Using a separate RS-485 output for each 8870 has the advantage of isolating electrical (RS-485 and T-stat) faults. The 8811 is as complicated (and expensive) as it is in order to provide this feature. No good reason I know of not to make use of it. IIRC, at least the two RJ-11 have separate drivers.
For up to 3 thermostats, yep. The 8811 supports up to 32 thermostats, however, so if you ever had more than three, you would need to connect multiple thermostats to the same port. If you wanted to get the same troubleshooting capabilities with more than 3 stats, you would install a distribution panel.
I'm still stuck on the thermos. I've connected them a couple of different ways and will get the "mating computers" logo after restarting a thermo, but after a few minutes it gets an X over it and the Elk has yet to talk to the thermo.
Here's my setup:
At each of the two 8870's I have a piece of Cat five connected as such:
B- = blue/white
B+ = blue
A- = orange/white
A+ = orange
These terminate back to a 6-connector RJ11, connected as such (Pin references are looking at the gold connectors, with the wire coming out of the bottom of the RJ11 and numbered from left to right. I.e. Pin 1 is the leftmost pin if you are looking at the connectors and holding the cable in your fist as it drops to the floor)
1 = Not connected
2 = Blue/white
3 = Orange
4 = Orange/white
5 = Blue
6 = Not connected
I have one termo terminated to each RJ6 and connected to both the RS485 jacks on the 8811. Googling suggests opening the 8811 and moving a jumper, and connecting directly to the "flying leads" (aka the four wires on the 8811). What is the right approach?
If I had know this would be so confusing I would have just bought that 88whatever termination block piece!
Thanks for any help!