New with a Kegerator - getting it set up and ready to use - tower cooling question

[rkhanso]

Hello,
I bought a used kegerator. I switched the control of it over to a CraftbeerPi controller.
I'm wondering about two things before I keg for the first time:
1. Tower temp - how high is too high?
2. Cycle time of the compressor

I put a fan blowing up through a tube into the tower. The temps are cooler, but I'm wondering if still too warm and I'll end up with foamy beer the first pour.
Here's a graph of the temps over the past hour or so. Keep in mind, I have 2 EMPTY kegs in the kegerator and no CO2 tank yet. I have a temp probe taped to one of the kegs and one up into the top of the tower. The tower temp is about 5.5 degrees F higher than the kegerator. I have the kegerator set to 38F now. Tower is 43.5F. Will this change much once I get a full keg(s) in the kegerator? Should I try to lower the tower temp? I could put a copper pipe up into it, extending down into the fridge and running the beer line through it to get it a little colder. Not sure what else I could do.

2nd question -- Are these cycle times OK for my kegerator? Not too frequently on/off/on to shorten the life of the compressor or other parts in the kegerator? It appears to cycle about every 5-10 minutes. I think that's OK, thought I'd ask for a second opinion. I suspect it'll probably be a bit better if the kegs are full, right?

The top graph is the Kegerator temp. The bottom graph is the tower temp.

 

[rkhanso]

I tried it with the main temp sensor in a bottle of water. It's not running with much lower cycle times on the compressor.
Maybe a CraftbeerPi isn't the best controller for a Kegerator? Or, maybe I need to mess with the offsets? I'll take a look at those, but I'm not sure that will help a whole lot. If I get a wider swing in temps, won't the compressor just be on longer then trying to drop the temp to the lower limit again? Not really helping it out?

Maybe better insulation is the correct option?

I'm also wondering if the quick changes at the ends and beginnings of the on/off are really telling the compressor to go on/off quickly and might damage it.

EDIT ----- Crud, I just caught the kegerator at a transition of temp from the compressor off to on, and it is matching the quick changes above/below the line with the compressor power. Not good.

 

[rkhanso]

I do see an Add-On by Carl Allen on the list for Compressor Delay actor. I installed it, but don't see it showing up as an option in the drop-down list.

Am I missing something?

 

[day_trippr]

It's a bit hard to discern how close those compressor cycles are, but I would be concerned that there appears to be no "short cycle delay" mechanism shown in the trace. That's hard on the compressor. If there isn't a plugin that actually accomplishes that function, try immersing or strapping your temp probe in/to a larger vessel of water/beer...

Cheers!

 

[rkhanso]

For some reason, after about the 5th or 6th reboot of the Pi, the Compressor Addon is showing up.
I don't understand why it didn't show up right away.
I'll give this Add-On a test.

 

[rkhanso]

Trying it out with 9-10 gallons of water in the kegs to see if the temps are more stable than when it's empty.

 

[rkhanso]

Should I expect better "efficiency" with my kegerator? It appears to be running for 9 minutes and off for 4 minutes.
I have the 2 kegs inside filled with water for this test. The temp probe that controls the compressor is taped to the side of one of the kegs.
I'm worried about the compressor.

And here's the tower fan keeping it cool(ish)

 

[day_trippr]

Yeah, that can't be good.

"Taped to the side" could be the issue - you need to isolate the temperature probe from the chamber (fridge) air, so it better tracks the actual beer temperature and is less subject to chamber temperature influence.

Also, check your temperature differential setting. If it's set really low that's going to cause more frequent cycling.

fwiw...I use 2" x 30" Velcro straps and pin my keg (and carboy) sensors under ~4x4" squares of inch-thick closed cell foam scavenged from product packaging. This provides good thermal contact with the keg and very good thermal isolation from ambient air.

my 13cf 6 keg keezer compressor typically runs for one hour every 5 to 6 hours depending on room temperature, using a +2°F differential, but with the Set Point one degree below my 36°F target, so the kegs cycle between 35°F and 37°F. A first pour will usually end up around 45°F which is great for all my neipas as it opens them up nicely...

Cheers!

 

[rkhanso]

With some extra insulation over the temp probe taped to the keg full of water, I got the cycle time to about 30 minutes on, 30 minutes off. It's pretty consistent like this. I do have the differential set to just .2 and -.2 degrees.

I do understand the small differential will cause it to cycle more frequently, but if the differential is wider - won't it just cause the compressor to have to stay on longer? I'm not sure I'd gain much by this if the compressor has to run for an hour instead of 30 minutes, unless this is actually better for the compressor.

Is this OK for the compressor? Is it OK for it to run for 30 minutes straight?

I'm guessing a small dorm size refrigerator may not be insulated as well as a freezer. If I could only get this thing to hold the cold temps longer/better..

 

[day_trippr]

All else equal, cycle time is driven by the differential setting. And tbh, 0.2°F is aggressively small.
Try increasing it to 1.0°F and see what happens. Then try 2.0°F...

Cheers!

 

[rkhanso]

I upped the differential to 1 degree F on each side of the set point. 2 degrees total differential

Now the fridge runs for 2.5 hours and is off for 2.5 hours. Isn't this an excessively long run time? Am I better off dropping the range to a smaller difference so the run and off times aren't so long?

 

[duncan.brown]

I don't know if there are any HVAC engineers on HBT, but modern compressors are pretty rock solid and can run and run quite happily, as long as their input voltage is stable, they are adequately cooled so they don't overheat, and the capacitors don't fail.

I think you're putting more stress on the compressor having it cycle on an off more often than having longer cycles. Generally starting a motor puts more strain on it than leaving it running. A419's have an ASD (anti-short delay) setting that is designed to prevent turning the plant on too often. I have this set to the maximum (12 mins) on all my chest freezers.

 

[day_trippr]

^Correct^. There's a lot more drama starting a compressor than having one just running along as designed.
ASD is a good thing to avoid hot-starts, as is cutting down the number of starts per time.
And I'd be surprised if someone would notice +/-1°F differential in the beer.
I certainly can't tell the difference between a pour at the bottom vs at the top of my 2°F differential.
Tighter control than that is appropriate for fermentation, not necessary for dispensing...

Cheers!

 

[rkhanso]

Thanks for the info.
I just bumped it up to +1.5 and -1.5 and will check the cycle time.
I also have the GPIOCompressor Add-On delay set to 15 (which I'm assuming is 15 minutes).

 

[rkhanso]

Well, the on/off count sure has gone down a lot!!!
Now at +/- 1.5F offset, I'm getting just 4 off and 3.5 on cycles in 24 hours.

The compressor ON cycles are about 2.5 hours long and the OFF cycles are about 4 hours average.

Hopefully the compressor likes being on for 2.5 hours straight just 4x per day.

 

[duncan.brown]

I know it can be hard to believe, but it will like being on continuously much more that the brief moment when it turns on. There's physics behind that statement

https://en.wikipedia.org/wiki/Inrush_current

 

[day_trippr]

I think you have hit the sweet spot. I'd leave that right there...

Cheers!

 

[rkhanso]

I finally kegged Biermuncher's OktoberFAST.
It's odd though, that the kegerator is behaving differently. It's not just running 4x a day for 2.5 hours per time.
Instead, it's running for about 30 minutes out of every hour.
I didn't change any settings. Still a +/- 1.5F offset. The temp probe is maybe not quite the same on the keg, but very close.
I have 2 kegs of beer in it, along with the CO2 tank. Same as before, but testing it with water.

 

[rkhanso]

I checked the tower temp chart and it has weird high temps intermittently. I'm wondering what might cause this?
It doesn't seem to happen if I raise the target temp, but I'd like the lower target temp if possible.
Something with CraftbeerPi?
Something with the hardware I'm using?
I can hear the tower blower fan running even when the temps are much higher. I suppose it might be when the kegerator compressor is off and the actual temp in the kegerator is higher?
Any ideas?

Here's the tower temp. I have a 1-wire temp probe up in the tower, about 2-3" from the top.



Here's the kegerator temp. I have a 1-wire temp probe bungee'd to the outside of the keg with a piece of pool noodle foam over it to keep it a little more separate from the kegerator air temp.

 

[day_trippr]

Were those two plots covering the same time period?
What's going on with the "Target Temperature" in that first plot? Seems like the tower probe is trying to track that - which is kinda weird - and your compressor was cycling with around a 3:45 period...

Cheers!

 

[rkhanso]

Same time period on the graphs.
I changed the target temp on the first graph to see how the temp reacts.
The kegerator compressor is pretty consistent on the temps and on/off times.
It's the tower fan that has those high spikes I can't figure out why they're there.

 

[rkhanso]

I checked timestamps on each of the graphs.
The kegerator temp is affecting the tower temp. The spikes in the tower temp happen at the same time the kegerator temp is at its peak.
I should have figured that out in the first place.