All,

Does anybody understand what the zone-level temperature schedule does for a PIU system with parallel-PIU fan control (in eQuest)?

My understanding is that for a PIU system, zone level fans (in a parallel configuration) are only activated during heating hours (is this true?) and draw return air from the plenum to mix with the primary air, thereby taking advantage of the heat in the plenum. It would be counterproductive to do this in cooling mode as the primary air is typically at 55F, much cooler than plenum air.

If my assumption is correct, I am confused by the definition for the Temperature Schedule (called Zone-Fan-T-Sch in the help file), which reads: "Required if Zone: Terminal-Typ = PARALLEL-PIU. Takes the U-name of a schedule (type = temperature) that gives the zone temperature at which the terminal blower turns on. This temperature must be above the heating range."

Why should this temperature be above the heating range? What heating range is this referring to? I would have thought the temperature would be the temperature BELOW which the fans turn on to provide additional heating...in other words, if you're trying to maintain 70F in the space, the fans would be activated at 69F or thereabouts. Does anyone know what this Temperature Schedule does exactly?

Any insight is appreciated.

Chris