Daikin DPS Installation And Maintenance Manual page 114

Supplemental Heating/Compressor Heating Transitions
Special action is required when the unit transitions from using
compressor (heat pump) heating to supplemental heating and
vise versa . Normal operation is for the compressor heating
to turn on first and ramp to full capacity before turning on any
supplemental heating . Once the compressor heating is at
full capacity, the supplemental heating will then ramp up and
down as necessary to satisfy the load . There will however be
instances when heating is required and compressor heating is
unavailable in which case the supplemental heating must turn
on first. These include the following cases:
• Compressor heating operation is disabled
• Heat pump defrost operation is active
• Dehumidification is active
• Unit is 100% OA and the OAT is below the low limit set
point of about 0° F [adjustable .] This is adjustable such
that heat pump operation can be locked out at ambients
where gas heat is more economical .
OM 1141-3 • MICROTECH UNIT CONTROLLER
In the cases where compressor heating becomes available
while the supplemental heating is operating it is desirable
to shift as much of the load as possible to the compressor
heating . This is accomplished with the following sequence
which occurs whenever compressor heating enters the Normal
Heating state or leaves defrost operation while supplemental
heating is active:
• Inverter compressor speed is increased 5% every 15
seconds up to maximum speed .
• Fixed speed compressor is turned On when the inverter
compressor reaches maximum speed.
Supplemental heating is allowed to cycle off normally while the
compressor heating is ramping up . When the supplemental
heating has been off for one stage time period, normal
modulating compressor control begins from the current
capacity .
When compressor heating is operating while supplemental
heating is inactive, the supplemental heating is held inactive
until then compressor capacity has been operating at its
maximum capacity and the fixed compressor is on for one
stage time period . At this point the supplemental heating is
enabled to start cycling to meet the load .
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