Aprilaire 8870 wiring confusion

[robolo]

I bet this is an easy answer but I am confused by the installation manual for the Aprilaire 8870. just started connecting my thermostats tonight. I have everything working in standalone mode with 5 wires to thermostat including "C" wire and RC/RH - R jumpered. The manual seems to say that if connecting to a automation system, which I assume means the 8811 then you should not connect the "C" or the "R" wires. When I connect the 8811 (powered of course) and disconnect the "C"and "R" I have no visible display on the 8870.

Are the "C" and "R" wires supposed to still be connected to the 8870 while the 8811 is attached?

Also, is there a way to have the display stay lit all the time?

robolo

 

[magrann]

I left mine connected since I did not have the 8818 to provide the power back to the Tstat. Some people may recommend that you use a seperate power source for the Tstat but I just used the power from my Hvac unit. I then just ran the cat5 into the 8811. I hope this makes sense.

 

[robolo]

I left mine connected since I did not have the 8818 to provide the power back to the Tstat. Some people may recommend that you use a seperate power source for the Tstat but I just used the power from my Hvac unit. I then just ran the cat5 into the 8811. I hope this makes sense.

Yes that makes a lot of sense. When the manual talks about wiring for automation they were probably expecting both the 8818 distribution unit and the 8811 interface adapter would be used and that the 8818 would supply the power to the T-stat. I will not be including the 8818 since I only have a couple of T-stats to wire. The point is that when only the 8811 is used, the C and RC/RH - R wires must be connected like in a standalone situation to supply the 24VAC to the T-stat.

Makes perfect sense to me now. I only wish it said it that clearly in the manual !!

Thanks Magrann

 

[bingl]

Also, is there a way to have the display stay lit all the time?

robolo
[/quote]
Just reading from the 8870 manual...the backlight turns on when a button is pushed OR it can be disabled altogether. Nothing about staying lit all the time.

Since my original t-stat had NO lighting, I am pretty happy with my 8870 lighting up at all.