Installing a new PV system

Raj174

Hey guys,
This is my first post here and I wanted to discuss a new system I am putting together. I have an electrical, mechanical and computing background and wanted to try my hand at solar. I have been researching Panels , charge controllers, e-panels, inverters and etc,. So over the weekend, Renogy had their 300 watt panels for 234.59 plus 10 percent off site wide. Well, I snagged 8 at 71 cent per watt. During a search for an inverter I got a link to this forum and I found 5 precent off at the NAWS store. They had the next item I was looking for and at an awesome price, an MN Classic 150. And now that on its way to my house.
I have a question for the experienced members here. The next item on my list is a MidNite Solar MNE175DR/TR/SLX-L E-Panel. I know, you need to know which inverter I will be using. To start, I have a Cotek SK-1500-124 but I will be getting a SK-3000-224. I know this panel is over rated for the first inverter and a bit under rated for the second. Thus the question. Can I use the 175 amp e-panel? I saw only a 125, 175 and 250 amp in that line. If not can you suggest something else. By the way the battery bank will be 24 volt 250 amp hours maybe 375. Array will be 4 strings of 2 in series. I expect a load of 3 to 4 kWhs over night. Any pointers helpful, more questions coming.
Thanks much……Rick

TucsonAZ

Re: Installing a new PV system

Woot woot, welcome to the forums and I like the avatar!

I thought about buying those same panels, cost of shipping was a killer though. I have the Classic 150, nice choice there and I also bought the same Cotek so we seem to be on the same page.

I can't actually answer your question but am wondering where the install is and if you have to be up to code? That may make a difference in the responses you get, I had a lot of issues initially with people giving me advice that was following code when I couldn't care less about passing an inspection.

Photowhit

Re: Installing a new PV system

Raj174 wrote: »

....By the way the battery bank will be 24 volt 250 amp hours maybe 375.../
/...I expect a load of 3 to 4 kWhs over night.

Well we like to start with loads when designing a system, 3-4 KWh over night is a heck of a load.

Consider that a 24v 250ah has roughly 6kwh total and normal use we suggest not taking the battery bank down below 80%(allows for those cloudy days when you might have minimal or no charging, yet keeping the bank above 50%. Below 50% and you have a hard time keeping the bank from sulfating before getting it charged back up)

How are you calculating your loads? is the 3-4 Kwh before you consider that the inverter is only 85-90% efficient? Does that include the 400+watthours that the charge controller is going to use? Will this be your year round base line?

So I'll fess up, I like to use 5-6 kwh over night during hot summer months, but I have abundant sun when I do this and a 4Kw array and 800Ah battery. My system would NOT like a 3-4 Kwh load over night during the grey winter days...

Raj174

Re: Installing a new PV system

I agree, the shipping charge was too high at 346.00. About 100 dollars more than most competitors., but 10% off brought that down to 160.00 and that sealed the deal for me. As far as the Classic goes I wanted CC with a web interface and it needed to be able to handle a 2400 watt array at 24 volts and that is the classic 150.

This system will not be inspected but safety is a major concern. I will not risk the lives of my family nor my property over a few dollars skimping on breakers and wire size. Doing the job right is important. Thanks for the comments.

Raj174

Re: Installing a new PV system

Thanks for the advice Photowhit, I understand, proper use and maintenance of the batteries will extend their utility. So far I have only purchased the PV panels and the charge controller. I will be buying my batteries last and will be asking questions along the way. I am here to learn. Thanks for giving me these points to consider.

vtmaps

Re: Installing a new PV system

Raj174 wrote: »

Thus the question. Can I use the 175 amp e-panel? I saw only a 125, 175 and 250 amp in that line.

Welcome to the forum,

Check to see if you can find the Cotek manuals on line. Virtually all inverters specify a fuse/breaker size and minimum cable gauge and length.

Before I make any comments on the ePanel or anything else... What is the purpose of your system? Do you have grid power available?

--vtMaps

Photowhit

Re: Installing a new PV system

Lots of good info in the FAQ's!

Raj174

Re: Installing a new PV system

Hi vtMaps, thank you for considering this issue. The recommended cabling for the Sk-1500-124 is #4 no more than 10 feet long and fuse or breaker size is 100 amps. For the Sk-3000-224, cabling is 2/0 no more than 10 feet long and fuse or breaker size is 200 amps. So, my electrical experience with a/c tells me do not exceed the maximum recommended amperage. So that rules out the 250 amp e-panel. Would using the 175 amp e-panel be feasible? Maybe, get the panel and replace the breaker? What's a mother to do?
Yes I am on the grid. The reason I want an off grid PV system is the same reason I have silver and gold. I is a hedge against rising energy costs (inflation) and insurance in case of catastrophic economic or fiscal events resulting in extended grid outages. I would rather be prepared for such circumstances and save a little money along the way than find myself one day sitting in the dark wondering when the lights will come back on. Having you own source of power in that case is invaluable. Electricity is a very precious resource and it is easily taken for granted until one has to live without it and that experience is an eye opener.

Thanks, Rick

Photowhit

Re: Installing a new PV system

Keep you cabling as short as possible, regardless of the 10'. 175 amp breaker in 24 volt system should be good for 4200 watts, for a peak starting load this should be fine for your 3000 watt inverter. Might just go with a 100 watt din rail breaker for the smaller inverter for the time being, I have a 1100 watt inverter hooked up to a 90 watt and it has been Okay. I don't think Midnite recommends them for this use, not sure why...

BTW - I use to be a photoj for the Dummycrat (or mullet wrapper) my mom use to help with the sustainable living conference. I can't stand the heat and humidity of Tallahassee, hope your handling it better than I..

zoneblue

Re: Installing a new PV system

There are two reasons why you might want to use an epanel instead of midnites smaller more generic MNDC style disconnects. First obviously the epanels are designed to simplify mounting and wiring of certain brand inverters. Secondly, if you have an inverter that has in inbult charger for use with a genset and all the assoicated transfer circuitry. I gather you are on grid, thus this might apply to you, even if you dont have a outback or similar inverter. You might want to ponder how to manage the redundancy involved in these setups. You can either run seperate AC distribution to specific loads, or you can do a transfer switch system that passes supply from grid to inverter. If you are a little more serious about it youd be looking at an inverter with AC interactive modes, like an Outback Radian, or Scheider XW. While expensive these have the ability to intelligently transparently swap, backup, mix etc multiple ac sources. This applies even if you dont want to go to the extent of selling to the grid. Thats a subject a bit off the topic of this particular subforum, but good to keep the options in the back of your mind.

vtmaps

Re: Installing a new PV system

Raj174 wrote: »

Hi vtMaps, thank you for considering this issue. The recommended cabling for the Sk-1500-124 is #4 no more than 10 feet long and fuse or breaker size is 100 amps. For the Sk-3000-224

Give some thought to buying an inverter/charger (Outback, Magnum, SMA) for an off-grid system.

Raj174 wrote: »

Yes I am on the grid. The reason I want an off grid PV system is the same reason I have silver and gold. It is a hedge against rising energy costs (inflation) and insurance in case of catastrophic economic or fiscal events resulting in extended grid outages. I would rather be prepared for such circumstances and save a little money along the way

You are very mistaken about saving money. Battery based systems produce power that costs at least 5 times (often 10 times) the cost of grid power.

A grid-tied system may have a reasonable return on investment.

As far as extended grid outages, a generator is cost effective, especially if combined with a small battery so that you can have lights and radio in the evening without running the generator.

As far as prepping for cataclysm... I don't want to discuss that.

--vtMaps

Raj174

Re: Installing a new PV system

Thanks, Photowhit. That's great news. I'll look into the din rail breaker setup. Yes it is hot here, but not as humid as in Miami where I used to live. Big cultural difference too. You know I was actually called a tourist there by someone because I didn't speak spanish.

Photowhit

Re: Installing a new PV system

I think they are staying with a grid and have this against a situation you don't want to discuss, if you could go 'native' in North Flordia (NO A/C) it might be close to cost effective as the user fee is $20 a month for Talquin Elec, a minimal user might be able to come out close to cost effective use there in an off grid situation.

Raj174

Re: Installing a new PV system

Hi vtmaps, I will look into the inverter chargers. When I said saving money along the way. I meant, since I am putting several thousand dollars into an off grid system. I will be moving some of the load from the grid to the pv system to help recoup some of the costs, although that reduction may only be 20 or 30 % something is better than nothing.
Thanks again,
Rick

ButchDeal

Re: Installing a new PV system

Raj174 wrote: »

Hi vtmaps, I will look into the inverter chargers. When I said saving money along the way. I meant, since I am putting several thousand dollars into an off grid system. I will be moving some of the load from the grid to the pv system to help recoup some of the costs, although that reduction may only be 20 or 30 % something is better than nothing.
Thanks again,
Rick

Going with off grid is the least effective way to do this. I understand you want to have off grid capability but to recoup any costs and get maximum performance out of your system as well as to be able to move things reliably to it you should consider a bymodal or hybrid system.
I have one from Outback (Flexpower One) but there are several. We just had a 27 hour power outage and I was able to keep my emergency panel hot through the whole thing (freezer, fridge, well pump, internet, some lights, etc).
The system works just like an off grid system when there is no grid power BUT when there is grid power it feeds power to the rest of the house reducing the whole house bill as well as into the grid further reducing the bill, AND keeping the batteries charged.
You would be able to take advantage of the incentives with a bymodal system since it is grid tied, and it would be able to reduce your bill far more than trying to move some load to a fully isolated off grid system.

Raj174

Re: Installing a new PV system

From what I have read about those systems, I agree. But I think they are a bit too expensive for my budget. My 2.4 kw system should be around 4500 bucks when finished. Your Outback setup must have been a good bit more than that. I would love to have a setup like yours. It"s the best of both worlds. Thank for the suggestion ButchDeal

ButchDeal

Re: Installing a new PV system

Raj174 wrote: »

From what I have read about those systems, I agree. But I think they are a bit too expensive for my budget. My 2.4 kw system should be around 4500 bucks when finished. Your Outback setup must have been a good bit more than that. I would love to have a setup like yours. It"s the best of both worlds. Thank for the suggestion ButchDeal

My 3kW system was just under $12k for everything, all parts, wires, bolts, batteries, permits, inspections, etc. including certified electrician time, and SRECTrade.com registration in PA market. After federal 30% incentive (WV doesn't have any incentives), comes to $8,400. It saves me about 40% off my electric bill, around $800 a year. Generates about 3.5 to 4 SRECs a year on the PA market for an additional income of ~$160 annually. (some states have much better SRECs)
Not sure what state you are in but your incentives probably would be more than mine since WV has none.

Yes it costs a little more but incentives may alter that for you and it would also do more.

Raj174

Re: Installing a new PV system

That's a great price. The break in Florida for solar is no sales tax. Not much of a break. Your system is still about twice as much as I could afford, even though it looks like it will eventually pay for it's self. I hope others reading this conversation can use this information to their advantage.
Thanks
Rick

PNjunction

Re: Installing a new PV system

It is a shock for those new to solar to discover that off-grid means about 10x the cost of the poco. And don't forget, unless you are just doing a 4-6 year experiment, you'll be replacing those batteries after 4-6 years at even more inflated prices. Instead of just investing in silver and gold, you may also want to add lead to your investment portfolio.

Also consider that many don't really get their power budget just right the first time, and in order to save money usually underestimate their battery needs - especially if they don't take into account geographical solar-insolation hours, which are far different from sunrise-to-sunset hours. Most tend to repurchase their very first set quickly with a new capacity. It pays to take it slowly and pour over the faqs and stickies here.

Can you REALLY live with the psychological impact of extended outages, or will you go stark raving mad in a few days? Once you have your setup, try a little practice, say over the weekend of running solely from your system.

Raj174

Re: Installing a new PV system

Thanks for the advice PNjunction, Photowhit also told me how important proper battery bank sizing is. Testing the system in a mock extended outage is a good idea and I had planned to do so. I was in Miami in 1992 when hurricane Andrew devastated the area just south of the city. I was about 20 miles north of that and we were without power for 3 weeks. We had natural gas for cooking and hot water but no generator. Well, some months afterward I installed a 6000 watt natural gas generator at that house. Only used it about 3 times over the years other than testing.

Photowhit

Re: Installing a new PV system

We haven't discussed battery types and such, many start with golf cart batteries from Sam's Club or Costco, at about $80 each and often a liberal trade in/core charge they tend to be a good value.

2 strings of 4 would give you 440 Ah battery bank at 24 volts, which would be pretty good match for 2400 watt array (slightly over paneled, but will help on those cloudy days)

Please note that if your using these at home, and you don't rent(I think you must own the home, not sure) you can take a 30% federal tax credit off you tax liability! Link to Federal info. http://www.dsireusa.org is down right now but there is a link at the bottom of the page. I thought there was some other incentives in Florida with limited funding. The Unitarian Church in Tallahassee took advantage of them a few years back.

Raj174

Re: Installing a new PV system

Thanks Photowhit, I was considering four 12 Volt - 250 Ah - UB-8D - AGM Batteries because they will be inside the house and space is limited. That's 500 Ah. Is that about the right size? Best price I could find is 447.00 each delivered.
Yes, Florida did pay for 20 or 30 % of solar some years back, but now just a break on sales tax. I plan to get the federal tax credit.
Thanks again

Raj174

Re: Installing a new PV system

Glad to hear it Greenbotalltet1973, speaking of information, I have another question. I need to buy breakers for each string and a PV breaker for the + input of the charge controller. The PV panels are wired as 4 strings of 2 in series. This is the panel info….
Optimum Operating Voltage (Vmp): 37.46V
Optimum Operating Current (Imp): 8.01A
Open - Circuit Voltage (Voc): 46.12V
Short- Circuit Current (Isc): 8.56A
Module Efficiency: 15.5%
Cell Efficiency: 17.3%
Operating Module Temperature: -40°C to + 90°C
Maximum System Voltage: 600 V DC (UL) / 1000 V DC (IEC)
Maximum Series Fuse Rating: 15A

I configured each string with a 12 amp breaker and the PV input breaker to the CC at 50 amps. Is this correct?

Thanks

vtmaps

Re: Installing a new PV system

Raj174 wrote: »

Glad to hear it Greenbotalltet1973, speaking of information, I have another question. I need to buy breakers for each string and a PV breaker for the + input of the charge controller. The PV panels are wired as 4 strings of 2 in series. This is the panel info….
Optimum Operating Voltage (Vmp): 37.46V
Optimum Operating Current (Imp): 8.01A
Open - Circuit Voltage (Voc): 46.12V
Short- Circuit Current (Isc): 8.56A
Module Efficiency: 15.5%
Cell Efficiency: 17.3%
Operating Module Temperature: -40°C to + 90°C
Maximum System Voltage: 600 V DC (UL) / 1000 V DC (IEC)
Maximum Series Fuse Rating: 15A

I configured each string with a 12 amp breaker and the PV input breaker to the CC at 50 amps. Is this correct?

Thanks

You can use 15 amps for the string breakers.

The size of the combined PV breaker depends on the size of the cable. That PV breaker is for your convenience... use it as a PV switch. Make it the right size to protect the cable. Your cable needs to be thick enough to handle the array without nuisance tripping. That means the array cannot make enough current to overheat the cable or trip the breaker.

--vtMaps

Raj174

Re: Installing a new PV system

Got it, Thanks again vtmaps