How to approach smart controls for a complicated system with 11 thermostats?

eyyadao

Hi all,

I recently moved into a new house, and I'm looking for suggestions on how best to approach setting up smart controls for a fairly extensive set of existing, dumb thermostats.

I have 11 thermostats connected to a variety of different heating systems and I'm having trouble seeing how to easily integrate all of them.

Overall goals: I'd like to be able to control setbacks during the evenings and time away from home, as well as have some sort of preprogrammed schedules that can be manually activated. (For example, my kids are not with me 100% of the time and I'd like to be able to easily dial down the temperature in their spaces during those times, but leave the rest of the house alone.) My electric utility also offers occasional credits in the winter for reducing electricity usage during certain periods, so I'd like to be able to dial everything down on an ad-hoc basis as well.

The heating systems I have are as follows:

• three low-voltage thermostats, connected to a zoned hydronic floor heating system on the main level (two zones for the living area, one zone for the garage). The floor in the living area and garage is a concrete slab, so it seems to take a long time to heat up or cool down.
  
• one high-voltage thermostat, connected to a noisy ceiling-mounted radiant heater/fan in the garage (note that the garage is also used as a living space and there are no vehicles there)
  
• two wall-mounted ductless heat pumps, one on the main floor living area and one for the second floor living area, controlled by IR remotes
  
• three high-voltage thermostats, each connected to a baseboard heater in each of the three second-floor bedrooms
  
• two more high-voltage thermostats, each one connected to the heated floor tiles in the two upstairs bathrooms
  

All of these thermostats are "dumb" without any programming capability or timing controls. I live in eastern Canada and the temperature swings can be significant over the course of the year (and the outside temperature regularly goes down to -20ºC/-5ºF in the winter).

How would you approach this? I've done some basic digging and I see that there are brands like Mysa that would potentially support most of the HV thermostats as well as the IR-controlled heat pumps; if I went that route, how would I make that play well with the hydronic floor heating, since I don't see any manufacturer that does both HV and LV smart thermostats?

Or is there a better approach? I've read some things about how the hydronic heating with concrete does not tolerate setbacks very well (it takes too long?), that perhaps an outdoor reset might be useful, etc...but I am new to the house (as well as to this type of automation) and I'm wondering if there is a more-comprehensive way.

Thanks for any suggestions!
-S

Alan (California Radiant) Forbes

Tekmar has a tN4 home automation system and Aprilaire has something as well.

Dave Carpentier

I have 1000 sqft of house and 600 sqft of garage with in-slab heating, and yes it does react slowly due to the thermal mass. One advantage to that, is that it 'holds' it heat quite well during a power outage. I dont currently have a modulating boiler, so no outdoor reset. Once I get my modcon next year, for sure I will be incorporating an ODR to allow the boiler to dial-back the burner for the condensing advantage.

Jamie Hall

The zoned floor heating had best be left alone -- it takes so much longer to heat up or cool off that it is best to leave it sit at one temperature.

The others... have fun!

ratio

An appropriate relay will let you use any kind of thermostat to control any kind of load, so you don't need to be too hung up on low voltage vs high voltage.

It does sound like you're going to need someone with some experience to tame this, or spend a lot of time on teaching yourself what you'll need to know.

eyyadao

ratio said:

An appropriate relay will let you use any kind of thermostat to control any kind of load, so you don't need to be too hung up on low voltage vs high voltage.

It does sound like you're going to need someone with some experience to tame this, or spend a lot of time on teaching yourself what you'll need to know.

Hi Ratio--I don't mind teaching myself (I do have an engineering degree, although admittedly not related to HVAC!), but I guess I'm looking for suggestions of a good place to start in terms of brands or ecosystems.

With regards to the difference between HV and LV, I understand that relays can be used, but I also read that it's important for the thermostat to "understand" the type of load being controlled, and that most standard LV smart thermostats may not do this. For example, it seems like a baseboard heater responds differently (in terms of heat output over time) from a forced-air blower, so even if I rig up a relay to allow it to be controlled, will this really work well?

And if I were to get (say) smart thermostats that did "understand" the HV loads (like the Mysa series), would those play well with other brands (say, Ecobee or Nest) if I did also hook those up to control the LV loads? (And does integration with HomeKit make any difference?) Or is it better to stay with one manufacturer/brand?

And, for example, does anyone have any opinions on automation of the mini-split heat pumps? The Mysa product I found seems to be able to control these by emulating the transmission of IR commands from the handheld controller, but is there a better way?

My first inclination would be to try to grab some of the Mysa stuff since the majority of what I need to control is supported by their controls, and perhaps worry less about the hydronic slab (which maybe I want to leave alone anyway)...but is it then a problem to have two different controls trying to manage the heat within one room (the hydronic slab and the heat pump together)? Or am I making a mistake by trying to use consumer-grade gear for all this?

If it turns out that this is really difficult (for which I do not discount the possibility), I am also willing to hire someone to deal with it...but they would also have to confront the same question of which base system/controller to use, would they not?

Thanks, all!
-S

Jamie Hall

Let me reiterate: don't even think about trying to integrate the radiant slab with the resst of it. Control it with outdoor reset and an in-slab thermometer, and set it to hold a base temperature say 68 F (20 c). and leave it alone.

Second, smart thermostats. Smart thermostats don't understand the heating system they are paired with. You have to tell them what they are controlling, and some of them work well with most systems. Most of them work well with rapid response systems such as forced air or air heat pumps. What the "smart" features amount to is that, in theory, they "learn" how long it takes for the space to adjust to a change in commanded temperature. So, however, do almost all digital thermostats today. Some also have room occupancy sensors, or learn what your personal schedule is, and are alleged to adjust the command setpoint accordingly. Some work well. Some don't. Again, on fast response systems, they're not too bad.

Perhaps the most important thing to understand, though, is that with the exception of some high end devices communicating with their own hardware -- notably some heat pumps -- all thermostats are, fundamentally, on/off devices -- so it doesn't matter a bit whether it's controlling a relay controlling something else, or doing it directly.

pecmsg

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hot_rod

If you are up for that much of a challange, maybe a building automation control or a PLC, that you program to your exact needs? 

Raspberry Pi?  Especially after thanksgiving 🍰