TStat10 Multi Zones - Single Fan Coil Unit

Tstat10
1

Hello All!

I’m enjoying working with the Temco control system so far, and love to see all the discussion here in the forums.

My project has a hydronic fan coil unit suplying heat, cool and dehumidification. The fan coil unit is also supplying multiple hvac ductwork supplied zones (in my case 5 from this one unit)

It is a unit that has 4 pipes so it can do heating or cooling depending on the demand. It can also do dehumidification because it can have cool water to condense the water trapped in the humid air and then heat it back up as it passes the heating unit before leaving the fan coil unit.

So the question is, the Tstat10 can output a heat signal, a cool signal, a fan signal, a signal to my zone air dampers in the hvac piping, and a modulating signal to my modulating valves that will control the flow of hot or chilled water to the fan coil unit. HOWEVER, if I have 5 Tstat10 sending signals, I assume I will have to have them interconnected to a central controller and then the controller decide which signals to process first etc.

Anyone have experience in doing this?

Thanks in advance~

2

I think it would help to add more detail. Is there a specific reason why you would want to have 5 TStat10 units or are you feeling like that is what you have to do? How many signals are you controlling in total? switched plus analog? The TStat10 has 5 switched outputs and 2 analog outputs like (2-10V) so you could write a few control basic programs and run them on the TStat10 for controlling several of the operations. The TStat10 can run 16 small programs if needed. If you need more than 1 TStat10 because of the output counts, you could probably have them send commands between them with one acting like a master.

Jason

3

So I am using it in a commercial space where there are 5 rooms.

Each room needs its own tstat10

And each room also has its own hvac zone running off the same fan coil unit.

Does that make sense ? I can’t use one tstat to control all the room. So I need to use 5 and they will all communicate to the fan coil but I need a “order of operations” so the fan coil can process the signals in a specific order.

4

So if you have the TStat10 units already, that is a different story. You don’t need one for each from the standpoint of the TStat10 units, but there many other reasons why you might want for each room.

That said, you probably don’t need a central controller. You could run a coordinating master application on one of the thermostats and have the other slave thermostats communicate with the master. The TStat10 is a wrapper around the T3 controller so you can write that logic on it in the T3000 software and send it to the master. The coordinator application could sequence the other thermostats that want heating/cooling by locking them out and enabling them according to your needs.

This would assume using reads and writes over a network shared by the thermostats.

5

Can you briefly explain a coordination controller or program that you said ?

Does that basically run a program that would take the signals from the other tstats , and decide what to do for example:

Tstat#1 looking for heat, so open the hvac damper to this zone. Turn on the hot water supply to the fan coil( valve) and turn on the fan. But if tstat#2 is looking for cooling , do not open the damper to this zone. And wait until the program identifies that there is cooling valve open and the heat is off etc.

I know there is a lot of steps in logic here but is that basically the jist of it ?

I could use regular thermostats and then a central controller T3000. That maybe a better idea since I don’t have the tstat10’s and basically the tstat10’s are controller and thermostats etc.

Thoughts ?

6

You understood my general idea.

There are numerous ways to get there and you could either use TStat10s in each location with one as a master or a central TStat10 or other T3 based controller to coordinate the logic. When each is calling for heating or cooling, the central controller makes the decisions based on the request from the thermostats.

The only difference would be how much information you are getting from the thermostat with simple ones only providing the call for heating/cooling via direct wiring or more detail being provided over MODBus.

It really depends on your specific needs.

7

The Tstat10s can now share variables transparently over the RS485 network, I didnt realize we didnt have that feature actually so thanks to the person who pointed this out. You can update your firmware now and that feature will be enabled.

Next, as Jason mentioned, one Tstat10 can be called the coordinator which will decide the mode of operation, Summer, Heating, Unoccupied and so on. Create a variable and some logic for each of the modes you want to implement. Then in the programs of the other devices you can use those modes in your programs as well. The mode variable will be updated in the coordinator and passed around transparently to the other stats.

8

Hello @maurice and @jason.kania

So I have been taking some time to finalize my system and now feel like I have a firm grip on what I need inorder to make this work. Id like to outline my system and get your input I think everything you have said before makes sence and I think my proposal will make sence to you as well. There will be a number of questions for the programming side but not all together difficult i think. I think my control system would be a good application in the future and I already have a number of systems that I would be able to apply this to if I can get it functional.

So, I have 4 rooms that are zoned from one 4 pipe fan coil unit. Each of these rooms have a damper controlling the on or off of air flow to that room.

I plan to put 1 tstat10 in each room just so that in the future I can get more information (plan to add dehuidification in the future, want to get info on temp trends, etc) . Also if I get Wifi ones, I can pass the variable around to each unit wirelessly I assume?

The fan coil units will have three settings for fan speed (I have to install relay contacts in the units to do this because the unit has 3 leads on the motor but only one fan signal for some reason!!!). It also has modulating valves (for dehumidification in the future) which I will use as on and off for the time being on the hot coil and the cooling coil. And of course, the unit has a heat and cool contact on the fan coil.

So, the tstat 101 will call for cooling in room 101, and change the varialble called ISITCOOL to true (which will have to be passed around to the tstats ), and then it will follow the logic to open the dampers in that room, open the cooling valve, and turn the fan on. I will have to have separate logic to determine what fan speed I want (IE: one room is fan low, 2 rooms is fan medium, and 3 rooms or more is fan high)

If another tstat 201 comes on and demands heat, but if ISITCOOL is true, the logic will have to tell it not to come on and wait until ISITCOOL is false. And the same for vise versa.

If another tstat 301 come on and demands for cool, if ISITCOOL is true, then it will continue on its path to cooling down the room as well.

This is what I have been thinking and I think its the simplest way to approach it. With the setup we have, I do not actually think separate rooms will be demaning heat and cool at the same time but I have to be prepared for that case as well.

Any thoughts on it ?

ALSO: The tstat10 can send an open /close signal to the damper directly, and as well to the modulating valve I believe we confirmed that ?

9

You have a four pipe fan coil unit, in case anyone isnt familiar this is a fan coil with two valves, one for heating and another for cooling. Off of this fancoil there are 4 separate ducts leading to four zones, each of which has its own on/off damper.

You asked about wifi, the latest production of the Tstat10 has wifi by default, it is not an addon feature anymore. For the security concious, you can disable the wifi and use only the wired RS485 connection. All data and features are available over either network connection, so the question about passing variables around, the answer is yes, you can pass all info over Wifi just as well as over RS485 or both if you want.

I am not clear what you mean about the three leads on the motor but it sounds like you have it figured out. Some simple logic in the Tstat10 will select the speed based on the call for heating or cooling. The relays of the Tstat10 will energize the low/med and hi speed modes on the fan.

HEATING AND COOLING VALVES:
I am not too clear where the heat and cool contact you mentioned comes into play. How it will normally work with analog valves is you wire the valve to the analog outputs of the Tstat10 set them up as 0-100% = 0-10V analog valves as shown at Tab1. If you really want to program them as on-off you can set them up like Tab2, they will show up as open (10V) and closed (0V) as you describe.

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FAN SPEED:
The fan speed would be varied to match the amount of heating or cooling required in the building. Each zone will have a heating and cooling PID associated with it. Some voting logic will let you calculate whether the heating or cooling mode is in effect, you could indeed have a call for both heating and cooling so you’ll need logic to see who wins.

The maximum PID (max amount of heat or cool requested) from the 4 zones and number of dampers open will determine the speed of the fan. This logic runs in the ‘master’ thermostat for the system. All the setpoints, temperatures and PIDs from all four zones can be used in the logic running on the ‘master’ thermostat.

I am available to help in more detail with the logic as the project moves along. This is a good example of where you’d want a programmable Tstat10 versus a normal fancoil thermostat.