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the system is stopped. It is recommended that a safety valve be
installed in the hydraulic circuit to avoid hazards due to overpres-
sures, if there is no water flow through the recuperator.
The water temperature at the recuperator inlet (in stable operat-
ing conditions) must be in the range of 25ûC --- 45ûC, with an out-
let differential of between 3.5ûC --- 8ûC.
8.3 --- Water chiller with total heat recovery
(100%)
All heat discharged by the unit to the condenser is recovered
(see Tab. 3).
The system includes an additional refrigerating circuit made up
of 2 two---way solenoid valves, 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
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. 10, Fig. 11.
Expansion vessel volume: 12 litres for all units.
S
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 glycol percentage 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
on board: in the latter case the flow switch, if not installed on the
machine, must be installed on the hydraulic circuit by the install-
er and wired to the electric panel terminal board, as indicated on
the wiring diagram.
8.5 --- Water chiller with inertia tank
The machine can be supplied complete with a buffer tank; it per-
forms the inertial stabilizer function, for a better compressor op-
eration, summed up in the following two points:
S
S
The buffer tank is supplied complete with manometer and tem-
perature sensor well, air purge valve, discharge valve and sink-
ing connection for electric heaters; max operating pressure: 6
bar. Built in carbon steel and coated with anti ---condensate in-
sulation with PVC film proper for outdoor installation. It is
installed inside a cabinet which can be supplied either already
connected to the unit (mechanically and hydraulically jointed to
it) or loose (completely separate from the unit).
Technical data:
S
S
S
Heat recovery
exchanger
8
it reduces the frequency of the compressor start up and con-
sequent high current peaks, which is higher when the sy-
stem thermal inertia is lower, improving their performance.
it naturally eliminates the operation troubles caused by sud-
den load variations (shown by variations of the chilled water
temperature).
Internal volume:
1000 litres
Net weight:
400 kg
Working weight:
1400 kg
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