Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
Unexpected PV breaker trip
#1
Just a report to help others avoid potential troubles in the future.
TL;DR: Install breakers with high enough Amp rating to account for higher current during hot weather.


I have 3 solar chargers, each connected to their own oversized PV array, so that I can get enough power on days with less than ideal weather.
Each array is 3180Wmp, Vmp 91.8V, and Imp 34.63A.  The solar charger limits itself to at most 2285W, so the draw from the solar panels should never ever exceed 2285W/91.8V = 24.9A, right?  And in practice during spring, it was closer to 20A.
So I used 32A breakers for chargers #1 and #2, and a leftover 25A breaker for charger #3.  A bit tight, but they don't trip until at least +15% or so anyway...

It worked well for 5 months, but today #3 breaker tripped.  The weather was super hot, so according to the "temperature coefficient" stated in the datasheet and assuming panel temp of 55C, the panels now had a Vmp of just 81.3V (11.5% lower!!).  The solar charger compensated by pulling more than 28A.  The 40+C heat in the electrical room probably helped set off the thermal trip of the breaker, too.
Solution: replaced the 25A breaker with a 32A.
Korishan likes this post
Modular PowerShelf using 3D printed packs.  60kWh and growing.
https://secondlifestorage.com/showthread.php?tid=6458
Reply
#2
Yeah, a bit tight on the amp tolerances there. I suppose live and learn. At least they actually tripped and didn't cause other issues.
ajw22 likes this post
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
Certified 18650 Cell Reclamation Technician

Please come join in general chit-chat and randomness at Discord Chat (channels: general, 3d-printing, linux&coding, 18650, humor, ...)
(this chat is not directly affiliated with SecondLifeStorage; VALID email req'd)
Reply
#3
Correct. Its common that people underrate solar-breakers wrong. Seen it happen and been there as well Smile
ajw22 likes this post
NOTE! My links supplied in this message may be affiliated with Ebay and by clicking on them you agree on the terms.
YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 100kWh LiFePo4 | 20kWh 14s 18650 |  66*260W Poly | ABB S3 and S5 Trip breakers
Upcoming: 14S 18650~30kWh
Reply
#4
I had a related situation - doubled the panels going into an existing Midnite Classic 150 (winter time) while I was waiting for the new/additional one to arrive.   I have 80a breakers at the control box on the Midnite output.    It so happened that I got a perfect day and the Midnite went above 80a...  and tripped the breaker.

This was when I discovered that Midnite has the ability to limit the output power...   so I set it down from 85a to 80a...    to avoid tripping the breaker in the future.   Maybe your charge controller has an output amps limit setting?   You could use that to make sure it doesn't trip your 25a breaker?.
Reply
#5
Does limiting the output amps of the charge controller allow an array to be larger than what’s recommended for the charge controller?
Reply
#6
(08-28-2020, 05:08 PM)Cheap 4-life Wrote: Does limiting the output amps of the  charge controller allow an array to be larger than what’s recommended for the charge controller?
I'm talking Midnite Classic specifically - and I view your question as seperate aspects.

Aspect 1) The Classic is designed to let the user limit output and will throttle or discard the PV input to achieve the user setting.   This can run continuously... e.g. the Classic will not shutdown but continue to operate all day....


Here's what the current limits looks like in the interface of Classic 150 in 48v battery mode:



Aspect 2) If you exceed the max input design of 4420w and feed in 8000w (as an example) the Classic will protect itself (e.g. it won't burn up or anything) but I think it will shutdown / stop producing output to the battery.      However, I'm not sure and didn't find anything to reference in a medium google search.    Assuming wiring/breakers are not in the way...  maybe its temperature related more than anything else. 

Here's what the manual says....
Reply
#7
An array can almost always be bigger than the controller without limiting further. The controller always have a limiter per default. (Of course check this out first)

As an example. In Sweden most arrays are 10-20% larger than the inverter because its cheaper to do that and have more total power over the day than buying bigger inverter.

Limiting in this sense is to set a limit on the current so you dont trip the system if it isnt properly sized. I recommend to properly size it instead. Though it can be that you want to have more even curve during the day and limitng is cheaper than sizing.

I have not heard of any charger that is damaged by to much total "power" available as long as the Voltage range from the panels doesnt go above the Max voltage on the device.
Cheap 4-life likes this post
NOTE! My links supplied in this message may be affiliated with Ebay and by clicking on them you agree on the terms.
YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 100kWh LiFePo4 | 20kWh 14s 18650 |  66*260W Poly | ABB S3 and S5 Trip breakers
Upcoming: 14S 18650~30kWh
Reply
#8
(08-28-2020, 04:59 PM)OffGridInTheCity Wrote: This was when I discovered that Midnite has the ability to limit the output power...   so I set it down from 85a to 80a...    to avoid tripping the breaker in the future.   Maybe your charge controller has an output amps limit setting?   You could use that to make sure it doesn't trip your 25a breaker?.

Yes, my charge controllers are set to put out at most 40Amp. That results in 20A~25A on the PV side on typical days.
The problem was that as the panels heat up in peak summer, the panels put out 11.5% lower voltage, and the current increased 11.5%, thus tripping the breaker.



(08-28-2020, 05:08 PM)Cheap 4-life Wrote: Does limiting the output amps of the charge controller allow an array to be larger than what’s recommended for the charge controller?

Absolutely, and I absolutely recommend it. I have a +40% larger array than what my charger can handle. Results in more stable max charging output for more hours/day, even with less than ideal weather. Panels are cheap nowadays - put up as many as you can.
Modular PowerShelf using 3D printed packs.  60kWh and growing.
https://secondlifestorage.com/showthread.php?tid=6458
Reply
#9
That’s great! Why do they even have a recommended maximum amount of watts if it’s only the volts that matter. Outback and midnite both have a maximum amount of watts listed for their controllers. They both also have options to limit the amps they output
Reply


Forum Jump:


Users browsing this thread: 1 Guest(s)