EE3 High (primary) limit open

What the control is telling you

The primary limit circuit is open because the heat exchanger got too hot. The circulator blower runs continuously and the furnace will not fire.

Applies to: Daikin DR96TN (upflow/horizontal) and DD96TN (downflow/horizontal) two-stage 96% furnaces with 9-speed ECM motor, R-32 ready

Likely causes

• Dirty filter or restrictive / closed ductwork
• Heating blower speed too low (temperature rise too high)
• Failed circulator blower motor or loose motor harness
• Auxiliary (manual reset) limit tripped - blower failure in horizontal installs or power loss while firing
• Loose or miswired connection in the limit circuit

Test and repair steps

1. Warning: never jumper or bypass the limit circuit.
2. Check and replace/clean the filter; open closed registers and dampers; look for blocked or undersized return duct.
3. Measure total external static pressure (return + supply) with a manometer - roughly 0.5 in. w.c. is the design target; compare with the blower tables.
4. Run the furnace about 10 minutes and measure temperature rise (supply minus return). If it is above the rating-plate range, select a higher heating blower tap (gA1/gA2 menu) - see the Airflow tables.
5. Check the blower motor 115 VAC on the motor line leads and a tap signal from the control (24 VAC on single-stage, 3-15 VDC on two-stage per the manual) - replace the motor if it has power and signal but does not run.
6. With power off and the furnace cool, check the primary limit for continuity; replace it if open when cool.
7. Check the auxiliary limit(s) on the blower housing/deck: press the red reset once. If it trips again, find the cause before resetting again.
8. Tighten or correct wiring in the limit circuit and retest.

Settings for these units

• Normal status displays (7-segment) · Daikin DR96TN/DD96TN