Well, California has done it again— banned something we didn’t even know was a problem. You can either admire those people at the leading edge of the continent, or you can say they should jump off Big Sur and into the Pacific Ocean before the next earthquake.
What have they done lately? California banned bypass ducts in zoned air conditioning systems. As you know, other states in the nation often follow the lead of the Golden State. So what does this mean?
Basically, California’s state engineers have decided that bypass ducts, which introduce air flow into a multizoned air conditioning system, are costly in terms of energy usage. If you live in a large home with central AC, the system probably has several zones— say, one for the bedroom area; another for the living room and kitchen; a third for the basement. Whenever all three of these zones are not calling for conditioning, a bypass duct opens to equalize the pressure. This has a negative effect, however, on energy efficiency because it introduces un-conditioned air into the system and makes it work harder.
No! Not that kind of bypass!
Also this additional fresh air can make the evaporator coil freeze up. Truth is, there’s a lot of confusion and controversy about this law, especially among HVAC techs. Some experts say that the bypass duct is being blamed when the real problem is poor design of the HVAC system.
But the bottom line, for homeowners, is that bypass ducts can and do cause problems, loss of efficiency, and frozen coils.
So if you are thinking about having your system replaced or you are building a new home or adding on to an existing home or renovating an older home . . . . heed the bypass. (Here’s a little more detail from Green Building Advisor: http://www.greenbuildingadvisor.com/blogs/dept/building-science/achilles-heel-zoned-duct-systems.)