Discussion is with function of the K9 and K19 DX relays and the operation of the A2L sensor
- K9 has all dry contacts and enables the blower circuit, locks out the furnaces and closes the contact for stage 1 cooling on the condenser.
- K19 also has dry contacts and only enables the second stage of cooling on the condenser.
They are physically labeled with a sticker, and the terminals are numbered on the relay.
The TSTAT for cooling is field provided and shown in the diagram.
As an alternative to using the K9 and K19 provided dry contacts just energize the Y1 and Y2 at the condenser for cooling with the field provided TSTAT/ controller.
No need to use the relays if 24v power is sent to G for the fan in cooling.
- A2L sensor when in leak detection mode, enables the blower circuit (fan on), opens the dampers and shuts power down to R.
NOTE: Use R to power the stat/ controller to allow the A2L sensor to function correctly. - By powering the controller from R at the air handler, if the sensor detects a leak, power to the compressor is dropped due to power loss at the controller, turning off the compressor outputs.
See attached (SAMPLE SCHEMATIC)