circuit breaker and pv current

robocop

Hi  
To every body  wishing  a pleasant change of the year and hope the very best for 2021  hoping the covid will be far away 

Need a circuit breaker a need to know what amp

have a inverter with max amp imput of 18a*18a  500 vdc  it is a mppt solar 8048   8kw

will usae 12 panels 500w each 10.27 amp

Plse let me know how to combine if possible.

regards

Bob

BB.

Hi Bob,

Can you give us a link to your inverter/charger/solar charger system?

Specific solar panel ratings (Vmp/Voc/Imp/Isc and series fuse rating)

Battery bank voltage/AH rating (if not obvious from your links).

You are in a warm climate as I remember: Curacao

Need for breakers and such depend on your array configuration (and that needs to match your charge controller's input requirements).

Details matter here. 

-Bill

mike95490

Your inverter mfg will specify a style and value for the main breaker.  It has to allow enough current for the expected starting surges, and trip before severe damage is done.  I won't guess at if for you, but if I recall correctly, my main is 350A

robocop

Hi Bill and mike  

Happy New Year

the inverter is    max MPP SOLAR  8048    8kw 230vac  48v dc   12pc total panels

panel 500w greensun  imp 10.87 vmp 48.63 voc58.95  isc 10.28


hoping having  been clear 

regards

Bob

BB.

Is this the unit?

https://www.mppsolar.com/v3/catalogs/PCM5048_8048.pdf

If so, then

1. Vinput=140 VAC max (there is a higher voltage option, not yours?)
2. 70 Amps input max
3. 48 VDC battery bank
4. panel 500w greensun  imp 10.87 vmp 48.63 voc58.95  isc 10.28

2x panels in series:

• Voc-array= 2 * 58.95 volts = 117.9 volts Voc-array at 25C (assuming no "cold snaps")
• Vmp-array= 2 * 48.63 volts = 97.26
• Imp-array= 6 parallel strings * 10.87 amps = 65.22 Amps (is this Isc?)
• Isc-array= 6 * 10.28 amps = 61.68 amps (is this Imp?)
• Max series fuse guess= 10.87 amps (Isc?) * 1.25 NEC derating = 13.3 amps round up to = 15 amp fuse/breaker (spec sheet may say 20 amps max series fuse)
• Suggest wiring for array be rated for carrying 61.68 amps (Imp-array?) * 1.25 NEC derating = 77.1 amps minimum (wire and swirch/breaker if used minimum rated capacity).

2x panels in series works.

You would use a 6 to 1 combiner box with 15 (or possibly 20) amp fuses/breakers.

All make sense?

-Bill

robocop

hi Bill that is NOT the unti  is pip max 8048  8kw off grid  inverter als white in color and black piece on the botrtom  nblack color

Bob

BB.

This is the one?

http://www.mppsolar.com/v3/catalogs/PIP-MAX.pdf

• Vmp-min~100 VDC
• Vinput-array-max 500 VDC
• 2x Solar PV input with 18 amp max per channel.
• 120 amps max charging (into ~60 volts @ battery bus?).
• You have 12 panels.
• Guessing warm tropical climate with temperature not falling below 25C
  

Your 500 Watt solar panels have Imp~10.28 amps... But the PV channel has a maximum of 18 amps input... So you are limited to one series string per channel. (smaller Imp panels of ~9 amps or less, you could but 2 in parallel and get more solar energy into the unit).

Using 6 panels per string x 2 strings:

• 6 panels in series * ~60 volts Voc (guess) = 360 Volts @ 25C (good, below 500 vdc)
• 1x panel per strings = 10.28 amps per string (good, below 18 amps max)
• 12 * 500 Watt panels = 6,000 Watt array (good, below 8,000 Watts)
• 6 panels in series * 48.63 volts Vmp (?) = 291.78 volts Vmp-std (good, over 100 vdc minimum Vmp-array)
  

Assuming that 6s x 2p is correct to two separate Solar PV inputs for the inverter-charger--Then you do not need any circuit breakers/fuses for safety.

Note: With this controller--You have two separate 6 panel strings... One to each controller's PV input (2x PV input total)... So, you do not really have 2x parallel strings (the two strings are wired separately to the charge controller solar inputs).

If you would like circuit breakers for service (turn on/off array when working on system)--Then, the minimum circuit breaker/switch rating would be:

• 10.87 amps Isc(?) * 1.25 derating = 13.6 or round up to 15 amps minimum
• 360 VDC minimum working voltage

Note--Finding high DC Voltage rated circuit breakers or even switches will require looking around and may be very difficult to find. High Voltage DC works like a very nice DC Arc Welder which can have very long/large arcs. 

For example, here are 4x 150 VDC circuit breakers wired in series with a common trip to reach 600 VDC max working voltage:

http://www.midnitesolar.com/productPhoto.php?product_ID=336&productCatName=Breakers&productCat_ID=16&sortOrder=21&act=p

For ~$125 USD... And you would need two.

Do not use standard AC rated circuit breakers on high(er) voltage DC (or wire wrong polarity)--They will fail:

https://www.youtube.com/watch?v=Cup5fMGaE2g (various breakers on DC catching fire if used incorrectly)

https://www.youtube.com/watch?v=Zez2r1RPpWY  (knife switch on AC vs DC switching)

-Bill