DC250 HUMMMMMM [RE-wrenches]

[cvsolar at aol.com]

Hi wrenches,
   I recently upgraded my own home system with a Trace DC250 Dicconnect Box 
to replace the old fuse from years ago and now have strange noises coming 
from the box.  I get a variable pitch whine when the wind turbine is cranking 
(BWC1500) and otherwise have what appears to be a 60 cycle hum similar to a 
transformer when the inverter is loaded.  The only thing different between 
this setup and all the others I have done for customers is that the 4/0 
cables to the inverter are quite long at about 12' each (taped together to 
eliminate inductance) and also the DC250 is on a wall opposite the battery 
bank and I ran the plus wire out the lower left-hand knockout and thru the 
wall to the battery and the minus wire out the lower right knockout and thru 
the wall on that side to the batteries.  This does cause considerable 
distance between the cables (4/0).  Is this some kind of an inductive 
feedback?  Can I damage the inverter?  

On another note.  The problem customer I wrote about a while ago who wanted 
me to take the system back out is now happy with it.  He finally dropped his 
mental block to learning how it works and now likes what he has learned!   We 
are still dealing with a generator that is too small (an old 2000 watt 4 
cylinder Kohler.  It does run sweet and sips fuel lightly but I had to 
program the SW4024 to start it at 85% and run until the batteries are full to 
keep a good reserve for his huge loads.  The generator often cannot run the 
house and the inverter has to assist.  It has been quite a learning 
experience at carefully programming to be one step ahead in a bad situation.  
If the high autostart setpoints don't work, then he has agreed to sell the 
Kohler and buy a bigger generator.

Let me know if anyone has had a humming Box.

John Blittersdorf
Central Vermont Solar and Wind
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