19
O
F
F
O
F
F
O
O
F
Legend
O
Open
F
Closed
Water inlet
Water outlet
Pressure gauge
NOTE: Applies to units 040 to 080
If the pressure drop has increased, this indicates that the screen
filter must be removed and cleaned, as the hydronic circuit
contains solid particles. In this case close the shutoff valves at
the water inlet and outlet and remove the screen filter after
emptying the hydronic section of the unit.
Renew, if necessary, to ensure that the filter is not contami-
nated. Purge the air from the circuit (see 'Air vent' diagram).
Entering water pressure reading
Leaving water pressure reading
Air vent
10 - NOMINAL SYSTEM WATER FLOW CONTROL
The water circulation pumps of the 30RY units have been sized
to allow the hydronic modules to cover all possible configura-
tions based on the specific installation conditions, i.e. for various
temperature differences between the entering and the leaving
water (
∆
T) at full load, which can vary between 3 and 10 K.
This required difference between the entering and leaving
water temperature determines the nominal system flow rate. It
is above all absolutely necessary to know the nominal system
flow rate to allow its control via a manual valve provided in the
water leaving piping of the module (item 9 in the typical
hydronic circuit diagram).
With the pressure loss generated by the control valve in the
hydronic system, the valve is able to impose the system pressure/
flow curve on the pump pressure/flow curve, to obtain the
desired operating point (see example for 30RY 080). The pres-
sure drop reading in the plate heat exchanger is used to control
and adjust the nominal system flow rate. The pressure drop is
measured with the pressure gauge connected to the heat
exchanger water inlet and outlet.
Use this specification for the unit selection to know the system
operating conditions and to deduce the nominal air flow as well
as the plate heat exchanger pressure drop at the specified con-
ditions. If this information is not available at the system start-
up, contact the technical service department responsible for the
installation to get it.
These characteristics can be obtained from the technical litera-
ture using the unit performance tables for a
∆
T of 5 K at the
evaporator or with the Electronic Catalogue selection program
for all
∆
T conditions other than 5 K in the range of 3 to 10 K.
10.1 - Water flow control procedure
As the total system pressure drop is not known exactly at the
start-up, the water flow rate must be adjusted with the control
valve provided to obtain the specific flow rate for this appli-
cation.
Proceed as follows:
Open the valve fully (approximately 9 turns counter-clockwise).
Start-up the pump using the forced start command (refer to the
controls manual) and let the pump run for two consecutive
hours to clean the hydronic circuit of the system (presence of
solid contaminants).
Read the plate heat exchanger pressure drop by taking the
difference of the readings of the pressure gauge connected to
the plate heat exchanger inlet and outlet, using valves (see
diagrams below), and comparing this value after two hours of
operation.
