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RS8GX102 © Danfoss 10-2013
AK-LM 350
Consumption reading
This function registers the consumption of electricity, water, gas,
etc.
These readings are saved in the monitoring unit and can be re-
trieved later for presentation/analysis. An expansion module type
AK-XM 107A must be used. The module is a pulse counter module,
which measures pulses in accordance with DIN 43 864. Conver-
sion from, for example, current to pulses takes place in an energy
counter.
Energy counters can be divided into several groups, e.g. one main
meter and several ancillary meters.
The main meter measures all of the consumption for the installa-
tion. Some main meters are fitted with tariff and synchronisation
switches.
The AK-LM 350 can receive the synchronisation signal.
The synchronisation switch changes at regular intervals (typically
every 15 mins) and indicates that a new measurement period has
started.
Ancillary meters measure an element of consumption. It might be
interesting to know, for example, the freezer department’s energy
consumption.
Measurement intervals for synchronisation are set jointly for all
energy meters.
If the synchronisation signal is not used, the monitoring unit will
define its own measurement period.
The monitoring unit supports up to 8 energy meters.
Each consumption meter has the following available functions:
• Name
• Start/stop of consumption measurement
• Setting the consumption measurement
• Setting the meter
• Selection of number of pulses per unit of measurement
• The conversion factor is defined as primary/secondary ratio
• Setting the consumption value, e.g. by installation of counter
In addition it is possible to read historical and current values:
• Total consumption (since start-up or reset the counter)
• Consumption for past week (from Monday at 0 until Sunday at
24 o'clock)
• Consumption for past day (from 0 to 24 o'clock)
• Current output (average power the last 60 seconds. Updated
every 5
th
seconds)
• Average output (average power in the measurement interval,
typically 15 minutes).
COP
Coefficient Of Performance = the relationship between the
amount of cooling produced and the amount of energy con-
sumed.
The higher the value, the better.
If the COP value drops at a constant condenser temperature, this
is a sign that there are problems.
The COP can be used to compare systems of the same type.
The output values provide a momentary picture of the cooling
system’s energy efficiency, and the values are displayed as mean
values:
• Mean value over the last minute
• Mean value over the last hour
• Mean value over the last 24 hours
COP values are displayed for the MT group, the LT group and for
the entire system (COPS), as well as for the ideal value for each
group.
You can choose between the following 5 types of systems:
• CO2 booster
• CO2 booster with heat recovery
• CO2 booster with heat recovery and brine
• Cascade system
• Single system
The calculations regard the group of MT compressors as a single
MT compressor, and the group of LT compressors as a single LT
compressor.
All calculations are based on the ideal theoretical cooling process
and are compared with the system readings taken. Pressure read-
ings can be retrieved from the other Danfoss controllers. Tem-
perature readings must be obtained from separate sensors. The
following measurements are required:
• Outdoor temperature
• Temperature and pressure before the compressor (Ss and Po)
• Temperature and pressure after the compressor (Sd and Pc)
For b
• Pressure in receiver (Prec)
• Gas pressure and temperature after gas cooler (Pgc and Shp)
For heat re
• Gas temperature after heat exchanger (Stw2 and Shr)
• Position of three-way valves, on or bypass. (Vtw and Vhr)
For c
• Temperatures on LT side of heat exchanger (Scasc3)
• Temperature after condenser (S2cond)
For
• Temperature after condenser (S2cond)
In chapter 6, there are examples of systems and related signals.
As well as data for the compressor capacity:
• Swept volume (sum of all compressors in the group)
It is important that the value of the volume flow is as precise as
possible.
For a more precise calculation than that provided by the afore-
mentioned readings, current measurements can be connected so
that the controller knows how much power the compressors are
consuming. See energy consumption reading.
For cascade systems and single systems, the refrigerant must also
be set. Choose from among the following:
R134a, R170, R290, R404A, R407C, R410A, R507, R600a, R717, R744,
R1270.
(R744 cannot be selected for cascade systems.)