8
8 --- Options and Accessories
8.1 --- Pump set
On mod. 004---016 the centrifugal pump units are direct driven,
with close---coupled motorsand a single shaft; the induction mo-
tor has 2 poles with IP 54 protection and class F insulation.
The materials used for the pump main components are:
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Pump body in plastic material PA 6.6 (cast iron in all high
pressure freecooling versions and on model 016 in the Chil-
ler high head pressure version and Superchiller standard
head pressure version);
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Impeller in in plastic material PPO (stainless steel in all high
pressure freecooling versions and on model 016 in the Chil-
ler high head pressure version and Superchiller standard
head pressure version);
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Stainless steel shaft;
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Graphite impregnated ceramic mechanical seal (EPDM in
all high pressure freecooling versions and on model 016 in
the Chiller high head pressure version and Superchiller
standard head pressure version), suitable for the use of mix-
tures containing ethylene glycol.
The pump units have been chosen and sized to operate within
specific limits, namely:
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Water / ethylene glycol mixtures up to 65% / 35% by weight;
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Temperatures of the standard pumped fluid not lower than
4
°
C.
The hydrauliccircuitincludes, for each pump, a suction shut---off
valve and a delivery check valve if two pumps are installed, or
suction and delivery shut---off valves if a single pump isinstalled.
On mod. 017---032 the centrifugal pump units are direct driven,
with close---coupled motorsand a single shaft; the induction mo-
tor has 2 poles with IP 55 protection and class F insulation.
Pump casingsand impellersare in cast iron EN---GJL 200, shafts
are in stainless steel, the shaft seal is a unbalanced, mechanical
shaft seal with dimensions according to DIN 24 960 and assem-
bly length according to EN 12 756, brass neck ring permits ideal
conditions for the use of water mixtures containing ethylene gly-
col. The pump housing, the motor stool and the motor stator
housing are electrocoated.
The pump units have been chosen and sized to operate within
specific limits, namely:
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Water / ethylene glycol mixtures up to 65% / 35% by weight;
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Temperatures of the standard pumped fluid not lower than
4
°
C.
The motor stool forms connection between the pump housing
and the motor, and is equipped with a manual air vent screw for
venting of the pump housing and the shaft seal chamber. It is
very important to carry out this operation as the circulation of liq-
uid through the duct of the air vent screw ensures lubrication and
cooling of the shaft seal.
Between the outlets of the two chambers and the discharge
flange, twin---head pumps have a non---return flap valve in
EPDM rubber. The flap is opened by the flow of the pumped liq-
uid and cuts off the port of the idle pump chamber.
In the electrical panel there are, for all the models of pumps, au-
tomaticcircuitbreakers for each pump; the microprocessor con-
trol manages the operating rotation between the two pumpsand
start---up of the stand---by pump if the primary pump fails.
For the technical features of the pumps and the hydraulic sche-
matic see Tab. 8, Fig. 18, Fig. 19, Fig. 20, Fig. 21, Fig. 21 and
Fig. 22.
8.2 --- Water chiller with partial heat
recovery (20%)
This option enables the recovery of up to20% of the heatnormal-
ly rejected by the condensers. The system does not require any
adjustment and is made up of plate heat exchangers installed
on each circuit before the condenser. The exchangers are pro-
tected by a suitable anti---frost heater that operates when the sy-
stem is stopped. It is recommended that a safety valve be
installed in the hydrauliccircuittoavoid hazardsdue tooverpres-
sures, if there is no water flow through the recuperator.
The water temperature at the recuperator inlet (in stable operat-
ing conditions)mustbe in the range of 25
û
C --- 45
û
C, with an out-
let differential of between 3.5
û
C --- 8
û
C.
8.3 --- Water chiller with total heat recovery
(100%)
All heat discharged by the unit to the condenser is recovered.
The system includes an additional refrigerating circuit made up
of a three---way solenoid valve, supplying --- in case of hot water
demand --- a plate exchanger, usually by---passed and sized so
as to discharge all condensing heat (also installed before the
finned air condenser in series with it); a check valve, a liquid re-
ceiver at the exit of the finned air condenser working as storage
for the needed additional refrigerant charge (see refrigerating
scheme). The recuperator is insulated with closed cell polyure-
thane and is equipped with heaters activated when the recuper-
ator is deactivated to prevent frost in winter with the system
stopped or not perfectly drained.
The operation in total recovery mode is enabled by an external
contact. The Microface control will simultaneously suit the fan
speed changing the fan speed setpoint differently from the stan-
dard operation without recovery (practically slowing the fans
down till they switch off); anyway, the operation in recovery
mode is enabled also without load at the users. Indeed, if the us-
ers do not demand heat, the water flowing to the condenser
reaches a temperature that does not enable the total condensa-
tion of the compressed gas, and the remaining portion of the
phase change can thus take place in finned coil without inter-
rupting the recovery process through the intervention of the ma-
chine safety devices.
If the plate exchanger is supplied with too cold water, or if the sy-
stem is not preset by the installation technician with a three or
two---way proportional adjustment valve for the exchanger by-
pass (indispensable for cold starts, see following “Recom-
mended hydraulic circuit” ), the condensing pressure tends to
decrease too much; a prolonged condition of low condensing
temperature below the safety threshold leads the Microface mi-
croprocessor control to disable the heat recovery, protecting the
system from any possible malfunctioning.
Fig. e --Recommended hydraulic circuit
Heat recovery
users
Heat recovery
exchanger
8.4 --- Hydraulic circuit accessories
Made up of an expansion vessel (pre---charged at 1.5 bar, max.
operating pressure 10 bar) and a safety valve, set at 5 bar. Their
position in the hydraulic circuit is illustrated in Fig. 18, Fig. 19,
Fig. 20, Fig. 21, Fig. 21 and Fig. 22.
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Expansion vessel volume:
--- 8 litres for all 004---016 units,
--- 12 litres for all 017---032 units.
It is recommended that the total required expansion vessel ca-
pacity is always checked, depending on the unit’s internal hy-
draulic volume (with the volume of the buffer tank, if installed),
the user circuit volume, the glycolpercentage in the mixture, and
the expected maximum temperature variation of the mixture.
The water flow switch is a compulsory device protecting the unit.
It is installed, as standard, on units with the optional on---board
pump set, and is available as a option for units without pumps
