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John Brown

Equipment Verification Technician • Southeast Region

Installing Carrier VRF Part 1

Getting to know how a system works and what tools you have to solve common issues is a huge challenge in VRF. Today we will explore the install side of Carrier VRF to help prevent issues that may arise before the job is completed.

Some of the most common problems start right at the install of any VRF system. One of which we discussed towards the end of last month’s article regarding communication and ports being swapped on a Heat Recovery system. There are ways to help prevent this during install and minimize or even alleviate this issue all together.

From this picture below you can see that inside the MDC box there is A LOT going on:

This box provides you with simultaneous heating and cooling inside a space through a series of solenoids valves, EXVs, and communication wires to control it all. This is why it’s vital to communicate and document everything that is done to this box. I’m going to give an example below, and make this significantly easier for anyone to understand.

Port address is also known as the copper address. This is in reference to the copper stubs coming out the back side of the MDC box. Every copper port on the MDC has a number corresponding to it and is labeled inside where wiring attaches.

Electronic address is exactly as the name implies. It’s an electronic identifier used for labeling each indoor unit on the system. This is usually set via the thermostat, wireless remote, or in the case of Heat Pump, Auto Addressing. This is commonly confused with port address, and the two are rarely the same.

Room number or reference ID of an indoor unit’s location is vital in case an issue arises with any particular unit. This is highly recommended as it gives a good middle area between port and electronic address in case something gets confused. If you have the port addressed and the room referenced, the electronic address can easily be located and changed, if needed.

With this written on the MDC box, it gives a lot of information that can be quickly referenced when doing commissioning or service work. The crossing of communication wires from port to port is much less likely and makes finding them significantly easier.

Line length in the picture above can help with charging of the system and can be valuable later if a particular indoor unit has issues and needs replacing. This is the main reason we recommend and supply ball valves with every MDC box when purchased through Mingledorff’s. Having line lengths written on the MDC helps to translate back to a program called Vroom (becoming Vpro) that gives an indication o the additional and total refrigerant charge of the system.

I can’t stress enough how important proper documentation is when installing a Heat Recovery VRF system. The more information that’s kept documented and accurate the better for the flow of the job. A little extra time now saves a lot of time later.

I hope this article gives a bit of insight on installing a Carrier VRF system. Next month we will cover how to and why electronic addressing is important to any VRF system. What is the purpose? Where does it all tie in?

Disclaimer: The technical statements, information and recommendations contained herein are believed to be accurate as of the date hereof, but Mingledorff’s does not make representations or warranties, express or implied, as to its accuracy, its completeness, or the results to be obtained. The information is being provided for informational purposes only and is intended for use by persons having adequate skill and expertise regarding the proper selection, use and application of the products and recommendations and at their own risk and discretion. 

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