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Speed regulation of first fan + step regulation of the rest
The controller starts the frequency converter and increases the
speed of the first fan.
If additional capacity is required, the next fan cuts in at the same
time as the first fan switches to minimum speed. From here, the
first fan can increase speed again, etc.
Capacity limitation during night operation
The function is used to reduce the noise from the fans to a
minimum. It is primarily used in conjunction with a speed control,
but it will also be active when steps are cut in and out.
The setting is arranged as a percentage of the max. capacity.
The limitation will be disregarded when safety functions Sd max.
and Pc max. take effect.
AK-PC 772A
Capacity controller RS8HF102 © Danfoss 2017-07
Condenser couplings
Coupling of condenser steps
There are no time delays in connection with cutin and cutout
of condenser steps beyond the time delay inherent in the PI-
regulation.
Timer
The operating time of a fan motor is registered continuously. You
can read out:
- operating time for the previous 24-hour period
- total operating time since the timer was last set to zero-set.
Coupling counter
The number of couplings is registered continuously. Here the
number of starts can be read out:
- number during the previous 24-hour period
- total number since the counter was last set to zero-set.
Exercising fans
The last fans are unlikely to be activated during winter months. To
ensure that the fans are 'exercised' a test will be carried out every
24 hours to check whether all relays have been in operation. The
relays that have not been used will now be activated for 5 minutes
(from 13:00) but with a pause of one hour between individual
relays. A speed control is run at "Start speed".
Safety functions for condenser
Signal from fan and frequency converter's safety controls
The controller can receive signals on the status of each individual
condenser step's safety circuit.
The signal is obtained directly from the safety circuit and
connected to a "DI" input.
If the safety circuit is cut out the controller will give alarm.
Regulation continues with the remaining steps.
The ancillary relay outlet is not cut-out. The reason for this is that
the fan are often connected in pairs but with one safety circuit.
With fault on the one fan, the other will continue to operate.
105
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