Management Of Two Backup Units; Exceeding The Limits - Mitsubishi Electric s-MEXT-G00 006 Technical Manual

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TM_s-MEXT_ME28relC_00_12_19_EN

20.4.5

Management of two backup units

In the presence of two reserve units, always turn on the one with the lower address, while the other reserve unit keeps rotating normally, excluding a unit in alarm, given that

it may already be off or with limited performance.

In case of a second alarm event stopping another LAN local network unit, the second back-up unit also activates and the time count for rotation is suspended. If the cause

that brought to the activation of the first unit in stand-by should cease, the second back-up unit reactivates and the first stays idle.

20.4.6

Exceeding the limits

The backup unit activates and deactivates automatically depending of the four activation steps shown below. It is sufficient for one of the four steps to be active to request

unit activation.

ATTENTION

The set points in the following diagrams are different from those normally used in the regulation process, and are those purposefully set

for the reserve unit; as regards the differentials, they coincide with those used during normal regulation.

The Dehumidification and Humidification setting parameters are under the "Set Point" menu.

The Hot and Cold differential parameters are under the "Regulations" menu, which can be accessed by entering the "Service" password.

For the default values, see the parameters table.

Stand-by unit OFF

P50.05

Figure 20-3: Chart showing the activation of the reserve unit due to the exceeding of the Cold or Hot setpoint

Stand-by unit OFF

P50.07

Figure 20-4: Chart showing the activation of the reserve unit due to the exceeding of the dehumidification or humidification setpoint

When one of the above four steps is activated, 30 seconds (unmodifiable value) must elapse before the backup unit is actually active, meaning before ventilation is active.

After ventilation starts, wait for adjustment permission (60 seconds) before the conditioning unit adjustment devices activate. Humidity and temperature adjustment occurs as

per normal operation, the only difference being the active setpoints that in this case are those relative to the backup unit (stand-by).

The activation of the unit in stand-by for exceeding the limits lasts for a minimum of 10 minutes (cannot be set).

As regards the alarms for exceeding the temperature and humidity limits, the thresholds used by the backup unit for managing these alarms are moved (up or down

depending on whether the type of limit is high or low) by an amount equal to the difference between the normal setpoint and the one relative to the unit in stand-by.

There is also a procedure whereby, when the value of a setpoint is modified, the corresponding value relative to the unit in stand-by is automatically moved and updated.

Technical manual

Stand-by unit ON

P20.18

Differential

Stand-by unit ON

P20.20

Differential

Stand-by unit ON

(°C)

ambient

Stand-by unit ON

(%)