Poor Man's Distribution Panel for Aprilaire

[Sacedog]

In a lot of threads recently, I have noticed that many of you are using the Aprilaire Distribution Panel to hook up more than one 8870 to the protocol adapter. While the Distribution Panel is necessary for those situations where you cannot get power to your thermostat from your HVAC equipment, it is not necessary for those who have power at the thermostat already.

In the past, I have just used a B connector to crimp together the flying leads from the protocol adapter, to the Cat5 from the thermostat. Recently, I needed to troubleshoot a stat, and it was a pain to cut the flying leads, restrip, and reconnect multiple times. So I finally decided to connect the Cat5 cables to the flying leads using a standard block. This way, I can disconnect thermostats, without having to cut the flying leads. While this isn't as easy to troubleshoot as using the distribution panel, my thought was; once everything is connected and working, it would be pretty rare to have wiring problems. So I decided that this would be a great way to save $85, and to get one less thing out of the can.

 

[123]

I wish Invensys/RobertShaw made communicating thermostats. The one I have (9851i) handles two remote temperature sensors, controls a central humidifier, looks good, and is a breeze to program and operate. I got it on used on eBay, plus the sensors, for under $50. The only shortcoming is that it doesn't communicate with HA systems.

Back to the subject of handling multiple 8870's, here's an idea that may also work:
Wouldn't ELK's Data Bus Hub (ELK-M1DBH) be a useful and cost-effective device for connecting multiple 8870's to a common point?

Basically, the M1DBH is a passive device that creates a physical "star" network out of the RS-485's logical "bus" network. Instead of using it to connect multiple RS-485 M1 keypads, it'd be handling multiple RS-485 8870 thermostats via CAT5. Wiring would be identical to the arrangement described in the M1DBH's instructions. The BLUE pair is free and can handle the distribution of power. I believe the bottom two screw terminals on the M1DBH are reserved for this purpose.

By connecting the M1DBH to a Lantronix UDS-10 (a little bit of custom cablework is needed), it'll convert RS-485 to IP. The M1DBH is about $40 at Automated Outlet and a used UDS-10 can go for less on eBay.

 

[dBeau]

Back to the subject of handling multiple 8870's, here's an idea that may also work:
Wouldn't ELK's Data Bus Hub (ELK-M1DBH) be a useful and cost-effective device for connecting multiple 8870's to a common point?

Basically, the M1DBH is a passive device that creates a physical "star" network out of the RS-485's logical "bus" network. Instead of using it to connect multiple RS-485 M1 keypads, it'd be handling multiple RS-485 8870 thermostats via CAT5. Wiring would be identical to the arrangement described in the M1DBH's instructions. The BLUE pair is free and can handle the distribution of power. I believe the bottom two screw terminals on the M1DBH are reserved for this purpose.

I think you could make it work, and at half the price it might be worth it. However, your wiring suggestion is a bit off. Remember that the Elk uses a two wire (half duplex) RS485 while the Aprilaire uses a four wire (full duplex) RS485. This starts to matter when you get into how you are going to power your 8870s. With the distribution panel, four of the CAT5's conductors are used for data leaving the other four are available for power (of course you could use just two). Using the M1DBH as suggested would take all 8 conductors for the data (four out and four for the return). This then implies you'll need to power your 8870s via the HVAC control wires. Not a problem really, just something to think about.

By connecting the M1DBH to a Lantronix UDS-10 (a little bit of custom cablework is needed), it'll convert RS-485 to IP. The M1DBH is about $40 at Automated Outlet and a used UDS-10 can go for less on eBay.

I havent used the lantronix device you mentioned, but I do like and recommend the idea. I use a Neteon GW312, which i suspect has the same functionality. With this device there's no need for a protocol adapter, unless of course you want to connect your 8870's to something that has only an RS232 interface (like the Elk).

 

[AVID]

I know your post is a bit old, however, I'm in the process of running my single zone HVAC (Actually just H) to a Savant system in my home... I understand I'll need the following.
8870 Thermostat
6202 Control Panel
8051 Flushmount Sensor

The question I have for you is, I only have one thermostat, and one sensor... As far as I can tell, the 8818 is truly a distribution panel (assuming more than one thermostat) and can be
bypassed with no ill effect?

Thanks in advance.

Rob
AVID