I’ve had a nest for a few months now and it has finally annoyed me for the last time (battery wont hold a charge). I originally picked it up because I was pretty new and didn’t have any experience with zwave or zigbee and I needed a thermostat that could handle my duel fuel system (heat pump + gas).
I’m thinking of replacing it now but I would love some feedback on what other people have done here. Are there any local controlled thermostats that support dual fuel, and more importantly, let you control when the alternate fuel is used?
On the nest one of my biggest gripes is that the temperature it uses to decide if the gas furnace will start up is not exposed to the API. So at best, I can guess when the heat pump will be running vs not. Which is pretty annoying. The app doesn’t even really differentiate between fuel sources on the “consumption” page. Obviously the heat pump runs for way more hours than the gas system but is just lightspeed cheaper where I am.
Unfortunately no. I have been eyeing the Honeywell T6 because it is Zwave and supposedly works with dual-fuel systems. Seems likely that because it’s zwave that would be a configurable parameter.
I think there are some questions to be answered:
Where it will be installed? US has different cabling/standards vs EU.
Have you found if your appliances expose some kind of API or have some kind of controlling interface? (Bus, modbus etc.)?
How the appliances (hp, boiler) are started? Dry contact?
In theory you could use 2 dry contact relays to start the appliances, an external temp sensor to get air temp and an indoor one to detect room temp.
Whit this you could create an algorithm run by automation that based on your tariffs and based on the COP of the HP at the various external temps decide when to switch to the boiler.
Installed on the weekend, it does have the ability to trigger it to backup/aux heat through HA. Only downfall I am seeing so far is the configuration for what outdoor temp to kick over to AUX automatically isn’t easy to figure out. I just bought online the outdoor temp sensor that connects to the T6 for this. Also the T6 was short cycling my unit a lot one day, I changed some settings and it was good then got bad again. It would run on and off for like 30sec at a time.
