Grid tie inverters, a million and one questions

[jens]

removed

[captfred]

Hi Jens - don't have much to offer, but I'll do the best with what I've got

Ive an Outback VFX3524M (non- gridtie), continuous integrated into my home electrical for over 3 years - not one hiccup - tropical temperatures and humidity (today it's 90%) - not that it applies to your situation but I think it says something for quality.

The unit samples the grid power and if it is outside user set parameters it switches over to battery/inverter until power is back into normal range, when that occurs it then over back over to  grid power and the charger takes over and tops off the batteries.  Works just fine with my roid power too - with all our power outages (sometimes 3hours at a pop - 3 times a day) the roid has been doing a lot of the battery charging  - again mine is not grid-tied - but a friend is on occasion doing the same thing with his roid and grid tied Outback - more as a last resort emergency during extended outages.

He's got solar panels feeding his outback - when the grid drops out due to load shedding, no problem - still has power in the house running off the batteries being charged by the panels.

My guess on the recommendation to not use a generator -  if you're producing excess dc from solar wind etc the grid-tied units may want to sell to the grid, or in this case your generator - kinda bad for your generator.

Unfortunately, the only way for the grid tie inverter to put  juice back into the grid is if there is a surplus of power on the dc side - thats where that  big dc alternator would be nice (one reason I went 24volt instead of 48)

Don't know where Xantrax is but Outback is in Arlington WA, not too far south of the border- might be worth a trip - doubt they'd give up a service manual - but maybe a personal inquiry at their doorstep might help.

Hope you find something helpful, Good luck, Fred

[Tom]

Hi Jens,

In addition to the Outback inverters I also have a Trace SW2515 inverter, but no experience with newer xantrex technology. In answer to your first question both systems pass generator power straight through to the loads and any extra power, below the set points, goes into the batteries. So any voltage/frequency changes will be passed through to the loads, unless they are outside the inverter set points. In that case the inverter cuts off the generator power and switches to battery power.

As to your second question the answer is similar to above. If the grid goes outside of the inverter parameters the inverter cuts off the grid power and switches to battery power. In the case of the SW if the batteries get low it will start the generator to charge the batteries. When the grid comes back on the SW will shut down the generator and charge the batteries from the grid.

I hope that answers your questions. 

[mike90045]

The Xantrex (Canada) XW's have 2 different, 240 V inputs.  1 for Utility(Grid)  power (60.000HZ) and one for
Generator power 55-65HZ + -

I believe that when Grid fails, and generator is running, it will try to track the varying FQ of the Generator, and Pass-Thru power, till the genset voltage droops, and then it will attempt to "boost" the voltage. Otherwise, it will float charge the batteries.  This is all programmable by the user.

If no AC source, the inverter fires up to keep your loads happy, and runs off the batteries. You could use a generator to recharge the batteries at this time, as there is little "power quality" checking from the battery feed, only on the AC inputs (2)

 Disclaimer - I don't have one, but this is what I've gleaned from the solar forums.

http://www.xantrex.com/forum/default.asp
offices: http://www.xantrex.com/web/id/6/corp.asp
XW manuals  http://www.xantrex.com/web/id/1858/docserve.asp
http://www.xantrex.com/xw/

[MacGyver]

I am surprised that I didn't get more of a response on the issue of service manuals. I would have thought that in this group of self empowered people the subject of service manuals would have come up before. What happens if Outback or Xantrex close their doors and your equipment fails ? What happens if there is a major economic 'thing' happening and you are unable to ship the inverter to get repaired? I suppose you can always switch to raw generator power .... stilll ....

Jens,
I don't know the REAL answer to this question, but having spent a little of my life fixing electronics for a living and having seen the trends over the last few decades.... I'm gonna guess that very very few "modern" inverters are going to come with full schematics of the innards, and even if they did you probably couldn't buy the parts and if you could you'd need to be set up to work with a lot of itty bitty surface mount hardware. 

Most of the circuitry in stuff like that is proprietary these days. Most of these companies don't share their internal schematics with the public. Many of the key parts are likely to be special items, designed and built and programmed to spec specifically for that particular product.    Not likely to be found at Digikey, or Mouser, etc....

Some of the larger parts like the MOSFETS or IGBT's or whatever they use these days to switch the "big power" may be replaceable by mere mortals, but most of the electronics these days will likely be tiny little surface mount parts that require a bit of specialized equipment and skill to deal with (not saying you don't have it already) and parts that are not always readily available.

This ain't the 80's any more, and "through-hole" components are dead... if you aren't set up to do SMD then you're going to have a tough time repairing most modern inverters.

Don't get me wrong...  it can be done. I'm moderately well set up to do surface mount components and for all I know you are too. But if you aren't I'll bet you have a bitch of a time changing parts.

I doubt you can get full schematics anyway.

Just a guess. I'm probably wrong...

[t19]

Yeah I in an earlier life, designed computer rooms.  I wrote my spec so Liebert and Powerware could not be installed.  They are crap, like a Lada or a KIA.

If you can get an old Digital Equipment UPS or an EPE UPS you have the best of the best...easy to work on, and output power that on a scope looks better than Hydro.

[MacGyver]

Jens,
I understand the desire for schematics. You're preaching to the choir here... I think EVERYTHING should come with complete schematics (and part numbers). 
But almost nothing does anymore. In part probably because someones lawyers suggested they shouldn't for assorted liability reasons. In part because they just don't want to share all their "latest and greatest" technology with competitors or wannabe hackers.
And since most everything is surface mount anyway, and 99.99% of there users aren't going to be able to repair it with their trusty old Weller iron, what's the point in making schematics available?
It doesn't do them any good to have people mucking about inside the equipment. It's much better for them to have you send it to them for repair. Why would they want YOU to have schematics? That can only be a liability for them... 

I loved the 70's and 80's when a lot of equipment came with decent schematics.
Now it's all surface mount, and usually a custom processor surrounded by a few custom designed peripheral parts, and very little identifiable/obtainable/replaceable parts. And never schematics available. I'll bet it's been easily 10 years since I bought any kind of electronics equipment that had schematics readily available. (I've repaired lots of it anyway  )

I finally had to set myself up with a SMD hot air rework station and a custom made (DIY) reflow oven so I don't fear the surface mount devices so much anymore, but it's definitely become much harder to repair equipment than it ever used to be. No schematics, unmarked or house marked parts, custom designed proprietary parts, 132 pin BGA package IC's on a 6-layer board and you can't possibly replace it without mass destruction...   aaargh!!!
Ahhhh... sorry... I was having one of those flashback moments...

Anyway, I sincerely hope you find a good quality inverter that suits your needs AND has full schematics readily available. If you do, please post the make/model# here, because that's the one *I* want to buy too!
I would love to be proved wrong and find that some manufacturer still has balls enough to make good schematics available to consumers. Please keep us posted.

FWIW, most surface mount parts aren't all that bad to work with if you have a hot air station and a small reflow oven. I've got a project underfoot now that puts about 15 IC's and related parts on a patch of circuit board about 1 inch x 1.75 inch. The lighting (LED) controllers I'm using come in a 20 pin TQFN package (which isn't particularly small). Here's 4 of them on a US dime. Note that all the leads are on the bottom. Can't touch 'em with a soldering iron. Can't even see 'em or get a meter or scope probe on the pin when troubleshooting.
http://www.weirdstuffwemake.com/sweetwatergems/geek/images/smd_026.jpg

[mobile_bob]

i would be shocked and surprised if you get a schematic from any inverter manufacture,
i have tried believe me!

even the parts that have manufacture p/n's on them, try and call the manufacture vendor
and you will get the same, "we built that for abc inverter company 20 odd years ago, and cannot release info on any parts we sold them"

i got that recently on a pair of transformers from an inverter that was 15 years old.

or how bout this

i have a exide 15kva 3phase ups, i called exide and while they don't make or support them anymore they will sell me a manual,, cool 

1800bucks!!! ouch!!

so effectively you likely ain't gonna get any detailed info from the manufactures, unless you are a licensed/approved repair facility, and even then i have found that some of the info is not even provided to them,, they have to change out complete pcb's if there is a problem.

rat bastards anyway!!

lol
bob g

[MacGyver]

I'll bet 99+% of the companies making inverters won't sell you parts or schematics. At least Xantrex is up front about it enough to tell you on their website...

[Stan]

You'd better be careful Jens, running into the grid with some freaky frequences (say that 5 times fast)  might just flow back to the mainland and really mess up those poor people in White Rock with their new high tension lines running over their bedrooms.
Stan

[Jim Mc]

... I would like to sell the excess to the local utility company...

I've ruffled feathers before asking this (and that's not my intent); but I'm curious.  Why?

Do the economics of selling to your utility really make sense, or is it just an interesting project?

[mobile_bob]

i am very curious to understand the logic as well??

bob g

[Jim Mc]

...I want to have emergency power backup.

Understood.  Listeroids make decent prime movers for a standby set.

...Something to tinker with, something of an old area where tinkering was still allowed...

Yes Yes Yes.  Get one for this reason alone.  Don't spend another minute trying to justify the purchase.

...in this day of rising fuel costs, when heating your house is starting to cost a small fortune, the idea is to utilize all the waste heat of the engine. This last goal is a bit elusive...

OK, here's the sticky part.

Can you get me 'calibrated' to your situation?  For example, what price do you expect to receive for energy sold to the utility?, do you know the devilish details about selling into your grid? What size Listeroid are you planning?  What's your house's heat requirement?  What expectation do you have about the operating lifetime of the Listeroid?  And what is the true cost of that waste oil you'll be collecting, storing, and filtering?

Am I saying 'it won't work'?  No.  It's just that every time I've worked the numbers in my case, it hasn't...  But my utility is pretty stingy when it comes to buying back energy.

Some numbers for you:  According to Ronmar's recent post in this forum, a fully loaded 6-1 consumes about .35 gph and produces about 3kW.  That .35 gph equates to a heat input of about 50,000 BTU/hr, and with 3kW of electrical output equating to about 10,000 BTU/hr; there's 40,000 BTU/hr of waste heat available to be captured (how much of that is actually captured is another story), but I'd guess it's in the range of 60%, unless you plan to put the engine in a heated space, in which case it'll be closer to 80-90% (again, a guess).

[SteveU.]

Hello Jens
Reading your very well stated reasonable goals, and your well thought out understanding of your situational requirements I could not help but be struck how similar they are to Scotts in Connecticut.
If you haven't already you might review his posts. He's been working toward netmetering and cogeneration for several years now.
Yours has been one of the best posts of intentions I've read so far.

SteveU.

[oliver90owner]

Jens,

I am wonderinfg if you still lose about 40% of your power (battery charging, discharge, inverter, etc) with the energy going out as fast as it goes in (to the battery)?  Presumably a DC charger improves this problem?  Just wondering about the economics of grid feeding, that's all.

Regards, RAB