Fusing question for 4 x 260 Watt panels connected 2S2P (series/parallel)

[Silver_Is_Money]

My individual PV modules have the following specs:

Vmp = 31.0
Imp = 8.4
Voc = 37.8
Isc= 8.9

What would the proper fusing method and fuse rating(s) be for these panels both between them and then between them and the charge controller? I've heard of using standard automobile fuses. Are these acceptable, or are there better choices?

Are there any 'stickies' on this forum (or links to threads) which discuss the "hot too" of fusing in general for off-grid solar installations?

[Sunking]

None required or needed. They cannot generate enough current to damage any wiring. You are not required to use fuses with 2 or less strings. If you insist on using them, they are permitted, then 15 amps is the minimum size required and more than adequate for your application.

[Silver_Is_Money]

Well that makes it easy! Thanks again Sunking!

[Sunking]

You are welcome.

[Mike90250]

None required or needed. They cannot generate enough current to damage any wiring. You are not required to use fuses with 2 or less strings. If you insist on using them, they are permitted, then 15 amps is the minimum size required and more than adequate for your application.

Actually, it depends on where you put the fuses, after the 2 arrays are paralleled, you will have nearly 17 amps [Imp = 8.4] which will eventually [weeks, months] blow the 15a fuse.

But you should size your wires to handle 20A ( I believe that would be at least 12ga, maybe 10 depending on the length of the run) With a 20a rated wire, your 17a of panels won't be able to start a fire under most expected conditions.

[Silver_Is_Money]

What about fusing the connection between the charge controller and the battery bank? My charge controller is 40A max. So would 40A be the proper size for this fuse?

[Sunking]

Actually, it depends on where you put the fuses, after the 2 arrays are paralleled, you will have nearly 17 amps [Imp = 8.4]

That is true, but I did say Minimum Requirement or minimum code requirement.

[Sunking]

What about fusing the connection between the charge controller and the battery bank? My charge controller is 40A max. So would 40A be the proper size for this fuse?

Again the fuse size depends on the wire sire. Logically yes 40 would be minimum, 50 is ideal for a continuous 40 amp current. But they do not likely go where you think they go.

If your system is Floating you install 2 fuses, one on each terminal of the battery term post. Not at the controller. If your system is Grounded then on the Un-Grounded circuit conductor which is likely the positive terminal post of the battery.

You will need two fuses on each battery post. One to the controller, and another to the load like a Inverter. These are really good for the job.



You get them from Marine shops or online at Blue Sea Systems. MRB Fuses range from 30 to 300 amps. Another type some use, but I am not crazy about are, AMI, AMG, and ANL on battery post. They do not make for clean, secure, and insulated connections unless you are a good Fabricator.

[inetdog]

The Blue Sea sure look like a mechanically secure design which takes up a minimum of space around the battery terminal.
Do they make higher voltage components or are they only good for a nominal 48V maximum battery bank?

[Sunking]

The Blue Sea sure look like a mechanically secure design which takes up a minimum of space around the battery terminal.
Do they make higher voltage components or are they only good for a nominal 48V maximum battery bank?

They are for Marine and made for 48 volt max.

[Silver_Is_Money]

It appears that the MRBF fuses can be purchased online, but the Dual MRBF Terminal fuse block can't. I searched within 50 miles of my house and came up with nothing.

[Sunking]

It appears that the MRBF fuses can be purchased online, but the Dual MRBF Terminal fuse block can't. I searched within 50 miles of my house and came up with nothing.

So order online. You could have had them already. Yeah the fuses are easy, any boat shop has them. Even RV dealers carry them. Hint hint RV.

[inetdog]

So order online. You could have had them already. Yeah the fuses are easy, any boat shop has them. Even RV dealers carry them. Hint hint RV.

Silver_is_money: 'The double Dual MRBF Terminal fuse block cannot be purchased online."
Sunking: "So order online."

What is wrong with this conversation?

[paulcheung]

It appears that the MRBF fuses can be purchased online, but the Dual MRBF Terminal fuse block can't. I searched within 50 miles of my house and came up with nothing.

http://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Daps&field-keywords=Dual+MRBF+Terminal+Fuse+Block+-+30+to+300A

[Sunking]

Silver_is_money: 'The double Dual MRBF Terminal fuse block cannot be purchased online."
Sunking: "So order online."

What is wrong with this conversation?

LOL. Well I know for fact they can be ordered online. I read his mind, not his words.