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Reglermanual - VMGFF102

5.3 - Heat exchanger water pump control

The unit can control one or two heat exchanger water pumps.
The pump is turned on when this option is conﬁ gured (see
PUMPCONFIG) and when the unit is in one of the on modes
described above or in delay mode. Since the minimum value for
the delay at start-up is 1 minute (conﬁ gurable between 1 and
15 minutes), the pump will run for at least one minute before
the ﬁ rst compressor starts.

The pump is kept running for 20 seconds after the unit goes to
stop mode. The pump keeps working when the unit switches
from heating to cooling mode or vice-versa. It is turned oﬀ if
the unit is shut down due to an alarm unless the fault is a frost
protection error. The pump can be started in particular
operating conditions when the heat exchanger heater is
active (see chapter 5.5). See chapter 5.14 for the particular
heat exchanger pump control for the follower unit (master/
slave assembly).

If two pumps are controlled and the reversing function has
been selected (see PUMPCONF conﬁ guration), the control tries
to limit the pump run time delta to the conﬁ gured pump
change-over delay. If this delay has elapsed, the pump
reversing function is activated, when the unit is running.
During the reversing function both pumps run together for
two seconds. If the pumps are of the variable ﬂ ow rate type
pump reversal will take place at the next machine start-up.

If a pump has failed and a secondary pump is available, the
unit is stopped and started again with this pump.

The control provides a means to automatically start the
pump each day at 14.00 hours for 2 seconds when the unit is
oﬀ . If the unit is ﬁ tted with two pumps, the ﬁ rst pump is
started on odd days and the second pump is started on even
days. Starting the pump periodically for few seconds
increases the life-time of the pump bearings and the
tightness of the pump seal.

5.4 - Control interlock contact

This contact checks the status of a loop (water ﬂ ow switch
and customer safety loop, see chapter 3.6). It prevents the
unit from starting if it is open when the delay at start-up has
expired. This open contact leads to an alarm shut-down, if
the unit is running.

5.5 - Heat exchanger frost protection

The heater for the heat exchanger and the water pump (for
units with a pump) can be energised to protect the heat
exchanger, if it may be damaged by frost, when the unit is
shut down for a long time at low outdoor temperature.

NOTE: Heat exchanger heater control parameters can be
modifi ed, using the Service confi guration.

5.2.2 - Heating/cooling/auto selection

The table below summarises the unit heating/cooling opera-
tion, based on the following parameters:
•

Control type: indicates whether the unit operates in
local, remote or CCN mode. See section 5.1.

• Unit

on/oﬀ status: indicates whether the unit is shut

down (not authorised to start) or in operation (or
authorised to start).

•

Heating/cooling/auto selection in local mode: operating
mode selected via the user interface. See GENUNIT
menu.

•

Remote heating/cooling contacts: these contacts are
only active if the unit is under remote control.

•