Does anyone know of a thermostat that can act as a quasi-load controller?

[XILLA]

I have two 3-ton HVAC units on my house. Both have a micro air easy start, but I want to employ logic that if one of the HVAC units is running, the other one will wait to run until the first one cycles off and vice versus.

I have simple time-based programmable thermostats now and am sort of accomplishing this by staggering their time and temperature settings. The rest of my big electrical loads just run when there is PV power and the family is pretty educated on running just one big load at a time. So I don’t see the need to buy an expensive load controller for the whole house.

Ultimately my goal is to maximize my battery bank to make it last as long thru the night as possible, during hot summer nights.

Installing affordable programmable thermostats I am thinking would be cheaper and faster than installing a whole house load controller as it would help to control the two biggest loads in the house. Thoughts?

 

[Ampster]

Thoughts?

One simple way would be to use relays. I do not have a specific design but there is a way to stack relays to make them simple logic devices and latch in an on or off state depending on a trigger from another relay.

 

[XILLA]

That’s an interesting solution, is it diy friendly?

 

[efficientPV]

It is a very simple solution. About impossible for anyone here.

 

[millsan1]

Yeah, relays is the way to go. Basically when unit A is running, by a call on the HVAC wire from thermostat, put a relay that sees that signal and interrupts the call to unit B from thermostat, and vice versa.

 

[Dagoth Ur Does Solar]

The "lazy" way I would likely do it is by using HomeAssistant along with two smart thermostats and build some logic to handle it. Probably not optimal, but all I'd have to do is swap the thermostats to some Z-Wave models and then sit on my butt in front of my computer for an hour or two.

 

[Ampster]

is it diy friendly?

It would depend on the DIYer. The concept is simple. Before transistors, relays were used in many control applications. It is simple ladder logic. As already suggested, a script in Home Assistant and the right thermostats can do the same thing.

 

[XILLA]

Sounds simple but probably not a project I am comfortable doing as I am not super comfortable messing with 240v especially when it involves expensive HVAC equipment. I did think about using a Home Assist type of hub, so that might be an option but was hoping someone else had faced this issue and had found an off the shelf solution that could be more or less plug and play. I do appreciate the feedback.

 

[millsan1]

Sounds simple but probably not a project I am comfortable doing as I am not super comfortable messing with 240v especially when it involves expensive HVAC equipment. I did think about using a Home Assist type of hub, so that might be an option but was hoping someone else had faced this issue and had found an off the shelf solution that could be more or less plug and play. I do appreciate the feedback.

The relay solution I am proposing is on the 24 volt thermostat circuits.

 

[XILLA]

Ah, that I can do. Do you happen to know where to get plans for that?