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Date: 21 Aug 2007 17:12:11
From: jose
Subject: HERMS Thermocouple Question
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Hey guys, I finally got the gumption to build a herms system, and I am having an issue that hopefully someone here has also experienced. To get my thermocouple inlive with the
output of the heat exchanger, I purchased a pipe plug probe from omgega electorincs (http://www.omega.com/pptst/TC-NPT.html). I then purchased a 1/2" tee, that has a nipple on
each end for the wort input and output. The pipe plug probe is attached to the tee via a 1/2" to 1"4" reducer. The wort is pumped from the mash ton, through the heat exchanger,
and through the tee where the thermocouple reads the temperature.
Here is my issue, my temperature reads just fine on the way up, however the temperature reading does not drop as fast as the actual temperature of the wort. I have attributed
this to the bronze tee abosobing heat, and the heat of the tee itsself does not decrease as fast as the wort flowing through, and this is interfering with the thermocouple. I
have verified this by pouring cold water over the tee and I see teh temperature immediately drop to the actual temperature of the wort flowing through.
This is a fatal flaw in my design and need to get the thermocouple inline with the wort and away from any outside interference. I am going to try and replace the brass fittings
with plastic, but I am unsure if I can find the necessary parts locally. Just looking for feedback from some of the folks that have built HERMS/RIMS systems to see what others
have done to get inline measurements. As always, thanks for the feedback, this group rocks.
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Date: 22 Aug 2007 00:29:25
From: DonF
Subject: Re: HERMS Thermocouple Question
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On Tue, 21 Aug 2007 17:12:11 GMT, jose@jose.com (jose) wrote:
>Hey guys, I finally got the gumption to build a herms system, and I am having an issue that hopefully someone here has also experienced. To get my thermocouple inlive with the
>output of the heat exchanger, I purchased a pipe plug probe from omgega electorincs (http://www.omega.com/pptst/TC-NPT.html). I then purchased a 1/2" tee, that has a nipple on
>each end for the wort input and output. The pipe plug probe is attached to the tee via a 1/2" to 1"4" reducer. The wort is pumped from the mash ton, through the heat exchanger,
>and through the tee where the thermocouple reads the temperature.
>
>Here is my issue, my temperature reads just fine on the way up, however the temperature reading does not drop as fast as the actual temperature of the wort. I have attributed
>this to the bronze tee abosobing heat, and the heat of the tee itsself does not decrease as fast as the wort flowing through, and this is interfering with the thermocouple. I
>have verified this by pouring cold water over the tee and I see teh temperature immediately drop to the actual temperature of the wort flowing through.
>
>This is a fatal flaw in my design and need to get the thermocouple inline with the wort and away from any outside interference. I am going to try and replace the brass fittings
>with plastic, but I am unsure if I can find the necessary parts locally. Just looking for feedback from some of the folks that have built HERMS/RIMS systems to see what others
>have done to get inline measurements. As always, thanks for the feedback, this group rocks.
My first guess would be adding the 1/4 to 1/2 inch reducer prevents
the thermocouple tip from protruding into the flowing stream. In
effect, the probe is setting in a dead zone.
I recommend something similar to:
http://cgi.ebay.com/Thermocouple-2-J-low-temp-3-16-x6-w-6ft-lead-and-CF_W0QQitemZ290153117412QQihZ019QQcategoryZ50926QQssPageNameZWDVWQQrdZ1QQcmdZViewItem#ebayphotohosting
In other words, a simple thermocouple probe and a compression fitting
which allows you to set the exposed probe length. A two inch long
probe, rather than the 6 inch model shown in the ebay ad, would be
preferable.
You would obviously also need a 1/2 to 1/8 NPT reducer. Before
tightening the compression fitting, push the probe in until it "hits
bottom" on the inside of the 1/2 inch NPT tee, then retract it about
1/4 inch. That should place the probe tip more or less in the center
of the flowing stream.
Smaller diameter probes will give faster temperature response (at
least until they become so small they are, shall I say, delicate.)
Grounded tip probes respond quicker to temperature changes than
non-grounded or insulated tips.
DonF
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Date: 21 Aug 2007 12:59:54
From: Bill Velek
Subject: Re: HERMS Thermocouple Question
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jose wrote:
> Hey guys, I finally got the gumption to build a herms system, and I am having an issue ...
snip
I've been planning to build a system, but never did find the time or
extra money to get started, ... so I envy you. Anyway, If you don't get
an answer here, try my Yahoo Brewing Equipment; we have almost 700
members now, and quite a few of them have built HERMS/RIMS, etc. If
interested, please visit http://groups.yahoo.com/group/BrewingEquipment
Good Luck.
Bill Velek - PERSONAL sites = www.velek.com & www.2plus2is4.com
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