rada DRV40, Product Manual, Page: 38 / 72

38
SYSTEM PERFORMANCE
For effective DRV40 performance, the DRV must be able to experience a minimum
flow and a minimum temperature differential between its inlet and outlet supplies
when the system is in zero demand .
Zero demand
is defined as periods when there is no mixed water outlet usage on
the system.
Pre-installation calculations should have already determined the system heat loss
characteristics. For optimum performance the DRV40 requires a minimum of 1°C
differential between the digital display on the unit (the outlet temperature) and the
thermometer which is installed on the system return line.
When there is no system draw-off, the DRV40 reverts to a zero demand. The
recirculation temperature is continuously monitored and adjusted appropriately by
the DRV40. The circulating pump must operate continuously, the DRV40 requires
a minimum flow of 19 l/m.
Pump Capacity
The circulating pump is only required to keep water gently moving around the system.
The pump should be sized and selected to overcome the system resistance (feet of
head) at the minimum specified flow rate of 19 l/m while also accounting for system
heat loss.
System Safety Measures
System safety measures such as the installation of an aquastat linked to the
circulating pump which shuts the pump off if the system exceeds a given temperature
setpoint is not required. DRV40 can be programmed to issue suitable alerts and/or
system hot water shutoffs (DRV40) and shutdowns (Independent Solenoid Valve).