Daisy Chain Guide
There are several people that asked us questions about Tandem or Daisy Chain installation.
What kind of install that is?
Say, you have 2 swamp cooler and 1 thermostat. Is it possible to use our product to wire 2 or more coolers to one smart thermostat? Yes! Keep on reading about daisy chain installation!
First of all, lets figure out what would you need for such an install. You would need X number of controller boards per X number of the evaporative coolers. And one smart thermostat to control it.
The theory behind this is rather simple, just daisy chain the thermostat cables (the control line) and let smart thermostat to control it all. One gotcha, it is recommended to use single transformer in this setup. The smart swamp cooler board comes with a transformer included so you would just have to select one master out of your boards and X - 1 slaves. For the master board, keep the transformer jumpers installed. For the slave boards, remove the jumpers!
Ignore the wiring pictured for now. The pictures above is just to illustrate the jumpers J2 and J3.
Next, you can daisy chain the boards and finally bring the final connections to the thermostat.
To make it simple you can just wire every possible signal and decide what to use and not to use at the thermostat. So wire each board in this fashion. Please remember that the transformer jumpers will look different on your master/slave boards.
Simple Wiring Example
Here is the topology that you would go for. The slaves would have 2 sets of cables coming in and out. So just use the blue terminal block to join the wires in those cables together. Pretty obvious, keep consistent with color coding. Do not mix different colors. Keep the same color for each signal on the terminal block.
One more thing, this illustrates only thermostat cable. The cable that drives relays. There is no need to daisy chain power cables (Romex). It might be pretty obvious but just making sure that we are still on the same page..
Daisy Chain Topology, shown for 4 units
Once you get to the thermostat, you would just wire it in the same fashion as you would using a single board.
You would have to decide what functionality you are going for. Follow Installation Guide for more details.
Alright, lets talk more about the transformers. So why single transformer? Remember we are dealing with a 24 VAC so hooking up different transformers together would mean that they might try driving each other and destroy themselves in the process. The only time it is allowed to connect transformers in parallel if they are in the same phase and the same power rating (Read: physically the same part).
There is no good way of knowing if your power is going to be in the same phase. Unless you are using the same power cable (Romex) to power Smart Swamp Cooler controller boards. And even if you do use the same cable it is the best practice just to use one transformer over multiple transformers in parallel.
Now that you know all of this, there are less common situations. For instance you can use furnace transformer to drive everything or even external transformer. The transformer that we have on the PCB is not very powerful. It might handle 2-3 boards but consider more powerful external transformer if you are daisy chaining a lot of boards together.
Okay, let say your decided to use external transformer. How to wire? Setup all the controller board as slaves by removing the transformer jumpers. Install the transformer, use 24 VAC output to drive the controller power to all of the boards. In other words, connect R and C from the transformer to R and C in your daisy chain. No clue which one is R and which one is C? Does not really matter pick one wire and name it R. Pick the second one and name it C. It will work as long as you keep the wires separate.
One more thing, remember we wired all of the signal on the thermostat cable? So if there is a need to jump something or tie signals together it might be cleaner to do all that business at the thermostat. The installation guide gives you flexibility of doing those things at either end of the cable. But the installation guide assumes you have one controller PCB and one thermostat. Personally, I think it would be cleaner to keep wiring across controller PCBs consistent and do the jumping part at the thermostat.
Got any additional questions? Either comment on this blog post or send me a message at kirill@simplyworks.net. Or use the contact form.
Hope this guide is helpful! Happy Tandem Installations!
