Charles Ihler

Warning: Boilers can explode and kill you. See:   http://youtu.be/fCej2OQSKnY Making/using your own boiler may cause issues with your homeowners insurance, etc. Have I talked you out of this enough?

I have build my own hydronic hot water heater for my “retreat”. In an attempt to have an option to run my farm house off grid I installed hot water radiators and ran them off an old propane hot water heater but the heater was past it’s end of life by a decade or two and so I removed it eventually for safety reasons. I have decided I’ll likely build or buy another propane boiler or even perhaps a wood burning boiler but for the near future I built an electric hot water boiler. I’m installing this in two weeks when I’m “vacationing” to complete some projects on the house.

I have the necessary basic safeties for this boiler including a low water cut out and a high pressure relief valve. My boiler stages two hot water heating elements on and off to modulate the hot water to a temperature set-point that is reset based off outside air temperature. (The colder it gets outside the warmer the water). I’ve also have a outside air temperature disable feature. My set-points are 140-180 deg F and 65 deg F lockout temp. I’m staying far away from 212 deg F as steam is a really really bad thing to generate in this kind of boiler.

During testing I jumpered across my water low limit because I was having an issue with it being too near metal. I have to insert of PVC part to fix that later on but you’ll notice in the photo on top of the grey controls cabinet I blew a hot water element apart. Not a fun time!

If you look under the pump you’ll notice the heat exchanger I plan to use for an open loop (unpressurized) wood burning boiler or perhaps just a purchased propane unit. (we’ll see how ambitious I am later on)

Although I used and programmed an industrial process controller for this; it could have easily been a Raspberry Pi or whatever you had laying around. For remote monitoring I purchased a GSM cellular interface that can text message reports and alarms as well as sensor inputs. You can also call/text it up to get data out of it. I purchased it off eBay out of Romania for $140. You just need to pop a SIM card into it. I don’t have a land line so I purchased a pre-paid AT&T phone for 30$ and used it’s SIM card. I did have to call AT&T to ask them to “unlock” the SIM card.

The rolling cart stand was a nice find I purchased for $2 from a HAM radio club that had gutted a weather radar controls system. They wanted to use the radar and had sunk a lot of money into getting it operational for Moon bounce it ended up being scrapped by the land owner so that the USAF could put in a local aircraft landing radar system. It came with about 40 10-tun 2W potentiometers in the 2k-10k range.. let me know if you need one! I’ll never use 40 of them 🙂

A thought came to mind that when I need a PID controlled process or something on the side of industrial automation I just take an old “recycled” controller that was bound for the garbage heap and I make whenever I need. That’s great for me; my blog readers, not so much. I recently replied to a posting on an electronics forum with a guy looking for a cheap and easy way to control is variable frequency drive (VFD). This is a device that varies voltage and frequency to vary the speed of a motor. You can buy these in single phase for fractional HP motors thought they’re more commonly used in three phase applications. The poster was looking for a way to vary the control voltage (0-10V). I bit my tongue through the comments from people misunderstanding that it was control voltage an in fact the guy didn’t need a 10V 300A power supply. In his case he wanted to manually adjust the speed, but if it was to be an automated process and if I was him; I’d used a stand alone PID controller. These controllers are great for a pool pumps, hot water solar panels, exhaust fan controls, or something along those lines. I would use the Johnson Controls System 350 series controller. http://www.johnsoncontrols.com/content/us/en/products/building_efficiency/commercial-refrigeration/system-modular-control/350controls/a350/sysa350p.html

You can get these to control off temperature, humidity, or pressure to vary your output. They also come in staged outputs. I’ve seen these for green house controls, water pump VFDs, etc etc. It’s pretty simple; have a control sensor, and command an output, adjust the set-point and proportional band/integration to “tune” the loop.

Full disclosure: I work for Johnson Controls, However! I do not/can not sell or install these. These are generally installed by electricians but trust me.. anyone could install one of these. I’ve played around with them from a condenser deck we were working on one time. You can pick them up at grainger or anywhere you can buy HVAC components, likely eBay as well?

.. also forgive the liberties I took with “PID”, I do realize it’s only a PI controller. It’s rare to find full PID implemented in an industrial or energy automation controller; we usually don’t need to use derivative.

I was looking for some interesting news sites for electronics as I do from time to time. Not much out there… well at least none with articles that were of immediate interest to me.

I came across this article and nearly commented but it was from 2007 with zero comments, so there wasn’t much point:

http://electronicdesign.com/archive/whatever-happened-electronics-hobbyist

I’m an amateur radio operator/builder, I like building embedded systems and I’ve built a robot, so I guess I get to fit into all three of his “types” of electronics hobbyists of the future. I think he’s probably right on with the separation of electronics hobbyist .. unless you count students; I wouldn’t. Is that a big deal? I don’t think so. Technology had made it difficult to take the old “easy” kits to offer to youth to spark some interest. Who knows how long AM will be around? Give it a decade and someone will be leaning heavy on the FCC to shut it down and sell off the spectrum. AM isn’t making any money these days.  This article also feels a little “back-in-my-day” which gets eye rolls from anyone under 40.

So my only real beef with this article is his opinion that QST is a quality magazine that supports electronics hobbyist… I totally disagree. QST isn’t worthy of toilet paper in my opinion. It’s the ‘US Weekly’ of electronics magazines. All Ads, back-in-my-day articles, and sponsored reviews. QEX on the other hand is an EXCELLENT magazine, we are in agreement there. I would recommend QEX from non-hams if they’re looking for more reading material as there are plenty of projects that could be re-purposed.

If anyone coming across this happens to have some “favorite” generic hobbyist news feeds drop me a comment. I’m always looking for interesting articles.