[RE-wrenches] Trace SWs in Energy Management Mode

Fri Oct 4 12:42:30 PDT 2013

Hi Brian,
LBX would be better for the way this customer is using the system, because 
it only connects
 to the grid when the batteries get low. Unfortunately, the timers do not 
affect LBX, so charging 
may occur during the peak rate....or it may not :C)

Rgds,

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Eric Bentsen  |   Schneider Electric   |  Solar Business  |   UNITED 
STATES  |   Technical Support Representative 
Phone: +(650) 351-8237 ext. 001#  |   
Email: eric.bentsen at schneider-electric.com  |   Site: 
www.schneider-electric.com/solar  |   Address: 250 South Vasco Rd., 
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From:
Brian Mehalic <brian at solarenergy.org>
To:
RE-wrenches <re-wrenches at lists.re-wrenches.org>
Date:
10/04/2013 12:04 PM
Subject:
[RE-wrenches] Trace SWs in Energy Management Mode
Sent by:
re-wrenches-bounces at lists.re-wrenches.org

Have a friend that is on an electric co-op where peak $/kWh is 4x the 
off-peak rate.  Peak hours are 6-10 am in the winter and 12-6 pm in the 
summer.

He has relocated an older system from his previous house to his new one; 
circuits were separated out to sub-panel that is connected to the inverter 
AC output.  The reinstallation is very professional.

Two Trace SW4024 in series (04/96)
120/240 Vac Grid connected to AC1 of each inverter
575 Ah battery bank
Two C40s with digital displays, ~ 4.5 kW STC array total
Trimetric

The goal is to not use any utility energy during peak times, unless the 
low battery voltage setting is reached, and in general to run as an 
off-grid system, minimizing charge time from the grid during off-peak 
hours as well.  The assumption (I know it's a tough one, but I'm coming in 
after the transition) is that the PV array should at least be able to 
provide the bulk of the load; using the grid to charge the batteries to 
ensure they are regularly filled and to maximize their life expectancy. 
 The customer is also managing loads actively.

It's been a few years, but I used to work on these all the time; however 
it was usually off-grid with a genset, or fixing poorly maintained Y2K 
systems which were always in float. I'm attempting to use the energy 
management mode.

Inverter settings:
Clocks: Time is accurate
Grid AC1 amps AC: 60
Max charge amps AC: 10 (each inverter)

Grid usage: FLT
Set start charge time: 23:00
Start bulk time: 23:10
Set end charge time: 05:00
Set float volts DC: 25.4
Bulk volts DC: 28.8
Absorb time: 1.5 hours
Low battery cut-out: 22 
Low battery cut-in: 25.4

Okay, programmed the system, both inverters are inverting, AC1 is blinking 
green, looks good.  Then a well pump kicks on, registers 70 A DC on the 
Trimetric.  This causes inverter 1 to go into bulk charging and pass 
through about 10 additional amps from the grid to the load (inverter 2 
continued to inverter about 10 amps for the load).  Inverter 1 soon cycled 
into float, then went back to what invertering (amber light) and green 
blinking AC1 (which is what I want it to be at).  

Had to leave, both the customer and I had other obligations.

He took a picture of the inverter sat 11:15 pm, and they were in bulk, 
battery voltage rising...exactly as planned.  But then in the next set of 
pictures, taken at 7 am, after the end of the charge time, they were in 
float, not inverting, even though, based on the Trimetric readings at 11 
(64%, 85A charging), and the fact that charging would have been active all 
night, they were not in anyway at a low voltage condition (Trimetric 
readings am readings were 85%, trickle charge, 25.6 V).

Something seems amiss.  Any suggestions or insight?

Thanks!

Brian Mehalic 
NABCEP Certified Solar PV Installation Professional™ R031508-59
IREC ISPQ Certified Affiliated Instructor/PV US-0132

PV Curriculum Developer and Instructor
Solar Energy International
http://www.solarenergy.org

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