Keezer cycling too often

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jbritt

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I'm a new brewer, I started at the beginning of the year and have brewed 7 all grain batches. I recently got a really good deal on a chest freezer that someone had already converted into a keezer by putting a steel plate through the front wall with three tap holes. Its 15 years old and was originally white/pretty rusted in some spots so I sanded/repainted it and threaded an Inkbird IT-308 temp controller and fan through an existing hole drilled for the original temp controller. I finally finished recently and moved it to my basement. I bought 3 kegs and plan to have two more inside soon (only 1 in the keezer right now). Its been running for a couple days now and I noticed it seems to cycle too often so I sat and recorded the times: approximately 26 minutes off, 7 minutes on. Maybe this fluctuates but after some research it seems like this is way too often. I saw some people saying the probe needs to be in water and having more kegs inside will help, but that can't be the only reason? It does not seem like there is any cold air escaping from what I can tell and again there is no collar, it has the original gasket. Pictures attached and a few more specs below:

- Basement Temp: Ranges from 60F to 65F
- Temp control setting: 36F, cooling differential 2F. Temp gets down to 34.9F
 

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VikeMan

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You could set the differential value to something larger (and adjust the set point a little lower to compensate for the fact that the temp will now otherwise be a little higher when it reaches setpoint + differential and kicks on.
 
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jbritt

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I could. What would be the ideal cycling time to have (realistically)? Would it be better to have it running for longer when it runs than to have it running less time but more often than it is currently?
 

VikeMan

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Would it be better to have it running for longer when it runs than to have it running less time but more often than it is currently?
I would say that longer cycles (within reason) are pretty much always better than shorter/more frequent cycles.
 
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jbritt

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I think I'll check after I put the probe in water, looks like some people do experience some drastic changes in cycle times. Thanks
 

Beernik

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I assume that the probe taped to the compressor hump.

What the compressor does is take heat from the interior wall and radiates it out through the exterior wall. So the interior wall gets really cold really fast & that’s where your probe is mounted.

Either do the cup of water thing or tape it to the keg with several layers of paper towel insulating it from the air. That will get you a better reading of the beer temperature and not the air or wall temperature.
 
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jbritt

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Yep right on the compressor hump. That's where a mount already was with probe when I bought it so I just followed suit. I think I'll use some water first and see how that goes. Thanks!
 

Golddiggie

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I have the probe from the inkbird (308 wireless version) hanging roughly in the middle of the keezer (lower 1/3) handing free. I have a fan mounted to the collar in the back, right hand, corner to move air around. I have that aimed downwards so it creates more of a convection current. You might want to look into doing something like that with your fan. The fan I installed has a speed controller for it. I have it set to move a reasonable amount of air (less than 1/2 speed). I didn't want the air movement to give the sensor false readings.

Are the holes for the sensor and fan power sealed up? I made sure to apply silicone caulk to the holes placed for any wires going through the collar. My gas bottles are all outside, running through bulkheads. Which also makes sure they're sealed up nicely.
 
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jbritt

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@Beernik, what are optimal cycle times in your opinion?

@Golddiggie, that's interesting I could consider that in the future. Yep its sealed with good amount of spray foam insulation
 

Golddiggie

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@jbritt This is the fan I'm using.

The mount is a bit ghetto right now. I plan to do something nicer at a point in the future. Just need to get that to the top of the project list.
 
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jbritt

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@Golddiggie I should have bought this one it would have been easier to thread through with the wire set up. I hear ya too many projects
 

Konadog

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If you only have 1 keg in it, that's not much of a load for a freezer that can hold 3. The cycling will get better once you have a bigger load. Your temp probe stuffed into a beer koozie with a beer is a great inexpensive way to add stability also!
 

Beernik

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@Beernik, what are optimal cycle times in your opinion?
It’s hard to say because there are so many variables: age of freezer, efficiency of compressor, set temperature, & temperature differential.

A new freezer (running as a freezer) will run 80% of the time. And old freezer will run about 50% of the time. A full cycle will be about 30 minutes.

A new freezer running as a keezer with good insulation would only run a 2 - 5 minutes every 30 minutes. I don’t have my keezer built yet, but I’m running it as a beer bottle & liquor fridge. I think mine kicks on about once an hour. I have my probe in a thermos full of water because that’s my best approximation of a bottle.

More critical than cycle time, my goal would be to make sure the probe is doing a good job of approximating the beer’s temperature because it’s the beer’s temperature I would care about when I pour.

Once I was confident I was reading the beer’s temperature, if I was still worried the compressor is running too frequently, I’d set a bigger differential.

The other thing to balance is that the freezer isn’t running so long that condensation on the freezer walls becomes a problem.
 

McMullan

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I tried with the probe inside a thermowell sat in glycerol, which isn't that different from water, in respect to hoping naively to flatten out temperature swings in a keezer.

IMG_0417.JPG


It's a QA trick I used to argue against in the workplace, too, ironically. Unless you're storing glycerol in comparable vials in the fridge, what's the point? I found it just amplified the issue (the 'Wimbledon' effect) with my keezer, by promoting more overshooting. I figured we're using the freezer's internal 'ambient' temperature to maintain temperature of beer in a keg and, physics being physics, just monitor/control the keezer's ambient temperature. Sooner or later the beer temperature is going to match the ambient temperature, right? So I dumped the glycerol idea.

IMG_0453.JPG


I found it worked much better. As Beernik says, there are so many variables keezers aren't really comparable enough for generalisations. You'll just have to observe how your keezer behaves. For example, how far does the cooling overshoot the set temp, how long does it take to creep back up to the set temp and go above it? Use the answers to adjust the Inkbird settings. Observe and continue tinkering with the settings until you're happy with it.
 

jseyfert3

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It's a QA trick I used to argue against in the workplace, too, ironically. Unless you're storing glycerol in comparable vials in the fridge, what's the point? I found it just amplified the issue (the 'Wimbledon' effect) with my keezer, by promoting more overshooting. I figured we're using the freezer's internal 'ambient' temperature to maintain temperature of beer in a keg and, physics being physics, just monitor/control the keezer's ambient temperature. Sooner or later the beer temperature is going to match the ambient temperature, right? So I dumped the glycerol idea.
Yes, putting the probe in something with thermal mass decreases cycling by increasing air temp overshooting. There’s no way around that. You can’t decrease cycling without increasing overshooting. That’s just basic physics. So you trade shorter cycles and more stable temps for longer, fewer cycles and a bit more temp swing. The reason this latter is generally preferred is less wear on the compressor from cycling less as well as slightly better efficiency, as heat pumps are more efficient in general running in longer increments rather than shorter ones.

Also one thing to note is the temp of the beer itself doesn’t swing nearly as much as the air temp does. So putting the probe in something with thermal mass is better at mimicking the actual temp of the beer itself, which is what matters. For one of the most extreme examples of this, if I recall correctly it was @day_trippr that straps the temp probe to a keg and puts insulation on the outside. The cycle times went to around 4 hours (like half hour on, 3.5 hours off) and the air temps swung by like 20 degrees over the course of a cycle but the temp of the beer in the keg only changed by a couple degrees.
 

McMullan

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Yes, putting the probe in something with thermal mass decreases cycling by increasing air temp overshooting. There’s no way around that. You can’t decrease cycling without increasing overshooting. That’s just basic physics. So you trade shorter cycles and more stable temps for longer, fewer cycles and a bit more temp swing. The reason this latter is generally preferred is less wear on the compressor from cycling less as well as slightly better efficiency, as heat pumps are more efficient in general running in longer increments rather than shorter ones.

Also one thing to note is the temp of the beer itself doesn’t swing nearly as much as the air temp does. So putting the probe in something with thermal mass is better at mimicking the actual temp of the beer itself, which is what matters. For one of the most extreme examples of this, if I recall correctly it was @day_trippr that straps the temp probe to a keg and puts insulation on the outside. The cycle times went to around 4 hours (like half hour on, 3.5 hours off) and the air temps swung by like 20 degrees over the course of a cycle but the temp of the beer in the keg only changed by a couple degrees.
Has anyone got any convincing evidence for 'wear on the compressor' caused by cycling, as opposed to just being on? My fermentation fridge has been on continuously for about 8 years, controlled by an ATC800, and the compressor is fine. For my keezer, which I've insulated very well, with 2 layers of sealed XPS lining the inside of a timber collar and a perfect seal for the refitted lid, I find air temperature inside settles down quite nicely, once the beer is at the set temperature. It cycles more often, but not excessively. I rarely notice it on when I go get a beer. With the probe in glycerol I'd say the freezer appeared to be working a lot harder therefore promoting more wear on the compressor?
 

VikeMan

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Has anyone got any convincing evidence for 'wear on the compressor' caused by cycling, as opposed to just being on?
I don't have the data personally, but any Refrigeration Tech will say that frequent cycling is bad for compressors. It may be urban legend, but if it is, the professionals have bought into it.

I don't know if it's a great analogy, but I look at it like starting a car and letting it idles for an hour, vs. starting it, letting it idle for a minute, shutting it off, and repeating 59 times.
 

McMullan

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I don't have the data personally, but any Refrigeration Tech will say that frequent cycling is bad for compressors. It may be urban legend, but if it is, the professionals have bought into it.

I don't know if it's a great analogy, but I look at it like starting a car and letting it idles for an hour, vs. starting it, letting it idle for a minute, shutting it off, and repeating 59 times.
That's pretty much what I've been assuming for years, but I haven't ever observed any signs of it personally. Have we been misled by superstitious refrigeration engineers? Or compressor salesmen? 🤔
 
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jbritt

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Thanks, all. I put the probe in the bottle of water last night and as predicted in the thread it is overshooting cooling quite a bit but seems to be cycling substantially less. I haven't had time to observe it much yet though. There is also a lot of condensation now too so I ordered a dehumidifier.

@McMullan that Keezer looks great!
 

RolandD

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My keezer is about the same size and age as yours. I have the temp probe sealed in a water bottle with the temperature set to 37 degrees with a variance of 2 degrees. I cycles once every six hours or so.
 
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@RolandD How did you set up the water bottle seal? Just curious, I mine is currently stuck through the hole of the top of a water bottle but I plan on making it more secure
 

Golddiggie

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The controller I'm using for the keezer is set with a 5 minute delay so it won't short cycle. Obviously ambient/room temp influences how much it runs more than a little. In the summer it runs more often than in the cooler months. Especially if I'm not running the AC and it gets warmer where it sits.
 

Beernik

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I tried timing my freezer’s cycle today but gave up after the off cycle hit the 3.5 hour mark.

You have to remember that air is an insulator, which is why you need the fan to circulate heat to the interior wall where the compressor will remove it. But the air temperature is not going to be the same as the wall temperature or the keg temperature and it doesn’t need to be.

Long run times for a compressor shouldn’t be as detrimental for them as short run times. Like a car engine, the pump needs a certain amount of time for the lubricants to be functioning properly and the most wear on it occurs in that first couple minutes.

The risk from really long run times is that the condenser freezes up. They should have a built in defrost cycle to prevent it. But if it has run that way for several years and hasn’t frozen up, I wouldn’t worry about it.
 

ITV

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My preference to reduce cycle times and maintain stable beer temps is to tie wrap the probe to a can of beer and try to keep the keezer full (5 kegs).

My theory is that the 5 cold kegs perform as "ice packs" by radiating the cold inside the keezer.

I had a discussion with a Pipe Fitter in my beer club, who works on industrial refrigeration units, about using chest freezers at refrigeration temperatures. He stated that the chest freezer compressors like cold temperatures (below freezing) as opposed to running them at refrigeration temps (36 deg).

My last keezer only lasted 4 years (in my basement), if the new one only lasts a few years I may need to rethink using chest freezers as a keezer. Ideally the chest freezer should have a condenser cooling coil and fan.
 

jseyfert3

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The risk from really long run times is that the condenser freezes up. They should have a built in defrost cycle to prevent it. But if it has run that way for several years and hasn’t frozen up, I wouldn’t worry about it.
The condenser is the hot coil, so it wouldn’t freeze ;). Chest freezers have the evaporator attached to the inner wall of the chest. I’ve not seen one with a defrost cycle. In fact it wouldn’t be possible unless the chest freezers had a evaporator coil not built into the walls with a fan blowing air over it and a drain under the coil, which is how frost-free residential fridge/freezer combos work. This is why ice builds up on the walls of chest freezers. The defrost cycle is when you pull all the food out and unplug the freezer so the ice can melt. If the chest freezer had a defrost cycle all the ice on the walls would just run down to the floor where it would re-freeze again.

I can’t imagine ice building up permanently on the walls of a kreezer set around 38°F, as if any formed during running it would easily melt during the off cycle.


I had a discussion with a Pipe Fitter in my beer club, who works on industrial refrigeration units, about using chest freezers at refrigeration temperatures. He stated that the chest freezer compressors like cold temperatures (below freezing) as opposed to running them at refrigeration temps (36 deg).
Hmm. This makes me want to dig out my thermo books and review heat engine cycles…
 

McMullan

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Sorry, compressor, not condenser.

McMullan said he uses a fridge keezer that runs all the time.
Sorry, fermentation fridge that's been in continuous service for about 8 years. As I place the temp probe inside FVs, controlling temperature of fermenting wort, the 'Wimbledon' effect is much greater, but the fridge compressor continues to work fine (touch wood!). I have no idea about refrigeration compressors or whether fridge and freezer compressors differ enough to matter. Anyway, after sleeping on it, I think I might take onboard some of the logic and assumptions offered here and reassess probe position in my keezer. I might have been swayed initially by impatience, within hours of first powering up the keezer. What I don't want to do is accidentally on purpose kill it prematurely, due to my ignorance about refrigeration compressors. Cheers!
 

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@RolandD How did you set up the water bottle seal? Just curious, I mine is currently stuck through the hole of the top of a water bottle but I plan on making it more secure
Sorry for taking so long to reply.

I sealed the hole in the cap with silicon caulk.
 

jseyfert3

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Same here…but I get a headache just thinking about it… 🤪 Ahhh the good ‘ol university days…🤓
Yeah I never did dig them out. Honestly if it was such a problem nobody here would do them, but instead they are probably the most used style of DIY kegerator, so instead I’ll just RDWHAHB.
 
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