Connecting a Control4 thermostat to Daikin, Mitsubishi, LG, Samsung, Fujitsu, and Gree VRF systems can be a complex process. The following article will help clear things up.

Typical Control4 Thermostat Connectivity

Let's first look at a typical HVAC control use case. You have a Control4 thermostat that you would naturally connect as follows:

Control4 Central Controller and HVAC

 

Before we move on to explore the actual integration and control, let's start by discussing the relevant thermostats.

Five Wire Thermostats

A thermostat is an integral part of a unitary HVAC system, which requires control, a 'brain', and logic components to maintain set-point temperatures.

The traditional thermostat is the decision maker of the system, the 'brain', which engages with the air conditioning system using the well-known 5-wire configuration:

  • Cool (Y)
  • Heat (W)
  • Fan (G)
  • The other 2 wires are meant to power the thermostat itself
Going a bit deeper, a thermostat issues an on/off command via the relay it is connected to in the HVAC system.

Let's say you need to cool down a hot San Diego apartment to a comfortable 72°F. You turn on your AC in "Cool" mode and set your thermostat to 72°.

The HVAC system continues to cool until a thermostat senses a temperature of 72°F (or slightly below). Once the room temperature reading is 72°F, the thermostat switches the HVAC unit's cooling relay off using the Cool (Y) wire.

Thermostats operate on the principle of: "I will turn you off once you finish your job!" Pretty simple, right?

 

Control4 Central Controller and HVAC - On and Off

Two or Three-Wire Thermostats

However, once you try to connect a Control4 thermostat to a VRF system by Daikin, Mitsubishi, or LG (and other brands for that matter), the problems begin. At this point, you start wondering what to do about the missing HVAC indoor unit wires.

We are all accustomed to seeing the control panel as the thermostat, the 'brain' of the system. However, the 2- or 3-wire thermostat is, in fact, not a thermostat at all. It is a Wired Remote Controller (WRC) that communicates with the VRF indoor unit via a defined protocol.

The WRC that accompanies a VRF is essentially a control panel. It sends the user's climate requirements ("Cool to 72°F") to the VRF indoor unit. That unit then translates the request into an engineering demand and works to deliver the desired climate conditions. It serves a function similar to the Control4 central controller, which manages all installed devices by communicating with them over a network.

Because HVAC manufacturers use closed networks and proprietary, brand-specific communication protocols for external access, if you have a Daikin or LG VRF system, it 'talks' in a different 'language' and cannot communicate with systems from other brands or external devices.

How Do I Make the VRF HVAC Systems' Talk' With the Control4 Thermostat?

So, the question remains: how to make a Control4 Thermostat work with a highly sophisticated Daikin VRV? The answer is simple. You don't.  

It's like trying to make a digital I/O work with a communication bus.

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Connect the Control4 Central Controller to a VRF HVAC System Using CoolMaster!

It's a good idea for two reasons:
  1. You achieve bi-directional communication between the Control4 platform and the VRF HVAC system with zero latency, thereby meeting your initial goal of controlling the HVAC system.
  2. You can still install a Control4 thermostat on the wall, allowing your customers to control the HVAC system as they are accustomed to.
Just add a CoolAutomation gateway, which enables the commands to get from the controller to the HVAC system (with information also traveling back the other way) in the following manner:

 

Control4 Central Controller and CoolMasterNer

 

Now connect the Control4 thermostat to the system.

 

Control4 Central Controller, Thermoastat and CoolMasterNer

 

We are all creatures of habit, and many of your customers still expect a wall-mounted control interface. In this case, the interface connects to a central controller rather than to the HVAC system directly. Thus, your thermostat is operating through two intermediary devices that seamlessly connect the two distinct systems.

In Conclusion

If you are trying to control an advanced HVAC system, such as Daikin VRV or other VRF brands, using a 5-wire thermostat, remember this:
  • A 5-wire thermostat will not work with a Daikin, Mitsubishi, or LG VRF system.
  • Use a CoolMaster gateway that connects the Control4 central controller directly to the HVAC system.
  • Use a Control4 thermostat and connect it to the central controller, not to the HVAC system.
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