Running Mini-Splits AND propane boiler hydronic heat

Just got some Daikin Mini splits installed with the supported Wifi Adapters (updated the official docs page with my working units too).

I am trying to figure out the best way to combine the heating units. I can turn on my propane hydronic heat for zones in Home Assistant, and I can turn on the Mini-Splits for heat or cool.

I am trying to figure out the best logical way to heat the house when that time comes.

What I want to do:

Turn on Mini-Splits first.

  • If Mini-Splits cannot heat well enough, add propane hydronic heat
  • If rooms far from mini-split do not heat up within time x, add propane heat
  • Finally, I want to combine all this to function with an ecobee as the “driver”

Fortunally, I already have the Ecobee logic, just trying to figure out the best way to combine two different heating sources. Obviously, the mini-splits are cheaper/more efficient.

I could just set the hydronic to come on at a lower temp than the Mini-splits do, but the actual thermostats for those systems are in the same general area as the Mini-Split heads, so my guess is that the propane will never come on…

If you live in a cold climate, having an outdoor temperature sensor (or a weather integration) may help. Heat Pumps are less efficient at cold temperatures. The way Lennox hvacs work is there is a low temp lockout at which point only the furnace runs and the heat pumps do not.

I live in the Seattle area, so it very rarely gets cold. Most of the time the Mini-Splits will be the most efficient option. However, since we have one head unit on each floor, I expect that the rooms that are the furthest away from the head unit won’t get as warm, leading to cold spots.

It’s tough to figure out the best options.

Got it. So you got two choices boost the heat pump temp up more or turn the furnace on.

I have a similar issue, one zone AC for whole house and upstairs studio is always hotter than rest of house.

The first step is to create a generic thermostat for that room. Get that setup turning an input_boolean on and off. This is the trigger for when demand exists. You can then derive a binary sensor from this input boolean and put a delay_on on, so this would trigger when you’ve have demand for x minutes.

Next step is to sort through the logic. For example, If that demand exists and the heat pump is turned off - do you bump up the heat pump setpoint? Essentially on paper build that matrix of states and the desired behavior. Your challenge is there are two control points the heat pump setpoint and the furnace setpoint.

With the AC example, which is simpler, the only thing I can do is overcool the rest of the house in order to get the studio to where I want it. So I’d create some input numbers to hold the following config:

  • max overcooling - how many degrees am I willing to overcool the rest of the house

So the simplest approach is to set the AC setpoint to its current room temperature minus max overcooling when the generic thermostat triggers and then to restore the setpoint when the generic thermostat turns off. However, since I have a variable speed AC, I will slowly decrease the setpoint (maybe every 15 minutes) by 1 degree until I hit the over cooling threshold.

In your application, replace over cooling with overheating.

That makes perfect sense.

For the AC I am looking to trigger fans in the furthest rooms to circulate air - I could do this with the heat too, but of course, during the winter, who wants a regular fan on blowing air? Thus, it makes a lot more sense to use the propane hydronic baseboard heating.

I will get some temp sensors set up in the remote rooms, and if they are too cold, then turn on propane - and potentially increase the output of the mini-split/or have it fan-only (otherwise it will turn off) for a brief heat-boost.