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Jonathon Pullen

Technical Services Manager
Gulf Coast District

38MU/40MU Crossover System

In this article, I will explain how to wire the new crossover system for 24V communication or scenario 3 using a 3rd party thermostat.

There seems to be some confusion when wiring this system for scenario 3. Wire the system like any other multistage system. Wire the system for 3 heat 2 cool if you are using heat strips. The most important part of scenario 3 is setting the dip switches in the units.

First, set dip switch SW1 on the indoor unit. Also, SW1-1 and SW1-4 needs to be turned ON. This tells the indoor unit to look for 24V inputs like any other system.

The outdoor unit dip switch, SW1-2, needs to be set to ON. This also tells the outdoor unit to look for 24V inputs.

How I explain this to people when installing the systems is make it look like the picture in the install manuals.

Also, follow the wiring diagram in the install manuals and you will not have any problems.

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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