Hi,
I am working on a setup where two comap generators are connected to a Cerbo GX over Modbus TCP (the communication with the generators is working as it should) and noticed some things:
There are three ways to set generator start/stop conditions when the two generators are hooked up to the Cerbo: in the normal Cerbo settings under “Generator Start/Stop” and when I select one generator in the device list under its own settings.
The problem is, as soon as the second generator is connected, the option to enable generator start/stop disappears completely.
The way the generators are set up is that the Cerbo relay 1 should close when the conditions for generator start are met, and our own PLC then decides based on other parameters which generator is started and does the rest. The generators are connected (over an interlocked contactor setup) to the AC In 1 of the three-phase Multiplus-II 48/10000 setup. Also, the AC In 1 input type is set to “generator” in the Cerbo’s settings.
The other thing is, when I manually start the generator 2 over my PLC, on the dashboard it shows Generator Power 0 W and tapping on the generator tile it takes me to the device overview of generator 1 (I assume because that one is device instance 40 and generator 2 is device instance 41). When I select generator 2 in the device list, it shows the generator power just fine.
Is there a way to fix this (for the second issue maybe make it display the active power source), or could it be considered in a software update?
We plan to assemble this same setup 80 times in total and really like the data we are getting from the generator communication.
thanks for your question. It’s a somewhat unusual setup you have and, as you have noticed, it’s currently not supported to have more than one generator connected via Modbus or CAN communication. At least not for the use of generator start/stop.
I understand that you are only interested in reading out the parameters of both generators on the GX device. For the control signal to your PLC, using relay 1 with “Genset start/stop” is the best choice here, as this one does not interfere with the Modbus-connected gensets.
Thanks for your reply! The data for the generators is showing up fine when both are connected.
I am actually using relay one as genset start/stop. The problem is that when both generators are connected over Modbus, the option “automatic generator start/stop” in the Cerbo setting is turned off and can’t be activated until I disconnect one of the generators again.
Also when I manually start generator 2, on the overview page it shows Generator 0W (and when I touch the generator tile it takes me to the page of generator 1 (I assume because it is the lower instance ID device), even when I’m drawing power from the generator
please note, that the Generator start/stop settings for Relay 1 are located in the Settings menu, it’s a different location than for a Modbus-connected generator.
The option for enabling generator auto start/stop in the Modbus device settings disappears completely (literally the menu option to switch it on disappears) once I connect the second generator, only the one in the settings menu still shows after that, but can’t be enabled anymore
As documentation for others who come across this thread:
We were able to solve this problem. There was a software bug which caused the start/stop functions to become unavailable in cases where several connected gensets were detected. The next beta version of Venus OS v3.60 will fix this problem.
Our systems will still only allow the control of a single genset controller via Modbus or VE.Can. If several genset controllers are detected, all can be read, but the one with the smallest VRM instance (see “Device” submenu) is selected to be controlled and shown. If necessary, the VRM instance can be adjusted in the GX settings under the VRM menu point, which requires a reboot of the GX device.
For more individual use cases, as here, where external logic is used to switch between several generators on the same AC-IN, we recommend installing an additional energy meter at the AC IN and configuring it with the “Generator” role. Its VRM instance can then be changed to a smaller value than the genset controllers, thereby the power and energy measurements used in the user interface of the GX device and VRM will be based on this energy meter instead of being stuck with the measurement of one of the genset controllers.
As the issue is resolved, I will mark this answer as a solution.