15
SECTION II: INSTALLATION AND MAINTENANCE
II.6.1.1
Installing and controlling the utility pump
The circulation pump installed on the chilled water circuit must have
characteristics that are not affected by any pressure drops of the entire
system and the machine heat exchanger, at the nominal flow.
The differential pressure switch that protects the unit also protects it
from any water flow interruptions. It is automatically reset and the unit
restarts automatically only when the water flow exceeds the calibration
setting differential.
In any case, after it intervenes, the control panel displays the
corresponding alarm to signal possible problems in the hydraulic
system.
The operation of the user pump must be subordinated to the
operation of the unit; the microprocessor controller checks the operation
of the pump according to the following logic:
at start-up, the first device to start in the system is the pump, which
has priority over the rest of the system.
during start-up, the minimum water flow differential pressure switch
installed on the unit is ignored for a preset time, in order to prevent
variations caused by air bubbles or turbulence in the water circuit.
once the set time elapses, final consent for the machine to start-up is
accepted and 60 seconds after the pump is started up, the fans are
activated (the anti-freeze alarm is bypassed during this phase). After a
further 60 seconds the compressors are activated according to the
safety times. The pump remains on for as long as the unit keeps
running and only shuts down at the switch-off command.
when the machine is switched off, the pump will continue to run for a
pre-set time before finally stopping, in order to disperse the residual
cold in the evaporator.
II.6.1.2
Minimum water circuit content
For the unit to run smoothly, a minimum amount of water must be in the
water system. The minimum water content is established on the basis
of the unit's nominal cooling capacity (A
Technical Data
), multiplied by
the coefficient expressed in l/kW.
If the minimum content in the system is below the minimum value
indicated or calculated, it is advisable to select the TANK&PUMP
accessory complete with inertial storage tank, and possibly install an
additional tank. However, in process applications it is always advisable
to use a storage tank or a greater system water content to guarantee
higher system thermal inertia.
The minimum water content of the circuit is 2 l/kW
Volume less than 2 l/kW would cause large thermal variation and
could reduce the life of the compressor.
IMPORTANT!
Volume less than 2 l/kW would cause large thermal
variation and could reduce the life of the
compressor.
II.6.2
Water data
II.6.3
Protection against corrosion
Do not use water that is corrosive or contains deposits or debris.
Specific heat exchangers must be used if the water used contains
chloride or is demineralised (stipulated in the documentation, where
available). The corrosive limits for braze-welded stainless steel
exchangers are found below:
pH
7.5 ÷ 9.0
SO4--
< 70
ppm
HCO3-/SO4--
> 1.0
ppm
Total hardness
4.0 ÷ 8.5
dH
CI-
< 50
ppm
PO43-
< 2.0
ppm
NH3
< 0.5
ppm
Fe+++
< 0.2
ppm
Mn++
< 0.05
ppm
CO
2
< 5
ppm
H
2
S
< 50
ppb
Temperature
< 65
°C
Oxygen content
< 0.1
ppm
Alkalinity (HCO
3
)
70 ÷ 300
ppm
Electrical Conductivity
10 ÷ 500
µS/cm
Nitrate (NO
3
)
< 100
ppm
If you are uncertain about the quality of the water in the above table or
you have doubts regarding the presence of different materials that could
cause gradual corrosion over time in the exchanger, it is always good
practice to insert an intermediate exchanger that can be inspected and
is made of suitable resistant material.
II.6.4
Protecting the unit from freezing
II.6.4.1
Indications for unit when idle
IMPORTANT!
If the unit is not used during the winter period, the
water contained in the system may freeze.
The entire circuit must be drained in good time. A drainage point below
the water exchanger must be used to make sure all the water empties
out. Moreover, use the valves placed in the lower part of the water
exchanger so that is empties completely.
If the draining operation is felt to be too much trouble, ethylene glycol
can be mixed with the water in suitable proportions in order to
guarantee protection from freezing.
Units are available with an antifreeze resistance (RA accessory) to keep
the evaporator intact, should the temperature drop excessively.
IMPORTANT!
The unit must not be disconnected from the
electrical power supply during the entire seasonal
break
Summary of Contents for EQU-PF 2100
Page 60: ...NOTE...
