A mini split will go into defrost mode is when the outside unit becomes frozen and needs to be defrosted.
It is normal for a unit to go into defrost mode, and it is usually only temporary and then goes away.
If the error does not clear, there may be a malfunction, or the outside temperature may be too cold for the unit to operate.
What is a Mini Split Heat Pump Defrost Mode?
A heat pump defrost mode is when a unit temporarily goes into air conditioning mode to melt the ice on the outside condenser.
Mini split heat pumps work very well but can have issues when the outside temperature becomes very cold.
Most units will keep working down to at least 10-20 degrees Fahrenheit but will periodically go into defrost mode to melt ice on the outside condenser.
To melt the ice, the unit will stop heating mode and go into a cooling mode for a short time to melt the ice on the outside unit.
This is normal for heat pumps when it is cold outside.
A large package heat pump unit with ducts will often have heat strips also called emergency heat installed that work as a large space heater and temporarily heat when in defrost mode.
Mini split units don’t have ducts to install heat strips into.
Each mini split will have a rated temperature range it can operate in before the outside condenser freezes up.
The manual for the unit will have the information for the temperature range it can work in.
Is a DF Code on a Mini Split a Malfunction?
Usually, a DF Code is normal and will go away shortly once a unit has defrosted the outside condenser.
If the code does not go away, then there may be an issue with the unit.
If the outside temperature is above 32 degrees Fahrenheit and the unit is displaying a DF code, there may be an error with the unit.
Heat pumps have a reversing valve that switches from cooling to heating. It uses a ball bearing that will block one port and close off another port to reverse the flow of refrigerant.
Often when a unit has an error that won’t clear, the reversing valve is having an issue.
A unit could also be low on refrigerant, have a bad sensor, or a bad main PCB board.
If the DF error does not clear, an HVAC tech will be needed to find the cause.
When to Call an HVAC Tech
If the outside unit is not frozen, the temperature is above what the unit is set to operate in, and the DF code will not go off, then a tech will be needed to troubleshoot it.
Most mini split units will not go into defrost mode when the outside temperature is above 32 Fahrenheit, but it can vary.
Unless it is very cold outside and the outdoor condenser is frozen, the DF code should not be on constantly and should go off.
It can vary on the model of the unit, so be sure to check your documentation.
When a mini split displays a DF code temporarily; it is usually normal.
This includes Mr. Cool, Pioneer, Senville, Carrier, Blueridge, Durastar, Samsung, Cooper and Hunter, Lennox mini split units, and more.
If the outside temperature is very cold, the unit may not be able to operate, and the manual should be looked at to find the operating temperature.
If the outside temperature is not very cold and within the units normal operating temperature, there may be a problem with the unit.
Mini split heat pumps both heat and cool by using a reversing valve to set the mode, which can cause issues if it fails.
Have you had issues with a mini split DF code? Let us know your thoughts below.