Mitsubishi Electric QAHV Série Manuel D'installation & D'instructions page 22

(2) Notes on other piping work
1 Notes on installation location of secondary side circuit
Install the secondary side heat exchanger, secondary side thermistor, secondary side flow sensor, and secondary
side pump indoors as shown in the figure for the secondary side circuit system. Also, take measures so that the
piping will not freeze.
Installation outdoors
QAHV-N136TAU-HPB
2 Notes on hot water supply piping
Be sure to connect the hot water supply piping to the lower part of the storage tank. If you connect it to the unit
inlet pipe, an abnormal stop (high pressure or gas cooler outlet temperature) may occur or the outlet hot water
temperature may decrease due to the sudden change of the inlet water temperature (5 K/min (9˚F/min) or more
instantaneously or 1 K/min (1.8˚F/min) or more consecutively) during operation.
QAHV-N136TAU-HPB
3 About anti-freezing operation
This unit performs anti-freezing operation. Furthermore, the control method can be changed according to the
system at the site. The following two items can be changed.
1. Prevent disturbance of thermal stratification in the tank
To prevent the disturbance of the thermal stratification in the tank while the indoor temperature is sufficiently high,
set the item code 1514 to "1" so that the judgment criterion for starting the anti-freezing operation of the
secondary side circuit matches with the secondary side circuit water temperature criterion.
Setting procedure and operation overview
Setting procedure
Item code 1514
2. Purpose and application: Prevent piping freezing when the secondary side control is used
If the compressor is not run during the anti-freezing operation in the secondary side control system, there is
a risk of the piping of the primary side freezing, so set SW2-5 to "ON" so that the compressor runs during the
anti-freezing operation.
Setting procedure and operation overview
Setting procedure
SW2-5
Secondary side
heat exchanger
Storage tank
QAHV-N136TAU-HPB
Water
supply
Performs anti-freezing operation in the secondary side circuit when the water
0 (Initial setting)
temperature in the unit side circuit becomes the standard value or below.
Performs anti-freezing operation in the secondary side circuit when the water
1 temperature in the secondary side circuit becomes the standard value or
below.
OFF (Initial setting) The compressor does not operate when the anti-freezing operation is performed.
ON The compressor operates when the anti-freezing operation is performed.
Installation indoors
Secondary side thermistor
T
Secondary side pump
Secondary side flow sensor
Storage tank
QAHV-N136TAU-HPB
Water supply
Operation
Operation
GB-22
Storage tank
Storage tank
Water
supply