MODBUS Registers for Tstat-10

I have only been able to find registers # 730 thru 734 for the Tstat10 device.
How do I read the ‘Inputs’, ‘Outputs’ and ‘Variables’?

I tried other methods to pull points in. No luck.

I am stuck.


In the big scheme of things you should consider Bacnet protocol if you’re integrating devices over the network from other vendors. Search the forum for ‘network programming’ for various scenarios.

If its all temco gear then the syntax is even simpler:
10 VAR1 = 2IN1 or whatever.

If you’re just using remote points from other controllers in a display or trend log then you just refer to the remote point as in 2IN1 above. No program is even required.

Let me know more about your project and I can make better suggestions.

So, I went the BACnet route and got spanked hard. Everything I’m using at this point is T3000 gear.
If you guys get some time I would appreciate having access to a few more Modbus registers:
Tstat10, VAR1 for the room setpoint.
Tstat10, IN1 for my supply air temperature.
Tstat10, VAR?? for supply air temperature setpoint.

what sort of problems did you have integrating with bacnet?

Maurice Duteau

When I set up the stats for BACnet, I left the baud rate at 19200 which was working fine for Modbus communication.

The 1st thing that I ran up against was addressing conflicts. I didn’t have any duplicate addresses. But the program insisted that I had address conflicts?

The tree on the left showed some of the Tstat-10 devices by their name but half of them showed mstp rather than the device name like HC2-1. I finally allowed the program to change the addresses which mostly failed. So I tried to renumber some but they would not take.

I had to remove each Tstat and connect them one at a time to a T3-LB and had similar struggles with connecting to the device. Finally, I went back to Modbus but struggled with setting panel #s back to their original address.

I would suspect that my bus wiring was not suitable for BACnet but when connected to a single LB and the Tstat cable was about a foot long, I had the same struggle as when the Tstat was connected to the full system.

I do have 5 Tstat-10 devices connected via wireless and that works fantastic. I definitely recommend wireless when possible.

I’m not complaining - just providing feedback.


Fandu will do a test with a T3-XX controller and five subnet devices. The task is to change the protocol from Modbus to Bacnet. I have seen the crew do this before and it was not a smooth process as you found out, we will work to make it smoother. More news shortly.

Thank you Maurice. :slight_smile:

Bret Burnett
Inside Passage Integrated Control Systems
Cell. (907) 957-1146
Email. Bret. (Icsak( AT)gmail( DOT)com)

I haven’t tried mstp on any temco devices recently only because it was so unstable previously. or modbus rtu either for that matter. Was forced to use either bacnet ip or modbus tcp as it was the only thing i was able to have stable comms.
have been afraid to try again.
and i have used mstp literally for years with other products, so am pretty versed in how to do it.

Feel free to give it a go with bacnet anytime. We’ve got a lot of clients out there integrating our gear to their’s and vice versa under bacnet on both MSTP and IP. And here’s a new feature that just came out for T3000, you can see the 3rd party bacnet devices in the tree. Here’s a Reliable MacPro showing the inputs and their current value. You can place any of these items in the displays, programs and trend logs of the temco T3 controllers.

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Maybe have a look at how t3000 is representing the actual values from the inputs and outputs in 3rd party panels. Something isn’t right.
The actual values and what gets displayed are not the same.

You can show us an example and we’ll straighten it out.