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Date: 07 Jun 2006 05:17:03
From: David Wuertele
Subject: Thermostat probe on fridge wall or in beer?
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My fermentor sits in a freezer which is plugged into a thermostat
controller. The controller probe is taped to the inside roof of the
freezer. I am satisfied that this keeps my freezer within two degrees
of my target fermentation temperature.
However, according to the stick-on thermometer on the side of my
fermentor, the beer temperature is about two degrees higher than the
freezer temperature, and it seems to vary a little more widely than
the freezer temp. I have been cranking my freezer's thermostat down
by a couple of degrees to compensate. It seems to work OK.
I think that I can improve the temperature stability in the beer if I
actually submerge the thermostat probe in the beer. But this adds
work: I have to clean the probe, sanitize it, and I have to make sure
that the seal around the probe lead is impenetrable.
Does anyone here keep their probe submerged in the beer? Is the finer
control over beer temperature worth the extra work? Is passing the
probe lead by the airlock's rubber stopper enough of a seal around the
lead?
Dave
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Date: 07 Jun 2006 21:59:12
From: Dick Adams
Subject: Re: Thermostat probe on fridge wall or in beer?
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David Wuertele <dave-gnus@bfnet.com > wrote:
> My fermentor sits in a freezer which is plugged into a thermostat
> controller. The controller probe is taped to the inside roof of the
> freezer. I am satisfied that this keeps my freezer within two degrees
> of my target fermentation temperature.
>
> However, according to the stick-on thermometer on the side of my
> fermentor, the beer temperature is about two degrees higher than the
> freezer temperature, and it seems to vary a little more widely than
> the freezer temp. I have been cranking my freezer's thermostat down
> by a couple of degrees to compensate. It seems to work OK.
>
> I think that I can improve the temperature stability in the beer if I
> actually submerge the thermostat probe in the beer. But this adds
> work: I have to clean the probe, sanitize it, and I have to make sure
> that the seal around the probe lead is impenetrable.
When I fill out medical forms and they ask for allergies, I
ways write down "Manual Labor." My motto is "Don't do it
unless you really want to do it or have to do it."
> Does anyone here keep their probe submerged in the beer? Is the finer
> control over beer temperature worth the extra work? Is passing the
> probe lead by the airlock's rubber stopper enough of a seal around the
> lead?
The temperature difference is normal and expected because of
the heat generated by fermentation.
Dick
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Date: 07 Jun 2006 19:48:11
From: John 'Shaggy' Kolesar
Subject: Re: Thermostat probe on fridge wall or in beer?
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On Wed, 07 Jun 2006 05:17:03 -0700, <dave-gnus@bfnet.com > wrote:
> My fermentor sits in a freezer which is plugged into a thermostat
> controller. The controller probe is taped to the inside roof of the
> freezer. I am satisfied that this keeps my freezer within two degrees
> of my target fermentation temperature.
>
> However, according to the stick-on thermometer on the side of my
> fermentor, the beer temperature is about two degrees higher than the
> freezer temperature, and it seems to vary a little more widely than
> the freezer temp. I have been cranking my freezer's thermostat down
> by a couple of degrees to compensate. It seems to work OK.
This is normal, fermentation creates heat. The temp of the fermenting beer
will usually be higher than the ambient air around it.
> I think that I can improve the temperature stability in the beer if I
> actually submerge the thermostat probe in the beer. But this adds
> work: I have to clean the probe, sanitize it, and I have to make sure
> that the seal around the probe lead is impenetrable.
>
> Does anyone here keep their probe submerged in the beer? Is the finer
> control over beer temperature worth the extra work? Is passing the
> probe lead by the airlock's rubber stopper enough of a seal around the
> lead?
This has been talked about several times in the past. IMO, no you do not
want to put the probe in the beer. It will actually make it more difficult to
keep a controlled temp this way. Because the beer heats/cools more slowly
than the air in the fridge, when your probe tells the fridge to turn on it
will run for a long time before the beer itself cools down. By then the
air temp in the fridge is going to be much lower than your beer temp. Then,
over time the beer will keep cooling down until it's way too cold. Basically
because the beer temp changes lag behind the fridge air temp changes, you're
going to be back and forth all over the place with regards to your beer
temp.
IMO, use the probe to monitor the air temp and set the fridge ambient temp to
be cold enough to keep the beer where you want it. Most likely the setting
on your thermostat will be a couple degrees colder because of the heat that
the fermentation creates. On mine, if I want to keep the beer around 65F,
I'll set the controller to something like 62F.
John.
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Date: 08 Jun 2006 00:21:54
From: Todd Carter
Subject: Re: Thermostat probe on fridge wall or in beer?
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You are probably right that you can get a smaller temperature range with
the probe in the air, but my experience has been that it works better
(appliance longevity) to put the probe in direct contact with the beer
vessel, especially stainless carboys.
The appliance cycles less because the higher specific heat of the liquid
requires longer run time to cool. While the beer may continue to cool
because of the lower air temp, I've never seen it less than a half
degree F below the hysteresis low point. Your mileage may vary.
I think what happens with the probe in the air is the appliance quickly
takes the heat from the air, shuts off, the air more slowly takes the
heat from the beer, appliance turns on, repeat frequently versus running
until the beer is at the low point and shutting off.
Add to it that opening the frig/freezer with the probe in the air will
often force on the cooling when the beer is in range.
So, a better question is, do you want a narrower temperature range or
longer appliance life?
Todd
John 'Shaggy' Kolesar wrote:
> This has been talked about several times in the past. IMO, no you do not
> want to put the probe in the beer. It will actually make it more difficult to
> keep a controlled temp this way. Because the beer heats/cools more slowly
> than the air in the fridge, when your probe tells the fridge to turn on it
> will run for a long time before the beer itself cools down. By then the
> air temp in the fridge is going to be much lower than your beer temp. Then,
> over time the beer will keep cooling down until it's way too cold. Basically
> because the beer temp changes lag behind the fridge air temp changes, you're
> going to be back and forth all over the place with regards to your beer
> temp.
>
> IMO, use the probe to monitor the air temp and set the fridge ambient temp to
> be cold enough to keep the beer where you want it. Most likely the setting
> on your thermostat will be a couple degrees colder because of the heat that
> the fermentation creates. On mine, if I want to keep the beer around 65F,
> I'll set the controller to something like 62F.
>
>
> John.
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Date: 08 Jun 2006 01:26:23
From: John 'Shaggy' Kolesar
Subject: Re: Thermostat probe on fridge wall or in beer?
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On Thu, 08 Jun 2006 00:21:54 GMT, <txspamcarter@kc.rr.com > wrote:
> So, a better question is, do you want a narrower temperature range or
> longer appliance life?
What's worse for the appliance, frequent short cycles or long sustained
ones? I don't know the answer, but I've seen people post before that
said these appliances are designed for short on/off cyles since they
were built to monitor the air temp in the first place. Long sustained
run times, according to them, were actually worse for the unit. Again,
I don't know if that's true, just passing on what I've read.
John.
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Date: 08 Jun 2006 03:42:26
From: QD Steve
Subject: Re: Thermostat probe on fridge wall or in beer?
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"John 'Shaggy' Kolesar" <spam@shagg.net > wrote in message
news:slrne8ev87.4oa.spam@weizen.shagg.net...
> On Thu, 08 Jun 2006 00:21:54 GMT, <txspamcarter@kc.rr.com> wrote:
>> So, a better question is, do you want a narrower temperature range or
>> longer appliance life?
>
> What's worse for the appliance, frequent short cycles or long sustained
> ones? I don't know the answer, but I've seen people post before that
> said these appliances are designed for short on/off cyles since they
> were built to monitor the air temp in the first place. Long sustained
> run times, according to them, were actually worse for the unit. Again,
> I don't know if that's true, just passing on what I've read.
>
>
> John.
I would have thought that the controller has an anti-cycling feature built
in. My Dixell unit certainly does and it's set to 10 minutes and overides
the temperature measured by the probe.
Picture of Dixell unit here http://blogadelaide.com/?page_id=39 ( scroll to
last picture)
Steve W (in Aus)
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