92 Capacity controller RS8GN202 © Danfoss 11-2013 AK-PC 783
Suction group
Controlling sensor selection
Depending on use, the capacity distributor can regulate according
to the suction pressure P0 or a media temperature S4.
Cap. Ctrl sensor = P0 / S4
Example 1 – P0
Example 2 – S4 media sensor
Used in brine systems in which the MT ttings are cooled by a
brine, and the LT provides condenser heat to the brine.
When the controlling sensor is selected as S4, P0 is used as a safety
function for low suction pressure and will ensure disconnection of
compressor capacity (frost protection).
Handling of sensor error
Cap. Ctrl. Sensor = P0
When P0 is used as the regulating sensor, an error in the signal will
mean that regulation continues with fx. 50% cutin in daily opera-
tion and 25% cut-in at night, but for a minimum of one step.
Cap. Ctrl. Sensor = S4
Provided that S4 is used as a regulating sensor, an error in this sen-
sor will mean that regulation continues from the P0 signal, but in
accordance with a reference that lies 5K under the real reference.
If there is an error on both S4 and P0, regulation will continue with
fx. 50% cut-in in daily operations and fx. 25% of cut-in in night
operations, but for a minimum of one step.
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