WOW, what a price difference between HAI and Aprilaire!!! What would we get out of the Aprilaire to justify this?
2 Aprilaire Thermostats setup with ELK-M1:
$200 2 8870 thermostat (on sale now. normally $230)
$100 1 8818 distibution panel
$100 1 8811 protocol adapter
$80 1 ELK M1XSP Serial Port Expander
----
$680 TOTAL
2 HAI Thermostats setup with ELK-M1:
$125 2 HAI RC-80B Thermostat
$80 1 ELK M1XSP Serial Port Expander
----
$330 TOTAL
edit: typos
Some points, with the caveat that that I have no experience whatever with the HAI or their t-stats but I have been using Enerzone Statnet devices (now Aprilaire) for almost 10 years. They have been supported by PC-based HA systems since before then.
1) The list price of the "$125" RC-80B is $184.50; Everyday price for the Aprilaire 8870 Communicating Thermostat is $199.95 at
http://www.iautomate.com/8870.html
2) The RC-80B is a *single* stage thermostat whereas the Aprilaire 8870 (like its equivalent Enerzone predecessor) can handle *multi-stage* heating and cooling. So if you decide to upgrade from AC + gas to heat pump (+ gas or resistance electric) + AC, your RC-80 will become obsolete.
Ditto for adding active hot water heating. HAI devices that begin to be comparable in function to the 8870 are the RC-112B and RC-122B which are $217 at SH.
IOW, the 8870 provides the functionality of at least 4 different HAI models (including the RC-100B).
3) Also, you added into the cost of Aprilaire system a $100 8818 distibution panel which is completely unnecessary for a two or three or four thermostat 8870 system. IIRC, the 8818 is a passive 'device' that allows one to (dis)connect individual T-stats from the system for trouble-shooting. This is handy in an apartment complex with many (dozens?) thermostats but more of a nuisance (and expense) than it's worth for only 2-3 T-stats.
4) Also the Aprilaire uses RS-485 (the 8811 protocol adapter is a RS-232--> RS-485 adapter) exclusively. If you run into signal reliability issues with the RC-xxx's RS-232 comms, the factory fix is to buy a RC-202 RS-232 Serial Booster (list $100) or as I understand it, add an Omni panel ($) so as to be able to use RS-485 ? Whereas the Aprilaire obviates those problem by design, in advance, robustly by using RS-485.
5) The 8811 RS-232--> RS-485 adapter has the virtue that it electronically segments the RS-485 network. So shorts or other damage in one segment will not affect others. I dunno if that's the case with the HAI t-stats but it is another example of the robustness of the Enerzone/Aprilaire solution (IMO/E).
6) The Aprilaire/Enerzone/Statnet system allows addition of external and additional temperature sensors for averaging and humidity control without recourse to an Elk or Omni Pro or PC. I dunno what HAI t-stats _standalone_ capabilites are in this regard. If you have a heat pump, it becomes a significant issue. I want my HVAC systems to operate completely standalone is needed. It is not acceptable (to me) that it depend on an easily misprogrammed panel or PC.
7) The Aprilaire 8870, owing to its intrinsic flexibility and capabilities, is somewhat future-proofed. In any case in the context of the total cost to install and operate (!) two HVAC systems, the price difference (once corrected from what was posted) melts away.
Lastly, I like the Statnet/Aprilaire ASCII communication protocol enough to be contemplating adding other foreign gizmos to the network. Since the protocol can handle many devices, and existing devices will inherently ignore commands not addressed to them, one can build DIY devices (ADC, DAC, DIO, etc) that use that RS-485 network instead of reinventing the wheel and adding yet more hardware.
...Marc