20 minutes break between. This can be controlled a few different ways depending on the controller.

Could this be the culprit here?

Sent from my SCH-R970 using Home Brew mobile app

Thanks for the feedback and it is a good suggestion. But, no that should not have been a problem. I set it to have down time between cycles and once I had fermenters inside, the temp would hold for quite a while between cycles. I believe the manual on this new one says three minutes.

I have to wonder if just cutting the power while the compressor is running could have killed it. That can't be good for it. When using the STC 1000, it does just cut the power when the sensor hits the set temperature and often times, the compressor will be running at that point. Under normal operation without an external control such as the STC 1000, the fan continues to run after the compressor goes off. I experimented yesterday with the probe still attached to the inside and the compressor would shut off before STC 1000 shut off power. I have it set for 68F and the compressor was turning off right before that point and just the fan was running. The temperature display continued downward a few more degrees after everything was off. So, I may try it with the probe on the inside. I'm also going to go back to the CoolBot site and see if it keeps the fan running after the compressor turns off.

 

[limulus]

I just went out into the garage and ran a little experiment:

The Conditions

1. garage ambient temp = 24.5C (76.1F). My wife just came in from running at the park and her car heated up the garage. But in the middle of summer, it is in the 80s in the garage.

2. The STC 1000 was set to 19.9C (67.8F)

3. The temp differential was set to 1.0 C

4. The delay was set from 3-min to 1-min. I will probably change that back if I see it starts to cycle quicker.

5. The cabinet is 4ft x 4ft and insulated with foam panels on top and sides. The floor is 4" thick and filled with compressed insulation. It only took one bag and it is tight.

6. The GE AC that died was sealed in with Great Stuff Foam. For this experiment, I just sealed the gaps with tape. I'll use Great Stuff once I decide on the AC probe position (inside or outside)

7. The AC probe was left attached to the inside

The Results

1. Achieved 19.9C in just under 2 minutes

3. After power shutoff, the temp continued down to 19.1C

4. From 19.1 back to the set point of 19.9C took 4:05

5. From 19.1 to 20.1 took 4:35

6. From 19.1 to 20.9 took 9.5 min
a. This is where the STC 1000 re-started the AC

7. At 20.0C, the compressor turned off which was about a minute of run time

8. About 1.5 - 2 seconds later the STC killed the power.

9. The temperature this time went all the way down to 18.8C

The cabinet was empty and the probe was just hanging in the air. I know that taping it or using a thermowell cause the cycles to take even longer. The Great Stuff foam will also seal it much better. I recall last year, it was going >30-min between cycles.

I think I may just leave the probe inside if it turns off the compressor at 20C which is 68F. I believe I can set the STC 1000 a little lower and the fan will run a few seconds longer after the compressor turns off. Hopefully, that will cool the compressor a little.

 

[cjgenever]

I wouldn't leave the ac thermocouple in there. Your previous setup, with it outside the cabinet, allows it to double as a lagering chamber and for cold crashing.

I could be wrong, but as far as I know the ac simply cuts power to the compressor. Shouldn't be a problem there.

For the sake of covering all the bases, are you sure the compressor died? Could the coolant be low?

Sent from my SCH-R970 using Home Brew mobile app

 

[cjgenever]

Danfoss service bulletin 007:

" NOTE The longer the OFF cycle, the greater the degree of liquid migration. The colder the oil, the greater the degree of liquid to oil migration that takes place"

A short on cycle does not allow the oil to heat up, increasing the probability of coolant migration into the oil. This cuts the oil and kills the bearings. I think you may need a larger beer cooler? I'd be surprised if this is the issue, but something to chew on

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[limulus]

I wouldn't leave the ac thermocouple in there. Your previous setup, with it outside the cabinet, allows it to double as a lagering chamber and for cold crashing.

I could be wrong, but as far as I know the ac simply cuts power to the compressor. Shouldn't be a problem there.

For the sake of covering all the bases, are you sure the compressor died? Could the coolant be low?

Sent from my SCH-R970 using Home Brew mobile app

Thanks. It could be a coolant issue, but I really don't hear the compressor come on with that little thump it makes. I have a keezer in my basement and also a large fridge in the garage. The fridge is mainly for extra food but I have a section for cold crashing before kegging. So, I reallly don't need the fermentation cabinet to go that low in temp. Although last year, I did take it down to 10C with no problem.

I just ass-u-med that the other AC would be a throw away and could not be recharged with coolant. I still have it and if I can recharge it, I may give that a try. Is that a diy type of project or do I need an HVAC guy. If the latter, I'll just toss it since it was only $99. I can keep buying new ones for less than an HVAC service call. I have three AC zones in my house and I have never had a service call that was less than $200 when something goes wrong with one of those systems.

 

[cjgenever]

It's diy with some research. The point I was bringing up earlier is the short run times. You said it may run for a min or two before shutting down, right? That could cause the compressor lube to be compromised destroying the bearings. I'm no hvac expert though. Good luck!

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[limulus]

It's diy with some research. The point I was bringing up earlier is the short run times. You said it may run for a min or two before shutting down, right? That could cause the compressor lube to be compromised destroying the bearings. I'm no hvac expert though. Good luck!

Sent from my SCH-R970 using Home Brew mobile app

I do appreciate the feedback. I hope the new one lasts a little longer than one summer. Those short run times could be the problem. Now that the new one has been running all day, each run cycle is less than two minutes and then it is off for quite a while. I'm probably just going to get rid of the other one, I have too much crap in my garage. It is a 3-car garage and can only accommodate my wife's car. I built two wooden boats in 2010 and 2011 and a lot of that crap is still in my garage (not the boats).

 

[sfgoat]

No idea between the two. I do know that refrigerant compressors like some down time between cycles. If the system cuts power, only to startup again a few minutes later, it will kill the compressor. It is optimal to have a min of 15-20 minutes break between. This can be controlled a few different ways depending on the controller.

Could this be the culprit here?

Sent from my SCH-R970 using Home Brew mobile app

This .

Window ac needs it's cycle time and will not last long hooked up to a temp controller like that

 

[limulus]

This .

Window ac needs it's cycle time and will not last long hooked up to a temp controller like that

30-min between on and off times is pretty long and that is what it is up to again now that I have stuff inside again. Last year, the old one was going longer than that when I had 2-3 fermenters inside. But, it only runs a minute or two when it comes back on. Is that what you are referring to? I know there are quite a few others on this forum who are using this type of controller with a window AC unit but I have not heard from any of them since I posted this. I honestly can't see how a little mini fridge could last any longer cooling a cabinet, but there are tons of them posted on HBT. Maybe I should just buy a CoolBot controller.

 

[sfgoat]

30-min between on and off times is pretty long and that is what it is up to again now that I have stuff inside again. Last year, the old one was going longer than that when I had 2-3 fermenters inside. But, it only runs a minute or two when it comes back on. Is that what you are referring to? I know there are quite a few others on this forum who are using this type of controller with a window AC unit but I have not heard from any of them since I posted this. I honestly can't see how a little mini fridge could last any longer cooling a cabinet, but there are tons of them posted on HBT. Maybe I should just buy a CoolBot controller.

The problem with the ac is it needs to run through its own warm up and cool down cycles and the temp controller just cuts its power abruptly so it cannot complete them. 30 minutes of rest or 5 minutes of rest really isn't the problem it's that the power is cut too abruptly.
Have you ever noticed that your central ac runs for an additional minute or two before finally shutting down once it reaches temp

 

[limulus]

The problem with the ac is it needs to run through its own warm up and cool down cycles and the temp controller just cuts its power abruptly so it cannot complete them. 30 minutes of rest or 5 minutes of rest really isn't the problem it's that the power is cut too abruptly.
Have you ever noticed that your central ac runs for an additional minute or two before finally shutting down once it reaches temp

That is what I was getting at in post #3.