AK-PC 781A
Capacity
controller RS8HE202 © Danfoss 2017-07
111
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.
Intelligent fault detection (FDD) on the condenser’s air flow
(The function is not active when the selected refrigerant is CO2).
The controller collects measurements from the condenser control
and will advise if/when the condenser’s capacity is reduced. The
most frequent reasons for the information will be:
- gradual accumulation of dirt on the fins
- foreign body in the suction
- fan stop
The function requires a signal from an outdoor temperature sensor
(Sc3).
In order to detect accumulation of dirt it is necessary for the
monitoring function to be connected to the relevant condenser.
This is accomplished by tuning the function when the condenser is
clean. The tuning must not be started until the plant has been run
in and runs under normal operation conditions.
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.
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/P-
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 seconds
(from 13:00) but with a pause of 5 min. between individual relays.
A speed control is run at "Start speed".
EC motor
The voltage signal to the EC motor is defined by the following
settings:
EC min (0%)
EC max (100%)
EC absolute max. (overcapacity)
Summary of Contents for AK-PC 781A
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