Trace gridtied [RE-wrenches]

[Travis Creswell]

A couple of the benefits of Sell vs. LBX that I can see are

Sell mode is simple.  I have seen too many systems that were abandoned by
the owner because  his solar installer went out of business and he couldn't
get a regular electrician (PV
systems)  or plumber (SDWH) to work on it.  I often get calls to remove a
system (mainly SDHW) that could be fixed easily but the customer doesn't
want it because it's "too complex" and he is right.  Trace along with many
other manufacturers could be to blame for some of this.  I work towards as
simple as installations as possible. 
I feel like we are still on the bleeding edge with solar and we don't need
any more black eyes than necessary.

Batteries are always fully charged ready to backup the Sub panel.  It would
be unfortunate if the batteries were nearing LBX when the grid went down and
needed charged within minutes into power outage.

>From what I can see Sell mode produces more watts than LBX mode.  This is
probably more obvious in systems where the solar is barely keeping up with
the loads but could also be obvious where the solar far exceeds the loads. 

In sell mode - a 30 amp array operating at 53.6 volts you are getting 1608
watts out of your array.  I think we can agree on this?

in LBX mode the system voltage is going to be all over the place.   We could
use 50 volts at
the same 30 amps then your only getting 1500 watts out of your array.   When
there are few or no loads and the system voltage climbs up towards 57.6 then
the charge controller starts to limit the array output where if you were in
sell mode you would still be turning the meter at 1608 watts.

I don't know how much of that 1608 watts gets to your meter (assuming the
house doesn't use any) but shouldn't it be over 90%.

Travis Creswell
travis at ozarksolar.com
Neosho, Missouri   
----------
>From: Jason Fisher <aurora at toad.net>
>To: Wrench List <RE-wrenches at topica.com>
>Subject: Trace gridtied [RE-wrenches]
>Date: Sat, Apr 15, 2000, 9:13 PM
>

>Greetings wrenches,
>
>I had a question which is based on:
>
>Kurt Nelson wrote:
>
>> the Trace is left in the LBX mode, which is a lot less efficient than
>> grid-tied.
>>
>
>Why is this?  I have a bunch of net-metered systems selling away and I'm
>not too sure about the performance of the Trace and battery versions.
>While the sell mode is the most hands-off and convenient for a grid-tied
>backup system, I'm dubious as to how good it is at selling that power.
>In the typical system with battery backup, I have a 4 kW or even 5.5 kW
>inverter selling around 1.5 kW worth of PV for most of the day.  I've
>been planning on setting up a monitored system to get some hard results
>but based on what I've witnessed, and what I've heard from others, the
>overall efficiency of the unit in this mode seems to be in the 70% range
>or so.  I've been considering shying away from the sell mode and using
>the LBX mode for clients who are willing to get more hands on with their
>system.  This way I can put the inverter back in search mode and be
>confident that the PV will be used to its full capacity so long as the
>batteries aren't at float.  This also gets rid of that daily float
>charge cycle that they set up in the sell mode, this must waste some
>juice.  The big drawback is of course that most people want more backed
>up loads than the PV they bought can handle on a daily basis but that
>could be worked out.  The thing I like about it is that it keeps the
>consumption issue out in front, instead of blurring it behind a slightly
>smaller utility bill.  I also thought it should be better for the
>typical flooded batteries to see some use.  What do you all think?
>
>Keep it up.
>--
>Jason Fisher
>
>Aurora Energy
>86 Conduit St.
>Annapolis, MD 21401
>USA
>
>Voice/ Fax: 410-268-3088
>email: aurora at toad.net
>
>
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_________________________________________________________
Enlighten your in-box.         http://www.topica.com/t/15