# Critical loads causing excess export when setting modbus register 37 **URL:** \ **Category:** Modifications\ **Tags:** modbus\_tcp, vrm, multiplus-ii, ess\ **Created:** [31 December 2024 16:46 UTC](https://community.victronenergy.com/t/critical-loads-causing-excess-export-when-setting-modbus-register-37/17111 "2024-12-31T16:46:53Z")\ **Posts on this page:** 19\ **Page:** 1
**Author:** ![christophedm](https://avatars.discourse-cdn.com/v4/letter/c/7c8e57/32.png) [@christophedm](https://community.victronenergy.com/u/christophedm)\ **Post date:** [31 December 2024 16:46 UTC](https://community.victronenergy.com/t/critical-loads-causing-excess-export-when-setting-modbus-register-37/17111/1 "2024-12-31T16:46:54Z")
I am sending -500w to modbus regster 37 on unitid 228 (VE.Bus) To feed back 500w to the grid. I am also reading back the value from modbus to ensure I had written it correctly, no issue here. I am reading what I am writing. But in actuality I am getting ± 857w feed back to the grid. I dont understand why, when checking the VRM I can see Critical Loads being added to the grid feedback? Can I disable the critical loads import ? I have connected the wiring up to AC OUT 1. And ofcourse AC IN. VRM : ![-500](https://europe1.discourse-cdn.com/victron/original/2X/3/3385385555bbc70943005192e59291623a9e8653.png) Readings : ![image](https://europe1.discourse-cdn.com/victron/original/2X/8/81f6ba1abac1c239e1eb3a6d24b2adef09e8d4af.jpeg) Thanks for any insights/help. ---
**Author:** ![lxonline](https://dub1.discourse-cdn.com/victron/user_avatar/community.victronenergy.com/lxonline/32/25567_2.png) [@lxonline](https://community.victronenergy.com/u/lxonline)\ **Post date:** [31 December 2024 18:46 UTC](https://community.victronenergy.com/t/critical-loads-causing-excess-export-when-setting-modbus-register-37/17111/2 "2024-12-31T18:46:07Z")
Help me understand here. 1. You have a load ln the inverter output 2. . You are discharging from battery to grid (target 500W) 3. You don’t want the battery to discharge to the load- where do you want the power to come from for the load? The target to grid is being met (shy of a few watts). What is being discharged from the battery is load + grid is how i understand your vrm upload. ---
**Author:** ![christophedm](https://avatars.discourse-cdn.com/v4/letter/c/7c8e57/32.png) [@christophedm](https://community.victronenergy.com/u/christophedm)\ **Post date:** [31 December 2024 21:08 UTC](https://community.victronenergy.com/t/critical-loads-causing-excess-export-when-setting-modbus-register-37/17111/3 "2024-12-31T21:08:04Z")
Hi LX, I would expect if I send -500 that I would get approximately -500 feedback to the grid. I dont understand why this “Critical Load” is also added ontop of the feedback, generating a surplus on the requested feedback. I would be very happy if only the left side was fed back (-480). Any ideas how to improve or how other people deal with this ? ---
**Author:** ![DuivertNL](https://dub1.discourse-cdn.com/victron/user_avatar/community.victronenergy.com/duivertnl/32/279_2.png) [@DuivertNL](https://community.victronenergy.com/u/DuivertNL)\ **Post date:** [31 December 2024 22:44 UTC](https://community.victronenergy.com/t/critical-loads-causing-excess-export-when-setting-modbus-register-37/17111/4 "2024-12-31T22:44:02Z")
Its called critical loads for a reason, so that means it always have to have power… System is functioning as it should, supply power to critical loads and still keep your grid at setpoint… ---
**Author:** ![lxonline](https://dub1.discourse-cdn.com/victron/user_avatar/community.victronenergy.com/lxonline/32/25567_2.png) [@lxonline](https://community.victronenergy.com/u/lxonline)\ **Post date:** [1 January 2025 05:40 UTC](https://community.victronenergy.com/t/critical-loads-causing-excess-export-when-setting-modbus-register-37/17111/5 "2025-01-01T05:40:07Z")
They have their grid set point at 0w and allow battery discharge. ---
**Author:** ![christophedm](https://avatars.discourse-cdn.com/v4/letter/c/7c8e57/32.png) [@christophedm](https://community.victronenergy.com/u/christophedm)\ **Post date:** [1 January 2025 11:50 UTC](https://community.victronenergy.com/t/critical-loads-causing-excess-export-when-setting-modbus-register-37/17111/6 "2025-01-01T11:50:12Z")
1. Is there anyway to disable the critical loads ? 2. Is there some calculation behind it ? What is the logic here ? I am still not understanding why if I say -500, it will trigger the critical loads also. Here are some more examples Value : -100, no effect, works as expected, I am feeding back to my grid 84w ![-100](https://europe1.discourse-cdn.com/victron/original/2X/b/bcf7982a446854fa0309bc60d359e5c241334060.png) Value : -200, adds 296w of Critical Loads, I am feeding back to my grid 502w ![-200](https://europe1.discourse-cdn.com/victron/original/2X/3/33189dff96cc196cbd0e8d663bf44725bac62b8a.png) Value : -500, adds 377w of Critical Loads, I am feeding back to my grid 857 ![-500](https://europe1.discourse-cdn.com/victron/original/2X/3/3385385555bbc70943005192e59291623a9e8653.png) Then when I request the battery to charge, there is also a surplus of power draw. Value : 100, getting 147, still acceptable for me in a way. ![100](https://europe1.discourse-cdn.com/victron/original/2X/3/3d9bdb78fe32452d1cbfd20f3e8a9464105fff2c.png) Value : 200, getting 511, more then double of what I requested. ![200](https://europe1.discourse-cdn.com/victron/original/2X/3/3fc0d60e8756661083a2265f40b4d529bdd1df44.png) Value : 500, getting 1168w, again more then double of what I requested. ![500](https://europe1.discourse-cdn.com/victron/original/2X/2/2f48a0ef1134b266ad4cbb5511023478c4b15aef.png) I must be missing a big clue or have something misconfigured. If it is normal behaviour can you please explain the logic behind it so I can take it into account when steering the charging/discharging of the battery. Thanks! ---
**Author:** ![lxonline](https://dub1.discourse-cdn.com/victron/user_avatar/community.victronenergy.com/lxonline/32/25567_2.png) [@lxonline](https://community.victronenergy.com/u/lxonline)\ **Post date:** [1 January 2025 12:17 UTC](https://community.victronenergy.com/t/critical-loads-causing-excess-export-when-setting-modbus-register-37/17111/7 "2025-01-01T12:17:05Z")
> [@christophedm](#): > > misconfigured Do you have a grid meter? Where is it physically vs where is it in software position? It is likely that as an issue. Do you actually have loads on the output? ---
**Author:** ![DuivertNL](https://dub1.discourse-cdn.com/victron/user_avatar/community.victronenergy.com/duivertnl/32/279_2.png) [@DuivertNL](https://community.victronenergy.com/u/DuivertNL)\ **Post date:** [1 January 2025 14:53 UTC](https://community.victronenergy.com/t/critical-loads-causing-excess-export-when-setting-modbus-register-37/17111/8 "2025-01-01T14:53:37Z")
Maybe make a drawing how your system is connect to grid and house (grid meter?) ac loads, ac in, ac out 1/2? ---
**Author:** ![christophedm](https://avatars.discourse-cdn.com/v4/letter/c/7c8e57/32.png) [@christophedm](https://community.victronenergy.com/u/christophedm)\ **Post date:** [1 January 2025 15:28 UTC](https://community.victronenergy.com/t/critical-loads-causing-excess-export-when-setting-modbus-register-37/17111/10 "2025-01-01T15:28:51Z")
Marc, here is the wiring. ![WhatsApp Image 2025-01-01 at 16.27.29](https://europe1.discourse-cdn.com/victron/original/2X/2/2c72e94aab64ad57f2b88b7b639634896d420863.jpeg) ---
**Author:** ![christophedm](https://avatars.discourse-cdn.com/v4/letter/c/7c8e57/32.png) [@christophedm](https://community.victronenergy.com/u/christophedm)\ **Post date:** [1 January 2025 15:29 UTC](https://community.victronenergy.com/t/critical-loads-causing-excess-export-when-setting-modbus-register-37/17111/11 "2025-01-01T15:29:52Z")
> [@lxonline](#): > > Do you actually have loads on the output? It is physically exporting that value, I can see it in the homewizard app, see my initial post, the one with the graphs purple and green. ---
**Author:** ![DuivertNL](https://dub1.discourse-cdn.com/victron/user_avatar/community.victronenergy.com/duivertnl/32/279_2.png) [@DuivertNL](https://community.victronenergy.com/u/DuivertNL)\ **Post date:** [1 January 2025 15:41 UTC](https://community.victronenergy.com/t/critical-loads-causing-excess-export-when-setting-modbus-register-37/17111/12 "2025-01-01T15:41:01Z")
You clearly dit not read the manual… get the ac out connection out asap, connect only ac in why did you do that?😊 Thats causing weird issues Whats connected to ve bus? ---
**Author:** ![christophedm](https://avatars.discourse-cdn.com/v4/letter/c/7c8e57/32.png) [@christophedm](https://community.victronenergy.com/u/christophedm)\ **Post date:** [1 January 2025 16:00 UTC](https://community.victronenergy.com/t/critical-loads-causing-excess-export-when-setting-modbus-register-37/17111/13 "2025-01-01T16:00:46Z")
@DuivertNL I have removed the bridge between AC IN and AC OUT 1. Looks alot better now, I did read the manual but failed to find the info on which AC the feedback would occur, apparently it can just go out on the AC IN. ![image](https://europe1.discourse-cdn.com/victron/original/2X/c/cde2f0fb750978044b38cdfecd93510560a3cd6c.png) ---
**Author:** ![christophedm](https://avatars.discourse-cdn.com/v4/letter/c/7c8e57/32.png) [@christophedm](https://community.victronenergy.com/u/christophedm)\ **Post date:** [1 January 2025 16:00 UTC](https://community.victronenergy.com/t/critical-loads-causing-excess-export-when-setting-modbus-register-37/17111/14 "2025-01-01T16:00:58Z")
> [@DuivertNL](#): > > Whats connected to ve bus? MK3 to usb ---
**Author:** ![DuivertNL](https://dub1.discourse-cdn.com/victron/user_avatar/community.victronenergy.com/duivertnl/32/279_2.png) [@DuivertNL](https://community.victronenergy.com/u/DuivertNL)\ **Post date:** [1 January 2025 16:01 UTC](https://community.victronenergy.com/t/critical-loads-causing-excess-export-when-setting-modbus-register-37/17111/15 "2025-01-01T16:01:50Z")
You cant connect a mk3 at the same time with the GX running… ---
**Author:** ![DuivertNL](https://dub1.discourse-cdn.com/victron/user_avatar/community.victronenergy.com/duivertnl/32/279_2.png) [@DuivertNL](https://community.victronenergy.com/u/DuivertNL)\ **Post date:** [1 January 2025 16:02 UTC](https://community.victronenergy.com/t/critical-loads-causing-excess-export-when-setting-modbus-register-37/17111/16 "2025-01-01T16:02:32Z")
Yes its like a normal pv inverter so thats how it feeds back to grid ---
**Author:** ![christophedm](https://avatars.discourse-cdn.com/v4/letter/c/7c8e57/32.png) [@christophedm](https://community.victronenergy.com/u/christophedm)\ **Post date:** [1 January 2025 16:05 UTC](https://community.victronenergy.com/t/critical-loads-causing-excess-export-when-setting-modbus-register-37/17111/17 "2025-01-01T16:05:42Z")
@DuivertNL the MK3 is just connected and wired through a cable gutter to an electric box, if I need it I can just grab it from there without needing to unscrew the Multiplus at the bottom again, I had already noticed it goes into “Blocked” when MK3 is connected. Thanks for your help 🙂 ---
**Author:** ![DuivertNL](https://dub1.discourse-cdn.com/victron/user_avatar/community.victronenergy.com/duivertnl/32/279_2.png) [@DuivertNL](https://community.victronenergy.com/u/DuivertNL)\ **Post date:** [1 January 2025 16:06 UTC](https://community.victronenergy.com/t/critical-loads-causing-excess-export-when-setting-modbus-register-37/17111/18 "2025-01-01T16:06:05Z")
Ok! ---
**Author:** ![lxonline](https://dub1.discourse-cdn.com/victron/user_avatar/community.victronenergy.com/lxonline/32/25567_2.png) [@lxonline](https://community.victronenergy.com/u/lxonline)\ **Post date:** [1 January 2025 16:43 UTC](https://community.victronenergy.com/t/critical-loads-causing-excess-export-when-setting-modbus-register-37/17111/19 "2025-01-01T16:43:48Z")
Also on the GX, you can switch in software ac output not in use as well. (Under ess settings) ---
**Author:** ![system](https://europe1.discourse-cdn.com/victron/original/1X/21a9a7b5db7c6339715f993568736a7053199995.png) [@system](https://community.victronenergy.com/u/system)\ **Post date:** [15 January 2025 16:43 UTC](https://community.victronenergy.com/t/critical-loads-causing-excess-export-when-setting-modbus-register-37/17111/20 "2025-01-15T16:43:56Z")
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