A Few Questions About Inverters

[WStayton]

I had previously thought to use two Outback model VFX-3648, inverters tied togather to give 120/240 but they seem to have some significant shortages as to their ability to recharge the batteries quickly from an engine-generator setup.  So I have been looking around at other inverters.

  I have not previously looked at grid tied inverters since it doesn't make sense to make electicity for $0.30 per kW and sell it to the electric company for $0.10.  (Note: not necessarily real numbers but the ratio between them is probably like what I will have with my engine-generator).   However, I haqve dixcovered a grid tie inverter that, I think (always dangerous!) will satify my requirements with only one, instead of two as with the Outbacks.

  The one that I have discovered, after some prompting by other members, is the Xantrex XW6048, which would satisfy my desire for having 120/240 with only one piece of equipment, plus it has a generous charging circuit that would satisfy my requirements.  However, one questions I have is:  What happens if I just leave the two output to line terminals blank and hanging there?  These are in addition to the 120/240 terminals for my own domestic use and are designed to/for selling power back to the utility.  Can I just leave the unit sitting there with everything else hooked up and working except for the "back to the line" terminals, and just leave those open?

  Anybody have any experience with this model of inverter?

  Regardz,

Wayne Stayton

[Tom Reed]

No problem, these are an off-grid/grid-tie with battery backup inverter.

[LowGear]

I have not previously looked at grid tied inverters since it doesn't make sense to make electricity for $0.30 per kW and sell it to the electric company for $0.10.

This only happens once you start producing more than you're using.  Once we get fully installed, leg one is 3 KWH in PV, we will still only meet about 75% of our electrical needs.  Our beloved electrical utility, privately owned, does not pay for excess power but will graciously accept it as a contribution towards the security of the community.  I wouldn't mind a few KWHs a month but we're still planning for about 75% of total needs.  (What happened to the devil smiley face?)

Casey

[WStayton]

  LOWGEAR:

  I suppose selling power back to the utility only makes sense if you install enough photo cells/panels so that in the really short, dark days of winter you have enough so, then, you would have vast excess in the summer.

  Here in upstate New York, down wind of the great lakes, we get days at a time where we don't see the sun in the winter - I would have to have every square inch of the house roof, the garage roof, the chicken house roof, etc., etc. covered with solar cells , to have enough electrity during this period.  Only makes sense if you have loads of cash sitting around and don't know what to do with it!  That is ONE problem that I do not, and will not, have, for the forseeable future!! <grin>

Regardz,

Wayne Stayton

[LowGear]

Aloha Wayne,

One word can tell you a lot about a persons orientation.  Here, the sun goes beyond 90 degrees for a few weeks in June.

I'm pretty sure that the excess KWH accounting time is accounted annually.  It's determined in most areas by the state legislature or regulatory rules. 

I would have to have every square inch of the house roof, the garage roof, the chicken house roof, etc., etc. covered with solar cells

Hence my question about the 145 watt PVs.  Right now I see 70 Watters going for $1.20 or so a Watt out of California.  But my 15 panel 3,450 array would require 49 * 70 Watt panels.  Even though they're 2/3rds the sized that'd still be a lot more roof required than I have available.  Twice the space cost without counting mounting hardware, installation and copper.

Aloha,

There's that word again.

[Crofter]

A few folks who cannot shovel the snow entirely off their solar arrays are not too happy with their return on investment. A big rack of panels is necessary to support even a modest electricity dependance at 46 Deg. N.

Roof mount is cheaper and appears like a quick and easy place to park solar panels. Not so good if you are in a heavy snowfall area. Panels are much more efficient if you can tip them up to vertical to dump the snow off; otherwise near zero output. 

[mike90045]

XW6048 is fine with AC 1 (grid ) un connected, and AC 2 (generator) connected to  ....  a generator.


2" of snow, and my panels were at about 60% of normal !!  Then they warmed up, and the snow slid off - just gravel under them.

[Crofter]

XW6048 is fine with AC 1 (grid ) un connected, and AC 2 (generator) connected to  ....  a generator.


2" of snow, and my panels were at about 60% of normal !!  Then they warmed up, and the snow slid off - just gravel under them.

If you are in a heavy snowfall area and cold temperatures the snow doesn't slide off of a roof unless it is quite steeply pitched. We quite commonly have to shovel several times a winter even without panels on the roof. The south shore of Lake Ontario is famous for their winter snows.

Output drop from a given percentage snow cover will vary depending on panel type and connection layout. Partial shading can be a source of disappointment. 

Lots of newly minted installers the last few years with the all the incentive programs and they are sometimes not the best people to take advice from. As always, caveat emptor

[LowGear]

I went with a SunnyBoy 6000 because when I contacted Xantrex about the XW6048 system I was informed that the generator hook-up was for battery charging only and the inverter was not designed to move 3KWH through to the net tie syncing section of the inverter.  I'm beginning to suspect I talked to the wrong "expert" at Xantrex technical support.  SMA has much better support here in the islands than Xantrex.  (Some being better than none.)

Hey mike90045

Then they warmed up, and the snow slid off - just gravel under them.

Did you see the reply a few months ago where the fellow got better winter output from his panels while they were leaning up against his shed in the winter than on the roof.  His theory was reflection off the snow covered concrete pad they were setting on. 

Casey

[bschwartz]

    "................south shore of Lake Ontario is famous for their winter snows"

I went to college at SUNY (not sunny) Oswego.  I made parole in '91 with my BS in Technology Education.

I couldn't wait to get out of that God forsaken cold, overcast, snowy, wind tunnel of a place.

I now reside in Southern New Mexico

[WStayton]

  I'm in a location where snowfall should be less of a problem than it is for folks nearer the lakes.  We have gotten about 48" so far this year which is pretty paltry compared to Syracuse's 190" or so!

 I'm planning on mounting on the roof with a slight incline, relative to the roof, to achieve a better performance in the winter at the sacrafice of a little performance in the summer.

 I fully expect to do a little snow burshing from time to time! <grin>

 I AM glad to learn that the Xantrex inverter won't care that I'm not hooking it to the line - I would think that that information would be available somewhere in Xantrex's website, but I could find absolutely nothing.

[LowGear]

Yo Bret,

I'm sure if it wasn't for that fantastic solar window there in New Mexico you still be back in beautiful down town Suny.  Me too.

But to digress back to inverters. 

Is there someone out there that is actually passing generator power back to the grid?

Casey

[bschwartz]

Casey,
I was backfeeding the grid from a 48v power supply (27 amp) through my GVFX-3648.  The PS was of course being fed 120v from my 6/1 
The PS is having issues right now, but it did work for a while.

[deeiche]

rm /