Circ means Circulate: the blower runs periodically between heating and cooling calls. Compare fan Auto, On and Circ, with documented details for supported Honeywell models.
These modes control blower operation. Heating and cooling are selected separately. Available fan modes and equipment delays depend on the installation.
| Setting | Requested behavior | What it does not tell you |
|---|---|---|
| Auto | Fan operation with heating/cooling calls, subject to equipment controls. | Not system Auto. Configured accessories or delays can also run the fan. |
| On | Continuous blower operation between calls. | Not a request for continuous cooling or heating. |
| Circ | Periodic blower operation between calls on models that offer it. | Not continuous On, an outdoor-air setting or a guaranteed hourly schedule. |
TH6210U2001, TH6220U2000 and TH6320U2008 only. Not T6 Pro Smart or Z-Wave.
The family manual describes Circ around 33% of the time. The number is approximate; it does not promise an identical hourly run pattern on your system.
Read this family’s manual ↗TH1110U4000, TH1210U4001 and TH1320U4002.
The family manual describes Circ around 33% of the time. The number is approximate; it does not promise an identical hourly run pattern on your system.
Read this family’s manual ↗THX321WF3003W, THX321WFS3001W and THX321WFS3024W.
The family manual describes Circ around 33% of the time. The number is approximate; it does not promise an identical hourly run pattern on your system.
Read this family’s manual ↗Fan operation can include equipment delays. On a configured T10/T10+, humidifier, dehumidifier or ventilator controls may also request the fan in Auto. A mode label alone cannot identify a fault. Check the equipment and accessory manuals if behavior differs from their instructions.
For the supported models, no. On requests continuous blower operation; Circ provides intermittent circulation. Neither setting alone requests heat or compressor cooling.
Use the modes it actually offers. Circ may be absent or unavailable with the configured system. This guide does not supply a hidden installer-menu change to add it.
This guide cannot establish either outcome. Extra fan operation uses electricity, and the result depends on the fan, ducts, controls and room conditions. The mode comparison is not a savings calculation or room-balancing design.
Official Honeywell/Resideo fan-mode references checked October 14, 2026. The linked model manuals take precedence over general support percentages.