Automating HVAC Controls

[bfisher]

I need a little help... putting together my order for purchasing some RCS HVAC equipment to automate my HVAC system, and I'm a little confused - hoping someone can help.

Background:
- I use HomeVision Pro as my controller, and it supports RS-485 communications.
- I have 3 zones in my HVAC system. I already have a 3 zone controller (connected to analog theromstats).

I planned on buying RCS TR16 thermostats (3 of them) since they communicate RS-485.

Questions:
- How do I wire RS485 with existing thermostat wiring (that's homerun to the 3 zone controller). I just can't picture how to do it.
- I believe the 3 TR16 base units will replace and look to the 3 zone controller as the existing analog thermostats. Correct?
- Am I better off purchasing RCS ZC4 4 zone controller? I assume this would replace my existing 3 zone controller (I wouldn't be using 1 of the zones on the new unit). What advantage does this buy me?
- and what is the difference with the RCS ZCV4? How do I know if I need this or the ZC4 above? It's $100 more... so I bet I need it LOL
- If I buy the ZC4, I would then use the RCS TS16 instead? Is there an advantage to this option?

Thanks!
Bruce

 

[upstatemike]

When you say "analog" thermostats do you mean plain old mechanical stats with a contact that opens and closes or are they something specific to the zone controller?

Also does the HVPro support RCS multizone thermostat models directly or does it just have a single general RCS thermostat type you can select?

How many coductors are in the wire running from your "analog" stats to the existing zone controller?

 

[bfisher]

When you say "analog" thermostats do you mean plain old mechanical stats with a contact that opens and closes or are they something specific to the zone controller? How many coductors are in the wire running from your "analog" stats to the existing zone controller?

Yes - using 3 wires - heat, cool, com (but there are 6 wires behind the stat, 3 unused). Each stat wires to a zone on the existing zone controller. There is one seperate "main" switch that switches between Fan, Cool, Heat, Off. and a switch for auto versus always on.

Also does the HVPro support RCS multizone thermostat models directly or does it just have a single general RCS thermostat type you can select?

It supports RS-232 and RS-485 communications. It has the ability to control up to 16 HVAC zones. There is no specification or limitation about the type of thermostat to be used.

I believe (based on my limited understanding) that if I used TR16's - the 3 stats will wire directly into the RS485 port (assuming I can wire in this fashion with existing wiring). If I use the ZCV4 (controller with TS16 displays) instead, the displays go to the ZCV4, and it connects directly to the 485 port.

I think my fear of using the ZCV4 is I have to rewire everything going to the HVAC unit (damper motors, fan/auto switches, etc)

I talked to CSI (makes HVPro) and they suggested using the ZCV4, but the TR16s will work fine too.

Thanks!

 

[upstatemike]

Sounds like you can use the TR16s in place of the existing thermostats on the existing zone controller. You need 4 conductors beteen the TR16 wall display units and the TR16 control units which will mount next to the zone controller. The TR16 control units connect to the zone controller and the RS485 line from the HVPro will daisy chain to all three TR16 control units.

As far as the HVPro is concerned you will have three thermostats running three different systems (not a single system that is zoned). I don't think that will cause you any problems.

If the HVPro has some built-in support for zoning than you would have to go the ZCV4 route. For example, in my Stargate you specify the model of the thermostat you are using and if it is a zoned unit it lets you set up additional info about the number of zones in use, etc.

 

[bfisher]

thanks Mike - the scenario you describe is what I was visualizing as being the easiest to implement. However, I can't picture how I will wire the TR16 stats in a 485 daisy chain since they are all homerun. Any ideas on how that will work?

I may still opt to replace the zone controller. In reading the manuals, I don't see any disadvantage in doing this (other than a little more work) and the price is comparable. My existing controller is original with the house and is probably 15 years old so replacing it is probably not a bad idea.

<edit: after reviewing the zone controller manual again - not sure my existing dampers would work. They have more than 2 wires going to them (looks like 5 - but I don't know what they are all for - seems like a lot to tell the damper to open or close so I'll need to investigate more.)>

 

[upstatemike]

When you say they are homerun I'm not sure what you are referring to. Each of your existing stats has a homerun from the zone controller to the stat. With TR16s the stats get replaced with RCS wall display units and the other end of the wires get disconnected from the zone controller and connected to the display outputs on each of the 3 TR16 control boxes that you will have mounted next to the zone controller. (RCS refers to these as being the actual TR16 thermostats as distinct from the wall display units). You then wire the thermostat outputs from the 3 RCS boxes into the points on the zone controller where the old thermostats were connected.

You then need 0ne 4-conductor cat-3 or cat-5 cable between your HVPro and the RS-485 terminals on the first RCS control unit. THIS is the wire that gets daisey chained to the other two units so that all 3 RCS control units (that are mounted right next to each other and next to your existing zone controller) are connected to the same RS-485 feed from the HVPro. Of couse you have to set each RCS unit to a different RS-485 address.

 

[bfisher]

Thanks Mike. This morning (at church) - it hit me that this is how it needs to be wired. For some reason, even though I knew it was 2 pieces per RCS thermostat, I kept trying to picture 485 stat to stat (display units)... not base units.

Thanks for confirming this is how to do it! I think this is the best route for me... I don't want to replace the existing dampers (they are very large rectangular ones in the plenums, not the round ones I normally see) and require 5 wires (1,2 are power, 3-4 short to open, 4-5 short to close). I know I could come up with something to make this work... but I think it would be easier to use the existing setup and replace the stats themselves.

Thanks for your help!