3. System design
The Filax is typically used in backup systems to ensure that the critical load is always powered by an AC source.
The function of the Filax is as follows:
The critical load is normally supplied by the priority source. In case the priority source is interrupted, the load is transfered to the alternate source. Once the priority source is restored and is stable for 30 seconds, the load is transfered back to the priority source.
This chapter describes a few different type Filax system designs.
Notice
Note that the Filax should not be used in systems where ultra fast switching is not needed and where typically a manual or a more general transfer switch is used. An example of such a system is a boat where there are two possible AC sources, like shore power and the generator, both are feeding into the onboard inverter/charger system. In these systems the function of the transfer switch is to detect if one of those sources is active and if active, to pass the active source on to the loads. For these systems use a Quattro inverter/charger or a VE Transfer Switch 5KVA or 10KVA.
Grid (or generator) with inverter backup:
If the grid fails (blackout) or if the generator fails (no fuel) the Filax will transfer the load to the inverter. Once the grid (or the generator) supply is restored, the Filax will transfer the load back to the grid (or generator).
Filax system with inverter backup to the grid or generator
Grid (or generator) with inverter backup and battery charger:
If an inverter is used as alternate source it is important that the battery is kept in a good working condition. The battery should be timely and regularly recharged. Do this by adding an AC charger or a solar charger to the system.
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Filax system with inverter backup and AC battery charger and/or solar charger
Grid (or generator) with inverter/charger backup:
It is also possible to achieve backup (UPS) functionality by using a Victron inverter/charger unit (without a Filax). The inverter/charger by itself will already provide backup (UPS) functionality.
In case an extra level of redundancy is required a Filax can be added to an inverter/charger system. This provides backup in case the inverter/charger develops a fault. It also allows for inverter/charger replacement without interrupting supply to the critical load.
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Filax system with inverter/charger backup
Gird (or generator) with two inverter/chargers backup:
When the generator or grid has failed, the first inverter/charger will power the load. In case the priority inverter/charger has stopped operating or has developed a fault, the Filax will transfer the load to the second inverter/charger. This adds an additional level of redundancy, compared to the previous system.
There are two ways of designing a system like this. Either with an individual battery bank, one for each MultiPlus, or using a single battery bank for both MultiPlus units.
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Filax system with two inverter/chargers connecting to individual battery banks or a single battery bank
Consider adding isolation switches
It is good practice to add isolation switches before and after each inverter/charger. This will allow the inverter/charger to be easily isolated and removed should it need maintenance or need to be replaced, without losing power to the critical load.
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Filax system with two inverter/chargers and isolation switches
Consider adding battery monitoring
It is important to monitor the battery. If the grid or generator supply is not restored, the inverter or inverter/charger will discharge the battery. Eventually the battery voltage will drop to such an extend that the inverter or inverter/charger stops operating. To monitor the state of charge of the battery or to get an advanced warning in case of low battery voltage or low state of charge add a battery monitor to the system.
The BMV battery monitor is equipped with a relay, that can be programmed to engage or disengage depending on battery state of charge or battery voltage. The signal of the relay can be used for monitoring purposes.
If remote monitoring is needed, the BMV or the SmartShunt battery monitor can be connected to a monitoring device, such as the Globallink 520 or a GX device, like the Cerbo GX. This allows for remote monitoring of the battery voltage, state of charge and alarms (for a GX system see next paragraph).
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Filax system with battery monitoring
Consider adding full system monitoring
For full system monitoring add a GX device, like the Cerbo GX. The GX device does not monitor the Filax directly, but it monitors the Victron inverter/chargers, battery monitors and/or solar chargers that are part of the Filax system. System monitoring can be done locally via WiFi, Ethernet, a display or GX Modbus-TCP, or remotely via the Internet and the VRM portal.
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Filax system with full local and remote monitoring