There are two types of fan-powered terminal units – series and parallel. Every manufacturer offers both types and special variations such as low profile and quiet units. Although the type of unit to use is often up to personal preference, there are distinct differences:
Series fan-powered terminals have fans that must run throughout the occupied mode in order to deliver ventilation air to the zone:
Parallel fan-powered terminals have fans that only switch on during the heating mode to pull warm return air from the ceiling plenum:
An ASHRAE research project (RP-1292) completed in 2007 was conducted to determine which type of fan-powered terminal used the least energy from a whole building perspective. The report said that either unit could be equally efficient when properly sized and applied. This original report only included units with standard PSC fan motors. A subsequent addendum to the report, paid for by a consortium of interested parties, took the newer ECM technology into account in the same energy model. It gave more of an advantage to the series fan units. Get the research project report from ASHRAE here.
Download this interesting white paper on ECM Motors in Fan Powered Terminal Units.
Click here to learn more about Terminal Units by Krueger.
Climate Systems of Sioux Falls is an expert in commercial HVAC design, installation and management. Call 605.334.2164, email info@climatesystemsinc.com or visit climatesystemsinc.com.
