Advice needed with solar setup

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DiabloSV

New member
Joined
Nov 23, 2021
Messages
4
Good day Everyone,

I am looking on buying a full solar system in the next month.

I am looking at the inverter and it mentions the following:
1 x InfiniSolar V IV 5.6KW
1) MPPT Voltage Range - 280VDC - 500VDC
2) Max input Current = 1/1x18A
3) MaxPV Input = 6000W

The panels I want to get are the following:
14 x LG370S1C-U6 [In Series
MPP Voltage (33.95)
MPP Current (10.91)

OR

12 x LG450S2W-U6 [In Series]
MPP Voltage (40.91)
MPP Current (11.43)


The way I understand the inverter to be in spec, I will need not be able to go more than 14 panels in series as (14 x 33.95 = 475.3VDC) or (12 x 40.91 = 490.92VDC) and I can't do any Parallel as going parallel will be over the Max Input current of 18A

I just want to make sure that I am planning my system in the correct way.
 

OffGridInTheCity

Active member
Joined
Dec 15, 2018
Messages
1,863
The way I understand the inverter to be in spec, I will need not be able to go more than 14 panels in series as (14 x 33.95 = 475.3VDC) or (12 x 40.91 = 490.92VDC) and I can't do any Parallel as going parallel will be over the Max Input current of 18A

I just want to make sure that I am planning my system in the correct way.
In general, you're comments indicate your on the right track and congratulations at getting close to pulling the trigger! :)

However, 476v for the 1st option and 491v for the 2nd option are pretty close to the 500v max. In most equipment, you cannot exceed the max at all without damage. Cold temps can cause significantly higher voltage in your situation. Here's a link to explain how to figure this out - https://gold-coast-solar-power-solutions.com.au/posts/solar-panel-maximum-voltage-calculator/ There are others / good info on this subject with a little searching.

The link above shows for option 1 - 476v.... at just 20F/-7C low temp comes out at 635v!
1639928126502.png


1639928433925.png



In addition, its common even after taking into account the cold temps is to leave a little head-room between the cold temp string voltage and the max the equipment is rated - like 10% = 50v or a max of 450v in this situation.
 
Last edited:

cak

Member
Joined
Mar 14, 2021
Messages
97
I second factoring the cold temp equations because I did not in my system and now need to redesign as my voltages are getting too high, so far the charge controller safety shutdown has saved things from damage but we will see how long that lasts.

Secondly my research indicated that one should be using the Open Circuit Voltage for deciding on how many panels to put in series and it looks like you are using the MPP Voltage from the specs which is lower.

So by my math you would want to have no more than 9 in series minus any allowance for cold temps. Which means you may want a different inverter if you need the full 6kw since 2 parallel runs of panels would exceed the current rating. Although I believe current maximums are less concerning as far as damage as long as the electronics limit themselves(which they should in a well designed inverter) so having the panel specs say 22is max amp output would lead to them being underutilized but not damaging the system. Others should correct me if I am wrong on that common interpretation of current not pushing like a pressurized water pipe, instead current is drawn like a pump only providing as much as is demanded. Hope that makes sense and indeed does apply to this use case.
 

Solexx X

Member
Joined
Nov 16, 2017
Messages
59
Your panels will not exceed their maximum VOC at your minimum temperature. If it's under the capacity of your panel string, you are fine. Google your panel number if you don't have the spec sheet and don't exceed that number of panels in your strings and you are golden. Make 2 or three strings and keep your amps within the capacity of your charge controller. You usually can oversize the maximum amps of your controller slightly but not the maximum volts. All the ratings in solar are for 100% and nobody gets that. The cabling alone will reduce power by 2 to 5 % Use a correctly rated breaker or fuse to protect your battery. If your battery is capable of 200 amp output then install a 150 or 175 amp fuse or breaker.
 

italianuser

Member
Joined
Feb 25, 2020
Messages
397
Another thing to keep into consideration is house wiring if you'll be connecting solar to the house (connecting inverter's AC output to the house electricity panel).

Be sure wires have sufficient diameter to carry the current coming out of the inverter. My 14AWG house wiring can't carry the 5KW coming out of the inverter, I can't go over 3.3/3.5KW.
 
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