[RE-wrenches] 10 kW Trace System

[R Ray Walters]

I like the SW4024, but I never liked the SW5548. It actually had less surge capability than its little brother.
Either way, I would never recommend the Trace SW series for grid tie. They are very inefficient in that mode. 
(As for the noise, I seem to recall an issue with old SWs where the windings came delaminated and made noise? But I don't remember.....)
We typically run around pulling those SWs out and replacing them with Outbacks.
The SW5548s do have a resell value of around $1500/ ea. for the off grid market.
I'd build a whole new power panel with Outbacks, MPPT controllers, and if the backup loads don't need that much inverter, I'd consider using a combination of Outbacks, and put one of the roofs on a GT inverter without battery backup. (rewire the array for higher voltage)
Sounds like the batteries are gone too (10 years old, 1 failed string)
Once you do all that, they should notice the difference on their next electric bill; it will produce much more net energy.
I'd also ask the question: Have you really used the backup in the past 10 years? (sounds like it was originally a Y2K fear system)
Might just go all GT, no batteries. Be cheaper and even more efficient.

R. Walters
ray at solarray.com
Solar Engineer




On May 6, 2010, at 11:33 AM, Peter Parrish wrote:

> This one is for the grey beards.
>  
> I was asked to look at a slightly funky, ca 10 year old, Grid-tie Battery Back Up System, with 2 ea SW5548s, 100 ea Astropower Ap-100s, 3 ea C-40 (I think) charge controllers, 3 ea strings of 4 ea Sun Extender PVX12100T (100 A-hr) batteries. The PV modules are wired in strings of four. II strings reside on a west facing garage roof (3:12) and 14 strings reside on a south facing main house roof (3:12). Strings are combined using Pulse combiners with up to 8 PV circuits on the input. Everything was buttoned up in rain proof cabinets in such a way as to make inspection (including observation of LCD displays) very difficult. Not a lot of wire marking, etc.
>  
> The client called us to look at the system. Prior to my arrival, the client had done two things:
> -          One battery string had been decommissioned due to a bad battery and
> -          One of the inverters had been put into bypass because of fluctuating output and noise
>  
> We put the inverter in question “on line” and sure enough the critical loads (bathroom lights for example) began to fluctuate on a ~1 sec interval. The inverter also had a fairly loud continuous hum punctuated by a “boing” which occurred at exactly 1 sec intervals. After a while (10 minutes) the fluctuations went away and so did the “boing” but the inverter still exhibited a loud hum.
>  
> I spent a lot of time looking at the PV strings, circuit combiners and the inputs to the CCs. Everything actually looked okay, except for one loose PV circuit input at a circuit combiner. Due to the way the inverters and CC are installed in the cabinets (CC in the back and inverters face up in front of them), It is very hard to trace wires and view displays/LEDs.
>  
> The AC voltages appeared okay (117.5 to 119.6) and here is what we got on the AC currents:
>  
> Inverter A (funky one)
> AC Hot In1, 9.58 A
> Neutral In 1, 10.09 A
> AC Hot Out, 1.47 A
> Vdc=56.4 V
>  
> Inverter B
> AC Hot In1, 7.2 – 8.4 A
> Neutral In 1, 8.6 – 9.4
> AC Hot Out, 1.57 – 1.86 A
> (these currents were fluctuating and my clamp on ammeter has about a 1 sec settling time)
> Vdc=54-64 V
>  
>  
> Where do I start with this system? Obviously out of warranty, but people on this email list seem to like these old inverters. What do the symptoms suggest? Is there a company that repairs these inverters? What kind of additional diagnostics should perform? The customer would like to keep the battery back up functionality (which we didn’t test), so for now I would like to focus on determining the problem(s) and fixing it (them).
>  
> - Peter
>  
> Peter T. Parrish, Ph.D., President
> California Solar Engineering, Inc.
> 820 Cynthia Ave., Los Angeles, CA 90065
> CA Lic. 854779, NABCEP Cert. 031806-26
> peter.parrish at calsolareng.com  
> Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885                                                                                                   
>  
> 
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