I have a 3x MPII 48 5000 (400VAC Three phase system, one unit per phase 552 ) with Cerbox (v3.54) and BYD in an Offgrid Config with Gen.
I am using NR to control the AUX 2 to Switch ACout2 on/Off (configured in the Asstant of the Multis).
When i tested the Config, i seems that each AUX 2 must be switched by the Cerbo, to switch the ACout2 off for each device. Nice for having single phase loadshedding but not usable for 400VAC application. Note that ACout1 is working only 400vac, if one MP switches off all MP will switch off.
I cant use the AUX 2 Input of the MAster as a condition in the Assitant programming of the Slaves ACOut2.
My Question ist if i can switch all AUX2 (minus and Plus connected from each device) with one relay in the Cerbo via Node red or if i might have issues with the voltages of the AUX2 of each device being contected in parallel on the same relais?
I am worried of differnt potetial and thus generating to high input voltage on 10kOhms
@nickdb sry if i put it in the wrong category, but my question is not about the NR programming, but simply:
Why is it not possible in a threephase system to switch ACout2 for all devices simultaneously via an external input. In my case the input being the relais of cerbo, which is controlled by NR.
And if i can use my workaround by bridging AUX2 inputs?
I would appreciate a feedback on my workaround from victron staff @guystewart ?
I’ve done this before on a parallel setup, working perfectly. My argument was that the neutrals and 0V are common, so the internal references should be the same. Obviously all connections were made prior to power up.
If you’re paranoid, let the Cerbo drive a 3 or 4 pole interposing relay
Thx for the sharing of your experience, this helped me @deon.korb .
I am paranoid thought about this external contactor but hence it needs another power supply via fuse from battery i discarded this. Another workaround would be using only one AUX in in the relay of cerbox an prgramming the contactor k1 of the to switch the next devices aux 2 and so on.
But in my opinion the best way.would be bridging the aux2 of the devices as described, but i need to make sure not to fry the plc in the mp2 in some crazy coincidence.
Only thing I might add would be to add diodes in series with each AUX input to give reverse blocking. Otherwise it should be fine. No worries about connecting the ground side of the aux inputs together.
@mpvader Sry to bother you, but maybe you can give me a short feedback if i can bridge AUX2 potential of multiple device in three phase operation to switch via relais ? TIA
I don’t know if there’s a difference between AUX1 and AUX2 but FYI I use AUX1 in the way you describe to open or close the ACout2 relay. Also coming from Relay 2 on the Cerbo. All 3 AUX1 are connected to each other without components like diodes or resistors. It works flawlessly for half a year or so now.
thought about this external contactor but hence it needs another power supply via fuse from battery i discarded this. Another workaround would be using only one AUX in in the relay of cerbox an prgramming the contactor k1 of the to switch the next devices aux 2 and so on.