Mitsubishi Electric QAHV Série Manuel D'installation & D'instructions page 20

3 Configuration method and selection criteria of flow rate adjustment device
In this system, a flow rate adjustment device is installed in the secondary side circuit to perform secondary side
flow rate adjustment control by outputting 0 to 10 V from the unit.
* 10-V power supply is not supplied.
The following shows a system configuration example of the flow rate adjustment device and notes on the
system configuration.
The following three system types are recommended as flow rate adjustment devices:
1. System using a three-way valve
2. System using a two-way valve
3. System using an inverter
1. System using a three-way valve
0 to 10 V output
Notes on selection method and system configuration
Notes on pump selection and connection
• Calculate the total pump head according to the system at the site and then select a pump capable of outputting
the minimum flow rate of about 3 ℓ/min (0.8 GPM) and maximum flow rate of about 30 ℓ/min (7.9 GPM) with the
necessary pump head for the piping at the site.
• When selecting the pump, please note that output at a high flow rate will not occur if the flow rate with the pump
head of the system at the site is low, and output at a low flow rate will not occur if the flow rate is too high.
• Be sure to check that the flow rate becomes 20 to 30 ℓ/min (5.3 to 7.9 GPM) at the maximum output during a flow
rate adjustment test run (refer to page 40).
For how to check the flow rate, refer to page 41.
* If the flow rate is not within the range of 20 to 30 ℓ/min (5.3 to 7.9 GPM), select a different pump or adjust the
maximum frequency using an inverter, etc. so that the maximum flow rate of 20 to 30 ℓ/min (5.3 to 7.9 GPM) is
achieved.
* To select a proper pump, first select a pump that supports slightly high flow rate, and then adjust the frequency
with an inverter so that the flow rate becomes 20 to 30 ℓ/min (5.3 to 7.9 GPM) at the maximum output.
(In that case, an inverter is necessary to be prepared separately.)
Notes on three-way valve selection and connection
• Use a valve that is capable of adjusting the flow rate with a 0 to 10 V input.
• Calculate the Cv value and select a valve that supports an appropriate rate.
• Select a valve of which the ratio of the maximum flow rate and the minimum flow rate will be at least 1:10.
• Place the three-way valve downstream of the pump. Connect one outlet to the heat exchanger.
Connect the other outlet to the lower part of the tank.
• Carefully read the instruction manual and use the three-way valve in accordance with the usage procedures.
ON/OFF signal
Three-way Pump
valve
Overview of system
This system has a pump provided at the outlet
of the tank and a three-way valve provided
downstream of the pump, and adjusts the flow
rate by controlling the opening and closing of
the three-way valve.
Wiring
connection
places
GB-20
Flow rate
Flow rate
adjustment
output device
device
Three-way
Pump
valve
1-3 of CN512 of Sub box
control board terminal block
(ON/OFF output) No. 10, 11, 12