Kegerator compressor cycling question

[diannotti]

Sorry for the double post - I cannot figure how to delete the original post in the Equipment / Sanitation section

So I read about a dozen threads on compressor cycling but none that I found answered what a "good" or normal cycle should be, just to avoid short cycyling. So here is my question / scenario:

DAR44BL converted to kegerator, Ranco etc controller set to 42 with 3 degree variance.
I just started to closely observe my kegerator and here is how it is "cycling"
7:10 am Compressor kicks on at 45
11:04 am Compressor turns off at 42
12:58 pm - it's currently at 43
* I changed Ranco to a 2 degree variance and it hit 44 at
1:02PM and compressor is on again
2:04 PM Off
3:27 PM On
4:34 PM Off
5:52 PM On
7:05 PM Off
8:32 PM On
9:43 PM Off
*Changing variance to 2 degrees lowered the running time from 4 hours to 1hr. My "off" time decreased from just under 2 hours to right about 1 hour 15.

Anyone have any input? How long is too long for the compressor to run? How short is too short for the compressor to have to come back on?

 

[truckmann]

I can't give you any hard numbers, but it sounds like your compressor run time is quite long. I don't think it should have to run that long to cool the space inside a keg fridge. I would be checking to see if the compressor is overheating if it has to run more than about 30 minutes to cool the space a couple of degrees. The compressor probably has a thermal shutdown to keep it from being damaged, but repeated overheating is hard on them. I'm not sure what your kegorator setup is, but it sounds like the cooling system may be a bit to small for it.

As for the off time it generally only needs to be off a few minutes to allow the pressure in the system to equalize. That way the compressor isn't trying to start under pressure, which is hard on it. Of course if your compressor is constantly cycling, once again you may end up with an overheating problem. If it is staying off for over 30 minutes that should be plenty of time for the system to cool down.

 

[diannotti]

I can't give you any hard numbers, but it sounds like your compressor run time is quite long. I don't think it should have to run that long to cool the space inside a keg fridge. I would be checking to see if the compressor is overheating if it has to run more than about 30 minutes to cool the space a couple of degrees. The compressor probably has a thermal shutdown to keep it from being damaged, but repeated overheating is hard on them. I'm not sure what your kegorator setup is, but it sounds like the cooling system may be a bit to small for it.

As for the off time it generally only needs to be off a few minutes to allow the pressure in the system to equalize. That way the compressor isn't trying to start under pressure, which is hard on it. Of course if your compressor is constantly cycling, once again you may end up with an overheating problem. If it is staying off for over 30 minutes that should be plenty of time for the system to cool down.

It's a DAR440BL with two corny's
Sounds like your advice would indicate dropping the variance to 1 degree.
Do you think it being on for about 1 hour is too long?

 

[day_trippr]

Where do you have the Ranco's temperature probe? I strap my Ranco probes to whatever I'm trying to keep cool with a velcro strap, trapping the probe under a palm size chunk of 1" closed cell foam. It really cuts down the cycling to the point that I can set the differential to 1°F...

Cheers!

 

[diannotti]

Where do you have the Ranco's temperature probe? I strap my Ranco probes to whatever I'm trying to keep cool with a velcro strap, trapping the probe under a palm size chunk of 1" closed cell foam. It really cuts down the cycling to the point that I can set the differential to 1°F...

Cheers!

That is what I am doing, although using the Reflectix insulating metallic bubble wrap. (side of one of the two full corny's)
Based on my tracking at this point and the fact that the compressor stays off a good hour now I think it is safe to switch to 1 degree variance. BUT
Right now I am about 1 hr on and 1 hr off which seems like a pretty good balance to me. However I have no idea what is considered ideal.

 

[shortyjacobs]

It's basic heat transfer folks. The heat entering the fridge, (or the "cold escaping") is a constant, no matter how you set your thermostat.

If you:

*Tape your probe to the keg with insulation - the fridge will have long "on" and "off" times. I.e. off for hours as the keg slowly warms, on for hours as the keg takes time to cool off. That's a lot of thermal bulk. This will mean your keg actually has MORE variation, as you are waiting for a good chunk of thermal bulk to warm before you kick on the compressor. (See second scenario below, then think of the opposite, to see why this is true).

*Leave your probe hanging in the middle of the air - the fridge will cycle frequently, as the air temp will move up and down a lot faster....this will keep the keg at a more constant temp though! As the air cycles between, say, 42 and 44, the keg will constantly be playing catch up, and will probably stick at 43, (either absorbing or releasing heat depending on air temp).

*Set a small variance - fridge cycles a lot, as the temp yo-yos. It will cycle FASTEST with the probe in air and a small variance. Slower with the probe taped to the keg and a small variance. Both situations will probably keep the keg more constant than the scenario below, (but see the "order of cycle operations" I have down below...two of the situations are probably mostly equal).

*Set a large variance - fridge cycles less, temp yo-yos over a wider range. Again, more frequent with probe in air, less with it taped to the keg.

In terms of cycle time, (order of cycle operations), it would probably go "probe in air/small variance"<"probe in air/large variance" ~= "probe on keg, small variance"<"probe on keg, large variance".

Point is, duty cycle is the same. Over a sufficiently long period, 24 hrs for example, the compressor should be on for about the same amount of time, and off for about the same amount of time, regardless of which scenario you choose above.

Which one is best? I don't know. Probably one of the middle ones, since this strikes the happiest balance between not cycling too often and not having huge beer temp swings. YMMV.

 

[day_trippr]

Horse pucky.

I have run my ferm fridges and my keezer both loosely coupled and tightly coupled, with both LC thermometers and IR thermometers to check keg & corny temps, and tightly coupled probes keep the brews much more stable than loosely coupled. Especially when I'm running primaries. This has allowed me to tighten the controller differentials down to 1 degree on all three chillers without excessive cycling.

Of course, these are full size fridges and a freezer, not mini fridges, which are challenged by btus...

Cheers!

 

[truckmann]

Personally I don't see the point in using a temp controller on a kegerator unless it's to control a converted freezer. My little Sanyo keg fridge has been keeping my beer at a good temp for several years now. I guess it's not really that important to me to have my beer kept at some exact temperature.

 

[diannotti]

Personally I don't see the point in using a temp controller on a kegerator unless it's to control a converted freezer. My little Sanyo keg fridge has been keeping my beer at a good temp for several years now. I guess it's not really that important to me to have my beer kept at some exact temperature.

Great post

 

[day_trippr]

Personally I don't see the point in using a temp controller on a kegerator unless it's to control a converted freezer. My little Sanyo keg fridge has been keeping my beer at a good temp for several years now. I guess it's not really that important to me to have my beer kept at some exact temperature.

Do you do fermentations in your fridge?

Cheers!

 

[truckmann]

Do you do fermentations in your fridge?

Cheers!

Not in my kegerator. I have a separate fridge for that and yes it is temp controlled.

 

[terrapinj]

Personally I don't see the point in using a temp controller on a kegerator unless it's to control a converted freezer. My little Sanyo keg fridge has been keeping my beer at a good temp for several years now. I guess it's not really that important to me to have my beer kept at some exact temperature.

if you are concerned about proper carbonation levels it matters

 

[day_trippr]

Not in my kegerator. I have a separate fridge for that and yes it is temp controlled.

Consider yourself long-distance-beyotch-slapped for the fibbing thing.

Cheers!

 

[truckmann]

if you are concerned about proper carbonation levels it matters

Sure it makes a difference, but not enough that I can tell without an expensive carbonation meter. I still don't see the need for precise temp control on a fridge that is just for serving beer. My beer coming out of the tap has always had adequate carbonation levels. Ideally I should also have a dual CO2 gauge instead of just a manifold to be able keep my kegs under different pressures depending on style. Hasn't been a big enough issue to warrant me to do that.

Consider yourself long-distance-beyotch-slapped for the fibbing thing.

Cheers!

Sorry I didn't mean to imply I don't believe in temp control, I just don't think it's necessary on a fridge that is strictly for serving beer. It's most definitely important for fermentation.

 

[diannotti]

I wish people who had interest in the topic would comment. Oh well I think I am good with my 2 degree swing, seems to be nicely balanced and my carbonation at 12 PSI will be nice and steady.

 

[day_trippr]

Sorry I didn't mean to imply I don't believe in temp control, I just don't think it's necessary on a fridge that is strictly for serving beer. It's most definitely important for fermentation.

There ya go. I use my two fridges for fermentation, hence the controllers. And the keezer has to have one lest I lose 30 gallons of beer to ice...

Cheers!