Grid Use mode for FX2024ET

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Grid Use mode for FX2024ET

Postby mrrover on Mon Jul 10, 2017 4:59 am

Hi,
I have recently installed a small hybrid system using an FX2024ET, FN-DC, FM80 and MATE 3. Given this is an older model FX unit it doenst have all the functionality as the VFXR units. This system is simply setup to charge from PV during the day and run lights and small appliances each evening. I havent connected the PV up yet so wanted to just charge from the grid in off-peak and use outside of this time. The HBX mode should be fine once the PV is connected however there are a couple of questions i was hoping someone could assist with in the interim.

1. The modes available during setup are Off Grid, Grid Tie and Backup. Can the FX2024ET be used in Backup Mode and if so would this be of benefit at all? What is the difference between Backup and Off grid modes?
2. Are Grid Use times for charging/discharging available? I have tried to set up charge/discharge times from the grid but this doesnt seem to work. Whenever there is an AC source connected (the grid) the unit begins charging even when outside these grid use times?
3. I have trialled HBX mode already with a full battery bank (400Ah, 24V nom). In HBX mode the battery SOC% drops to 60% then switches to grid to supply the loads (charger disabled). This works fine but then the MATE 3 flagged an FN-DC fault for low SOC% - the battery dropped to 59%. Is this normal for this mode as the Event had to be acknowldged to clear the flashing red Event LED?

Cheers,
Carl
mrrover
Junior Member
 
Posts: 3
Joined: Sat Jul 08, 2017 4:17 am
My RE system: 1 X FX2024ET, 1 X FM80, FN-DC, HUB4, MATE3
1500W PV and 400Ah, 24V battery bank.

Re: Grid Use mode for FX2024ET

Postby klundquist on Mon Jul 10, 2017 7:43 am

Welcome to the OutBack Forum mrrover. Thank you for filling out your profile!

mrrover wrote:1. The modes available during setup are Off Grid, Grid Tie and Backup. Can the FX2024ET be used in Backup Mode and if so would this be of benefit at all? What is the difference between Backup and Off grid modes?


Backup mode is for inverters that have utility grid power as the AC source. Off Grid is for inverters that have a generator as the AC source. Selection of Backup or Off Grid merely changes the Mate3 main status screen. You should choose Backup.

mrrover wrote:2. Are Grid Use times for charging/discharging available? I have tried to set up charge/discharge times from the grid but this doesn't seem to work.


Yes the Mate3 Grid Use setting controls the inverter connection to an AC source based on time of day. This could work well for your desire to charge while rates are off peak. Grid Use is a Mate3 function that forces the inverter to disconnect from the Grid during the DROP time and connect to the grid during the Use time. When the inverter is disconnected from the AC source it cannot charge the battery bank. When the system disconnects from the grid you should see a blinking amber light on the Mate3 AC INPUT button. The Inverter AC IN Led will also blink.

mrrover wrote:Whenever there is an AC source connected (the grid) the unit begins charging even when outside these grid use times?

How is there an AC source connected when you are outside the Grid Use time? You are either in Use mode with the inverter connected to the grid, or DROP mode with the inverter disconnected. Try setting up your Grid Use times to DROP when your peak rates are high and USE when the rates are low.

mrrover wrote:3. I have trialled HBX mode already with a full battery bank (400Ah, 24V nom). In HBX mode the battery SOC% drops to 60% then switches to grid to supply the loads (charger disabled). This works fine but then the MATE 3 flagged an FN-DC fault for low SOC% - the battery dropped to 59%. Is this normal for this mode as the Event had to be acknowldged to clear the flashing red Event LED?


The FNDC low SOC fault is merely a default informational warning. You can set the SOC warning level to something lower if you want so you don't get a low SOC error every time you hit the connect SOC.

For best performance make sure you do not use both Grid Use and HBX modes at the same time.

-Kurt
Kurt Lundquist
Alpha Energy Systems Engineer
http://www.alpha.com/solar
klundquist
Alpha Energy Engineering
 
Posts: 660
Joined: Tue May 31, 2011 7:23 am
Location: Arlington, WA
My RE system: VFX3524, Mate, 200Ah 24V AGM Battery Bank

Re: Grid Use mode for FX2024ET

Postby mrrover on Tue Jul 11, 2017 6:11 am

Hi Kurt,

Thanks for the response. I should have given you some more detail in my last post. The explanation on the modes was as i thought - it just wasnt explained in the manual it seems. With the Grid Use function I had set it up previously and it still doesnt appear to work. I have just ran through the existing config wizard and set the following again.

So I have set the mode to Backup.
HBX disabled
In the MATE3 the menu "Grid Use Time"
Period 1 is enabled (Y) (other periods disabled (N))
I have set the Weekday Use and Weekend Use at 23:30
Weekday Drop and Weekend Drop to 02:00

The charger control is ON
The AC-Input state I can change manually to USE or DROP.
The time is set correctly in the system
Current battery SOC% is 97%

When I program the unit it just says "System Programmed" The FX2024 doesnt restart or anything. I have tried programming with the inverter ON and OFF with/without AC present. Just wondering if it should restart or anything? As soon as the AC source is connected it starts charging and supplying the loads and ignores the Grid Use Times - I tries this again at 22:30 today. I can change the AC input state to DROP but then the system never connects to the AC.

Do you have any other suggestions or thoughts I could try? The HBX function works fine but the Grid Use doesnt want to play nicely it seems...

Thanks for your assistance.
mrrover
Junior Member
 
Posts: 3
Joined: Sat Jul 08, 2017 4:17 am
My RE system: 1 X FX2024ET, 1 X FM80, FN-DC, HUB4, MATE3
1500W PV and 400Ah, 24V battery bank.

Re: Grid Use mode for FX2024ET

Postby klundquist on Tue Jul 11, 2017 1:03 pm

mrrover wrote:I have set the Weekday Use and Weekend Use at 23:30
Weekday Drop and Weekend Drop to 02:00


2.5hrs doesn't seem to be enough time to fully recharge your battery bank. Chronic undercharging of the battery bank will cause pre-mature cell failure. If your off peak rates cover more than 2.5 hours a day I suggest increasing the Grid Use time so you can properly charge the battery. Most battery banks need at least 2-4 hours of Absorb charge time.

I mention the battery charging because the inverter has a low battery cut out (LBCO) setting that will force a connection to the grid regardless of the grid use programming. By default LBCO is 21Vdc on a 24V battery bank. When the system hits 21Vdc it will connect to an AC source if present and start charging your batteries. This is a safety feature designed to protect your expensive battery bank from extensive damage due to deep discharge. Realistically you should keep the battery bank above 23V when under load. Chronic discharges to 21V is not ideal.

Your 400Ah 24V battery bank has ~4.8kWh of usable energy based on a 50% depth of discharge over ~20 hour period. Your load would need to be <200W continuous for the battery bank to support your programmed drop grid period (assuming the battery is fully charged). If your load is greater than 200W then your battery bank has something less than the 4.8kWh that I listed above. 4.8kWh is best case scenario as ambient temperatures, age, and other variables will inevitably reduce the listed capacity. For example a 1000W load could reduce your usable 4.8kWh down to 2.0kWh which would mean you only have 2 hours of running off the battery bank before the system needs to connect back to the grid. Battery capacity vs load is a somewhat complex issue so I'm simplifying my explanation quite a bit here.

When programming Grid Use the system needs to actually go past the time you program for the Mate3 to take action. In your example you would need to wait until 2:00 AM until the system would drop the grid. If the batteries do not hit the LBCO setting then the system will reconnect to the grid at 23:30. As a test I suggest you set the drop grid time to something that is ~5 minutes past the Mate3 time and then wait to see how it goes. Instead of using the Wizard every time I suggest you go into the LOCK > 141 > Settings > Mate3 > Grid Use menu to program. Leave the system in Use mode and it should drop once it hits your drop time.

Let us know how it goes.

-Kurt
Kurt Lundquist
Alpha Energy Systems Engineer
http://www.alpha.com/solar
klundquist
Alpha Energy Engineering
 
Posts: 660
Joined: Tue May 31, 2011 7:23 am
Location: Arlington, WA
My RE system: VFX3524, Mate, 200Ah 24V AGM Battery Bank

Re: Grid Use mode for FX2024ET

Postby mrrover on Wed Jul 19, 2017 2:42 pm

The system is working fine now - the trick was as you said, for grid use time to be active it must cross the DROP time period first and only then will it work (this little note should be in the manual).

Thanks for your concerns regarding the system. I am very familiar though with the limitations and parameters regarding the installation as I work in the industry. I just hadnt encountered the Grid Use mode as all systems to date that I have installed are Off Grid.

I appreciate your support.

Regards,
mrrover
Junior Member
 
Posts: 3
Joined: Sat Jul 08, 2017 4:17 am
My RE system: 1 X FX2024ET, 1 X FM80, FN-DC, HUB4, MATE3
1500W PV and 400Ah, 24V battery bank.


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