4-Way Valve Control - Mitsubishi Electric PURY-M200YNW-A1 Service Handbook

[5-3 HBC Control ]
5-3-2

4-Way Valve Control

4-way valves (21S4M (a, b)) turn on or off according to the operation mode.
For 21S4Ma, ON indicates switching to the cooling side and OFF indicates switching to the heating side. For 21S4Mb, ON
indicates switching to the heating side and OFF indicates switching to the cooling side. For 21S4Ma, ON indicates switching
to the cooling side and OFF indicates switching to the heating side. For 21S4Mb, ON indicates switching to the heating side
and OFF indicates switching to the cooling side. When energized: ON; When de-energized: OFF
No. Operation mode
1 Cooling-only
2
3 Cooling-main
4 Heating-main
5 Heating-only
6
7 Defrost
8 Stopped
Operation mode change
(Mixture of units in cooling and heating
→ Cooling-only/Heating-only)
Mixture of units in cooling and
heating(No.3 or 4)
(21S4Ma: OFF, 21S4Mb: OFF)
Operation mode
change
Cooling-only
Switches to the mild-cooling control (No. 2).
(21S4Ma: OFF, 21S4Mb: OFF)
The elapsed time since
the control mode is changed
≥ 30 minutes
The opening of VB3
is too large.
Switches to the cooling control (No. 1).
(21S4Ma: ON, 21S4Mb: OFF)
1) Select the installation site carefully, as some noise may be produced when the 4-way valve is switched.
Install the unit in a place where the noise from the unit will not be problem.
(Install the indoor units and HBC at least 5m [16-6/16ft] away from each other when installing in a space with low background
noise, e.g., hotel rooms.)
Install the unit in the ceiling of an area that are not always occupied by people, e.g., hallway, office kitchen, restrooms. (Do
not install the unit in the middle of a room.)
2) The elapsed time is used to reduce the switching frequency of the control modes between No. 1 or No. 6 AND No. 3 or No. 4.
3) Capacity control is determined depending on the opening of VB3 that adjusts the water flow rate.
BS_05_M
4-way valve control
mode
Cooling
Mild-cooling
Cooling-main
Heating-main
Mild-heating
Heating
Defrost
Stopped
* Note 2
No
Yes
* Note 3
No
Yes
4-way valve
21S4Ma
ON
OFF
OFF
OFF
OFF
OFF
The status before defrosting
maintained
OFF
Heating-only
Switches to the mild-heating control (No. 5).
(21S4Ma: OFF, 21S4Mb: OFF)
* Note 2
The elapsed time since
the control mode is changed
≥ 30 minutes
Yes
* Note 3
The opening of VB3
is too large.
Yes
Switches to the heating control (No. 6).
(21S4Ma: OFF, 21S4Mb: ON)
21S4Mb
OFF
OFF
OFF
OFF
OFF
ON
The status before defrosting
maintained
OFF
No
No
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