Rail Heat - Danfoss AK-CC55 User Manual

AK-CC55 Single Coil and Single Coil UI
When the temperature has dropped to "the middle of the differential", the compressor with the longest operation
time will be cut out.
The running compressor will continue until the temperature has reached the cut-out value. Then it will cut out.
When the temperature again reaches the middle of the differential, a compressor will again be started.
If one compressor cannot maintain the temperature within the differential, the second compressor will also be
started.
If one of the compressors has run on its own for two hours, the compressors will be changed over so that
operational time is balanced.
The two compressors must be of a type that can start up against a high pressure.
The compressor's settings for "Min. On time" and "Min. Off time" will always have top priority during normal
regulation. But if one of the override functions is activated, like e.g. defrost, door open function, case shutdown,
forced closing, the "Min. On time" will be disregarded.
Sequential control
Compressor steps are controlled in the same manner as described for cyclic control, but compressor step 1 will
always be started first and cut out as the last one. No time equalization is available in sequential control mode.

Rail heat

It is possible to pulse-control the power to the rail heat in order to save energy. Pulse control can either be
controlled according to day/night load or dew point.
Relay or analogue output
A relay output can be used when long cycle times are permitted. If fast pulsing is required, the AO1/PWM output
can be used. The output must be connected to an external power solid state relay. The cycle time must be
configured for the relay output in o43 or for analogue output in P82.
Pulse control according to day and night
Various ON periods can be set for day and night operation. A cycle time is set as well as the percentage part of the
period in which the rail heat is ON.
Figure 13: Rail heat control, day/night load
Pulse control according to dewpoint
In order to use this function, a system manager of the type AK-SM is required which can measure ambient
temperature and humidity to calculate dew point and distribute to the appliance controllers. For this the rail heat's
ON period is controlled according to the distributed dewpoint.
Two dew point values are set in the appliance control:
• One where the effect must be max. i.e. 100%. (o87)
• One where the effect must be min. (o86)
At a dewpoint which is equal to or lower than the value in 086, the effect will be the value indicated in o88. In the
area between the two dew point values, the controller will manage the power to be supplied to the rail heat.
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