Re: [new_distillers] Re: PID Controller
- Gavin,I own a 12HL (a little less than 300 gallons) brewery and we use a 6000W RIMS tube for our mash tun temp changes. Two things we have solved that have made this possible.1.) We realized not only did we need to know the temp of the grain bed (mash temp), we also needed to know the temp of our RIMS tube output (rims temp). We were recirculating our wort out of the RIMS back into the mash tun near the top (I think some breweries call this the "vorlauf"). This freshly heated wort would remain at the top of the mash, and only slowly work it's way down until it was replaced by enough hot wort to reach the thermometer. Often overshooting your the mash temp and denaturing the enzymes that were responsible for starch conversion; depending when this occurs, we could end up with significantly less sugar to ferment. We solved this problem by averaging the mash temp and the rims temp. Most PIDs cannot do this, so for a while we used pencil and paper with a manual thermometer on the mash tun and PID (with SSR) on the RIMS tube. After a bit of mucking around we discovered this problem on our 100liter (about 20 gals) system too.2) we feel like everyone should take good care to have a gentle vorlauf, it will rebuild the grain bed to act as a filter for the husks and whatnot. Clear flowing wort ferments better and leaves less residue in your kettles and fermenters. Low splashing and avoiding wort from channeling through the grain bed will make things much better for in the boil and subsequently whirlpooling, chilling and fermenting.
On Nov 22, 2012, at 7:20 PM, Gavin Flett <gavin_flett@...> wrote:Now that's what I have been searching for. a lamens description of what a PID and an SSR does. ThanksHow do the beer brewers do this then, what kind of W heating element do they use? Is it multiple low wattage elements?
Date: Thu, 22 Nov 2012 23:48:08 +0000
Subject: [new_distillers] Re: PID Controller
> Cool, great info. I am actually using it for a barley mash process. So if I understand correctly, an SSR performs the same functions as a PID, but better?
No, they're completely different things. The PID is a logic "brain" that attempts according to the parameters you program in to shoot for a particular temperature. It determines how long the element is "on" or "off" and makes adjustments according to results.
SSR stands for Solid State Relay. It's really just an electronic switch - it has no moving parts. It is the equivalent of the contactor but because the contactor has moving parts it is not capable of switching power off and on to the element frequently without destroying itself.
Your PID itself is able to switch loads of up to 3 amps, but this is well short of 2000 Watts. Remember that Watts = Voltage x Amps. Re-arrange this formula to get W/V = A, and depending on what your voltage is this will tell you how many Amps capability you need.
So you employ a contactor, or SSR, to do the heavy-duty switching because these are capable of handling many more amps.
There is one thing to remember with a SSR, and that is if they fail they switch, as far as I understand, to full on and will not turn off. The SSR has its own connection to voltage mains. So, as with all setups like this, you should always supervise operation.