Folks, I have panels on my shop. They are grouped into 6 groups of 2 panels each. I would like to monitor current flow on each group. I figure I can use a smart shunt on each of the 6 legs, but want to run this by. The reason is I found a bad connection on the combiner box, it had got so hot it was deformed due to softening. I figure if I had a way to monitor the current flow I would have seen something before the damage occurred.
Do you mean that you have 6 parallel strings of 2 series panels?
If so, it might be more efficient to turn this into a 3 or 4 series system. This would produce lower combined current that is easier to manage.
If you are combining more than 2 strings of modules in parallel, then each string should be properly fused in both positive and negative lines.
While it would be possible to monitor each string with a shunt, it is an expensive exercise. It might be better just to monitor the junction temperatures with a remote reading thermal device. Usually on large installations, this is done by manual inspection with FLIR monitor every 6 months or so.
Yes, that’s the problem with PV generators: they’re practically impossible to switch off.
You can install temperature monitoring (wireless sensors, etc.) and have the system switch off automatically or issue a warning when the relevant temperatures are reached inside the enclosure.
You might be able to pair the sensors with the Cerbo and assign control and alarm functions to them, where applicable.
If you haven’t installed string fuses, make sure you retrofit them, as a fault in the generator field could otherwise cause a fire if module components become overloaded!
I am using a combiner box which has both fuses and thermal breakers. So we are protected there but would like to monitor each string to make sure they are all putting out what they should be.
There is no easy/cheap way to acomplish monitoring.
As ready made devices, depending on string configuration, you may choose MPPT’s for each string, microinverters or string inverters with optimisers.
A DIY solution should involve DC current transducers and a logging/monitoring module.
As mike mentioned, is much easier to manage higher voltage strings.
There are monitoring relays, e.g. from Bender, for DC as well.
If you set them to the appropriate voltage, they could trigger the inputs on the Cerbo!
Come up with something!