Too many Panels
Copperking
Registered Users Posts: 17 ✭
Well-
I was ready at my County Building Department. Then as I computed the final numbers I noted that my 7 strings of 3 Evergreen 200 ES-E Panels was going to come in at a Temp Compensated wattage of 4216 watts. My Outback 3648 has a Max of 4000.
Originally I figured that the 80% loss coupled with a few other losses would get this number under 4000 watts.
But the Building Dept looks at the total so I seem to have little choice but to drop three panels and use them on my phase 2 expansion.
My question is: in real life will I actually ever exceed that 4000 watts or am I just asking to smoke the Inverter?
I also considered putting up the extra 3 and just tripping the breaker in the combiner box if the data from the Mate looks too high. If it stays off more than on I can just take them down. But I just hate the idea of storing 3 panels in the Garage.
Any Ideas?
I was ready at my County Building Department. Then as I computed the final numbers I noted that my 7 strings of 3 Evergreen 200 ES-E Panels was going to come in at a Temp Compensated wattage of 4216 watts. My Outback 3648 has a Max of 4000.
Originally I figured that the 80% loss coupled with a few other losses would get this number under 4000 watts.
But the Building Dept looks at the total so I seem to have little choice but to drop three panels and use them on my phase 2 expansion.
My question is: in real life will I actually ever exceed that 4000 watts or am I just asking to smoke the Inverter?
I also considered putting up the extra 3 and just tripping the breaker in the combiner box if the data from the Mate looks too high. If it stays off more than on I can just take them down. But I just hate the idea of storing 3 panels in the Garage.
Any Ideas?
Comments
-
Re: Too many PanelsCopperking wrote: »Well-
I was ready at my County Building Department. Then as I computed the final numbers I noted that my 7 strings of 3 Evergreen 200 ES-E Panels was going to come in at a Temp Compensated wattage of 4216 watts. My Outback 3648 has a Max of 4000.
Originally I figured that the 80% loss coupled with a few other losses would get this number under 4000 watts.
But the Building Dept looks at the total so I seem to have little choice but to drop three panels and use them on my phase 2 expansion.
My question is: in real life will I actually ever exceed that 4000 watts or am I just asking to smoke the Inverter?
I also considered putting up the extra 3 and just tripping the breaker in the combiner box if the data from the Mate looks too high. If it stays off more than on I can just take them down. But I just hate the idea of storing 3 panels in the Garage.
Any Ideas?
1. You will rarely if ever get the full rated output from the panels. Your best output will probably be a solar noon on a very clear, cold, winter day.
2. Having a panel array capable of more power than your Inverter can handle will usually just result in the inverter choosing to operate at a lower power point from the array. But check the specifications of you GTI (or CC for off-gridders) to see what they list as the maximum panel wattage you can connect. It will always be greater than the nominal power of the unit.
3. Using an inverter or CC rated at less than the panel output is common, and the effect is called "clipping". Usually the panel power "wasted" by clipping will be far less than the power you gain by getting closer to the max from your array under less than ideal conditions (more current on partially cloudy days and during low sun hours.)
4. If you are talking about the GVFX 3648 (Hybrid Grid Interactive Inverter-Charger), the only power figures in their specifications (that I could find) are the AC output specs, and those have no direct relationship to any DC input limitations. Excess panel power will either go to the batteries, if they can take it, or will just not be used and will not be drawn from the panels. If the AHJ has problems just comparing numbers, you may have to find a way to explain it to them.SMA SB 3000, old BP panels. -
Re: Too many Panels
You are cheering me up.
Yes this is a grid tie GVFX 3648.
I ran the set up through Outbacks String Tool and at the addition of the last string got ---Array Wattage more than Charge Controller output.
The FM 80 says it will accept 5000 watts. So how does that compute?
I ran several other panels and chargers and came up with the String tool always giving that message when its recomended array wattage was exceeded. G in G out.
So I still have to assume that the Inverter is the limiting factor at its limit of 4000K.
As for that clear, high and cold. That is me, 9200 ft Colorado and due south.
To get this past the Building Dept I think I will drop the 7th string from the Calcs and just keep an eye on the data and if it looks right add that string later. Is there any reason I couldn't just leave the string on the roof but flip the breaker off in the coldest part of the Winter? -
Re: Too many Panels
There is absolutely no limit to the number of panels you can use with an FX3648, whether grid-t (GTFX) or not. This is because the panels do not power the inverter, they power the charge controller(s) which recharge the battery bank that powers the inverter. Regardless of the size of the array and/or battery bank the inverter is only capable of 3600 Watts output. You could over-size it by a factor of 2 and not have any problem. You would be able to produce power to sell on a cloudy day.
If this were a standard GTI it wouldn't matter either, as any panel capacity beyond the inverter's output is simply not utilized. The only way you can get in trouble here is if the array Voltage exceeds the inverter's input maximum. Then it will turn off due to "over Voltage".
If the Building Department told you to lose three panels it's just another example of bureaucracy not having an understanding of what it's doing.
Because it needs to be asked: what size battery bank do/will you have and what charge controller(s) are you using? If you've left them out of the mix the FX won't even function. And don't forget the MATE for programming the inverter; absolutely essential. -
Re: Too many Panels
At 9200 feet your 4200 Watt array will run about 83% efficient. That means:
4216 * 0.83 = 3499 Watts / 48 Volts = 72.9 peak Amps. The FM80 will have no trouble with this. Also, it means you can run a fairly sizable battery bank to keep things humming when the grid goes down: 730 Amp hours @ 48 Volts is up to 17.5 kW hours roughly speaking. -
Re: Too many PanelsCopperking wrote: »Is there any reason I couldn't just leave the string on the roof but flip the breaker off in the coldest part of the Winter?
If the inverter can be damaged by full output of your panels in cold weather, it can also be damaged in warmer weather by edge of cloud effects.
--vtMaps4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i -
Re: Too many Panels
Incidentally, your biggest concern with the array is not the Watts or Amps but whether the Voc of those panel strings will exceed the input max of 150 Volts on the FM80 when the weather goes cold. That could be a real problem. -
Re: Too many PanelsCariboocoot wrote: »There is absolutely no limit to the number of panels you can use with an FX3648, whether grid-t (GTFX) or not. This is because the panels do not power the inverter, they power the charge controller(s) which recharge the battery bank that powers the inverter.
Because it needs to be asked: what size battery bank do/will you have and what charge controller(s) are you using? If you've left them out of the mix the FX won't even function. And don't forget the MATE for programming the inverter; absolutely essential.
The GVFX 3648 includes an integrated Charge Controller, so in the absence of any other reason, there will be no other CCs in the mix. The Charger component in the 3648 has a maximum continuous DC output of 45 amps into a 48 volt battery bank.
I can't tell whether is it MPPT or just PWM, but it has a nominal DC input of 48 volts and an allowed range of 42-68 volts DC.SMA SB 3000, old BP panels. -
Re: Too many Panels
Who said FM80? .....Cariboocoot wrote: »... the input max of 150 Volts on the FM80SMA SB 3000, old BP panels. -
Re: Too many Panels
copper king
Are you sure the fm80 is good for 5000 watts. I did not read its spec sheet but did go to its forum and they were saying 4200 watts was a little higher then they normally recomend. I think as long as you string the pv in such a maner as to not exceed the voltage limmit of the charge controller even during cold whether you may be ok. I believe you can exceed the amp rating of the charge controller but when you do it will cut back on the current even further then what it is rated based on heat. It probly wont hurt the equipment but may not give you all your panels could make. Maby two charge controllers would be worth the money maby not. The inverters take from the batteries which always have more power then can be used instantly. I totally agree with the previous comments and thought I would add the voltage one for safety of your charge controllers.
Cheers
gww -
Re: Too many PanelsThe GVFX 3648 includes an integrated Charge Controller, so in the absence of any other reason, there will be no other CCs in the mix. The Charger component in the 3648 has a maximum continuous DC output of 45 amps into a 48 volt battery bank.
I can't tell whether is it MPPT or just PWM, but it has a nominal DC input of 48 volts and an allowed range of 42-68 volts DC.
Since when?
The difference between a GT FX and an OG FX is the programming. Neither has a built-in charge controller to handle solar panels. Both have built-in AC charging circuitry.
GTVFX specs: http://lib.store.yahoo.net/lib/wind-sun/GTFX-GVFX.pdf
Show me where it says anything about a built-in solar charge controller.Who said FM80?
The OP. Post #3 -
Re: Too many Panels
inetdog
I have the gvfx 3648 inverter and what you describe is the charge capibility of the inverter. You must still have a charge controller to handle the pv imput.
gww -
Re: Too many Panels
The mate and charge controller has been mentioned. You also need a hub to tie it together and if there are temp swings in your batteries you need a battery temp sencer. I also have the dc breaker box and ac sub panel for the inverter powered loads. Sorry if you know all this, just trying to help.
gww
cariboohoot
I hit enter and your post was all ready there. -
Re: Too many Panelsinetdog
I have the gvfx 3648 inverter and what you describe is the charge capibility of the inverter. You must still have a charge controller to handle the pv imput.
gww
It may not be ideal (or even very good), but you can just use the 3648 inverter if the panel/string output stays within the 42-68 volt range.
As a practical matter, you get a lot more flexibility if you use an MPPT CC to feed the Outback.
Note: Since GT inverters need local energy storage (1/2 cycle worth at least) to allow them to efficiently generate AC output with full peak current, the added expense of giving it MPPT capability too is low. For a PWM CC with appropriately sized panels, the marginal cost of adding MPPT circuitry is higher. I think that you are confirming that the 3648 incorporates just a PWM CC.SMA SB 3000, old BP panels. -
Re: Too many PanelsIt may not be ideal (or even very good), but you can just use the 3648 inverter if the panel/string output stays within the 42-68 volt range.
No. Don't do this. In the real world it will give far from satisfactory results.As a practical matter, you get a lot more flexibility if you use an MPPT CC to feed the Outback.
Especially if you don't get your batteries for free and want your system to stay working.Note: Since GT inverters need local energy storage (1/2 cycle worth at least) to allow them to efficiently generate AC output with full peak current, the added expense of giving it MPPT capability too is low. For a PWM CC with appropriately sized panels, the marginal cost of adding MPPT circuitry is higher. I think that you are confirming that the 3648 incorporates just a PWM CC.
This is not accurate. There is no solar charge controller in any model Outback inverter. -
Re: Too many PanelsCariboocoot wrote: »Since when?
The difference between a GT FX and an OG FX is the programming. Neither has a built-in charge controller to handle solar panels. Both have built-in AC charging circuitry.
GTVFX specs: http://lib.store.yahoo.net/lib/wind-sun/GTFX-GVFX.pdf
Show me where it says anything about a built-in solar charge controller.
The OP. Post #3
You got me there. :-)
I was extrapolating from the specification:DC Input Range 21.0 to 34.0 VDC 42.0 to 68.0 VDC 21.0 to 34.0 VDC 42.0 to 68.0 VDC Continuous Battery Charge Output 55 amps DC 35 amps DC 85 amps DC 45 amps DC
where the last column is the 3648. I just assumed that the DC input was going to be used for battery charging instead being the battery. My mistake.
I also just though that the OP was using the FM80 selection on the string sizing tool rather than necessarily having an FM80.
The string sizing tools do seem to ignore the strategy of using clipping as part of the design.SMA SB 3000, old BP panels. -
Re: Too many Panels
inetdog
Or you could just hook the panels strait to the batteries and then feed the grid, but if the grid goes down you smoke the batteries. I know of no panel that has a small enough voltage range during temp swings to meet the inverter voltage requirements. Also I would have to addmittidly have to plead that I was not confirming or denighing what you are saying as I had never sit and thought of the possibilities of just using the inverter as a charge controller. I just took it for granted to work smoothly you had to have one "charge controller". interresting thought.
gww
PS inetdog and cariboohoot
You must both type a heck of a lot faster then me as i typed my little statement hit enter and you both were there. -
Re: Too many PanelsI also just though that the OP was using the FM80 selection on the string sizing tool rather than necessarily having an FM80.
The string sizing tools do seem to ignore the strategy of using clipping as part of the design.
Yes; you always have to adjust for individual site installs. In some locations going over by a lot may be a darn good idea, so long as you don't exceed the input V max.
That's why I'm my own string sizing tool.
-
Re: Too many Panels
Not so. Cold weather increases DC voltage while edge of cloud effects increase available current.If the inverter can be damaged by full output of your panels in cold weather, it can also be damaged in warmer weather by edge of cloud effects.
--vtMaps -
Re: Too many Panels
If you're lucky. I'm pretty sure that overvoltage shutdown is an uncommon feature of GT inverters. Overvoltage can damage many/most inverters. Voids warranties, too.Cariboocoot wrote: »If this were a standard GTI it wouldn't matter either, as any panel capacity beyond the inverter's output is simply not utilized. The only way you can get in trouble here is if the array Voltage exceeds the inverter's input maximum. Then it will turn off due to "over Voltage". -
Re: Too many PanelsIf the inverter can be damaged by full output of your panels in cold weather, it can also be damaged in warmer weather by edge of cloud effects.
--vtMapsNot so. Cold weather increases DC voltage while edge of cloud effects increase available current.
I was answering the OP's concern that he might put too much power (not voltage) into his inverter. Its not an issue anyway, his inverter will not be harmed by a few extra panels.
--vtMaps4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i -
Re: Too many Panels
OK, Thanks for all the replies.
Cariboo hit it. The Inverter is not the limiting factor, it is the FM80. This has been derated per the NEC by 20% from 5000K to 4000K on Outbacks String Tool.
This seems a bit over cautious to me since the Tool factors in the Coldest clear day factor of 1.25 onto the STC of the Panel. That gives out the best case maximum power possible at 4216K and I just can't see what factor would further boost that over the 5000K FM80 limit.
But there is another factor which is a 64 amp incoming limit on the FM80 which I read in my manual. The ISC of 7.81 x 1.25 x 7 strings comes in at 68.3amps. This is at STC at real (more real) NOCT ISC of 6.21 x 1.25 x 7 strings is 54.3 amps. Now over on Outbacks site one poster had run into his FM80 shutting down due to power spikes from Cloud Edge phenom. That is going to be a bit hard to factor, but for the most part in Colorado's High Altitude it is either clear or cloudy with little between.
So, bottom line I am going to run the numbers for the AHJ and explain it, and if I have to flip the breaker on the 7th String so be it. Worst case is that I buy another FM80, and since I will need another for my phase two plan that is no loss.
And yes I already bought the Outback FP1-4 with all the goodies including the Batt sensor and FM80.
Once again thanks for all the Info, I cannot imagine how long it would take to learn all this without the forum to read through.
I'll tell you what the AHJ decides.
G -
Re: Too many Panels
You won't see Isc coming from panels connected to a charge controller. if you do, it means the controller is shorted so all calculations are meaningless. Panels in operation don't produce more than Imp.
Just the same, I do often say that people who try to run on the edge tend to fall off it.
A well-balanced design is all about getting the tolerances right, because every day is not the same. -
Re: Too many Panels
I had a similar question before adding my second array. I have a GVFX 3648 and I sell back to the grid what my loads aren't using. Unless the grid is down, my charge controllers stay in bulk mode so never limit my PV output. My second array brought me to 4500 watts of PV. I have 2 charge controllers so no limits there. I typically see about 80% efficiency between PV output through to inverter output. I knew from experience with my 1800 watt array that frequent cloud edge effects can bring me well beyond STC output. I was worried that cloud edge effects could force my inverter to try and sell beyond it's rated output and shut it down or damage it. I asked this question on the Outback forum and some thought that might happen. But then I realized that my Midnight CCs allow me to set a limit on output amps. So problem solved! Yeah Midnight!:D
I don't know if the Outback CCs allow you to limit output amps but that might be one solution to satisfy the AHJ. I have yet to have my array addition inspected - but that's coming up soon so we'll see if it's an issue for me.
Good Luck. -
Re: Too many Panels
OK
Well Cariboo
You are right about riding the edge. As one who makes his living on the Sea I know that several marginals can make one Major.
The numbers came up in two places as over the CC's limit with 7 strings. So
I would still like to set up this 7th string---but----is there any harm to be had by setting up the last string and simply flipping the breaker?
Too much heat? -
Re: Too many Panels
The major concerns with "over-paneling" a charge controller are that you'll make the array too high a Voltage (instant fried controller) or that you'll spend a lot of money on panels that don't actually contribute to the charging most of the time. You can not force more current through an MPPT controller than it is designed to pass. In other words the array may be capable of enough Watts to produce 100 Amps @ 48 VDC, but the 80 Amp charge controller passes 80 Amps. Regardless of Voltage or SOC of the batteries that is the upper limit.
The FM80 does have an "over current" warning should more than 100 Amps flow from it to the battery, for whatever reason. And yes you can program a current limit less than maximum into it. Whether or not this would satisfy an inspector is anybody's guess.
Sometimes it's nice to have more panel, like on those days when output is less than stellar due to inclement weather. -
Re: Too many PanelsCariboocoot wrote: »Sometimes it's nice to have more panel, like on those days when output is less than stellar due to inclement weather.
And here I thought we were talking about solar PV rather than stellar PV. (The latter needs some seriously large panels.) :-)SMA SB 3000, old BP panels. -
Re: Too many Panels
Ol' Sol is a star too. -
Re: Too many Panels
No I got that.
I will not add in the 7th string of Panels to the FM 80.
What I want is to set them up on the roof and later combine them into another FM80 along with more panels all part of Phase 2.
Will it hurt anything to leave them wired to a breaker but with the breaker off. This way I could add them in on a marginal day but mostly they are just for show. Or will the heat be too much? -
Re: Too many PanelsCopperking wrote: »No I got that.
I will not add in the 7th string of Panels to the FM 80.
What I want is to set them up on the roof and later combine them into another FM80 along with more panels all part of Phase 2.
Will it hurt anything to leave them wired to a breaker but with the breaker off. This way I could add them in on a marginal day but mostly they are just for show. Or will the heat be too much?
There is no heat associated with a solar panel that is not connected to any load. Except the same heat from the sun that is heating a loaded panel, plus the amount of heat that is being produced by that sunlight that is not being converted to electricity. Not an issue with 20% efficient panels.SMA SB 3000, old BP panels. -
Re: Too many PanelsCopperking wrote: »Will it hurt anything to leave them wired to a breaker but with the breaker off. This way I could add them in on a marginal day but mostly they are just for show.
As has been explained, just hook them up. You will not harm anything with all 7 strings. There is no reason to turn off a string on a sunny day.
--vtMaps4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
Categories
- All Categories
- 222 Forum & Website
- 130 Solar Forum News and Announcements
- 1.3K Solar News, Reviews, & Product Announcements
- 192 Solar Information links & sources, event announcements
- 888 Solar Product Reviews & Opinions
- 254 Solar Skeptics, Hype, & Scams Corner
- 22.4K Solar Electric Power, Wind Power & Balance of System
- 3.5K General Solar Power Topics
- 6.7K Solar Beginners Corner
- 1K PV Installers Forum - NEC, Wiring, Installation
- 2K Advanced Solar Electric Technical Forum
- 5.5K Off Grid Solar & Battery Systems
- 426 Caravan, Recreational Vehicle, and Marine Power Systems
- 1.1K Grid Tie and Grid Interactive Systems
- 651 Solar Water Pumping
- 815 Wind Power Generation
- 624 Energy Use & Conservation
- 611 Discussion Forums/Café
- 304 In the Weeds--Member's Choice
- 75 Construction
- 124 New Battery Technologies
- 108 Old Battery Tech Discussions
- 3.8K Solar News - Automatic Feed
- 3.8K Solar Energy News RSS Feed