[Ralph Doncaster] has a geothermal heat pump which is responsible for providing heat for his home. He’s been looking into some hacks that would make it more efficient and decided that the freon (R-22) needed to be tweaked. Some would say the stuff is bad for the environment, so he decided to go a different route. He replaced the Freon with propane, using this rig to make the fuel-grade propane more like cooling-grade propane called r-290.
He purchased the gauge set which is used whenever a technician services an A/C system (but you can also see it in this other A/C propane hack). That’s important because it’s responsible for making sure the old coolant is recaptured (his hose failure nixed this part of the plan) and the new coolant goes where it should at the correct pressure. But before dumping in propane from the local hardware store he needs to dry it out. Fuel-grade propane can have moisture in it, which can be bad for the cooling system. He bought a drier device, the grey bulb seen above, and soldered it on one end to a propane torch fitting and to a valve connection on the other. Now he could remove moisture as he pressurized the system.
Everything is working again, and the cooling side of the system gets much colder. He plans to do more testing as time goes by.
The heat pump which cools [Chris LeBlanc's] home lacks the sort of control he was looking for. It’s just got a timer, which switches it off automatically. He wanted to the ability to schedule the cooling cycle like you would with a thermostat-driven arrangement. He ended up build his own controller to automate the cooling process.
The heat pump came with an IR remote control which provides the access point for the project. [Chris] set out to emulate the remote protocol which saved him the trouble of having to crack open the unit and wire in a controller. He went with the IR Toy from Dangerous Prototypes as this device is able to record and transmit IR signals — it’s basically a universal remote for your USB port. His Raspberry Pi, seen to the left, controls the system. It’s connected to the red IR Toy board via a USB hub which is used to interface a WiFi dongle as well. The system works alongside Google Calendar to allow [Chris] to schedule his home’s cooling just by adding an appointment. A Python script queries the calendar, then selects and sends the appropriate IR command. He shows off the build in the clip after the break.
Continue reading “Developing a thermostat for a heat pump that only has a timer”
The 1-Wire HVAC monitoring system is for residential Geothermal HVAC systems. This project utilizes the so called 1-wire temperature sensor. A single board computer handles the brunt of the work including web accessible trend data. With access to the underling temperatures, the over all system performance may be gauged. Earlier this year we covered a HVAC web enabled monitor that adds an element of control. As the industry adopts modern control architectures, we hope to see more HVAC hacks around.