What about no Thermostat?

[CharlieWayne]

I can't help but ask with 6 heat pumps how much sqft do u have and what's ur electric bill every month?

6 tstats @ $100 is only 600 dollars. (Run all ur secondary heat wires parallel to ur furnace)

I personally have 4 ton heat pump thats under sized for the front side of my home, so I plane to zone out the area with 3-4 zones using the Venstar T1900 with Insteon module for each zone. That combo is no 100 dollar set up but it will control my heat pump, secondary heat, and an aux whole house dehumidifier and the features of the T1900 are insaine. Just read the 140 page manual and u will understand.

[hult]

I just bought a hosue with 6 full Heatpump systems, 1 huge furnace for E-heat integrated into all the HPs, multiple de-humidifiers, etc. it has individual manual thermostats and humidty controls from the 80's. It seems clear to me that automating the management of the multiple systems will help me save money.

I have a similar situation with four ground-source heat pumps using eight circulating pumps + fresh air intakes + humidity control. However these GSHP's are a rebuild/retrofit of a HVAC system that has long used Enerzone / Aprilare communicating thermostats + PC-based HA software including HomeSeer. I have about a dozen years experience with it.

As others have pointed out, most HVAC control functions are bang-bang ON-OFF.

So the existing control relay/switches in the existing thermostats can be overridden with two single-pole, single throw (SPST) relays -- one normally-closed SPST in series with the existing SPST switch/relay/contact to override (disable) an ON signal, *and* another, normally-open SPST relay in parallel with the existing switch to override an OFF signal.

My advice is that you leave the tried-and-true manual controls in place and design a system to override using the simple relay strategy in the sentence above. You can take over complete control over everything, something(s), or nothing.

Note that in this scheme, you can 'easily' disable part or all of your home-brew system by de-energizing ( "unplugging the power to") that added, experimental system.

(In my opinion and experience, and as others have emphasized, a HA sub-system as important as HVAC control to basic function of a building needs to have a fail-safe default mode. It needs to be designed with the reality that it *will* screw up from time to time.)

The easiest way I've found to interface both to Homeseer, and independently to the internet, and to have some smarts (logic + computation), digital I/O, analog, humidity and 1-wire temperature inputs and as well as other functions such as real-time clock and email is with WebControl devices. http://www.cainetworks.com/products/webcontrol/ Also: search HomeSeer and CocoonTech.com forums for "WebControl". They cost ~$45. Note that there are two major versions that use different programming language but are web-accessed n the same way.

I'll post further discussion to a more specifically titled thread. This may include discussion of a HomeSeer product exit strategy if, as it seems, support for expensive hardwired infrastructure such as Centralite lighting and Napco security is to be abandoned by HomeSeer in HS3.

Hope This Helps ... Marc