Advise for wiring and fuse

Gilberto · January 2018

Hello! I am new in matters related to solar energy, I have only read a little and until now I have bought the following to install a basic Off grid system for future emergencies in Puerto Rico.

. 3 PV Boviet 260w 60 cel Poly
Model BVM6610P-260
Vmp 30.7v
Imp 8.42a
Voc 38.0v
Isc 9.01a
Max series fuse rate 15a

. SRNE ML4860 mppt CC 60a
. Jupiter 12v inverter 2000w continuous
. 2 Autocraft Deep Cicle Marine 85ah 12v
. Also have a 60a DC breaker and another of 30a

I know it is not the best but I hope in the future to make upgrades little by little.

*I need to know what gauge wires and fuses or breakers I need to use between...
. PV to CC, need fuse for each panel? Parallel or series?
. CC to batteries and
. Batteries to inverter

I will greatly appreciate the guidance they can offer.

Gilbert

mcgivor · January 2018

With the panels listed, parallel would be the best option for a 12V nominal system, each panel should be fused with a 10-15A fuse before the combination. The gauge of the conductors PV to CC will depend on the distance between the two ( need this information for an accurate size recomendation ) as well as distance between CC to battery and battery to inverter. Keeping all as short as possible will keep costs to a minimum, the 30A breaker could be used as a disconnect PV to CC the 60A breaker could be used, for now, battery to inverter, since your battery capacity is low it would be advisable to keep loads to a minimum, this would allow ~750W maximum of the inverter's maximum capacity. Working with loads including when used to suit what you have would be advisable, as it stands the battery is small, the inverter too large but it's what you have, it's not necessarily the information you requested, but it is important to understand the limitations.

Estragon · January 2018

For CC and inverter to battery connections, I would use the largest wire that will physically fit on the terminals of each device. To parallel the batteries, I would use minimum 2/0. As well as keeping costs down, keeping distances short minimizes undesirable voltage drop.

Gilberto · January 2018

Thank you very much for the help!
My plans are to locate the CC, the batteries and the inverter close to each other, between 2 to 3 feet. From the PV to the CC it will be approximately 30 to 35 feet. I also got another 80th breaker.

Estragon · January 2018

Wired in series at ~35' you could use regular 12-2 or 14-2 copper wire to the array IMHO. Just make sure the insulation is right for the use (ie in conduit, overhead, buried...).

You might want to check max voltage allowed for the controller to be certain the Voc of the string at record low temps in your location is within the limit. In PR, it should be okay, but worth checking the manual and doing the math anyway just in case.

mcgivor · January 2018

For the PV to charge controller using 35' with a current of 20A at 30v, 8 AWG copper would be the minimum conductor size needed to be close to a 3% volt drop, using 6 AWG would naturally be better or 4 AWG aluminum to save on installation costs,, just be sure to use an anti oxidation compound on all splices with aluminum..

Estragon · January 2018

Just to clarify, the smaller wire is for series connected panels, the larger wire is needed for parallel connected panels.

Gilberto · January 2018

ok, the inverter specifies that it has 8 x 30a internal fuses. An external 240a fuse or breaker between the batteries and the inverter does the same job? This to never have to open the inverter.

Gilberto · January 2018

PV and Inverter...

Gilberto · January 2018

CC specs...

Gilberto · January 2018

Mcgivor, its ok to use this type of fuse before the combination for my 3 panels?

mcgivor · January 2018

Those are very convenient fuses and would work in your application, just remember they, and all MC-4 connectors for that matter, are not disconnects, as such should NEVER be disconnected under load, hense the reason for having a disconnect, circuit breaker, near the controller.

Gilberto · February 2018

I made this diagram summarizing his advice, although I put the 60a breaker between the DC and the batteries and another 80a between the batteries and the inverter. What do you think...

Estragon · February 2018

The wire size from controller to batteries isn't shown, but assuming it will be large, the 60a breaker should be ok IMHO. The controller (and inverter) manual should have a recommended size.

All breakers should be DC rated, and if applicable, installed with proper polarity.

Gilberto · February 2018

Thank you! I'm thinking of buying 6awg between CC and the batteries. Regarding the breakers, someone told me that I can leave them direct on the positive cable, but I do not know if it should be this way or if it is really necessary to use a box. I do not know much about that either.

Estragon · February 2018

If possible, I'd go to a 4ga wire.

Using a box is a good idea, if only to immobilize the breaker and avoid wiggling and loosening connections. If you need code compliance, it may be required.

Gilberto · February 2018

It is true, if I then do some Updates I should consider awg 4 so I do not have to buy wire again. Thank you!

Gilberto · February 2018

Hi. I think I need additional help. I do not know how I can use the 4awg wire with the PVs. I do not know if it exists but I have not found mc4 connectors for 4awg. What I can do?

mcgivor · February 2018

If using the in line fuses, you will need something like this, mount in a PVC box.... one suggestion
https://www.solar-electric.com/outback-power-insulated-terminal-bus-bar-black.html

Wheelman55 · February 2018

Gilberto said:

Hi. I think I need additional help. I do not know how I can use the 4awg wire with the PVs. I do not know if it exists but I have not found mc4 connectors for 4awg. What I can do?

Are you running the PV panel wires to a combiner box? Then from the combiner box to the CC. I don't think that you need the big wire for the short run from PV panels to combiner box.

You will need the big wire from combiner box to CC. Do ask one of the experts though.

Estragon · February 2018

For the run from pv to combiner, you would normally use a ~10ga mc4 extension cable about twice as long as the distance from pv to combiner. It has a male end and a female end, which are used to connect to pv, and it's cut somewhere in between to connect to the combiner.

Gilberto · February 2018

Sorry for the delay in answering. Still here in PR I am solving many things at once.
Thank you very much for all your suggestions.
In principle I thought that this would be easier but, the more I read and study on the subject, the more complicated.
Now I do not know if, it is or not necessary to use ground connections. If necessary, how should I do it? In each part of the system or only in the panels?
Soon I will update the list of the parts that I have and the diagram of my little system.

Estragon · February 2018

Generally speaking, there will be a single ground point (rod or plate driven/buried, or sometimes a "UFER" ground incorported into concrete building strucure) for the AC and DC sides of the system. Panels are typically grounded with clips on each, designed to penetrate aluminum frame oxidation layer.

The details vary a bit depending in situation and equipment.

Gilberto · February 2018

Thank you. I will continue reading about that in which some cables arrive from Amazon, to finally start to assemble my mini solar system!m

Gilberto · February 2018

I wonder if these Default Charge Controller Settings are acceptable for my 2 batteries connected in parallel. I recognize that it is little storage but later I hope to improve it.

I review again what I have available.

3 Boviet Monocrystallines 260w each. I will connect them in parallel.
http://www.solardesigntool.com/components/module-panel-solar/Boviet/3383/BVM6610P-260/specification-data-sheet.html

1 MPPT Charge Controller, SRNE SR-ML4860 (60a)
http://www.srnesolar.com/index/show/id/105.html
http://www.srnesolar.com/index/down/id/154.html

2 AutoCraft Marine and RV 12-Volt Deep Cycle Battery, Group Size 24M, 550 CCA, Reserve Capacity: 140, 85Ah each.

A Jupiter Power Inverter 2000w continuous, 4000w Peak. I also know that it is not the best but I will also improve it in the future.
https://manuals.harborfreight.com/manuals/63000-63999/63429.pdf

~CC Default Settings:~

Overvoltage Disconnect Voltage: 16.0v

Equalizing Voltage: 14.6v

Boost Voltage: 14.4v

Floating Voltage: 13.8v

Boost Restoring Voltage: 13.2v

Low Voltage Disconnect Restoring Voltage: 12.6v

Under Voltage Alarming Restoring Voltage: 12.2v

Under Voltage Alarming Voltage: 12.0v

Low Voltage Disconnect Voltage: 11.1v

Discharging Limit Voltage: 10.6v

Over Discharge Delay Time; 5s

Equalizing Duration Time: 120min

Equalizing Charging Interval: 30 Days

Boost Duration Time: 120min

*Will this be fine for my two batteries?
Tks again!

Estragon · February 2018

You may want to try it with defaults for a while.

The "boost" (absorb) voltage and time may be a bit low/short. You should see a bit of fizzing (like when you open a soft drink) if you look in the battery toward the end of the 2 hour boost cycle. If not, you might want to increase the boost voltage a bit in 0.1v increments until you do. You should also watch electrolyte levels in the battery - with daily use and proper charging, you should need to add a bit of distilled water every couple of months. If needed more often, charging voltage is too high. If needed less often, charging voltage is too low. If possible, getting a hydrometer to check specific gravity will be helpful in monitoring the health of the batteries and fine tuning charging.

Note that this inverter should only have loads connected directly using the AC recepticles. If you try to backfeed an AC panel with a neutral-ground bond, bad stuff will very likely happen.

Gilberto · February 2018

Ok but, the batteries are sealed and I do not know if there will be a way to monitor the liquid. Regarding the Inverter and the AC Panel, could you explain a little more? Honestly that part I do not understand, although I have only thought of adding a multi Outlet that also has USB Ports.

Gilberto · February 2018

Ah, rereading the part of the AC Panel I think I understand it. For example connect a male to male cable from the Inverter to a receptacle in the house. Is my interpretation correct? Ok, for now my plans are to connect independent hardware to the system, that is, separate from the house. I hope it is my hurricane survival system in a separate room with maybe, a small refrigerator, a TV or radio, a fan, some lamp and where to charge cell phones and laptops!

Estragon · February 2018

If the batteries are sealed, ignore the advice to increase charging voltage. Sealed batteries are sensitive to overcharging and excessive voltage. When I tried to find specs on the batteries, they appeared to be flooded, with two rectangular caps which pry off to expose three wet cells per cap.

Connecting loads, like tv or whatever to the inverter is fine.

I think your interpretation is correct. Sometimes people will try to connect an inverter so it runs things from the same panel, branch wiring and outlets they run on with grid power, which is possible if done properly, but shouldn't be attemped with what you have. Running an extention cord plugged into the inverter with multiple outlets for loads is okay. Just don't try to connect to the normal house wiring.

westbranch · February 2018

this...."connect a male to male cable from the Inverter to a receptacle " is known as a 'Suicide cord' and it is
highly NOT RECOMMENDED!
Do you have access to Square D Electrical products? If you do and need a combiner box and you can use the circuit breakers for up to 48 volts DC. I believe the CB type you need are the QO type... Ask the dealer.
see these threads
http://forum.solar-electric.com/discussion/comment/379074#Comment_379074
http://forum.solar-electric.com/discussion/16474/wiring-diagram-needed-for-squared-qo-breaker-box

there are others... if you want to search a little deeper. BE SAFE get a bypass switch so you can use your Solar Power in your house and not send it to the ''GRID'' or what is left of it... there could be someone harmed if you energize the damaged grid..

Gilberto · February 2018

More or less this is what I'm designing. I already have everything that is in the images ...

Advise for wiring and fuse

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