Don’t Damage your AC System Trying to Make it More Efficient

Closing off too many AC ducts can cause damage to your compressor

This tip gives more details on why closing off AC registers can cause damage to your AC compressor and result in a huge repair bill. To read the original tip click here.

A 6 inch duct will carry 100 cubic feet of air per min (cfm). If you close off one register, you might be able to force 125 cfm through another 6 inch duct, but you have lost 75 cfm in the process. You can’t force all the air for the system through one duct. There is too much static air pressure. AC systems require around 400 cfm per ton. Closing off ducts can reduce your airflow to perhaps 300 cfm per ton. This is not enough to give full evaporation to the refrigerant. If this occurs, you can start to get liquid refrigerant into your compressor. Compressors have very low tolerance for liquid inside. The valves are very thin pieces of steel like the thickness of cardstock paper. When liquid hits them, it can break out chunks and cause holes in there. It just breaks them up.

Liquid refrigerant is also a solvent, so it absorbs oil. If you get liquid refrigerant in your compressor, it takes away the oil lubricating the compressor. You end up with an increase in friction, resulting in less efficient operation and probable damage and early failure of the compressor. Interestingly, refrigerant gas will carry oil and the designers rely on this property to lubricate the inside of the compressor whereas the liquid refrigerant will wash it away. You can see scratches inside the cylinder of a compressor where liquid refrigerant has run through it.

It’s very bad for the compressor to restrict air flow through the ducts of your AC system by closing off too many registers. Please exercise caution when closing registers.

If your AC needs repair or service, please call us at 562-944-2118 to set up an appointment.