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Old 04-08-2011, 05:52 AM   #1
evanos
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Heyyo HBTer's,

Is an external thermostat hard on a chest freezer's hardware?

Muchas gracias guys!

 
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Old 04-08-2011, 06:16 AM   #2
samc
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You just need to have a thermostat that has a short cycle delay, which prevents it from cycling on and off too quickly. Mine is set at the max which is 12 minutes, although in practice it would be rare for it to want to go on/off so fast unless you were constantly opening it for some reason.

 
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Old 04-08-2011, 06:17 AM   #3
djsethall
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Duty cycle can be hard on compressor/condensers. Iknow that the johnson digital controls have a function which allows the cooler to go a few degrees above the desired temp before turning on the unit. I'm sure you can look for this in your temp controller.

 
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Old 04-08-2011, 06:27 AM   #4
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I had an old (really old) freezer that died not long after using it as a keezer with external temp control. Got a new freezer and it's still going. Turning on and off the compressor too frequently can definitely be hard on it but if it is set right and doesn't do it too frequently, the freezer is off which means the compressor isn't running at all, particularly in cold months (assuming ambient temp doesn't drop way below freezer level). I think of it as cancelling each other out. Compressor on/off frequency = compressor not running time. I'll let you know when my keezer dies but it's been going about a year now with no probs.
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Old 04-08-2011, 10:17 AM   #5
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Yeah, I use a Ranco and it has the ability to set a range. The wider you set the range, the easier it is on the compressor. I think I have my keezer with a four degree range, which takes a long time to warm up to that when it's full.

 
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Old 04-08-2011, 04:30 PM   #6
mcl
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Quote:
His latest argument is that an external temperature controller for the keezer is going to burn out the compressor faster because it will work at full bore, then shut off, then full bore, off, etc etc etc.
As far as I know compressors are always running "full bore". The only thing you are changing is what is triggering the compressor to turn on. It is operating at a higher temp than it would as a freezer which means it has to be on less often(this may not be the case with a collar and more leakage).

 
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Old 04-08-2011, 05:34 PM   #7
cwi
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Preventing short cycling will be gentler on the compressor. Besides buying a controller with a short cycle delay setting, putting the sensor in/on a container of liquid to dampen its response will prevent short cycling without having the large temperature swings a large offset can cause (edit- For clarity, I should have added that this was in combination with reducing the "temp differential" parameter available on most controllers. It make no sense otherwise, as the liquid temps will vary at least as greatly as the "temp diff" range.- end edit). Sensor response varies based on the type, but the way we use them, most will benefit from some damping. A combination of sensor response dampening and short cycle delay (for insurance) is one of the better approaches, since it maintains a tight temperature range, with guaranteed short cycle protection.

Damping the sensor response will also prevent cycling due to lid openings, which will happen if the sensor is a fast responding type, and is in air only.

For fermenting in a keezer, putting the probe directly on/in the active vessel will give the tightest control over ferm temperature. Short cycling could occur for a vigorous fermentation, but as long the controller has a cycle delay, it isn't an issue.

 
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Old 04-08-2011, 06:48 PM   #8
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"Besides buying a controller with a short cycle delay setting, putting the sensor in/on a container of liquid to dampen its response will prevent short cycling without having the large temperature swings a large offset can cause."

Not true. You will have even larger temperature swings with a submerged probe. That's what the differential setting on the controller is for.

"Dampening the sensor response will also prevent cycling due to lid openings, which will happen if the sensor is a fast responding type, and is in air only."

So what? That's what the anti-short cycling feature is for. Mostly this doesn't happen much anyway as the cold air stays put in a chest freezer. IMO, fast probe response is advantageous and there is no need to dampen it.

"For fermenting in a keezer, putting the probe directly on/in the active vessel will give the tightest control over ferm temperature. Short cycling could occur for a vigorous fermentation, but as long the controller has a cycle delay, it isn't an issue."

Except that IMO, it doesn't. Your freezer will become an ice box by the time the controller responds when cooling and the reverse on temperature rise.

I've found that the positioning the controller probe in the air near the bottom of the freezer works best (when using a fan, where you place the probe makes little difference). Then, a separate digital thermometer is used to monitor the fermenter temperature with the probe attached to the side and covered with some bubble foil (or any other) insulation. I adjust the controller based on the thermometer reading. It holds within about 1*F. The thermometer probe could also be used with a thermowell in the fermenter, but not the controller probe.

At one time, I thought that putting the probe in a container of water would be a good idea. The problem is that it is difficult to use the controller as both a controller and a thermometer. We need to know the temperature in two different locations at the same time. Tough to do with a single probe.

 
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Old 04-08-2011, 06:50 PM   #9
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You can set ASD of about 10 minutes OR damp the sensor by taping it to the fermenter and also putting a square of bubble wrap over the probe. This is required with an analog controller.
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Old 04-08-2011, 06:57 PM   #10
motobrewer
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catt speaks the truth.

My fridge controller is able to log data. here is some:
https://spreadsheets.google.com/ccc?...UNk0wU0E&hl=en

note that i didn't set up the logs to record at the same time intervals. i can get better data when i get home. but there are two time columns so you'll have to match up accordingly.

my probe is sitting in air. just hangin' in the air. i have a big, 27cuft, 6x2.5x2 (ish) freezer.

as you can see in the data, my compressor runs for 2-4 minutes every hour.

catt is dead on about fermentor control. if you send a probe down the thermowell, the freezer will get very cold by the time the setpoint is satisfied. if you really wanted to go that route put the probe in air for the first 24 hours or so to let the beer temp get down, then you can send it down the thermowell

note, i just lagered at 35F with the probe in air temp, but i had another probe down the thermowell just to see. the probe down the well never changed temp.
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