27 The hydrobox that
The hydrobox is designed to run in an operation
mode with a higher priority (i.e. DHW mode in this
was running in the
case) at power recovery.
heating mode before
power failure is
running in the DHW
mode after power
28 Cooling mode is NOT
Dip SW2-4 is OFF.
29 The cooling system
does not cool down to
the set temperature.
30 The electric heaters
The setting time period of Heat-pump-only opera-
tion is short.
are activated shortly
after DHW or LP
mode starts running
after Cooling mode.
31 During DHW or LP
The unit runs in Cooling mode when the outdoor
ambient temperature is lower than 10ºC (outside
mode following the
of the guaranteed operating range).
cooling mode, error
(When defrosting operation is running at such a
L6 (circulation water
low outdoor ambient temperature after Cooling
mode is switched to DHW or LP mode, the water
error ) occurs and the
temperature in the cooling circuit drops too low,
system stops all the
which could result in L6 error to stop all the opera-
It is essential that the hydrobox is serviced at least once a year by a qualiﬁ ed individual any spare parts required MUST be purchased from Mitsubishi Electric (safety
NEVER bypass safety devices or operate the unit without them being fully operational.
<Draining the hydrobox>
WARNING: DRAINED WATER MAY BE VERY HOT
1. Before attempting to drain the hydrobox isolate from the electrical supply to prevent booster heater burning out.
2. Isolate hydrobox from primary water circuit and drain water from hydrobox. Use a suitable heat resistant hose to assist in these operations.
3. Drain any remaining water from booster heater using ﬁ tted drain cock and hose to safely drain the unit.
4. After the hydrobox is drained, water remains in the following component parts. Drain water completely by checking the inside of the parts.
• Strainer (Remove the strainer cover.)
• Pressure relief valve (Operate the valve.)
<Annual maintenance points>
Use the Annual Maintenance Log Book as a guide to carrying out the necessary checks on the hydrobox and outdoor unit.
When the water in the circulation circuit is un-
duly hot, Cooling mode starts with a delay for
the protection of the outdoor unit.
When the outdoor ambient temperature is
lower than the preset temperature that acti-
vates the freeze stat. function, Cooling mode
does not start running.
Explanation - Solution
• Normal operation.
• After the DHW max. operation time has elapsed or the DHW max. temperature
has been reached, the DHW mode switches to the other mode (ex. Heating
Turn Dip SW2-4 to ON. (Refer to "6-9 Dip switch settings" in this manual.)
To run Cooling mode overriding the freeze stat. function, adjust the preset
temperature that activates the freeze stat. function.
(Refer to "<Freeze stat function>" on Page 37.)
Adjust the setting time period of Heat-pump only operation. (Refer to "<Electric
heater (DHW)> on Page 36.
Do not run Cooling operation when the outdoor ambient temperature is lower
To automatically stop or recover only Cooling operation and keep other opera-
tions running, the freeze stat. function can be used. Set the preset temperature
that activates the freeze stat. function to adjust the outdoor ambient temperature
as follows. (Refer to "<Freeze stat function>" on Page 37.)
Outdoor ambient temperature
3ºC higher than the preset temperature
5ºC higher than the preset temperature