OM 1263 • MICROTECH UNIT CONTROLLER 54 www.DaikinApplied.com
Table 37: Alternate Initialization Sequence, 16–28 Tons
Device Step 1 Step 2 Step 3 Step 4
Inverter Compressor & Comp3
Inverter Compressor Speed =
Minimum
Comp3 = O
Inverter Compressor Speed =
Step 2
Comp3 = O
Inverter Compressor Speed
= Increasing 1 step every 5
seconds if PTD-PTD < 26 PSI
Comp3 = O
A
Inverter Compressor Only
Inverter Compressor Speed =
Minimum
If OAT ≥50°F or RAT ≥73°F,
Inverter Compressor Speed =
Smaller of Step 12 or Maximum
If OAT <50°F or RAT <73°F,
Inverter Compressor Speed =
Minimum
A N/A
Outdoor Fan
Outdoor Fan = 0% if OAT < 68°F
Outdoor Fan = 5% if OAT ≥ 68°F
B ← ←
4 Way Valve (Heat Pump) OFF ← ← ←
Indoor Coil
Expansion Valve (EVI)
EVI = 0% C ← ←
Time Duration 5 Seconds 5 Seconds
E = 25/28 Ton size
F
D ≠ 15 Ton size
A. Inverter compressor speed is increasing until the 4-way valve is seated (discharge minus suction pressure is >57 psi) and
as long as the suction pressure is above 43 psi. Inverter compressor speed is increased if the suction pressure remains
above 71 psi. Comp3 turns ON if the inverter compressor speed is at maximum and these conditions are not met. Comp3 is
turned back OFF afer 20 seconds if the suction pressure is below 43 psi
B. Outdoor fan capacity is controlled to maintain the discharge pressure between 171 psi and 221 psi. Outdoor fan capacity
is set to 100% if discharge pressure is above 427 psi. Outdoor fan capacity runs at least at minimum capcity if heat sink
temperature is >167°F
C. The indoor expansion valve is to keep the suction superheat between 7.2°F and 20°F
D. The standard initialization lasts a max of 15 minutes. It is completed early anywhere between 20 and 15 minutes if the
4-way valve is seated (dierential pressure above 57 psi and discharge superheat above 34°F)
E. Step 3 ends when the compressor has reached 65% full speed, dierential pressure is >26 psi for 3 seconds, the stage has
been active for 3 minutes, or Comp3 is active
F. Step 4 (initializaiton) is complete when the stage has been active for 15 minutes, or 4-way valve has set and discharge
superheat is above 34°F
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