What is a heat pump unit?

Over the years, HVAC professionals all over have experienced this call –

HVAC Company – “Good morning, Putnam Mechanical, how may I help you?

Home owner – “I JUST WOKE UP AND LOOKED OUT THE WINDOW AND MY AIR CONDITIONER IS COVERED IN ICE AND SMOKING, I THINK IT IS ON FIRE!”

HVAC Company – “Is your system a heat pump unit?”

Home owner – “Yes it is a heat pump unit., BUT WHY IS IT SMOKING?”

HVAC Company – “That is most likely steam, not smoke and it is perfectly normal for a heat pump unit”

What is a heat pump unit?

A heat pump condenser unit is an outdoor unit seen frequently in North Carolina.  When a heat pump is used for heating, it utilizes the same refrigeration cycle used by an air conditioner, but in the opposite direction.  This releases the heat into the air-conditioned space rather than the surrounding environment.

Why does steam sometimes come from the unit?

Unlike a traditional furnace system, a heat pump unit is equipped with a “defrost mode.” During the heating season the outdoor coils tend to frost or potentially ice-up during the winter months causing the unit to lose efficiency.  By regularly defrosting itself, the unit keeps the outdoor coils clear to maintain proper air flow and keeps the unit running efficiently.   Most heat pump units are automatically set to run defrost mode every 60 or 90 minutes.

How does defrost mode work? 

During defrost mode the first step is the outdoor fan motor stops running.  This helps to build-up pressure and heat to assist in melting the ice away.  Second, the reversing valve shifts from heating mode to air conditioning mode.  By shifting to air conditioning mode, the outdoor unit becomes the condenser and allows warm refrigerant to pass through the coils to defrost the unit.  Finally, the supplement (electric) heat in the air handler will energize to provide heat during this process.

How long is the defrost process?  

The unit should only be in defrost mode for a few minutes, on an as needed basis.

If the unit is constantly in defrost mode or does not defrost there is likely a problem with the unit and you should contact Putnam Mechanical immediately.  

Don’t be left in the cold, contact Putnam Mechanical at 704-799-3665.  Our technicians are available 24/7. 

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