Mitsubishi Electric CAHV-P500YB-HPB Service Handbook page 103

[ VII Control ]
Emergency Operation Mode
-11- Multiple system control
1. Electrical wiring diagram
(MAIN circuit)
External water
Circuit board
temperature sensor
Field-supplied dry contact
switch/relay or remote controller
( * ) Main/Sub units and switch settings
Main unit (Unit to which the external
water temperature sensor is connected.)
Sub unit
2. Water piping system configuration
Circuit board
Preset water temperature (tshs)
External water temperature sensor
(ex) Attached to the outlet
a. Changing the number of units to go into operation and changing the startup sequence of the units
(controlled by the main unit)
Check interval : Variable between 1 and 5
DIFF2 : Differential (Variable between 0 and 8 K)
1) One unit will stop when the external water temperature meets the following formula: External water temperature ≤
[Set temperature (Tshs)] + [DIFF 2 value divided by 2].
If two or more units are operating at the same frequency, the one with more hours of cumulative operation hours will be stopped first.
2) One unit will go into operation when the external water temperature meets the following formula: External water temperature ≤
[Set temperature (Tshs)] - [DIFF 2 value divided by 2].
The unit with shorter cumulative operation hours will go into operation first.
The cumulative operation hours of a given unit is determined by the cumulative operation hours of the compressor with more hours
than the other compressor.
b. Operation control based on the compressor frequency (Each unit controls its own frequency.)
Each unit increases or decreases the compressor frequency based on the difference between the preset and the current water
temperatures.
The frequency of the compressor is adjusted to a range between 50 and 70 Hz to optimize operation efficiency.
Only when all units are under the Thermo-ON condition, the operating frequency may exceed 70 Hz.
HWE15070
Main unit
Unit Unit
(SUB circuit) (MAIN circuit)
Circuit board Circuit board
M-NET cable
SW2-8
( Use of external water temperature sensor)
Main unit
Circuit board
The target outlet water temperature of each unit will be
set as Tshs, and the water temperature is controlled
based on the compressor frequency. (See item b below.)
Sub unit
Unit Unit
(SUB circuit)
Circuit board
SW2-9
( Multiple system)
ON
OFF
The main unit will determine the Tshs (the target outlet water temperature)
for each sub unit as well as the number of units to put into operation as
explained under item a below.
Sub unit
- 96 -
Sub unit
Unit
(MAIN circuit) (SUB circuit)
Circuit board Circuit board
ON
ON
Sub unit
Circuit board
Unit
GB