User manual
Document nr. : 012063
Version : V2.0
FC 785-PC
Client : General
Page : 6 of 20
2.
Functional specifications
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The FC-785 PC has three function-modes namely;
1. Standby-phase:
The controller switches only on when hot-gas for another controller, to defrost, is needed.
2. Pre-cooling-phase:
The controller continuously cools (if temperature is higher than set point).
Controllers with the same pre-cool group number (P 806) within the same subnet (P 807)
will start cooling at the same time.
3. Store-phase:
The controller cools only once during the cycle-time (P 307) minutes, until the temperature
is lower or equal to it’s set point. During this cooling the other controllers, in the same
subnet, are blocked as the maximum number of simultaneously cooling controllers during
storage (P308) has been reached. Within a subnet a controller can be assigned to a
storage group (P802). If a controller of a particular storage group (P802) starts to cool
during the store-phase , the other controllers with the same storage group number (P802)
(and subnet numbers) also start with cooling, independently of the mentioned maximum
number (P308). If the temperature exceeds the set point plus the forced-cooling
temperature (P 306), the cooling will also be turned on, even though the controller in the
subnet may still not cool. The temperature is then cooled down to it’s set point. This is to
prevent, that not all controllers succeed in cooling to their set point within the cycle time,
when the number of controllers is large.
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The control parameters can be set in the internal parameter settings. There is a selection of
several defrost-modes like; No defrosting, off cycle defrosting, electrical defrosting or hot-gas
defrosting. Defrost will start on real-time (with max. 12 start-defrost-times) or on interval base.
The interval time (P 516) is adjustable between 1 and 48 hours. As long as the defrost
temperature sensor measures a temperature higher than the defrost-release temperature
(P517), the defrosting can not be started. After defrosting the fan will only start when the fan-
delay-time (P 521) is finished. After defrost the fan is activated as the fan delay time (P 521) is
finished.
a. no defrosting
The fan relay is active when the thermostat requires cooling. If the cooling stops, the fan
will stay on during the programmable delay-time (P401).
b. off cycle defrosting
Fan control during cooling same as at a). During defrosting the fan is continuously on and
none of the programmed defrost relays will be active.
c. electrical defrosting
Fan control during cooling same as at a). Defrost starts on real-time or on interval-time. The
relay for electrical defrosting becomes active. The defrosting will stop on the end-of-defrost
temperature (P 519), with a time limitation (P 518). During defrosting the fan is deactivated.
After defrosting the cooling and the fan will be blocked during the drip-off-time (P 520).
After this time the fan will start if the fan-delay-time (P 521) has ended. If the fan-delay-
time (P 521) is negative, the fan will be activated for (P 521) minutes before the cooling will
start.
d. hot gas defrosting
Fan control during cooling same as at a). Defrost starts on real-time or on interval-time.
The relay for hot-gas defrosting becomes active. For hot-gas defrosting it is necessary that
one or more controllers on the network are cooling. If non of the controllers is cooling, the
controller will wait for 30 minutes. If there is still no unit cooling after this period, then the
controller which temperature has the largest differential to it’s set point, will be activated. In
this way, there will be hot gas available for defrosting. The defrosting will stop on the end-
of-defrost temperature (P 519), with a time limitation (P 518). During defrosting the fan is
deactivated. After defrosting the cooling and the fan will be blocked during the drip-off-time
(P 520). After this time the fan will start if the fan-delay-time (P 521) has ended.
If the fan-delay-time (P 521) is negative, the fan will be activated for (P 521) minutes before
the cooling will start.
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If an alarm input becomes active, the cooling and fan are being stopped and the alarm LED
lights up.