RHOSS H57603 Instrucciones De Uso página 66

II.2.7.3 Utility pump installation and management
The circulati on pump to be i nstalled in the cooled water circuit should
be s elected to overcome any press ure drops, at nominal r ates of water
flow, both i n the exchanger and i n the entire water s ystem.
• The differential pressure s witc h positioned to protect the unit,
protects the same for m any interruptions of the flow of water. This has
automatic rear m. T he unit re-starts automaticall y onl y when the water
flow r ate exceeds the calibration set differenti al.
• In all c ases, after its intervention, the c ontrol panel keeps the
corresponding al arm displayed in order to signal possi ble problems of
the hydraulic s ystem.
• The operation of the us er pump must be subordinated to the
operation of the unit; the microprocess or controller chec ks the operation
of the pump accordi ng to the following logic:
• when the start-up command is gi ven, the first devic e to start is the
pump, which has priority over all the other devices .
• During the start-up phase, the minimum water flow differential
pressure s witc h fitted on the unit is temporaril y excluded, for a preset
period, in order to avoid oscillations caused by air bubbles or turbulence
in the water circuit.
• when this ti me has pass ed, the definiti ve consent for start-up of the
mac hine is accepted and after 60 s econds from pump switc h-on, the
compressors will be enabled for functioning (respec ting safety ti mes).
The pump keeps on wor king all the time the unit is in operation, and it
shuts down only at the s witch-off command.
• In order to dispose of the residual col d on the evaporator, on
mac hine s witc h-off, the pump will continue to operate for a pre-set time
before finally stopping.
II.2.7.4 Water content in the system
The s ystems ser ved by water c hillers usually have limited water
vol umes/capaciti es. In these conditions, in particular at reduced heat
loads, the compr essor would be s ubjec t to start-up and stops that are
too cl ose together. In or der to protect the elec tric motor of the
compressor, the microprocess or board ti mes start-ups preventing start
of the s ame compressor for 10 mi nutes after it has stopped. T his
operating method penalises the efficienc y of the s ystem c onnected to
the unit as accentuated temperature s wings of the c hilled water may
occur. It is recommended to install a c hilled water inertial stor age tank
on the s ys tem, whose function is that of i ncreasing the amount of water
contained in the circuit where necess ary, in a way to drasticall y limit the
swinging effect of the water temper ature. The volume of the storage
tank depends on the type of s ystem, the potenti ality of the chilling unit,
the temperature differential of the indi vidual partialisation steps of the
wor k ther mostat. D ependi ng on the inerti al effect desired on the
temperature of the water, the total quantity of water Q(l) (sys tem +
storage tank), c an thus be deter mined:
P (kW) = Project cooling capacity.
¨T (K) = Differential of the work thermostat (2 ÷ 6K), i.e. r egulation
differential on the return.
t (sec.) = Compress or standstill ti me (ti ming is managed by the
microproc essor; to determine a mini mum amount of water
that limits temperature s wing in utility, place t≥100 sec., +60
sec. for ever y minute of li mitation desired).
n (n°)
= Number of partialisation steps.
The correct organisation of the tank is downstr eam from the poi nts of
use and upstream fr om the cooling unit. In this way, the temperature of
the water at the termi nals unit is reached i mmedi atel y when the
compressor starts to function. During compressor functi oning, the
temperature of the water c an drop slightly bel ow the proj ect value.
SECTION II: INST ALL ATION AND MAINTEN ANCE
66