D
–EIMAC01905-23_00EN - 33/53
4.6.3 Flow switch option installation
To ensure sufficient water flow through the evaporator, it is necessary to install a flowswitch on water circuit. The flow
switch can be installed either on the inlet or outlet water piping. The purpose of the flow switch is to stop the unit in case
of water flow interruption, thus protecting the evaporator from freezing.
The manufacturer offers, as optional, a flow switch that has been selected for this purpose.
This paddle-type flow switch is suitable for heavy-duty outdoor applications (IP67) and pipe diameters from
1” to 8”.
The flow switch is provided with a clean contact which must be electrically connected to terminals shown in the wiring
diagram. The flow switch must be set up to intervene when the water flow of the evaporator reaches 50% of the nominal
value.
4.6.4 Heat recovery option
Units may be optionally equipped with heat recovery system.
This system in made by a water cooled heat exchanger located on the compressors discharge pipe and a dedicated
management of condensing pressure.
To guarantee compressor operation within its envelope, units with heat recovery cannot operate with water temperature
of the heat recovery water lower than 28°C.
It is a responsibility of plant designer and chiller installer to guarantee the respect of this value (e.g. using recirculating
bypass valve).
4.7
Water treatment
Before starting unit operation, clean the water circuit.
The evaporator must not be exposed to flushing velocities or debris released during flushing. It is recommended that a
suitable sized bypass and valve arrangement is installed to allow flushing of the piping system. The bypass can be used
during maintenance to isolate the heat exchanger without disrupting flow to other units.
Any damage due to the presence of foreign bodies or debris in the evaporator will not be covered by warranty
.
Dirt, scales, corrosion debris and other material can accumulate inside the heat exchanger reducing heat exchange.
Pressure drop can increase as well, thus reducing water flow. Proper water treatment therefore reduces the risk of
corrosion, erosion, scaling, etc.. The most appropriate water treatment must be determined locally, according to the type
of system and water characteristics.
The manufacturer is not responsible for damage to or malfunctioning of equipment caused by failure to treat water or by
improperly treated water.
Table 13
– Acceptable water quality limits
DAE Water quality requirements
BPHE
DX S&T
Ph (25 °C)
7.5
– 9.0
6.8 ÷ 8.4
Electrical conductivity [
μS/cm] (25°C)
< 500
< 800
Chloride ion [mg Cl
-
/ l]
< 300
< 150
Sulphate ion [mg SO4
2-
/ l]
< 100
< 100
Alkalinity [mg CaCO3 / l]
< 200
< 100
Total Hardness [mg CaCO3 / l]
75 ÷ 150
< 200
Iron [mg Fe / l]
< 0.2
< 1
Ammonium ion [mg NH
4+
/ l]
< 0.5
< 1
Silica [mg SiO2 / l]
-
< 50
Chlorine molecular (mg Cl2/l)
< 5
< 0.5
4.8
Hydronic free cooling system
Introduction and system description (P&ID)
Free cooling units have additional coils used to pre-cool the glycol mixture using ambient air when the latter has a
temperature lower than that of the return mixture. If the external temperature is low enough to dissipate the entire thermal
load, compressors automatically turn off and the mixture temperature is controlled by fan speed regulation. If the mixture
temperature is too high, compressors will run as long as necessary.
In the free cooling hydaulic circuit, two motorized two-ways valves are installed. They work in opposition: when one is
open, the other is closed.