AprilAire 8870 Help Please

[KB4OB]

OK, I have an AprilAire 8870 and 8811 Protocol Adapter set up on my bench and simply cannot get the thermostat to respond to command from Hyperterminal.

1. Thermostat is powered with 24 VAC transformer and the only other connections to it are the (4) RS-485 Data bus wires going to the protocol adapter.
2. Thermostat poers up fine and I have set up the communications in same per instructions in manual.

When I send SN command from terminal, I get absolutely no response back from the thermostat. I do get a TX data ligh flashing on the 8811 and and the communications indicator on the thermostat flashes momentarily but it sends nothing back and I get no RX indicator on 8811.

The 8811 is the new type that has screw lugs instead of pigtails and I have checked and double checked the wiring which is straight through A- to A-, A+ to A+, B- to B-, and B+ to B+.
I can loop the data around at output of 8811 (without thermostat connected) and it will echo everything sent from terminal so I am pretty sure it is OK.

I just sent a 8870 back to dealer because of this problem and beginning to think I am doing something wrong somewhere. Does the thermostat need other wiring to work?

 

[comet48]

OK, I have an AprilAire 8870 and 8811 Protocol Adapter set up on my bench and simply cannot get the thermostat to respond to command from Hyperterminal.

1. Thermostat is powered with 24 VAC transformer and the only other connections to it are the (4) RS-485 Data bus wires going to the protocol adapter.
2. Thermostat poers up fine and I have set up the communications in same per instructions in manual.

When I send SN command from terminal, I get absolutely no response back from the thermostat. I do get a TX data ligh flashing on the 8811 and and the communications indicator on the thermostat flashes momentarily but it sends nothing back and I get no RX indicator on 8811.

The 8811 is the new type that has screw lugs instead of pigtails and I have checked and double checked the wiring which is straight through A- to A-, A+ to A+, B- to B-, and B+ to B+.
I can loop the data around at output of 8811 (without thermostat connected) and it will echo everything sent from terminal so I am pretty sure it is OK.

I just sent a 8870 back to dealer because of this problem and beginning to think I am doing something wrong somewhere. Does the thermostat need other wiring to work?

I had to hook mine up to a pc to debug and get it working. Also had to set the baud rate to 9600.

 

[KB4OB]

OK, I have an AprilAire 8870 and 8811 Protocol Adapter set up on my bench and simply cannot get the thermostat to respond to command from Hyperterminal.

1. Thermostat is powered with 24 VAC transformer and the only other connections to it are the (4) RS-485 Data bus wires going to the protocol adapter.
2. Thermostat poers up fine and I have set up the communications in same per instructions in manual.

When I send SN command from terminal, I get absolutely no response back from the thermostat. I do get a TX data ligh flashing on the 8811 and and the communications indicator on the thermostat flashes momentarily but it sends nothing back and I get no RX indicator on 8811.

The 8811 is the new type that has screw lugs instead of pigtails and I have checked and double checked the wiring which is straight through A- to A-, A+ to A+, B- to B-, and B+ to B+.
I can loop the data around at output of 8811 (without thermostat connected) and it will echo everything sent from terminal so I am pretty sure it is OK.

I just sent a 8870 back to dealer because of this problem and beginning to think I am doing something wrong somewhere. Does the thermostat need other wiring to work?

I had to hook mine up to a pc to debug and get it working. Also had to set the baud rate to 9600.

I think I found the problem, namely (HYPERTERMINAL).
It finally occured to me to simply hook it up the the serial expander on my ElK M1G and it works.
I went back and looked at it on Hyperternial again and noticed that Hyperterminal sends ASCII characters immediately when you enter them on keyboard and apparently the AprilAire wants them sent as string of two or more characters ie..SN?. I have been unable to figure out any way to get Hyperterminal to do this?

Wonder why AprilAire issist's on using Hyperterminal to check out thermostat?

 

[AceCannon]

I used the old model 8811 along with a distribution panel (?8818) for my four 8870 tstats. I used Hyperterminal without a problem to ping all four stats. However, there were SEVERAL hyperterm settings that had to be changed from default (all well-documented in the Aprilaire installation manual).

After talking to the stats via Hyperterminal, the Elk worked the first time I plugged it in.

 

[icellama21]

Did you connect the data reference voltage terminal? If you are using 2 different power supplies this can be an issue. See the manual for a clear explanation, this is often overlooked as it is listed as "optional", but in many cases it is necessary.