DC250 [RE-wrenches]

[Bob Ellison]

John,
Is the hum coming from the breaker, the box or both?

Can you twist the inverter cables together? That seems to work better at
reducing the inductance than taping them together. It could be a combination
of distance and inductance causing it.

Thanks,
Bob Ellison

-----Original Message-----
From:	cvsolar at aol.com [mailto:cvsolar at aol.com]
Sent:	Saturday, April 22, 2000 4:12 PM
To:	RE-wrenches at topica.com
Subject:	DC250 HUMMMMMM [RE-wrenches]

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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for info contact: <michael.welch at homepower.com>
_________________________________________________________
Enlighten your in-box.         http://www.topica.com/t/15