Advice on RV Set up & Wiring?

[Sunking]

Actually the MidNite Baby box is much less expensive than posted above.
Alt-E sells it for $37.XX https://www.amazon.com/MidNite-Solar.../dp/B007IAIW7S

There is a misconception here about the requirement for overcurrent protection on PV systems..

There is no misconception, it is even written into electrical codes clearly stated. Example in NEC 690.9, although does not apply to RV,s clearly states under Exceptions OCPD SHALL NOT BE REQUIRED where circuit conductors are sized in accordance with 690.8 where one of the following applies.

No parallel external sources.
Short circuit currents do not exceed the ampacity of the conductors or the maximum OCPD size specified by the panel manufacture.

Could not be any more clearer than that. If the panel manufacture specifies a 15 amp OCPD and you panels adjusted ISC is 15 amps or less, no OCPD is required or needed. There is no possible way for the solar panel to generate enough current to even heat up a wire, let alone operated a fuse. Solar panels are limited current sources. They cannot possible generate more current than their ISC rating.

Does not mean you cannot use them if you want, but there is no requirement or need for them.

[rgudgel]

Actually the MidNite Baby box is much less expensive than posted above.
Alt-E sells it for $37.XX https://www.amazon.com/MidNite-Solar.../dp/B007IAIW7S

There is a misconception here about the requirement for overcurrent protection on PV systems. I will try to clear it up here.
Overcurrent and disconnect is required down at the point where all other solar equipment disconnects are located. You only get 5 motions of the hand to shut everything off. That typically is not a problem, but you do need an overcurrent device and disconnect even for one string. The concept of not being required until you have three strings is meant for combiners. Here is the rationale. Take a solar panel that has a UL listing for a 15 amp overcurrent device. UL or ETL or TUV has tested and certified the design of that panel to not burn up with 15 amps of current flowing in the traces. Most panels have a short circuit rating of only 10 amps or so. You do not need a combiner for this as you are not combining. Now add a second one of those panels in parallel. You now have about 20 amps of current capability, so your disconnect/OCPD needs to be sized accordingly. (156% of short circuit current). You still do not need a combiner for this paralleled configuration. If one of the panels develops an internal short, the good panel is going to back feed it. The good panel can only produce 10 amps of current, but UL has determined that each of those panels is safe with up to 15 amps of current flowing, so you are still safe from causing a fire. Now let's add a third panel in parallel. If one of the panels develops a short, there will be two good panels backfeeding the bad one. The two good panels can put out a total of 20 amps. This exceeds the tested and certified rating of a single panel. This is now where you need a combiner with three breakers or fuses. In off-grid applications people always opt for breakers. I hope this clears up the mystery. Most professional installers do not even know the reasoning for this, but what I explained is the way it works.

[Sunking]

You are aware that fuses cannot be used to manually open a circuit . Breakers (esp the Midnight DC rated ones) can be used as switches for troubleshooting.

Remember, touch safe fuse holders are only safe to open when the current flow is stopped, either blown fuse, or manual cut off somewhere.

I tried to tell him. He wants to waste money for something he does not need or really wants if he knew the restrictions. He just added expensive eggs to his basket.

[Mike90250]

....... So for the extra $90 I saved not going that route I'll be able to get the other fuses I need and still saved some money and have the same breakers. As far as I'm concerned this is the much better alternative for those who are watching their $$$.

You are aware that fuses cannot be used to manually open a circuit . Breakers (esp the Midnight DC rated ones) can be used as switches for troubleshooting.

Remember, touch safe fuse holders are only safe to open when the current flow is stopped, either blown fuse, or manual cut off somewhere.

[Carv]

Too bad you didn't get the MidNite Baby Box for those breakers. No modifications required.

Actually it's ALL GOOD, the midnite box is $132 and I do NOT think it even includes the breakers. So for the extra $90 I saved not going that route I'll be able to get the other fuses I need and still saved some money and have the same breakers. As far as I'm concerned this is the much better alternative for those who are watching their $$$.

[Sunking]

It is required by NEC to have an overcurrent device and switch between the solar panels and controller.

1. No Sir OCPD are not required or needed for a single string of panels to comply with NEC. Only required when 3 or more strings are used.
2. It is an RV so NEC requirements do not apply.

[sensij]

It is required by NEC to have an overcurrent device and switch between the solar panels and controller. It is more of a convenience in my mind, since you won't ever trip the breaker, but if you plan on meeting code, you would need that breaker.

Overcurrent device is only required when more than 2 panels or strings are in parallel.

Requirements for disconnects depend somewhat on how the system is installed.

[littleharbor]

I am curious how Littleharbor has a 'new" Trace 4024? Those went out of production about ten years ago. They were great inverters though.I had a couple of them until recently.

I bought the Trace SW 4024 in a factory sealed box from a guy who had it in the back of his warehouse and had forgotten about it. I held onto it for a few years until I set up my system in Baja. It was nice to pop the tape and staple clad top of the box to reveal the pristine inverter and all the paperwork,, manual and accompanying parts under the plastic sheeting. It has a Mfg. date of 2001.

[rgudgel]

Too bad you didn't get the MidNite Baby Box for those breakers. No modifications required.
It is required by NEC to have an overcurrent device and switch between the solar panels and controller. It is more of a convenience in my mind, since you won't ever trip the breaker, but if you plan on meeting code, you would need that breaker.
I am curious how Littleharbor has a 'new" Trace 4024? Those went out of production about ten years ago. They were great inverters though.I had a couple of them until recently.

[Carv]

Here is midnite solar talking about there breakers including that they are designed to be switched under load, AKA switch rated.

https://youtu.be/Mtq3cs9Gucc

Midnite solar breakers are inexpensive. https://www.solar-electric.com/mnepv.html They are dedicated DC breakers. DIN rail mount. Not made in China!

Went this route, with the square D box and the midnite solar breakers as switches and over current protection (even if it's not needed).

Thanks for the link Mike, Northern AZ sun & wind has them for $11 each, no tax, and $8 shipping so $31 out the door for 2 DC switch rated breakers, that's a good deal!

Super happy with this set up, I now have 2 DC switch rated breakers & a solid box for $43 VS the $35 I was going to spend on the wang alternatives like in the picture I posted above or the $60 I was going to spend on the blue sea 7180 resettables.

Finally a good solution that allows me to switch the incomming & outgoing feeds, have over currant protection, and all at a reasonable price., thanks again Mike!

(I will have to modify the square D box with a small DIN rail and a spacer to get the breakers faced in the box but that should be pretty easy).

[littleharbor]

Midnite solar breakers can be found for $12.50 apiece. I see some vendors getting 24 to 26 apiece but just a little shopping around online pays off

[Sunking]

Actually, many of the breakers carried/sold by Midnight, ARE rated for switch duty use, I use them in combiners and both sides of the Controller as needed and for my convenience, You must, however, have the Line and Load terminals identified and wired properly for the internal Arc Chute to work right.

My bad, forgot about those. Thanks for bringing it to my attention. Personally I would not use them as they cost way to much and other more suited product out there. I can see that say between the batteries and Inverter, but not between panels and converter that requires no OCPD or Switch, especially on an RV. He can get exactly what he want by just using Hot Pluggable Connectors for $10 to $15. He is certainly welcome and nothing preventing him to use expensive breakers or fuses between panels and controller.. My question is why? There is no gain, just an expensive failure point. Last RV I set up a while ago we used the Panel Mount Anderson with umbilical cord. For the cod we just used a heavy duty outdoor rated 12/3 extension cord. I suggested he use SO, but the cod he found had flex fine stranded tinned copper 12 AWg conductors. Slick, easy, functional, and inexpensive. That is how I roll.

[littleharbor]

I pull my batteries when parked, so I don't have to worry about false trips.


If I'm running a 30A epever mppt, should I run a 30, 35, or 40A breaker to the batteries?

Also on the PV feed to the charge controller should I use a 10, 15, or 20A?



I'm running 2 of the 260W panels in series, here's my panel specs Yingli YGE -60 Cell Specs.jpg





Thanks

I don't think there is PM ability available here (any more?) Give me a call if you have a few minutes.

[Mike90250]

.....

However Breakers are not meant to be used as Switches, and if you use them as Switches will weaken them, and you will get false and nuisance trips......

Actually, many of the breakers carried/sold by Midnight, ARE rated for switch duty use, I use them in combiners and both sides of the Controller as needed and for my convenience,
You must, however, have the Line and Load terminals identified and wired properly for the internal Arc Chute to work right.

http://www.midnitesolar.com/productPhoto.php?product_ID=183&productCatName=Breakers&productCat_ID=16&sortOrder=18&act=p

MidNite's breakers are rated to break the full rated load at the rated voltage repeatedly, with NO DAMAGE. Always use a properly sized breaker for disconnecting.

[Sunking]

If I'm running a 30A epever mppt, should I run a 30, 35, or 40A breaker to the batteries?

Anything larger than 35 amps with the Fuse connected directly on the Battery Term Post. Minimum Wire size is determined by the OCPD used. Example if you use a 40 amp fuse, use the charts from minimum wire size and voltage drop. If it were me I would use a 40 amp fuse with 6 AWG or larger wire.

Also on the PV feed to the charge controller should I use a 10, 15, or 20A?

None of the above. What fuse? There is NO need or requirement for a OCPD between the Panels and Controller. You need to understand that, There is no need to put anything in between the panels and controller other than say an Anderson or MC4 connectors.

So I ask you again, Why are you putting a junction box with fuses or breakers between the panels and controller? . All you are doing is putting more eggs in basket and throwing away money. All you need is $10 worth of connectors. Unless you have 3 or more strings of panels, no OCPD is required or needed. All you have is 1 string. It is impossible for a solar panel to burn wiring up unless there are 3 or more parallel strings, they are current sources. You can short out your panels all day long facing directly into the sun and they cannot generate more than 10 amps of current. The panel Isc is 9 amps. 9 amps on a 14 AWG is normal operating current. Solar panels are current sources, not voltage like a battery.

Short your panels out, if they are in strong sun at high noon may deliver 9 amps at most. Short out your battery and you have a fire, vaporized copper exploding, and boiling hot acid spewing everywhere. Short your panels out, you can relax and go to bed. Short your batteries out, and you will be in a hospital bed recovering.