Management Of The Boilers In A Cascade Arrangement; Domestic Hot Water Production - Siemens AVS 75.391 Handbuch

5.3

MANAGEMENT OF THE BOILERS IN A CASCADE ARRANGEMENT

The operation of the cascade boilers is managed by the electronic board of the MASTER boiler, via the AVS75, in order to assure
the following conditions:
• Same number of working hours of each boiler.
• Operation aiming to optimise the number of times each boiler switches on and off.
• Automatic change of the main boiler (the one that switches on first and switches off last) every 500 working hours. This interval
of time can be changed by connecting the Control Panel to the master boiler and changing the parameters as shown in the
following table.
• The boiler with address 1 (the first to switch on) and/or the one with the highest address (the last to switch on) can also be
excluded from the automatic change. As a result, the first and the last boiler to switch on in the initial configuration will not be
affected by the rotation and will always remain the first and the last to switch on.
Programme
Menu
row
Cascade 3540
Cascade 3541 First – Last – First and last
5.4

DOMESTIC HOT WATER PRODUCTION

Domestic hot water can be produced in three different ways:
• By a domestic hot water storage boiler connected to the system (see sect. 6.2). In this case connect the storage boiler down-
line from the hydraulic separator.
• By a storage boiler connected to just one boiler (see para 6.3) - The boiler must be the MASTER.
• By an instantaneous boiler (see para 6.4) - The boiler must be the MASTER.
THE DIAGRAMS OF EACH SYSTEM CONFIGURATION AND THE SPECIFIC PARAMETER SETTINGS ARE DESCRIBED IN
SECTION 6.
5.4.1 CONFIGURING THE CASCADE DHW PUMP
After connecting the pump to the relay, set the QX22 output as indicated in the following table.
Programme
Menu
row
Cascade 6031 Common flow sensor B10
5.4.2 DHW PRIORITY
It can be established which heat demand has priority between the CH circuit and the DHW circuit, if both demands are made at
the same time. DHW priority can be set as follows:
• Absolute: during a DHW demand, the CH pump is always off.
• Neither: both the circuits have the same priority; during the respective heat demands the DHW and CH pumps both operate
independently.
• Sliding and Mixed: not used
The default setting is "Absolute". To change priority, edit the parameter indicated in the following table:
Menu Programme row
Temps / mode
1630
hot water
7105035.03 (1-10/11)
Value to set
n° hours
Value to set
Value to set
Absolute - None
Description
Operating time before automatic change of main boiler sequence.
Exclusion of boiler/s from periodic sequence rotation
Description
ACS storage boiler pump control on relay QX22
Description
DHW and CH demand operating mode
18