Switching; Finish; Switching Of The Accessories; Second And Third Compressors - Johnson Controls York YKN2Open board Technical Information

4.4.2 Switching

When a defrost is started the following operations are carried out:
1. The 4-way valve is set to cool mode.
2. The outdoor fan is stopped.
3. The stage is inhibited. The demand control unit decides whether to start or not.
4. The compressor that is carrying out the defrost does not stop while the defrost is in operation, even
if the thermostat indicates to do so. If it is a tandem the two compressors start up.
5. The indoor fan stops if there is no stage that can generate heat and microswitch SW8 is OFF.

4.4.3 Finish

N O T E
[See the operating parameters in the section Rooms, see on page 25].
The operation lasts until one of the following conditions are fulfilled:
• Liquid temperature higher than 13 °C (DFRTPFIN_HI) during 2 seconds (DFRTIFIN_HI).
• Liquid temperature higher than 5 °C (DFRTPFIN_ME) during 30 seconds (DFRTIFIN_ME).
• Liquid temperature higher than 2 °C (DFRTPFIN_LO) during 2 minutes (DFRTIFIN_LO).
• Time lapsed since the start of the defrost more than 10 minutes (DFRTIMAX).
• The high-pressure switch fault signal is generated.
Switching
A T T E N T I O N
In units with more than one stage, the simultaneous defrost of two stages is not permitted; one waits until
the operation of the other has finished.
When a defrost is completed the following operations are carried out:
1. The outdoor fan starts and 10 seconds are timed (DFRTIVEX).
2. The 4-way valve activates in the heat position.
3. The compressor sets to on. The demand control unit decides whether to continue to operate or not.
The outdoor fan continues to operate for 1 minute (DFRTISECADO), even if there is no demand, in order
to remove drops of water from the coil.
If there is only demand to start a compressor, and this must perform a defrost, the following compressor
will start.
When the defrost is complete, the compressor responsible for that defrost stops and the outdoor fan
continues to operate in order to dry the coil. As long as there is demand, the compressor that was started
(in order to replace that carrying out the defrost) continues to operate.

4.5 Switching of the accessories

4.5.1 Second and third compressors

These accessories enable the control of the second and third compressors. Their operation is described
in the compressor section.

4.5.2 Presence detector

If no presence is detected the setpoints are established in Unoccupied only with the thermostat DPC-1.
If the thermostat is not DPC-1, operation is only permitted with the economiser in cool mode.
The presence detector input is pin 1 of connector J1 of the second compressor board.
• If it is open, i.e. unoccupied in this case, an incident indicates this.
• By default it is always closed.
Operation
Switching of the accessories
4
4.5
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