[RE-wrenches] Trace SW4024 feeding back to grid

[Sindelar Solar]

David,
I have pdf copies of the Trace SW manuals, rev. 4.01 (the most widely 
used) and rev. 1.0 (the first from around 1993, seldom still in 
operation). If you need either one contact me off list.

For a short period of time around 2002 there was a rev. 4.10 version of 
the SW that used a separate component called a Grid Tie Interface (GTI). 
The GTI was added to specifically address, as I recall, the possibility 
of grid backfeed when the AC input (from a generator, I think, but this 
may be incorrect) matched the AC output to the loads. It was an awkward 
and short-lived solution that was succeeded by the (also short-lived) 
SW+ series, before the XW series replaced it. I needed to include two of 
these in a GTBB (early Grid-Tie with Battery Backup) dual-inverter 
system that I installed for Jane Fonda at her New Mexico ranch. As Jerry 
says, fun times (way more fun than today, I suspect).

Your simplest real-world solution, which the utility may or may not 
accept, is to run grid power into AC2, the generator input hot terminal. 
Then the inverter functions only as an input source. If the utility 
determined the 1A backfeed on the basis of its own test, a retest may be 
sufficient to ascertain that there's no longer the possibility of backfeed.
Allan
>
> On 2026-01-12 11:28 am, Dave Angelini Offgrid Solar wrote:
>
>> Sounds like this could happen. The (really) old SW input had an 
>> option to do this. Disconnect this.  Do you have the manual?  I might 
>> but not nearby now.  Good Luck
>>
>> On 2026-01-10 1:12 pm, David Palumbo via RE-wrenches wrote:
>>
>>     Wrench,
>>     An off-grid installation of mine from many years ago has is now
>>     using grid power instead of a generator. The utility is telling
>>     the homeowner that they are going to disconnect him because his
>>     house is back feeding 1 amp into their grid power.
>>     I've been retired for many years now and did not do any of the
>>     work to connect the utility power to his Trace SW4024
>>     inverter/charger. The utility power became available when his son
>>     brought in utility power for his maple sugaring operation in the
>>     neighborhood, and the father connected power to his house to
>>     replace his fossil fueled generator for additional charging into
>>     his battery bank. They do not have a grid interconnect sellback
>>     agreement with the utility.
>>     I have no experience with this, but I'm assuming that the utility
>>     grid is seeing power from its input connection to his Trace
>>     SW4024. Does that sound right? If so, is there a simple solution
>>     to fix this problem while continuing to use the grid power
>>     through his SW inverter?
>>     Thanks for any advice that may help.
>>     David Palumbo
>>     Hyde Park, VT
>>
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