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Inverter Work Modes

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TonyM1958 edited this page Apr 10, 2024 · 60 revisions

Fox inverters can be set to a number of different work modes. These are:

Self Use

In this mode, the inverter allocates PV power generation as follows:

  1. House Load
  2. Battery Charging
  3. Export

The inverter determines the house load using the CT clamp or meter that measures the incoming grid supply current. The primary goal is to keep the supply current at or around 0A by pushing enough power into the house to stop the current draw from the grid. It does this using power generated from PV or at night, by drawing power from the batteries.

If the house load is being supplied from PV and there is power remaining, the inverter will use excess PV power to charge the batteries.

When the batteries are full, the inverter will send excess PV power to the house. If this exceeds the house load, power flows back out into the grid as export. The inverter monitors the power being exported via the CT clamp or meter on the incoming supply.

If there is an export limit set that is reached or if the inverter reaches it maxiumum output, and the batteries are full, it will reduce the power being generated from PV (known as clipping) to balance the overall power generation and consumption.

Feed In First

In this mode, the inverter allocates PV power allocation as follows:

  1. House Load
  2. Export
  3. Battery Charging

The house load is met first in feed in first mode because the load is connected across the grid supply (so the inverter cannot export without first satisfying the house load). Where there is no PV power e.g. at night, the inverter will supply the house load from the batteries and there will be no export.

If there is an export limit set on the inverter, and there is still excess PV power, the inverter will use the excess to charge the batteries. Once the batteries are fully charged, the inverter will clip to balance the PV power genration to match the house load and export limit.

When you are export limited and operating in Feed In First work mode, the inverter stores excess solar generation in the battery and recovers this during breaks (e.g. clouds pass over), to maximise your export. This reduces the clipping that happens when your batteries are full but can also lead to some discharging of your batteries in favour of export.

Backup

In this mode, the inverter allocates PV power generation as follows:

  1. House Load
  2. Battery Charging
  3. Export

The main goal of this mode is to keep the batteries charged so they can be used as EPS in the event of a grid supply failure.

PV power generated is first used for the house load and then to charge the batteries. When the batteries reach 100% or the limit set for charge current, excess PV power will be exported, up to the export limit. Above this, PV generation will be clipped. So far as PV generation is concerned, this is the same as Self Use work mode.

The difference with this mode is that the battery is not discharged. When PV power is less than the house load (including at night, when there is no PV generation) the remainder of the house load is drawn from the grid. Although this conserves the battery, some charge will still be consumed as the system runs from the batteries causing the battery SoC to drop steadily over time.

Force Charge Work Mode

This work mode can only be set as part of a schedule / strategy period (see below) and charges the battery from the grid using your max inverter power or max charge current, charging up to your Max SoC setting. Force Charge work mode differs from the 'Charge from Grid' battery setting in that, PV generation remains available when charging from grid (reducing the power drawn from the grid), but it is disabled in Force Charge Work Mode so all charge power is drawn from the grid.

There is no way to set 'Force Charge' (where the batteries do not discharge) using strategy periods. Instead, set a period where the work mode is Backup if you need to preserve the battery charge.

Force Charge work mode is available on H1/AC1 inverters from Master firmware v1.68. When setting this mode, you also need to set values for fdPwr and FdSoC, even those these values do not appear to do anything. The default values are fdPwr=0 and fdSoC=10.

Force Discharge

This work mode can only be set as part of a schedule / strategy period (see below). This mode discharges the battery to the inverter output, delivering power to your house load and grid export. There are 2 additional settings for this mode:

  • FDSoc: is the minimum battery state of charge for Force Discharge. When the battery reaches this level, discharging will stop and the inverter will resume normal operation delivering sufficient power for your house load. If the battery discharges to your Minimum On Grid SoC, the inverter will stop delivering power and your house load will draw from the grid.
  • FDPwr: is the output power level to be delivered, including your house load and grid export.

Force Discharge work mode is available on H1/AC1 inverters from Master firmware v1.70.

Before using Force Discharge, assuming you want to export to the grid, make sure you disable any solar diverters, such as water heaters or EV chargers that consume excess solar. If you don't, they will draw power to consume your power and reduced your export to zero.

You can also offset your house consumption during Force Discharge by manually setting an export limit. With this, the lower of FDPwr and your export limit will apply so, for example, if you set FDPwr to 6000 (6kW) and your export limit to 3680 (3.68kW), your inverter will adjust its output power to maintain 3.68kW export power, leaving up to 2.3kW head room for house consumption.

Schedules

Schedules, also known as strategy periods, are supported with updated firmware on various inverter e.g. H1/AC1 Master firmware 1.68 and later and are managed using Mode Scheduler. This allows you to set up to 8 time periods where a specific work mode will be active. The work modes include: Self Use, Feed In First, Backup, Force Charge and Force Discharge. Each strategy period includes an asociated Minimim On Grid SoC setting that over-rides any battery settings.

Schedules can be enabled / disabled as a block or individually. When schedules are enabled on the inverter, changes to work mode, export limit and min SoC are disabled via the inverter front panel and battery charge settings are cleared.

This page shows you how you can configure work mode schedules using foxesscloud.com. You can also configure schedules using the Fox apps and Energy Stats. In some cases, this feature is referred to as Mode Scheduler.

To build schedules using foxesscloud.com, add the periods you require and then Enable them so they are saved to your inverter. If you navigate away from the page without enabling, the periods will be lost. When you disable the schedules, they may be removed.

For all times / periods, you must set a value for FDSoc and FDPwr, even though these are not used. Use FDSoc = 10 and FDPwr = 0 as defaults.

If you want to be able to set or edit the times, go to the tab 'Template Preset' and click '+ newly added', give your template a name and comment that describes what it does. You can then add strategy periods and electricity price periods

Note that start and end times are inclusive: if you set an end time of 19:00, the period will end at 19:00:59. If you want the period to end at exactly 19:00, set the end time to 18:59.

When setting times, the end time must come after the start time, so you cannot set a 'wrap-around' period such as 23:30 - 04:59. Instead, use 2 time periods 23:30 - 25:59 and 00:00 to 04:59. If you find you can't change the start time, set the end time and then go back and do the start time.

When setting Force Charge work mode, do not set Min SoC to 100% as your battery will be unable to discharge after it charges. Just use your normal Min SoC value e.g. 10%.

If you want to charge your battery to a set level, you can use a strategy period with a higher Min Soc setting in Self Use work mode instead of Force Charge. If your battery is higher than this, it will discharge until you get down to Min Soc and then you will run from the grid. If you battery is lower, you will run from the grid and the BMS will request charge and your battery Soc will drift up until it reaches Min Soc. This charges at a reduced rate so you may need to set the period to cover the full time of your cheap rate in order to achieve your target Min Soc.

To activate a template, go to the tab 'Template', select your template and Enable it:

Note: it is recommended to use either stratey periods or charge times but not both, as setting one will disable the other and may have unexpected results where your battery does not charge

A strategy for Saving Sessions

Demand Flexibility encourages load shifting to help with peak shaving during periods of high demand. This example template (SavingSession) can be used to achieve this:

This charges the battery at standard rate between 2pm and 4pm to 100% SoC. Then between 4.30pm and 6pm, the battery discharges back to the grid at 6kW. I have set my export limit to 3.68kW, so the inverter will automatically adjust it's output to meet my house load (up to 2.3kW) while maintaining an export rate of 3.68kW for 90 minutes - so I discharge around 5.5kWh to the grid.

Using automation to change work modes

If you are using this Home Assistant integration, you can automate changing the work mode using the example yaml code below.

If you are using a different integration, the setup will be different - always check for information specific to your integration.

  • Go to Settings, Automations and click on CREATE AUTOMATION and select 'Create new automation'
  • Click the 3 dots in the top right hand corner and select 'Edit in YAML'
  • Delete the default YAML code and then copy and paste the following code. This changes Self Use to Feed In First, triggered at 11am:
alias: Set Feed In First at 11am
description: Change inverter work mode to Feed In First
trigger:
  - platform: time
    at: "11:00:00"
action:
  - service: modbus.write_register
    data:
      hub: FoxESSInverterModbus
      address: 41000
      slave: 247
      value: 1
mode: single

  • Click Save

  • Click RENAME to set the name of the automation

  • Click the arrow at the top left hand corner to return to Automations

  • Repeat this process, using the following code to create an automation that changes Feed In First to Self Use, triggered at 7pm:

alias: Set Self Use at 7pm
description: Change inverter work mode to Self Use at 7pm
trigger:
  - platform: time
    at: "19:00:00"
action:
  - service: modbus.write_register
    data:
      hub: FoxESSInverterModbus
      address: 41000
      slave: 247
      value: 0
mode: single

Click on an automation to change the time or add further conditions etc.

If you want to manually change work mode outside the set times, just go to Settings, Automations and click on the 3 dots and select Run.

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