Where to put probe for PID HX

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adan0327
Posts: 32
Joined: 13 years ago

#1: Post by adan0327 »

This is not a thread to say PID hx's are pointless.

Ive PIDd many smaller home machines but usually I put them outside of the boiler. This time for my Cimbali m32 dosatron I am able to put the probe within the boiler. The question is...

Do I make the probe contact the water.
Or above the water where the steam sits.

I have already made my own thread for the boiler (drilled a hole through the plug and tapped a plumbing 1/4" thread for my plumbing fitting).
I'm at the point where all I need to do is compress the probe to make a water tight seal.

Once someone can answer this question I will PID it right away.

The reasons why I'm PIDing. Easy adjust-ability, its cheaper than a pressure stat (I use ebay PIDs all the time), easy to replace the SSR cause its only 5 bucks free shipping on ebay.

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erics
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#2: Post by erics »

Skål,

Eric S.
http://users.rcn.com/erics/
E-mail: erics at rcn dot com

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boar_d_laze
Posts: 2058
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#3: Post by boar_d_laze »

As you know you can't get an accurate brewing temp on an HX by the PID alone, but must overshoot brew temp considerably in order to have a supply of steam; thus, PID or no PID, you can only achieve proper brewing heat levels by flushing. In other words, the purpose of converting from p-stat to PID is only indirectly related to temping.

If what you're trying to do with a PID is create temperature stability within the boiler once it comes to temp (i.e., no p-stat deadband); eliminate the mechanical wear inherent in p-stats; and expedite rapid recovery from temperature loss from using steam or water from the water tap, then probe placement won't do much to expedite or hinder. Let the best entry point for the probe on the boiler, and/or ease of mounting the probe determine its placement.

If you're trying to do something else, it depends what you're trying to do.

What ARE you trying to do?

BDL
Drop a nickel in the pot Joe. Takin' it slow. Waiter, waiter, percolator

pocojoe
Posts: 183
Joined: 12 years ago

#4: Post by pocojoe »

Is it true that if it is in the steam rather than in the water that scale won't build to the same extent?
That might be important for response time to temperature change
Joe
PocoJoe
Safety Third- First Roast, then Grind

adan0327 (original poster)
Posts: 32
Joined: 13 years ago

#5: Post by adan0327 (original poster) »

i'm trying to stabilize the boiler when it reaches a setpoint. The pressure stat has a higher dead band I personally don't like this. As well I want to be able to play with the temp to see if I prefer it at lower pressure vs higher pressure within the boiler. I mounted it near the top portion of the boiler. It is not in contact of the water. Also I don't like the clicking of the pressure stat mechanism I like SSRs cause they are silent.

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boar_d_laze
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Joined: 17 years ago

#6: Post by boar_d_laze »

After you've had a couple of weeks to dial in, start a new thread and let us know if the boiler pressure at your optimum temperature is outside the pressure range you used with your p-stat. Also, if you change your shot temping ritual.

Luck,
BDL
Drop a nickel in the pot Joe. Takin' it slow. Waiter, waiter, percolator