After many trials and tribulations, we have finally succeeded in creating a (partially) electric brewery! The original design remains in tact, but there were several missteps that lead to broken parts and new parts being ordered. Initially, the design included a few elements, the PID, SSR, and heating element. This is still true, but the original kit that included the PID, SSR, and heat sink (for the SSR) is no longer any part of the system.
The story began the day I finally got the kit from China. I was excited to start assembling the unit after all the waiting and anxiety, but I still needed a few pieces that I didn't necessarily consider at first. The PID needed some kind of enclosure to house it and all of the wires that would be connecting each of the elements. It also required a fuse to ensure a power surge wouldn't destroy it. The power I would be using was from my clothes dryer, which already had a socket and breaker connected. I just needed a dryer plug to connect my 10 gage wire to the outlet. Once all the additional pieces were purchased, I could start to assemble.
The enclosure I chose was a large sized plastic outdoor junction box. The fact that it was plastic allowed me to be able to cut it fairly easily as well as avoid incidental contact with the high voltage lines inside.
The dryer plug was a three pronged 220V type with a ground and two 110V pins. This was all I need to connect as the 110V lines were opposite poles (across which the 220V was supplied).
Inside the enclosure I used simple wire nuts to connect all of the necessary wires to their respective circuitry. (See schematic) The junction box also housed the heat sink and SSR (as I did not anticipate much heat being generated).
The two elements that needed control, were the PID and the heating element. I added separate switches for these pieces so they could be turned on and off independently. I thought it would be a nice touch to be able to avoid a boil over by simply flipping the switch on the heating element, thereby instantaneously removing the heat source.
The thermocouple used to provide feedback to the PID was screwed into a metric stainless steel nut that had been welded into the side of the keggle. It was connected directly to the PID inside the junction box.
The final piece of this puzzle is the heating element. It was merely screwed into a 1 inch NPT fitting welded into my keggle. The wiring was connected on one side from the SSR (which provided the switching on and off) and on the other from the negative 110V line.
Once completely assembled, I plugged in the dryer plug (wincing as I did). Nothing happened (thankfully!) as the switches to the PID and heating element were both in the off position. When dealing with any kind of power (as I am an electrical engineer by trade), I always expect the worst (something exploding), but hope for the best (no action whatsoever). Having the best of reactions to the last change of state of this new system, I was hopeful when flipping the switches to the on position. As I did, the display on the PID lit up and showed some numbers and the keggle did not spontaneously combust!
Things were really going well at this point. I had added some water to the keggle before this test began, so I was confident that the element would not be burning up if the PID came on and thought that it should enable the heating element. It was a good thing, as the PID was unable to sense that the water was being heated. As the element was turned on, the water started to heat and the PID read the temperature as decreasing. I had connected the thermocouple backwards. It was a minor mistake, but required me to open the junction box to rewire the thermocouple. Once all the hardware bugs were worked out, I set the PID on something above the boiling point of water and allowed the water to come to a full boil. During this process, I had been testing the temperature of the junction box by placing my hand on it from time to time. It did not feel too terribly hot at any point during the initial test.
Once I was satisfied that I was able to boil water, I decided to do some testing to see if I could set the PID to a particular temperature and have the water remain there for an extended amount of time. This proved impossible at this point. I set the PID to something like 70 degrees Celsius and watched as the water climbed right back to boiling. I noticed that the small LED on the SSR that indicated that it was active was no longer lit, but was confused when the water still climbed in temperature. I had blown the SSR! The heat inside the junction box and more critically the heat sink that was sent with it were no match for the heat generated by the SSR. It turns out that the SSR is only rated to run at an internal temperature of 70 degrees Celsius and that the heat sink provided was only for a 25 Amp SSR (when, in fact, the SSR was a 40 Amp!). Disappointed, I left the keggle filled with hot water, shut down the PID and heating element, and unplugged the junction box from the dryer outlet and went to bed.
The next day, I decided I would get things cleaned up, order a new SSR, and found that the keggle had rusted! The "stainless" steel nut that held the thermocouple as well as the thermocouple itself had rusted! Broken by the weight of these events, I called my welder and scheduled a replacement fitting to be welded in and ordered a new thermocouple (except this time I decided I would use an resistance temperature detector or RTD) that would fit into a standard 1/4 inch NPT fitting instead of that awkward metric nut that had been used before.
Several days later, the RTD arrived. Excited that I might finally be able to use my setup as I had originally intended, I connected the RTD, plugged in the junction box, and set a temperature. After several minutes and noticing that the water had begun to boil (at least above the heating element), I saw that the temperature on the PID read by the RTD was not increasing. I thought it might have been the connection and tried to tighten the screws holding the leads from the RTD, but there was no change. Next I thought there might have been an error in the directions I was reading for the PID as they had come with the PID from China and could have been poorly translated. Swapping the leads made little difference. Eventually I noticed in the directions that particular part numbers were associated with particular input devices and output parameters. I discovered that this PID was only designed to be used with a K type thermocouple (which it had been shipped with). Incredibly frustrated and angry at this point, I immediately ordered a new PID to replace the minimally functional PID I had been using. Little did I know, I could have just ordered a new thermocouple that would have worked with my original PID and saved me about 20 dollars, but that is a story for another day.
Finally, a few days ago, my new PID arrived. I replaced the old one, ran a few tests similar to those described above and decided that I can finally call the electric keggle project a success. The end result being that I had replaced every piece of the original PID kit I had ordered from China. The lesson here (to me anyway) is to only buy the good stuff and don't be cheap about it. Buying crappy unsubstantiated materials only leads to more frustration than necessary.
I'm excited as our inaugural brew is Sunday. We are brewing, what we consider, our legacy beer, the Hefewitzen (a mostly Wit style recipe with hefeweizen yeast). It is our legacy because every time it turns out pretty well, but we feel we can always do better.
Here is a link to a spreadsheet showing all of the elements I purchased, their prices, and where to find them: Electric Keggle Parts, etc.
No comments:
Post a Comment