Yet Another PV Panel Grounding Question
This one is a little different as it involves two disparate panel locations.
I'm upgrading an off-grid system from 1 to 5 kW. Most of the new panels (three strings) have to go on the roof due to rough terrain (no place for ground mounting). There is one existing ground mount tracker array (An old WatSun with the tracking disabled) which I intend to put the other two strings on.
For the roof strings I'll do a exterior down rod to the house GE from the racking and a EGC (EBC) in conduit with the PV wiring to the roof combiner. The combiner box ground will not be tied to the racking at the roof. Trying to keep the lightning outside the house.
The issue involves the old tracker array which is about 100 feet from the house GE. It has its own ground rod from a prior installation. My thought is to ignore that ground rod and run what is essentially a down rod to the house GE from the array frame. (the array is actually a little higher elevation than the roof racks). Then in similar fashion I'll run a EGC (EBC) to the combiner at the array which would be isolated from the down rod, as is the case with the roof.
Here's the question. The tracker pipe mast is anchored in a big chunk of concrete with rebar which goes down maybe 6'. It probably comprises a poor grounding electrode (Watsun instructions say it is not a good grounding electrode and to sink a proper ground bar). It is impossible to isolate the array frame from the mast and anchor so there will be some grounding from the mast and anchor. So, is it be better to ignore the tracker ground bar and just tie the array frame to the house GE or to tie the tracker array to its local ground bar and then tie that to the house GE? My thought is that if there is a nearby lightning strike the ground voltage differential on the tie to the house GE would be less from the mast and anchor than from the ground bar. Thoughts?
Thanks in advance.
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