OM 1263 • MICROTECH UNIT CONTROLLER 52 www.DaikinApplied.com
Table 35: Standard 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 2 steps every 5
seconds if PTD-PTD < 26 PSI
Comp3 = O
Inverter Compressor Speed
= Increasing 1 step every 20
seconds if there is no change
of 4 Way Valve call
Comp3 = O
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
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)
C ← ← ←
Time Duration 5 Seconds 5 Seconds
E = 25/28 Ton size
D
5 Seconds ≠ 25/28 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. Comp3 remains OFF
B. Outdoor fan capacity is controlled to maintain the discharge pressure between 256 psi and 313 psi. Outdoor fan capacity
is set to 100% if discharge pressure is above 384 psi. Outdoor fan capacity runs at least at minimum capcity if heat sink
temperature is > 167°F
C. The indoor expansion vavle is to keep the suction superheat between 7.2°F and 12.0 °F
D. The standard initialization lasts a max of 120 seconds. It is completed early anywhere between 20 and 120 seconds if the
saturation suction temperature is high (above 118°F), the suction pressure is low (below 79 psi) or once the 4-way valve is
seated (dierential pressure above 57 psi, suction below 142 psi, suction superheat above 27°F, and discharge superheat
above 34°F)
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