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 🙂
