Expanding existing system question?
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Re: Expanding existing system question?
Another question I have about my solar panel expansion. I will have (12) 235 watt panels on 1 roof facing slightly east of south. I have space on another building for another 6 panels. There is a slight deviation in the orientation of the smaller roof by about 13 degrees closer to facing true south.
One option is to run the 12 panels separately into a Midnite Classic 150, and have the separate 6 panels feed into a separate Midnite controller. Downside to this approach is I would be loosing some of the panels capacity at peak output and the controller would be maxing out on a fairly regular basis (ie running hot).
Other option is to feed 9 panels into each controller. This would divide up the load evenly between the controllers. Downside to this approach is the 13 degree difference in orientation, which could reduce the feed into that controller. Are there serious issues with going this route?
My system is currently 24 volt. I could switch to 48 volts which would help mitigate the problem, but would be dealing with a bit of a $ setback with the 24 volt inverter I currently have. -
Re: Expanding existing system question?
Um, twelve 230 Watt panels on one Classic 150? You want to try that out on the sizing tool first I think. By my estimate it's too big of an array for a 24 Volt system.
You can use panels facing slightly different directions on the same controller without any big hassle, providing they aren't divided amongst any one string. So if the strings are three in series and one of those strings is 13 degrees more easterly than the other two you won't notice any problems.
I'd go with nine on each of two controllers. -
Re: Expanding existing system question?Cariboocoot wrote: »Um, twelve 230 Watt panels on one Classic 150? You want to try that out on the sizing tool first I think. By my estimate it's too big of an array for a 24 Volt system.
Yes, and that's what I meant by losing some of the peak power. With the classic, you can set a limit to the amount of current in, but it's never good when you are not making use of available power! I would not have that loss with a 48 volt setup.Cariboocoot wrote: »You can use panels facing slightly different directions on the same controller without any big hassle, providing they aren't divided amongst any one string. So if the strings are three in series and one of those strings is 13 degrees more easterly than the other two you won't notice any problems.
I'd go with nine on each of two controllers.
Yes, the strings are 3 in series, so if there isn't a problem paralleling the 2 strings, sounds like the way to go. Thanks for the input! -
Re: Expanding existing system question?
My latest plan with my system expansion is to stick it out with a 24 volt system and only add one more bank of (4) L16, 6v batteries, well at least for now anyway. That actually was my original plan, and I left room for another box with batteries. I would have another year to decide if I wanted to add yet one more bank. There is the option to keep the 2 banks totally separate, although, I think it may be best if I avoid doing that. The only reason being is to avoid mixing the original (older) batteries with the new (ie if I did add one more bank in a years time).
In order to keep cable resistances equal, I was thinking of running a pair of cables from each bank of 4 into my DC junction box. I know that's a lot of copper, but it will give close to identical pathways to each bank, with the added benefit of a low resistance connection from batteries to inverter. I am currently using 2/0 cable which is easier and cheaper to find locally, and should be using 4/0 anyway. I would then run 4/0 to each of the 2 inverters. I think that will help preventing imbalances between the banks and give a really good low impedance connection. Has anyone else run more than one set of cables from the battery bank(s) to DC junction box/inverters? -
Re: Expanding existing system question?
Another option worth considering is to switch to a Xantrex 48v, 120/240 v inverter. For a backup inverter, I could use a smaller unit which I plan to use normally as dedicated power diversion for water heating. I still think 48 volts is the best way to go with my proposed system size, avoiding the 3 or 4 parallel 24 volt banks of batteries. How does the Xantrex inverter compare with the Outback? Are there any issues to be concerned with (other than customer support which I'm aware of)? Will a Xantrex inverter give very long life service like the Outback? -
Re: Expanding existing system question?
Xantrex: the pick of entomologists!
XW's have 240 VAC output, FX's have 120 VAC output.
XW's can be 6kW single, FX's stop at 3600 Watts single.
I think you'd have to be a bit more specific about which models you're comparing and what you need to get from them.
My Outback has already outlasted my Xantrex, and they're certainly more suitable for harsh climates (not a concern for everyone).
Other people have had excellent service from Xantrex equipment (various models).
You might also consider Magnum's 4kW 48 Volt inverter. It's less money than Brand X but similar features (240 VAC for example) and very easy install. -
Re: Expanding existing system question?Cariboocoot wrote: »Xantrex: the pick of entomologists!
XW's have 240 VAC output, FX's have 120 VAC output.
XW's can be 6kW single, FX's stop at 3600 Watts single.
I think you'd have to be a bit more specific about which models you're comparing and what you need to get from them.
My Outback has already outlasted my Xantrex, and they're certainly more suitable for harsh climates (not a concern for everyone).
Other people have had excellent service from Xantrex equipment (various models).
You might also consider Magnum's 4kW 48 Volt inverter. It's less money than Brand X but similar features (240 VAC for example) and very easy install.
Thanks for the feedback Coot! I currently have a 24 volt system and am using a VFX 3524. One option is to stay with this and add another inverter, plus auto transformer to give me 120/240 VAC. I plan to add more batteries and panels, as mentioned previously, and am thinking that a 48 volt system makes more sense. I would have less parallel banks, and dealing with lower currents, both charging and usage. Option for the Xantrex is the xw series, either 4548, or 6048.
I think the Xantrex system would be simpler and cheaper, and 48 volts is really a good way to go. Downside is I would take a loss selling the existing inverter, and I would want a good quality, pure sine inverter for backup (normally used for diversion water heating). It sounds like the Outback is a very reliable unit, with excellent customer support. It would cost more, but I'm thinking it would offer me a relatively worry free setup, once complete. Sticking with 24 volts may involve issues with multiple battery banks and working through a good cabling setup. If I sold the inverter I have and switched to an Outback 48 volt, that would work very well, but cost significantly more.
From what I've heard about the Magnum, I will stay clear of it. Surge handling is not good. -
Re: Expanding existing system question?
You can get 240 from your VFX3524 by just using the autotransformer if the load is not high Wattage. This is what I do for my septic pump (1 HP, once a day for about 30 seconds - not going to make a big investment to power that!).
Two VFX3524's can be wired to provide 240 without the transformer (series stacked). Or with the transformer to balance the 120 legs; allowing either to draw power from both inverters if needed.
If you need more battery capacity look at both options of higher system Voltage or larger battery capacity and compare the over-all costs of each. You would not want to just tack on more batteries to the existing bank if it's been in use more than a year, so replacing it entirely is probably necessary either way.
And there's always the expansion option of adding an entirely new system that's completely independent of the old one. That may be viable too. For instance the new system could be smaller and take on all the lower power loads like lighting, and then shift all the heavier loads to the larger system.
One of these days someone is going to introduce a truly expandable off-grid system that you can just plug more modules into like a micro-inverter GT set-up. Are you listening boB? We know you guys can do it!
I have not heard that Magnums are poor on handling surge loads. As far as I know they will handle 2X rating for 5 seconds and 1.5X rating for 30 seconds, which is really quite good compared to the cheap inverters. -
Re: Expanding existing system question?northerner wrote: »How does the Xantrex inverter compare with the Outback? Are there any issues to be concerned with (other than customer support which I'm aware of)? Will a Xantrex inverter give very long life service like the Outback?
I cannot compare to Outback, but looking at my Xantrex, I would say it is very high quality even though it is built in China. The software is not very well thought out, especially grid tie aspects. There should be no problem for off-grid. Surge capabilities are very good. Handling one-sided loads is very good.
The support is not that bad. You need to ask the right questions. If something's wrong, they will ship a new unit to your door with express shipment for free. You need however pay for the bad unit to be returned back afterwards. -
Re: Expanding existing system question?Cariboocoot wrote: »You can get 240 from your VFX3524 by just using the autotransformer if the load is not high Wattage. This is what I do for my septic pump (1 HP, once a day for about 30 seconds - not going to make a big investment to power that!).
Two VFX3524's can be wired to provide 240 without the transformer (series stacked). Or with the transformer to balance the 120 legs; allowing either to draw power from both inverters if needed.
If you need more battery capacity look at both options of higher system Voltage or larger battery capacity and compare the over-all costs of each. You would not want to just tack on more batteries to the existing bank if it's been in use more than a year, so replacing it entirely is probably necessary either way.
And there's always the expansion option of adding an entirely new system that's completely independent of the old one. That may be viable too. For instance the new system could be smaller and take on all the lower power loads like lighting, and then shift all the heavier loads to the larger system.
One of these days someone is going to introduce a truly expandable off-grid system that you can just plug more modules into like a micro-inverter GT set-up. Are you listening boB? We know you guys can do it!
I have not heard that Magnums are poor on handling surge loads. As far as I know they will handle 2X rating for 5 seconds and 1.5X rating for 30 seconds, which is really quite good compared to the cheap inverters.
I would really prefer to go the 120/240 split route, for several reasons. One is I would like to make use of my existing panel box which is designed for this. Second is I do have 2 circuits fed to my workshop that is 120/ 240 volt fed with 3 wire. I get the 20 amp rating by sharing a common neutral. I don't really look forward to digging up that line to replace it. Third is I would like to power a 240 volt dryer occasionally. I could switch to a gas dryer, but I usually, but not always, hang my clothes to dry anyway.
I was considering the option of keeping 2 battery banks separate, but combining the inverters, if I went the 2 inverter, 24 volt, Outback route. This would allow me to add another 4 batteries soon, and then another possible 4 in a year's time, but I am trying to avoid that option, if I can.
I'm favoring, sticking with the 24 volt Outback system, going with 2 inverters and auto transformer, and will add one more bank of 4 batteries and triple my solar panel array.
But still considering the switch to 48 volts and then of course would add another full bank of 8 batteries. This would also require taking a loss on the sale of my existing (2 month old) inverter too. -
Re: Expanding existing system question?I cannot compare to Outback, but looking at my Xantrex, I would say it is very high quality even though it is built in China. The software is not very well thought out, especially grid tie aspects. There should be no problem for off-grid. Surge capabilities are very good. Handling one-sided loads is very good.
The support is not that bad. You need to ask the right questions. If something's wrong, they will ship a new unit to your door with express shipment for free. You need however pay for the bad unit to be returned back afterwards.
After all the reading I have done, I get the feeling that if you go with Xantrex, sooner or later you will need support. Outback inverters appear to have fewer problems in the long term? -
Re: Expanding existing system question?
If you're thinking about running an electric dryer you may want to read through this thread: http://forum.solar-electric.com/showthread.php?2695-Clothes-dryer-propane-vs-electric
And some of the others in the energy use & conservation section about dryers. Including ChrisOlsen's experimenting with half-power on the heating elements.
In short, your standard electric dryer draws large amounts of current and you may need much bigger inverter/battery capacity just to handle it. They usually use a 30 Amp 240 VAC outlet, which is 7200 Watts (although of course they don't use all that capacity). Check the numbers on your dryer, if you can find them. -
Re: Expanding existing system question?northerner wrote: »After all the reading I have done, I get the feeling that if you go with Xantrex, sooner or later you will need support. Outback inverters appear to have fewer problems in the long term?
I'd say OB is better out of the box; the Xantrex stuff always seems to be behind in its firmware and often has bugs that prevent some aspect of it from working at all. OB stuff is so "old school" or "primitive" that this sort of issue doesn't seem to be as prevalent.
But lots of people use Brand X with no complaints too.
Yeah; wishy-washy answer. :roll: Hard to be more specific because every install is different. As such, one unit will have an advantage over another depending on the particular application. -
Re: Expanding existing system question?
I like the XW6048, but unless you have a dealer that does field service or Service Center close to you, remember it weighs 125 LB, not easy to ship or even pick up. Outback will ship you parts for the FX series, if you are competent to replace a board and it weighs 56 lb or so, if you had to ship it. With running 2 stacked you could get by in a emergency. You realize this as you have pointed it out.northerner wrote: »After all the reading I have done, I get the feeling that if you go with Xantrex, sooner or later you will need support. Outback inverters appear to have fewer problems in the long term? -
Re: Expanding existing system question?Cariboocoot wrote: »If you're thinking about running an electric dryer you may want to read through this thread: http://forum.solar-electric.com/showthread.php?2695-Clothes-dryer-propane-vs-electric
And some of the others in the energy use & conservation section about dryers. Including ChrisOlsen's experimenting with half-power on the heating elements.
In short, your standard electric dryer draws large amounts of current and you may need much bigger inverter/battery capacity just to handle it. They usually use a 30 Amp 240 VAC outlet, which is 7200 Watts (although of course they don't use all that capacity). Check the numbers on your dryer, if you can find them.
My dryer is a bit smaller. It draws up to 23 amps at 240 volts, which is 5500 watts. There is a low heat setting, which could be used if necessary. Might take a while to get the clothes dry though! -
Re: Expanding existing system question?Cariboocoot wrote: »I'd say OB is better out of the box; the Xantrex stuff always seems to be behind in its firmware and often has bugs that prevent some aspect of it from working at all. OB stuff is so "old school" or "primitive" that this sort of issue doesn't seem to be as prevalent.
But lots of people use Brand X with no complaints too.
Yeah; wishy-washy answer. :roll: Hard to be more specific because every install is different. As such, one unit will have an advantage over another depending on the particular application.
It's kind of a wishy-washy issue that I brought up! As you mention, there's often a lot of particulars involved with each system and the reason behind something failing. When it comes to inverters, I think old school or simple is better, as there is less to go wrong. I don't know much about the inner workings, but I also feel that OB has a better design for the long haul. -
Re: Expanding existing system question?Blackcherry04 wrote: »I like the XW6048, but unless you have a dealer that does field service or Service Center close to you, remember it weighs 125 LB, not easy to ship or even pick up. Outback will ship you parts for the FX series, if you are competent to replace a board and it weighs 56 lb or so, if you had to ship it. With running 2 stacked you could get by in a emergency. You realize this as you have pointed it out.
Yes, yes, that is a major consideration. There is not service center in the area, that I'm aware of. I'm definitely leaning towards the OB. -
Re: Expanding existing system question?
Will there still be an issue with keep batteries balanced in parallel strings, even though you make cable resistances identical to each bank? I'm still trying to decide whether I should make the switch from 24 to 48 volts with my system expansion. I currently have two 435 ah, 24v banks, and plan to add one or most likely two more banks. I would like to double my current storage, and triple my current PV array, plus add another inverter and CC. -
Re: Expanding existing system question?northerner wrote: »Will there still be an issue with keep batteries balanced in parallel strings, even though you make cable resistances identical to each bank? I'm still trying to decide whether I should make the switch from 24 to 48 volts with my system expansion. I currently have two 435 ah, 24v banks, and plan to add one or most likely two more banks. I would like to double my current storage, and triple my current PV array, plus add another inverter and CC.
Maybe we should carve the explanation in stone somewhere. :P
The more parallel connections, the greater the risk of uneven current sharing.
If the wiring is equal length, the risk is lessened. If it is not equal length, the risk is greater.
Lower Voltage systems suffer more from it than do higher Voltage systems.
(I've probably forgot some aspect of it here.)
So the worst case would be:
12 Volt system, more than four batteries in parallel, wiring 'laddered'
This is almost 100% certain to have problems.
But by the time you get to:
48 Volt system, four or less batteries in parallel, wiring equal with/without bus bars
You've got a lot less to worry about.
Inbetween it's sort of a question of risk management, not absolutes of will/won't work. -
Re: Expanding existing system question?
I think I can manage OK with a 24 volt system. I may just add one more bank of (4) Trojan L16's.
I'm now officially off grid, woohoo ($$$
)! It's all good though, and I plan to move the system to an acreage at some point, hopefully.
I just went through a stretch of cloudy weather, and actually had to run the generator (for the first time) for about 1 1/2 hours this morning, to give the batteries a boost, as they were getting below 50% state of charge, just a little. I am still taking in between 4.5 and 5.5 kwh per day on cloudy days with snow. Looks like plenty of sunshine in the forecast again. I could likely manage with the array I currently have through the summer, but I think I will do the up grade, with another 6 panels for now, plus another Midnite CC. That will give me plenty of coverage for the cloudy stretches. The 2nd inverter can wait, however. -
Re: Expanding existing system question?northerner wrote: »I'm now officially off grid, woohoo ($$$)!
Congratulations!!! How did the disconnection go? -
Re: Expanding existing system question?Congratulations!!! How did the disconnection go?
It went well! The lady technician from the utility company did ask about the solar panels, and whether they were somehow connected to the grid, lol. I reassured her they weren't. They just pull the meter off the base and put a couple of plastic sleeves in to 2 of the male terminals of the meter, and then reinsert the meter. That way, the electric system can still monitor the water meter, which is read through pings from the grid line.
She was interested in the system, as her husband was looking into putting in a wind generator. I recommended to go with solar, which of course is the way to go.
As far as I know, there will be no idle fees for being disconnected. They can charge idle fees in rural areas where you have the option of having them taking down the entire connection. Makes no sense to me, as wasn't that paid for by the original owner in the first place?
I made the connection to my electric house panel, from my AC inverter panel with 6 gauge, 3 wire. I also ran a 6 gauge ground wire to the frame of the house panel. Neutral/ground bond is at the inverter panel, and have a ground wire running directly out to my ground rods. I disconnected the house ground wire and moved it away from the panel. Everything is running fine and my Globe vanity bulbs don't flash any more, lol. -
Re: Expanding existing system question?
I just finished expanding the DC electrical connection panel in my off grid system. I piggy backed another midnite DC panel to the existing panel by cutting out the back of the latest one and screwing it to the front flange of the first panel. It's too bad you couldn't order the panels this way? This allows for additional breakers for the 2nd inverter (eventually), the GFP breaker, and heavier duty charge controller breakers.
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I have 6 more panels ready to install. Just need to pickup some aluminum in order to make the mounts. One really needs to shop around for metal. It cost me about $550 for the aluminum (locally) to mount the first 6 panels, plus another $350 in SS hardware. I will be able to get aluminum in GP for just over half that.
I will bring the panel ground into the DC connect box, according to the code requirement. For lightning protection, I will run a #6 ground wire down from the panel frames almost to ground (within an inch or so). I will run another ground wire from the metal roof in the same vicinity, and parallel that wire. The 2nd wire will be connected to ground. This will satisfy the code requirements giving GFP for the panels, and still should be very effective in directing a larger static surge to ground. -
Re: Expanding existing system question?northerner wrote: »I piggy backed another midnite DC panel to the existing panel
<snip>
It's too bad you couldn't order the panels this way
Did you ask Midnite? They are so accommodating, I wouldn't be surprised if they would custom make a double panel for you. --vtMaps4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i -
Re: Expanding existing system question?Did you ask Midnite? They are so accommodating, I wouldn't be surprised if they would custom make a double panel for you. --vtMaps
I didn't contact midnite about it. It wasn't too much work to cut out the back and drill holes to line up with the front cover screw holes. I raised the issue, as it may be a good option for others who are looking for a larger box or expanding their existing system. Whether they do the mod themselves, or ask midnite to consider options? -
Re: Expanding existing system question?northerner wrote: »I piggy backed another midnite DC panel to the existing panel by cutting out the back of the latest one and screwing it to the front flange of the first panel.
Very clever use of the space when you need to connect two inverters. -
Re: Expanding existing system question?Very clever use of the space when you need to connect two inverters.
Those midnite DC panels are not large enough for a bigger system. But I discovered that after the fact, and I had little extra space in any case. It makes sense to have all the DC connections in one box, and it turned out to be a great way to expand my system to add on the 2nd box. -
Re: Expanding existing system question?northerner wrote: »Those midnite DC panels are not large enough for a bigger system. But I discovered that after the fact, and I had little extra space in any case. It makes sense to have all the DC connections in one box, and it turned out to be a great way to expand my system to add on the 2nd box.
Yes, they're a little tight when you need to fit in a lot of stuff. But I managed to put in 2 shunts, 4 breakers for 2 charge controllers and an extra 1A breaker for powering a controller board. All that with grounding and with 4/0 battery/inverter cables. All fit in, but I don't have an extra space for wiring an extra controller. -
Re: Expanding existing system question?Yes, they're a little tight when you need to fit in a lot of stuff. But I managed to put in 2 shunts, 4 breakers for 2 charge controllers and an extra 1A breaker for powering a controller board. All that with grounding and with 4/0 battery/inverter cables. All fit in, but I don't have an extra space for wiring an extra controller.
Another issue is if you go with a midnite classic cc, you will need a larger breaker (ie 100 amp or larger) and they don't fit into the DIN rail. I have PV disconnects on the DIN rail. Also, there is no space for the GFP breaker, which takes up an entire breaker space. I cut out a separate square on the opposite side of the panel to accommodate the GFP breaker. -
Re: Expanding existing system question?northerner wrote: »Another issue is if you go with a midnite classic cc, you will need a larger breaker (ie 100 amp or larger) and they don't fit into the DIN rail. I have PV disconnects on the DIN rail. Also, there is no space for the GFP breaker, which takes up an entire breaker space. I cut out a separate square on the opposite side of the panel to accommodate the GFP breaker.
You can use the big "inverter" breaker from your second MNDC for classic's output.
Most modern chargers include "free" GFP. If not, I think you can also buy a DIN-rail mounted GFP breaker.
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