[RE-wrenches]

[Mark Frye]

I am working with small commercial group that runs various manufacturing 
equipment in a small building.

The aging service is a 3 phase, 240V delta, with a 208V leg opposite the 
neutral (I am not sure if it is called a "stinger leg" if it isn't 
277V.) The service entrance conductors include 1 - 500 MCM grounded, 2 - 
500 ungrounded, and 1 - 1/0 ungrounded (for the "stinger leg".) I have 
not yet determined what type wire they are.

My understanding is that the stinger leg wire in the service drop is 
also "undersized".

The service entrance conductors pass through a CT can and terminate in a 
3 phase, 240V, 400A fused disconnect. The fuses are 2 - 400A, and a 300A 
on the stinger leg (the 300A fuse is much newer than the other two.) I 
have not yet tested or determined what loads are connected to the 
stinger leg, what the demands actually are or why it was recently 
replaced.

The utility has inspected this equipment and said they were not 
interested in upgrading the service drop or requiring an improvement of 
the service equipment.

One question I have is who “owns” the service entrance conductors?  My 
understanding is that the they “belong” to the premise and in this case 
the stinger leg with the 300A fuse should be upgraded by the owner, 
regardless of what the utility does with the drop. Or else, they should 
replace the 300A fuse with a 150A.

However, since there is no capacity in the fused disconnect to back feed 
a 30kW PV system, I will be connecting on the line side, in the CT can. 
In this case the existing 1/0 is capable of handling the back feed 
current.

I guess I need to really find out what kind of current is running in the 
stinger leg.

If the 300A fuse is needed to serve the loads, I am thinking I will 
upgrade the service entrance stinger leg conductor and do a line side 
tap in the CT can.

Any advise on how to proceed would be welcome.

Mark Frye
Berkeley Solar Electric Systems


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