Author Topic: "Conventional" Inverters Vs Enphase Inverters  (Read 7476 times)

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freejuice

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"Conventional" Inverters Vs Enphase Inverters
« on: July 23, 2011, 05:30:26 AM »
Hi Folks since my magic smoke incident with my aims inverter...I will soon be switching over to an outback for the wind turbine...thanks  everyone for all the help on that one!

Since I live in sunny S.C. I will be soon adding my solar system too for grid tying.

So my question is:
Does anyone have any opinions....pro or con on conventional grid tying inverters (such as SMA & Outback) Vs the Enphase inverter?

Some of the pros I see in using an outback is that I can tie my wind turbine and solar together with my battery and grid tying combination, yet with the enphase, I see grid tying and somewhat of a seperate system issue untill it goes into the main breaker panel....along with less cabling issues in regards to heavy DC cables.

As a side note, I have a work shop behind the house which is also grid tied and one side of the metal roof is practically facing solar south, so it would be a good candidate for a roof mounted system....not a big fan of roof mounting,.... as Ghurd pointed out once, a hot roof is h-ll on panels. However I could have either type of inverter loacted in my building and then run a much less expensive AC line underground back to the house....with the properly approved grid tying measures in place  

I like the idea of the enphase system...its plug and play and easy to add too as I grow the system, but each inverter is about 175 bucks or so....but the math almost stacks out the same in regards to system size and inverter cost.


 Am I missing anything here.... does anybody see any pros or cons in one inverter vs another?????
 Thanks,
 Gavin
« Last Edit: July 23, 2011, 05:33:32 AM by freejuice »

ghurd

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Re: "Conventional" Inverters Vs Enphase Inverters
« Reply #1 on: July 23, 2011, 06:04:52 AM »
Am I up too early, or are you up too late?

Lets say you have 20 PVs.
It is hot out (reduced output), a bit humid (reduced output), a bit of dust and grime on them too (reduced output), and the PVs are a few years old.
But it is a pretty good day for solar power, over all.
The output is 20% less than you expected, but with all the factors to reduce the output, you are not surprized.

Or maybe 4 (20%) of the mini-inverters are blown?

Even if you think an inverter or 2 or 6 may be blown, how long will it take to figure out which work, and which do not?

Would you EVER notice if 1 or 2 blew up 2 days after the install?
That is a sugnificant % of money/labor/parts not doing anything for the next 25 years.
I suppose the same could be said about a PV failing, but that does not negate the inverter issue.

If the cost works out the same, I'd go with a single unit.

You might be missing the input voltage ranges too.
The bigger units take higher input voltage?  More efficient overall?  Save some money on wire runs and hardware?

I would like to change my 'hot as h-ll' remark to 'hot as OH'.
Seems like the winters are colder longer and the summers are hotter.
Probably nice and cool down there in SC.
G-
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ubud

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Re: "Conventional" Inverters Vs Enphase Inverters
« Reply #2 on: July 23, 2011, 10:04:46 AM »
I opted for the enphase system.
1. because It's one inverter per panel.
2. No high voltage series string, IF you loose a panel, or the single inverter you are out of production till replaced.
3. If you opt for the envoy, you can tell at a glance on your browser if a panel, or inverter is NOT working.
4. pricing, Overall system prices are about the same.

Now my system is only 1 week old, 29 panels 15 M190 inverters 7 M380 (duel) inverters, a mix of panels
From 180W (13), 220W (10), 230W (6)
Yes it's a mix of available parts, that took me over a year to put it altogether, but at this point in time
I'm happy with it, 1 week old and 108KW collected so far.
Just an aside, make sure you get the proper trunk cabling for your inverters if you go this route.
Frank   

freejuice

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Re: "Conventional" Inverters Vs Enphase Inverters
« Reply #3 on: July 23, 2011, 11:10:38 AM »
Hi Frank,
 Two questions....explain the trunk cabling to me...is this a wire /voltage gage size?
As Glen mentioned, I could have an inverter or two to blow and never know about this and  it would eat into my produced watts, however you mention the envoy.....how much is the envoy monitoring system?
 .....It looks like I need to do a bit more research here.

Glen, its hot...other than the vegetable garden I hate the summers!
I have seperate grid power ran to my man-cave/ work building behind the house,...that is to say I have two power company meters on the property....one on the house and the other on my outbuilding.... The outbuilding has a standard 200amp service panel...so does the house.....but my out building is a perfect place to hang my panels, so to cut down on DC cabling runs I would like to produce the power at the outbuilding and send it to the house as AC current....but grid tied at the house for net-metering.

I use very little power in my outbuilding each month....the power bill is about 14 dollars a month....I think they have a flat base fee even if you dont use a single watt during the month!

However the power company says I can net-meter two ways: first, I can do a KW for KW exchange rate, that is to say, if I use 600 kw one month from the grid and I produce 600 kw well I break even! This appears to be the best way to go....
 
The other method is they buy it back from me at wholesale rates which is about 4-5cents a KW, so I doesnt really help me to grid tie a solar system at the outbuilding's meter...I would be far better off grid tying it to the house, But if I can produce it at the outbuilding while avoiding heavy DC cabling runs it would be a perfect situation for me.

Years ago when I built that outbuilding, I had no intentions of mounting solar to it but the way I placed the building's layout I simply got lucky by having it facing almost true solar south.
  While I essentially have discovered  my outbuilding is the perfect "rack" in place I guess I should not squabble too much about some DC cabling costs....

 LOL, darn, I've just about confused myself on this on so far...if anyone can understand what I was just saying there...wow!
 Gavin
« Last Edit: July 23, 2011, 11:14:22 AM by freejuice »

Phil Timmons

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Re: "Conventional" Inverters Vs Enphase Inverters
« Reply #4 on: July 23, 2011, 11:28:56 AM »
We are mixed on the choice, as well, and we do some Serious PV installs.

So far only using the larger "string" inverters, or what you are calling "conventional."  As far as money price end of things -- all the systems keep chasing each other down in price.

As far as "long DC runs."  We tend to place our inverters very near or typically on the PV array rack.  All tend to be NEMA 3R rated (outdoor, raintight).  That allows use of the DC disconnect, combiner and fuses that are built right into the inverter, with no additional equipment.  The longest DC run comes out maybe ten feet from the end of the panel array string to DC disconnect terminal in the inverter.

AC power from the inverter to AC service (or panel) is ran as an AC Feeder, with wire large enough to cover any voltage drop issues.



 

freejuice

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Re: "Conventional" Inverters Vs Enphase Inverters
« Reply #5 on: July 23, 2011, 11:51:14 AM »
Hi Phil,
Thanks for the info. What kind of outdoor NEMA class inverter would be good in that kind of situation....SMA?
 Thanks,
 Gavin

Phil Timmons

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Re: "Conventional" Inverters Vs Enphase Inverters
« Reply #6 on: July 23, 2011, 12:44:06 PM »
Hi Phil,
Thanks for the info. What kind of outdoor NEMA class inverter would be good in that kind of situation....SMA?
 Thanks,
 Gavin

I have used SMA in the past, and they are good equipment.

For that matter most of the major brands are all fine, so this mostly becomes a case of optimization and personal taste, along with on-line monitoring choices (if you want to do that), that the various breeds and brands have.

At the volume we are doing now, cost and ease of install has become important.

We had been using mostly PV-Powered inverters up until this Spring.  But have switched to Solectria.  I can tell you why that choice was -- The Solectria weight (about 70 lbs, irrc) is about 1/2 of the PV Powered or SMA. 

That means one guy can easily handle a 5000 watt inverter (our typical) without injury or risk of damaging the equipment.   The Solectria has internal DC fuses with the internal DC combiner for sites that require it.  And at the time of our last buy, Solectria had the price lead. 

Next batch, dunno.  We get the stuff (inverters and panels) by the semi truck-full.  The business folks are doing equipment and pricing reviews, now.  I do the technical review before the orders get placed.

But for whatever you are considering, start with your DC watts.  That can be limited by some combination of your area to work with, utility rebates that are usually tied/scaled to your present use, and your budget. 

Those DC watts will combine in some collection of panels (aka Modules), which when you add them up, will then come out as "strings" or circuits of the panels.  Most of the inverter and panel manufacturers have some sort of "string calculator" on line to check yourself on that part.  From there, you match the inverters' sizes and AC voltages that match your site, and start optimizing for price and performance.





ubud

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Re: "Conventional" Inverters Vs Enphase Inverters
« Reply #7 on: July 23, 2011, 02:24:33 PM »
Gavin
Trunk cabling, On the M190, built with the inverter. On the M380, has to be bought separately. On the M215 (newest) Separate.
Envoy, the monitoring part of the system. Caught mine on ebay $200.
?'s for you
How large a roof facing south? Think # of D.C. Watts you can place there
How far from the house service panel, Think % of voltage drop, size & costs for cable, ect.
Can you get latitude angle on that roof?

I've been researching different systems since 2007, and ended up with what I have, watching were I bought as the monies
were there.
One other + for the micro inverters is you can add to it later, with a string system, its all right now.
Go to Do it solar website and look at Gary's system, haven't got mine documented yet.
Frank     

freejuice

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Re: "Conventional" Inverters Vs Enphase Inverters
« Reply #8 on: July 23, 2011, 09:36:51 PM »

Hi Phil I have not heard of the Solectria inverters...I need to look into those.....recently a radio ad has been played locally looking for emplyees in the neighboring city of Greenville SC, for people to build PV inverters...it a German company which has been around here for years...Prettle Electric.....They are also big into automotive, making wiring harnesses etc etc. since there is a BMW manufacturing plant here nereby.


Hi Frank,
Thanks for the information!
 The roof has about a 4-12 pitch...which trigs out to be about 18 degrees and 25 mins.
 The roof area which faces solar south is approx 11 feet by 35 feet...I think I could comfortably get 20 panels on this area?
 From this area's closest corner to the house service panel is about 75 feet, if I bury the cabling in underground conduit and ....go underneath of through the house foundation and enter from the bottom to the service panel.
 However I do have the room to sit the panels off the ground closer to the grid meter on the side of the house and cut the panel reach to the inverter to about 30-35 feet.
 If I went this route I would have to build the rack system...probably out of 6x6 treated lumber and use a rail system like some use from angle iron.....this would as ghurd mentioned some time ago allow more air flow to keep them cooler...lol if that's possible in the SC summers! However if I build the racks I could also hit the proper angle the panels need to be situated on if my current situation is not close to the proper roof angle.

Questions:
How is the enphase system grid tied? I went to their web site and that information was kind of murky... apparently its passing code in other parts of the nation, however if I go that route I need to be sure I can pass code here in my region...not that we are anything different from the rest of the nation...but just needing to be certain. If I go this route I would like to present this to the building inspector so as to be certain before any purchase was made.

Lastly, I like the idea of being able to see your output on a daily weekly or monthly basis, but can this be done without reoccurring fees?

 Thanks,
 Gavin

freejuice

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Re: "Conventional" Inverters Vs Enphase Inverters
« Reply #9 on: July 24, 2011, 07:18:21 AM »
Frank, Ok I found Gary's system and it appears to be easy enough to install....one last dumb question...I feel sure they disconnect when the grid goes down.....But to be certain and code compliant, I've got to ask....does it?
 Thanks,
 Gavin

ubud

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Re: "Conventional" Inverters Vs Enphase Inverters
« Reply #10 on: July 24, 2011, 09:08:58 AM »
Gavin
Google Enphase White Papers, LOTS of information. my stack of printed PDF's Is bout 3/4" thick.
The only part of the NEC I missed was the array, Lowest part of 240 vac cabling, was at 7'9" Code says 8'
had to dig down under lowest point to get clearance.
the array is 50' long and back side is 14 ish ' high
The enphase inverters ARE CODE COMPLIANT
Grid interactive is accomplished by back feeding a suitable breaker in your service panel, just pay attention to cable
length, % of voltage drop, size of  conductor ,ECT.
My envoy is not web tied, it still shows me System production, what is being produced (right now heavy cloud cover  235W)
It also lists all (22) of my inverters, and weather they are active or not. If this is enough info for your needs........no fees.
This connection is an Ethernet cable plugged into my puter, and looking at its ISP address, each unit has its own addy.
YES they do shut down with grid failure, mine take less than 1 second to do so, and Wlii not come back up for 5 min.
after a GOOD grid is found.
Try and get friendly with Your inspector person, ask ?'s, gather All pertinent information, but hay you already knew that.
Frank 

Phil Timmons

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Re: "Conventional" Inverters Vs Enphase Inverters
« Reply #11 on: July 24, 2011, 12:05:46 PM »

Hi Phil I have not heard of the Solectria inverters...I need to look into those.....recently a radio ad has been played locally looking for emplyees in the neighboring city of Greenville SC, for people to build PV inverters...it a German company which has been around here for years...Prettle Electric.....They are also big into automotive, making wiring harnesses etc etc. since there is a BMW manufacturing plant here nereby.

Germany, in general, is way ahead of US. 

California leads the US, and here is their list -- most of US across the US use them as the Go-To information source.  >>>

http://www.gosolarcalifornia.org/equipment/inverters.php

For TMI, wiki has a fair background on Grid-Tie Inverters >>>

http://en.wikipedia.org/wiki/Grid-tie_inverter

Quote

 From this area's closest corner to the house service panel is about 75 feet, if I bury the cabling in underground conduit and ....go underneath of through the house foundation and enter from the bottom to the service panel.


Might need to have a labeled knife blade lockable disconnect in there, as well -- Check with your utility, and inspector.  They usually speak in a 1-Line diagram.  You are familiar, or no?

Quote
However I do have the room to sit the panels off the ground closer to the grid meter on the side of the house and cut the panel reach to the inverter to about 30-35 feet.
 If I went this route I would have to build the rack system...probably out of 6x6 treated lumber and use a rail system like some use from angle iron.....this would as ghurd mentioned some time ago allow more air flow to keep them cooler...lol if that's possible in the SC summers! However if I build the racks I could also hit the proper angle the panels need to be situated on if my current situation is not close to the proper roof angle.

There are some long-term corrosion / dis-similar metal issues to consider.   Steel and Aluminum in direct contact are not usually considered such a good long term plan.  Galvanized and Aluminum are generally considered ok, if not near the coast, and the top-end uses Aluminum mounting frames to hold the Aluminum framed panels.   The commercial ones double as the grounding system, as well.

Some areas also require building permits (in addition to electrical) for structures and mounts.


Quote
Questions:
How is the enphase system grid tied? I went to their web site and that information was kind of murky... apparently its passing code in other parts of the nation, however if I go that route I need to be sure I can pass code here in my region...not that we are anything different from the rest of the nation...but just needing to be certain. If I go this route I would like to present this to the building inspector so as to be certain before any purchase was made.


For TMI, their manuals all have connection diagrams . . .

http://www.google.com/search?rlz=1C1GPEA_enUS364US364&aq=f&sourceid=chrome&ie=UTF-8&q=enphase+install+manual

Agreed you should speak to your local inspector, in advance.  We find they typically have concerns with the overall system grounding and array grounding.  When you consider that you/we are putting a lot of metal framing up in the air, that may be insulated from ground by being mounted on a wood building (aka, an un-grounded lightning rod), this a very good thing to do correctly.  We can do those details on here, as well.

You may want to take along (whatever breed and brand) the UL 1741 / IEEE 1547 certification.  Those are the specification(s) that show the equipment will automatically disconnect if the grid is lost.   Your power company will want to see that, too.

Chances are there are some special requirements from your utility, as well.  When you have complied with their requirements, it usually ends up with a "interconnection agreement," that spells out your responsibilities to be a grid-tied producer.  Most utilities now have a set go-to person who are specialists on dealing with folks like us.

Quote

Lastly, I like the idea of being able to see your output on a daily weekly or monthly basis, but can this be done without reoccurring fees?


Most of the inverters have their own local display of some sort.  When it all goes on-line, lot of different deals.  The on-line systems vary.  Lot of games in this regard. 

Solectria plays like things are free -- but the on-line portion needs a paid account.  PV-Powered -- the hardware is about $200, and then on-line to their site is free.  Sunny Boy (SMA) has some hardware you buy, and then I think their on-line is free.  Overall, I am not too happy with any of them.

Looking at building our own hardware (current transformer and potential transformer / energy monitor) and then bringing the data into our own website.  Since we will be able to tell much more detail from doing that, it looks like we can use it to tell when there is some array or inverter problem in the field -- even way before the customer notices.

Did not see you ask about REC (renewable energy credit) metering, nor the Lock-Out service disconnect, yet.  You already familiar with that part, or should we cover it?






freejuice

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Re: "Conventional" Inverters Vs Enphase Inverters
« Reply #12 on: July 25, 2011, 08:16:56 PM »
Hi Phil, Thanks for the detailed reply.
 Also thanks for the UL certification number for grid tying...that really helps alot!
After some research I have discovered that enphase is doing away with the paid portion of Enlighten....or web monitoring.  It appears customers will now have it for free....good deal.

From what I have discovered the Envoy monitorig system simply plugs into a recepticle and everything goes from there....neat stuff, it can provide feedback on power generated without a dedicated line. If I wanted to monitor the stats on the web, I could simply attach the envoy to an ethernet cable, hooked to my modem....amazing!

However one thing that really sells me onto the enphase micro inverters, is that their latest  215 model has a 25 year warranty....the same as the panels! This is the selling point which really carrys me over the top with enphase.....I dont know another inverter with that kind of warranty...they even go as far as to supplent to lost power you inccur from a down inverter for the maximum of a month at .20cents a kw.

 It appaers to be easy to install....Its is truly a plug and play system.


I have spoken to my local building code folks and they say I do indeed need the knife disconnect nearby the meter base, so the power company can disconnect the PV if necessary.....got one on order

 Thanks for  the heads up on the two dis-similar metals....I knew about that kind of reaction, but  forgot all about it in this situation.... duh! So I will stick with a good aluminum rack system...something made for solar panels!

wiboater

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Re: "Conventional" Inverters Vs Enphase Inverters
« Reply #13 on: August 24, 2011, 06:39:08 PM »
As far as that knife switch , You shouldn't need one with the Enphase inverters. Just turn off the  AC breaker. If you have to disconnect the DC going into the trunk cable you'd have to disconnect the MC4 connectors at the panels.  I just installed 2 enphase and ordered 2 more for my 4 panels. Haven't got the Envoy yet but planning on getting it. A guy by the user name of "Micheal 1970" on You Tube has a video comparing Enphase inverters to the Sun inverters. He gets about 40% more production out of the Enphase setup.