10 Tips for integrating VRF HVAC systems

Integrating VRF systems can be quite a task - even for professionals, when doing it for the first time. However, learning how VRF works and asking the “right” questions can save a lot of hassle during the integration.

Following, are some tips to get you started.

Control each indoor unit by unique address

The VRF HVAC system appears as a “closed-loop” communication network, where all indoors can be considered as "clients".

Each “client” has a unique address, given by the outdoor unit automatically, set up manually by dip switches, or set up from local wired remote controller (depending on the HVAC manufacturer).

Setting the addresses is part of the HVAC installation. Prior to beginning of the integration process, the integrator should obtain a list of addresses of the Indoor units and the corresponding room (space).

Do not control the uncontrollable

In VRF systems outdoor units cannot be controlled. The integration always relates to indoor units only.

Control and monitor the...

Those are the parameters that can be controlled and monitored for each indoor unit independently:

Control ParametersMonitoring parameters (feedback)
Operation state (on/off)Operation State (on/off)
Operation mode (Cool/Heat/Fan/Dry/Auto)

*Auto mode is only available for heat recovery systems

Operation mode (Cool/Heat/Fan/Dry/Auto)

*Auto mode is only available for heat recovery systems

Set point temperatureSet point temperature
Fan speed (high/medium/low/auto)Fan speed (high/medium/low/auto)
Room temperature
Error code (if any)
Filter sign notification

Change HVAC mode (Heat/Cool/Fan/Dry/Auto)

There is a difference between the various manufacturers on how the modes  are changed. Therefore, in order to make a common procedure, the following are the actions that should be carried out:

  1. All indoor units should be turned off
  2. Mode change command should be sent to all the indoors in the defined VRF system.

Be aware when a malfunction code appears in the VRF system

When an error code notification appears on the HVAC wired remote, it should show via Home Automation as well (so that the HVAC installer may handle and resolve the issue).

The indoor unit can still be turned on/off, the fan speed might work, but the led on the wired remote will blink, and the whole HVAC system will not function properly (won’t cool or heat). At this point system may not accept any command from Home Automation.

Do not consider “Return air temperature” as “room temperature”.

Usually, the VRF will report the temperature of the sensor mounted inside the indoor unit. This is most often mistakenly interpreted as room temperature. When the indoor unit is located in the ceiling, this reading would definitely not represent the room temperature!

No "dual set point" for VRF heat pump systems

Sometimes, traditional HVAC systems (or actually Thermostats that control them) incorporate 2 set points: one for cooling and one for heating. This is not the case in VRF system. Usually, there is only one set point, regardless of the operation mode.

Set each indoor’s parameter independently

Unlike traditional HVAC systems, all functions of the VRF indoor unit are independent: on/off, fan speed, temperature set point, mode, and should be set independently. Unless changed, they will remain the last setting.

e.g. When an indoor unit receives an "ON" command, it will turn on, at the last set fan speed, mode and set point temperature. No need to set all those parameters with every single call for "on" operation.

VRF Heat Pump systems will not support Auto mode switch

Heat pump systems should be set in Cool or Heat modes manually.

Only standalone splits and heat recovery systems (where each unit has independent cooling/heating possibility) can be automatically switched from Cool to Heat in AUTO mode.

Control “Grouped indoors” by the leading unit

When 2 or more indoor units are linked (physically chain wired to work as a group), the integration will only relate to the “leading unit” (the one with the lower address). Other units in the “group” will ignore commands.

Good luck on your next VRF integration!

Have questions? Feedback or Comments?

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