Marine Air Systems ECU-Maxx, Operation Manual

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PAGE 21
ECU-Maxx VER:10a 12/1/97
ECU-M
AXX
O
PERATIONS
M
ANUAL
T
HEORY OF
O
PERATION
ECU-Maxx System Timing
The following discussion explains the steps the ECU-Maxx control takes at the
beginning of a heating or cooling cycle. There are two different start-up
protocols: timed start and soft start. Soft start has been developed to reduce the
starting load placed on the electrical system by the compressor. It is an optional
feature and must be installed by the factory. Timed start does not provide the
load limiting features of soft start. System timing diagrams appear on the next
page.
Timed Start Timing
The need for heating or cooling is determined by the ECU-Maxx. This
determines the Valve logic; for instance, the Valve is energized in heating mode.
The ECU-Maxx executes the following timed steps:
1. The Fan turned On with the Power Button.
2. The Pump is turned on 6 seconds before the compressor is started.
3. The Valve is shuttled to release residual head pressure.
4. The Start Capacitor is switched on five seconds later.
5. The compressor is enabled at full voltage.
6. The Start Capacitor is switched off immediately after the compressor rotor is spinning.
The system is now up and running, and will remain running until temperature
requirements are met. The system shuts down by first turning off the compres-
sor. The Reversing Valve remains energized until the next cycle if the system
was in heating. Two minutes after the compressor turns off, the Pump turns off
and the Fan is set to Low Speed.
Soft Start Timing
The soft start feature has been developed to reduce the starting load on the
electrical system. Soft start is an optional feature on the ECU-Maxx. The soft
start ramp delay is programmable from 0 to 5 seconds. This delay may need
adjustment for optimal results with your particular system.
When Soft Start is enabled and the ECU-Maxx senses the need for heating or
cooling, the following actions are taken:
1. The Fan speed is reduced to Speed 1.
2. The Pump is enabled when the system calls for heating or cooling.
3. The Valve is shuttled to release residual head pressure.
4. The Start Capacitor is enabled.
5. The Compressor voltage is ramped up to full potential.
6. Once the compressor rotor reaches 75% of rated speed (in other words, the soft start
circuit senses the correct drop out voltage), the Start Capacitor is released.
7. Two (2) seconds later, the Fan is set to the correct speed.
The system remains up and running until the temperature requirements are
satisfied. The shut down sequence is identical to the timed start shutdown
sequence.