net metered system question [RE-wrenches]

Bill Brooks billbrooks7 at earthlink.net
Fri Mar 2 17:07:42 PST 2001


If Sparks is right about this, that's not a very good sign. I think it is
very common for some SW inverters to trip offline for one reason or another
and then lose their ability to charge control.

IMPORTANT setting point for SW inverters in grid-connected systems. Shut off
the bulk charge absorption time (set to 0:00) so that it will not bulk
charge every time you have an outage. If the grid is doing funny things in
your area, a 2:00 hour set time can keep the unit off all day long. Just set
the unit to float the battery at 54 volts (temperature compensated) all the
time. Make sure the PWM controller is set well above 54 (say 55.5V) and
temperature compensated to keep it from stealing power from the PV array.

Temperature compensators also fail and can cause the charge controller or
inverter to regulate at the wrong voltage. All kinds of things can be wrong
with your system. Good luck.

Bill.

> -----Original Message-----
> From: R. Sparks Scott [mailto:sharkey at mrsharkey.com]
> Sent: Friday, March 02, 2001 4:16 PM
> To: RE-wrenches at topica.com
> Subject: Re: net metered system question [RE-wrenches]
>
>
>
> 	David;
>
> 	If all of your SW setup values are actually where they
> belong, and the
> charge controller is operating properly (above the SW bulk voltage), then
> you probably have MOSFET damage in the inverters. The inverters will
> produce output that seems "normal", but they won't feed back the
> grid. Your
> best bet here is to look at the wave form on an oscilloscope, if possible.
> 	This was the situation with my SW 2512, it would connect to
> the grid and
> *act* like it was feeding the utility, but the batteries would
> boil away at
> 15+ volts (there's no other charge controller in my system). The inverter
> would power loads from the batteries in a seemingly normal manner. When I
> took apart the cabinet, I found four fried MOSFET's, all connected to one
> of the three transformers. The result of this failure was that
> the inverter
> could meet the voltage of the grid, but not exceed it enough to cause
> current to flow back unto the utility. No error indications were noted on
> the front panel, or in the faults menu.
> 	Time to exercise your (entended?) warranty.
>
> 	-S
>
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 www.homepower.com

For info contact list moderator by email:
 michael.welch at homepower.com

____________________________________________________________
T O P I C A  -- Learn More. Surf Less. 
Newsletters, Tips and Discussions on Topics You Choose.
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