20 amp fuse for 300watt Solar?

howdy!
I'm upgrading my wee little RV system to 300w of mono. (Mounted flat) I need a bigger fuse. According to this
equals (# of panels in parallel) x Panel ISC x 1.2
I came up with 21.6 amps so I guess a 20 amp fuse would be better than 25?
"What are your thoughts Hobson?"
I'm upgrading my wee little RV system to 300w of mono. (Mounted flat) I need a bigger fuse. According to this
equals (# of panels in parallel) x Panel ISC x 1.2
I came up with 21.6 amps so I guess a 20 amp fuse would be better than 25?
"What are your thoughts Hobson?"
Comments
- 14 AWG = 15 amps max
- 12 AWG = 20 amps max
- 10 AWG = 30 amps max
https://lugsdirect.com/WireCurrentAmpacitiesNEC-Table-301-16.htmIn detail--Insulation rating, ambient temperatures, conduit fill, etc. can also adjust the maximum allowed current.
Fuses and breakers (in general in North America) will not blow at 80% of rated current and well eventually trip at 100%+ of ratted current.
Isc is short curicuit rated current for a solar panel... But I would suggest heavier wire and a bit larger fuse/breaker to limit false trips and keep voltage drop low.
Also, note that for ~3 or more panels (or series strings of panels) in parallel--Each needs a series protection fuse per panel/string to reduce the chances of a single shorted panel from being overheated by the other 2+ solar panel strings. In the panel specification, you should see a series protection fuse rating (usually somewhere around 10-15 amps depending on size/amp rating of panel)--Using a combiner box with multiple breakers.
There is usually no reason for a siingle breaker between the array and the charge controller--The combiner box protects the individual panels/strings and the wiring from the combiner box to the solar charge controller panel input should be large enough to handle the Isc-array current directly.
However, many people still like a to install a single breaker (or switch) near teh charge controller panel input for easy array on/off when servicing the solar charge controller (especially if the combiner box is some distance away at the array).
-Bill
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A
solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-Lister ,
So, here is where I'm getting tossed around. This is what I got from "Tech Support" whom shall not be named after I sent in a pic of my setup. Maybe he doesn't think 300 watts is enough to worry about?
"Yes, you have too many things in your setup that will cause many issues.
First, remove all fuses from your setup.
Once the panels have been connected in a parallel connection connect them directly to the charge controller with the MC4 connectors you have installed.
If you install the system with the power converter and you find issues please remove the power converter from your system."
Because so many fuses get installed poorly and cause problems, could be the reason the mfg says not to use them. More than 2 parallel strings or panels, requires protection on all the panel strings, per series fuse spec on the panel sticker;
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A
solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-Lister ,
2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 700 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.
Here is my modified setup. If any of you have a chance to peruse it. I think the fuse on my battery is probably too big. 80 amps?
FYI... whats missing from here is my 2000w pure sine wave inverter, and 600 watt subwoofer.
Cheers
Note: You should only connect the solar charge controller to the battery bank first, then connect the solar panels to the charge controller--Otherwise the charge controller can get confused, or possibly even damaged. When turning off--Turn panels off first, then turn off the charge controller second.
If you do not have AC charging for days/weeks/etc..., a PWM charge controller usually draws very little current when "sleeping" (no sun).
MPPT type charge controllers generally draw more current, and if left connected to a battery bank without solar power (typically snow covered panels or other issues), a MPPT controller can significantly discharge the battery bank if left connected for weeks or longer without solar power (running the solar charger's computer and electronics).
For "storing" Lead Acid batteries (no loads, no charging)... A fully charged FLA battery can go about 1 month between charging. An AGM type battery can go upwards of 6 months between chargers--Both at 25C/75F... Hot batteries have higher self discharge (the rule is for every 10C/18F increase, 2x faster self discharge... For every 10C/18F below room temperature, 1/2 the typical self discharge rate).
-Bill
-Bill